JP2001183540A - Optical waveguide device, coherent light source, integrated unit, and optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems that a coherent light source which uses a conventional optical waveguide device (1) increases in size along the optical axis, (2) induces a light source noise owing to the feedback of a light reflected by a waveguide projection end surface to the light source, and (3) generates an interference noise owing to the rereflection of external reflected light on the optical waveguide projection end surface. SOLUTION: This optical waveguide device is equipped with a substrate (1) which has a 1st surface (S1) and a 2nd surface (S2) and an optical waveguide (3) which is formed on the 1st surface (S1) of the substrate (1) and has a light incidence end surface and a slanting surface slanting to the optical waveguide (3); and a waveguide light which is made incident on the optical waveguide (3) from the light incidence end surface is totally reflected by the slanting surface (4) and projected from the 1st surface (S1) or 2nd surface (S2) of the substrate (1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device, a coherent light source, an integrated unit using the same, and an optical pickup device used in the fields of optical information processing and optical communication.

[0002]

2. Description of the Related Art In the field of optical information processing, a compact short-wavelength light source is required in order to realize high-density information on an optical disk and high definition of a display. As a technique for shortening the wavelength, conventionally, an optical waveguide type wavelength conversion (Yamamoto et al., Optics Letters Vo) of a quasi-phase matching (hereinafter, referred to as QPM) method with a semiconductor laser.
l. 16, No. 15, 1156 (1991)) Second harmonic generation using a device (hereinafter referred to as SHG)
The technology is known.

FIG. 20 shows an optical waveguide type wavelength conversion device 8.
FIG. 2 shows a schematic configuration diagram of an SHG blue laser 2000 using the No. 3 laser. Here, a tunable semiconductor laser 80 having a distributed Bragg reflection (hereinafter referred to as DBR) region is used as the semiconductor laser. Hereinafter, a tunable semiconductor laser having a DBR region is referred to as a tunable DBR semiconductor laser. This wavelength tunable DBR semiconductor laser 80
This is a 100 mW-class AlGaAs-based DBR semiconductor laser in the 0.85 μm band, and includes an active region 81 and a DBR region 82. By changing the current injected into the DBR region 82, the oscillation wavelength of the semiconductor laser can be changed. The optical waveguide type wavelength conversion device 83, which is a wavelength conversion element, is provided with an X plate (X direction of a crystal perpendicular to the substrate).
The substrate is composed of an optical waveguide 84 formed on a MgO-doped LiNbO ₃ substrate and a periodically poled region 85. The laser light emitted from the emission surface of the tunable DBR semiconductor laser 80 is coupled to the optical waveguide 84 of the optical waveguide type wavelength conversion device 83. This FIG.
Configuration, 60 mW for a 100 mW laser output
Was coupled to the optical waveguide. And wavelength tunable DB
The amount of current injected into the DBR region 82 of the R semiconductor laser 80 is controlled to change the oscillation wavelength to an optical waveguide type wavelength conversion device 83
Fixed within the phase matching wavelength tolerance of
About 10 mW of blue light of 25 nm is obtained.

When such an SHG blue laser 2000 is applied to an optical disk recording / reproducing apparatus, it is mounted on an optical pickup 2100 having a structure as shown in FIG. Here, the module (SHG blue laser 200
0) is collimated by a collimating lens 86, and is polarized by a polarizing beam splitter 87 (hereinafter, referred to as a polarizing beam splitter 87).
PBS) and the 波長 wavelength plate 88. Thereafter, the direction is set to 9 by a rising mirror (not shown).
Bending 0 degree (perpendicular to the paper), objective lens 8
The light is condensed on the optical disk 95 by 9. The direction of the reflected light from the optical disk 95 is bent by 90 degrees by the PBS 87, and guided to a photodetector 91 (hereinafter, referred to as PD) by a detection lens system 90 including a detection lens and a cylindrical lens. Done. By using the optical pickup 2100, reproduction of a high-density optical disk of 10 GB or more is realized.

On the other hand, as shown in FIG. 22, a method has been proposed in which a 45 ° cut is made in an optical waveguide to form a total reflection surface, and output light is taken out in a direction perpendicular to the substrate (Uchida et al.). , IEICE Spring Conference, C3.28, 1
994). In this method, double ion exchange is performed on a glass substrate 92 to form an optical waveguide 93 made of glass, and a 45 degree cut 94 is made in the optical waveguide 93 by micromachining. This processing is performed using a special blade, and the cut surface of the cut 94 is polished simultaneously with the cutting. Thereby, a low-loss reflective surface of 0.3 dB is realized.

[0006]

In recent years, with the miniaturization of computers, small and thin optical pickups have been required. In order to reduce the size and thickness of the optical pickup, not only the size of the light source but also the configuration of the optical pickup is important. It is also important to take countermeasures against return light and interference noise as described below.

1) Miniaturization and Thinning of the Pickup In the configuration of the conventional optical pickup 2100 shown in FIG. 21, the optical axis direction of the module and the optical axis direction of the optical pickup are parallel, so that the optical pickup 2100 It becomes longer in the axial direction. When using a semiconductor laser chip,
Since the element length is 1 mm or less, there is not much problem. However, since the SHG blue laser 2000 is composed of a semiconductor laser and an optical waveguide type wavelength conversion device, the module size becomes about 10 mm in length,
The optical pickup becomes extremely long. Further, in the configuration shown in FIG. 21, since the light detection system (detection lens, cylindrical lens, and PD) is separated, the optical pickup becomes large.

2) Countermeasures for return light In a module composed of a semiconductor laser and an optical waveguide device, reflected return light from the output end face of the optical waveguide device returns to the semiconductor laser, and the semiconductor laser can have a multi-longitudinal mode. Occurs. For this reason, noise characteristics and the like deteriorate.

3) Reduction of Interference Noise In the SHG blue laser 2000, blue light is obtained by wavelength conversion using semiconductor laser light as a fundamental wave. Therefore, even if the return light component due to the external reflected light returns to the semiconductor laser, the semiconductor laser has a feature that the noise is not increased. As a result, the semiconductor laser operates in a single mode, and as a result, low noise (−140 dB / Hz or less) is realized. However, since blue light has high coherence, when an external resonator structure is used, an amplitude variation occurs due to interference when the resonator condition changes. In the configuration of the optical pickup 2100 shown in FIG.
The surface and the emission end face of the optical waveguide type wavelength conversion device form a confocal optical system. For this reason, when the optical disc rotates and the interference condition changes, the light intensity received on the PD 91 changes, and the signal waveform when the disc is reproduced is deteriorated.

The present invention has been made to solve such problems of the prior art, and can be made smaller and thinner, and can prevent problems due to return light to a semiconductor laser and interference noise. It is an object to provide an optical waveguide device, a coherent light source, an integrated unit, and an optical pickup device that can be used.

[0011]

According to the present invention, there is provided an optical waveguide device comprising a substrate having a first surface and a second surface, and an optical waveguide formed on the first surface of the substrate. The waveguide has a light incident end face and an optical waveguide having a slope inclined obliquely to the optical waveguide, and the guided light incident on the optical waveguide from the light incident end face is totally reflected on the slope. The guided light is emitted from the first surface of the substrate or the second surface of the substrate.

[0012] The guided light may be emitted from a first surface of the substrate.

[0013] The guided light may be emitted from a second surface of the substrate.

The substrate is made of a non-linear optical material, and the guided light incident on the optical waveguide as fundamental wave light is a second light.
The wavelength may be converted into harmonic light and emitted.

[0015] The second harmonic light may be emitted from a second surface of the substrate.

The thickness of the substrate is 0.3 mm or more.
It may be 0 mm or less.

[0017] A non-reflection portion that does not reflect the second harmonic light may be provided on the first surface of the substrate.

The non-reflection portion may be formed by an anti-reflection coating.

[0019] The second harmonic light may be emitted from a first surface of the substrate.

[0020] A non-reflection portion that does not reflect the fundamental wave may be provided on the first surface of the substrate.

The non-reflective portion may be formed by an anti-reflection coating.

The angle formed between the inclined surface of the optical waveguide and the optical waveguide may be 45 ° ± 1 °.

[0023] The second harmonic light may be in a guided mode.

[0024] The entire surface of the substrate corresponding to the slope of the optical waveguide may be inclined with respect to the optical waveguide.

[0025] The inclined surface of the optical waveguide may be formed by a notch formed near the first surface of the substrate and substantially orthogonal to the optical waveguide.

[0026] The inclined surface of the optical waveguide may be formed by a concave portion formed near the first surface of the substrate and substantially orthogonal to the optical waveguide.

At least a first portion of the substrate excluding the concave portion
May further have a protective layer on the surface thereof.

[0028] A protective layer may be further provided on the first surface of the substrate.

The refractive index n _{1 of the} protective layer and the effective refractive index n of the optical waveguide with respect to light guided through the optical waveguide.
₂ and an angle θ formed by a normal to the first surface of the substrate and a side surface of the concave portion may satisfy a relationship of Sin (θ)> n ₁ / n ₂ .

The inclined surface of the optical waveguide is formed by a concave portion formed near the first surface of the substrate and substantially orthogonal to the optical waveguide, and is provided with a waveguide mode of fundamental wave light guided through the optical waveguide. A depth t _1, and the second
The depth t ₂ of the guided mode of the harmonic light and the depth t of the concave portion
May satisfy the relationship of t ₂ <t <t ₁ .

A protective layer is further provided on the first surface of the substrate, and the slope of the optical waveguide is formed by a concave portion formed near the first surface of the substrate and substantially orthogonal to the optical waveguide. The refractive index nc ₁ of the fundamental wave light guided through the optical waveguide with respect to the protective layer, the refractive index nc _{2 of} the second harmonic light guided through the optical waveguide with respect to the protective layer, and the fundamental wave light of the optical waveguide. And the refractive index nf ₁ of the optical waveguide
The refractive index nf ₂ for the harmonic light and the angle θ between the first surface and the normal to the side surface of the concave portion are nc ₂ / nf ₂ <Sin.
The relationship (θ) <nc ₁ / nf ₁ may be satisfied.

[0032] A diffraction grating may be formed on the second surface of the substrate.

[0033] The substrate may be made of a first birefringent optical crystal.

[0034] A second birefringent optical crystal arranged in the optical path of the emitted guided light and having an optical axis orthogonal to the first birefringent optical crystal of the substrate may be further provided.

The surface from which the guided light is emitted may have a substantially cylindrical shape.

[0036] The apparatus may further include a cylindrical lens arranged in an optical path of the guided light emitted from the optical waveguide device.

[0037] The optical waveguide device may further include a concave package disposed therein, and the second birefringent crystal may seal the concave package.

[0038] The optical waveguide device may further include a concave package disposed therein, and the cylindrical lens may seal the concave package.

The substrate has a first end face including a light incident end face of the optical waveguide, and a second end face facing the first end face, and the inclined face and the first surface of the substrate are connected to each other. The angle between the intersection line of the substrate and the plane including the intersection line between the second end face of the substrate and the second surface of the substrate, and the direction in which the guided light is emitted is the second angle of the substrate. May be larger than half the divergence angle of the guided light emitted from the surface.

A plane including a line of intersection between the slope and the first surface of the substrate, a plane including a line of intersection between the second end surface and the second surface of the substrate, and a direction in which the guided light is emitted. Angle θ
And the spread angle θ1 of the guided light extracted from the second surface of the substrate may satisfy the relationship of θ1 / 2 <θ.

[0041] The semiconductor device may further include a periodically poled region formed on the first surface of the substrate.

The periodic domain inversion region may not be formed near the slope of the optical waveguide.

A coherent light source according to the present invention includes a semiconductor laser and the above-described optical waveguide device.

The semiconductor laser may be a tunable semiconductor laser.

The distance between the light emitting end face of the semiconductor laser and the light incident end face of the optical waveguide is 0 μm or more and 10 μm or more.
It may be as follows.

An integrated unit according to the present invention includes a coherent light source having a semiconductor laser and the above-described optical waveguide device into which light from the semiconductor laser is incident, and a light emitting device that emits light from the optical waveguide device. A light detector for detecting relevant light; and a submount on which the coherent light source and the detector are arranged on the same plane.

[0047] The image processing apparatus may further include a light shield disposed between the coherent light source and the photodetector.

The height of the photodetector surface from the submount surface may be higher than the surface of the coherent light source on the light emission side.

A recess is formed on the surface of the submount,
The coherent light source may be located in the recess.

An integrated unit according to the present invention includes a coherent light source having a semiconductor laser and the above-described optical waveguide device into which light from the semiconductor laser is incident, and a light emitting device that emits light from the optical waveguide device. A submount having a photodetector for detecting associated light, a first surface, and a second surface that is a back surface of the first surface, wherein the coherent light source is a first surface of the submount. A submount disposed on the second surface, wherein the photodetector is disposed on the second surface.

An integrated unit according to the present invention includes a coherent light source as described above, a concave package in which the coherent light source is disposed, and sealing the concave package.
A transparent substrate having a diffraction grating formed on the surface.

An optical pickup device according to the present invention includes the integrated unit described above, and a condensing optical system for condensing light emitted from the integrated unit, wherein the optical waveguide of the integrated unit is provided. A diffraction grating is formed on a surface from which guided light is emitted from the device.

An optical pickup device according to the present invention includes the integrated unit described above, and a condensing optical system for condensing light emitted from the integrated unit.

The photodetector of the integrated unit includes a first region at the center, and second and third regions on both sides of the first region.
The region may be divided into at least three regions, and the second region and the third region with respect to the first region may be arranged in a direction perpendicular to the lattice fringes of the diffraction grating.

An optical pickup device according to the present invention detects a semiconductor laser, the above-described optical waveguide device into which light from the semiconductor laser is incident, and light related to the light emitted from the optical waveguide device. Two photodetectors, a submount on which the coherent light source and the detector are arranged, a condenser optical system for condensing light emitted from the optical waveguide device, and a condenser optical system disposed in the condenser optical system A diffractive element having a lens function, wherein the two photodetectors are positioned to face the optical waveguide device, and
Each of the two detectors has at least a region divided into a central portion and a peripheral portion, and light diffracted by the diffraction element illuminates each of the two detectors.

Hereinafter, the operation of the present invention will be described.

According to the present invention, the guided light is totally reflected on the inclined surface provided on the optical waveguide on the first surface of the substrate of the optical waveguide device, and the first surface of the substrate provided with the optical waveguide is provided.
Light is emitted from the surface or the second surface. By forming a coherent light source (module) by combining this optical waveguide device and a semiconductor laser, light is emitted in the first or second surface direction different from the optical axis, so that the size of the optical pickup can be reduced. It becomes possible to plan. Further, as in the conventional structure in which the emission end face is vertically polished, light reflected on the emission end face of the optical waveguide and returned to the semiconductor laser is reduced, and noise characteristics are improved.

If the thickness of the substrate constituting the optical waveguide device is less than 0.3 mm, handling is difficult.
If it is larger than 1.0 mm, astigmatism will increase in the condensed spot, so that it is preferably 0.3 mm or more and 1.0 mm or less.

When the substrate constituting this optical waveguide device is made of a non-linear optical material and the wavelength of the fundamental wave light of the semiconductor laser incident on the optical waveguide is converted into the second harmonic light, the return light component (ref. Even if the second harmonic light) returns to the semiconductor laser, the noise does not increase. However, in the case of blue light, for example, since the coherence is high, when light is emitted from the second surface, an antireflection coating for the second harmonic light is applied to the first surface side so that the return light is Preferably, it is not re-reflected on the surface of the first.

According to the present invention, when the guided light is totally reflected on the slope provided in the optical waveguide of the optical waveguide device and is taken out from the first surface provided with the optical waveguide, the optical waveguide device Is combined with a semiconductor laser to form a module, light is emitted in a first surface direction different from the optical axis, so that the optical pickup can be reduced in size. Further, compared with the conventional structure in which the emission end face is polished vertically, less light is reflected on the slope of the optical waveguide and returns to the semiconductor laser, so that noise characteristics are improved.

When the substrate constituting this optical waveguide device is made of a non-linear optical material and the wavelength of the fundamental wave light incident on the optical waveguide is converted into the second harmonic light, the return light component (the second harmonic light ) Returns to the semiconductor laser, the noise does not increase. However, in this configuration, since the light reaches the first surface immediately after the light is totally reflected on the slope, the antireflection coating for the fundamental light is applied to the first surface side, and the fundamental light is re-reflected on the first surface. It is preferable not to return to the optical waveguide.

Further, in the optical waveguide device, when the slope of the optical waveguide is formed at an angle other than 45 degrees with respect to the optical waveguide, coma aberration occurs in the condensed spot.
It is preferable to form at an angle of 5 degrees (45 degrees ± 1 degree).

When the substrate constituting the optical waveguide device is made of a non-linear optical material, and the wavelength of the fundamental light of the semiconductor laser incident on the optical waveguide is converted to the second harmonic light, it is preferable that the harmonic light be in a guided mode. . In the waveguide mode, it is possible to make the substrate thinner than in the radiation mode, and to suppress astigmatism and the like. Further, when the light of the optical waveguide is in the radiation mode, the thickness of the substrate is required to radiate in the direction of the substrate, and when forming a slope with a concave portion or the like as described later, a deep concave portion is required. . Further, in consideration of application to an optical disk recording / reproducing apparatus, it is difficult to obtain good light-collecting characteristics in the case of the radiation mode.

In the present invention, a concave portion (groove), a cut portion, or the like is formed near the first surface so as to be substantially orthogonal to the optical waveguide, and a portion (for example, a side surface) of the concave portion or the cut portion is formed as a light guide. It may be a slope of a wave path. In this case, a concave portion having a slope can be formed by etching or the like used in a semiconductor process, and the slope can be formed more easily than by optical polishing or the like. It should be noted that, as shown in FIG. 22, the vicinity of the emission of the optical waveguide portion can be reduced more when handling the optical waveguide device when the optical waveguide device has a concave shape than when it has a convex shape as compared with the surrounding area. .

When the first surface side of the substrate on which the optical waveguide is formed is disposed on the submount, the contact loss between the optical waveguide and the submount greatly increases the propagation loss of the optical waveguide. Preferably, a protective layer is provided. In this case, if the protective layer is also provided in the concave portion of the substrate, the reflectance of the concave portion decreases depending on the refractive index. Therefore, it is preferable to provide a protective layer on the first surface of the substrate except for the concave portion.

When a protective layer is provided on the first surface of the substrate, in order to satisfy the condition of total reflection on the side surface of the concave portion (slope of the optical waveguide), the refractive index n ₁ of the protective layer and the optical waveguide The effective refractive index n ₂ of the optical waveguide with respect to the light propagating through the optical path and the angle θ between the first surface and the normal to the side surface (slope) of the concave portion satisfy the relationship of Sin (θ)> n ₁ / n _2. Preferably.

The fundamental wave and the harmonic wave propagating in the optical waveguide have different electric field distributions due to the relationship between the wavelength and the refractive index dispersion, and have different spreads in the depth direction. Therefore, the depth t ₁ of the guided mode of the fundamental light guided in the optical waveguide,
The depth t of the guided mode of the second harmonic light guided in the optical waveguide
_{If 2} and the depth t of the recess are set so as to satisfy the relationship of t ₂ <t <t ₁ , harmonics are totally reflected by the recess and taken out, and most of the fundamental wave passes through the recess. Then, the light propagates through the optical waveguide as it is, so that wavelength separation becomes possible. As a result, the output of the fundamental wave mixed with the output of the harmonic wave is reduced, and the output characteristic of the fundamental wave can be monitored by detecting the wavelength-separated fundamental wave light.

The wavelength separation is also possible because the refractive index of the protective film that satisfies the condition of total reflection differs between the fundamental wave and the harmonic. Refractive index nc for fundamental wave light of protective layer
₁ , a refractive index nc ₂ of the protective layer for the second harmonic light, a refractive index nf ₁ of the optical waveguide for the fundamental light, a refractive index nf ₂ of the optical waveguide for the second harmonic light, a first surface and the concave portion. If the film thickness is appropriately set using a protective film that satisfies the relationship of nc ₂ / nf ₂ <Sin (θ) <nc ₁ / nf _{1 with} the angle θ formed by the normal line of the side surface, harmonics can be reduced. Only for this, the condition of total reflection is satisfied and wavelength separation becomes possible. As a result, the output of the fundamental wave mixed with the output of the harmonic wave is reduced, and the output characteristic of the fundamental wave can be monitored by detecting the wavelength-separated fundamental wave light.

In the case where light is extracted from the second surface of the substrate on which the optical waveguide is formed, opposite to the first surface, a diffraction grating is formed on the second surface to obtain a conventional individual component. It is possible to reduce the number of parts by also using the diffractive element which was necessary as the above.

In the above optical waveguide device, when light is extracted from the second surface of the substrate, the light reflected on the inclined surface propagates as a divergent beam in the substrate, and becomes light having various directional components. When this substrate is made of a birefringent optical crystal, the refractive index for ordinary light and the refractive index for extraordinary light are different, so that the light beam emitted from the optical waveguide device is positioned in a direction parallel to the optical waveguide and in a direction perpendicular thereto. A phase difference occurs, and the collimated wavelength plate surface has an astigmatism component. Therefore, a second birefringent optical crystal whose optical axis is orthogonal to the birefringent optical crystal forming the substrate is arranged in the diverging light path of the light emitted from the optical waveguide device, and the astigmatism component is corrected. Is preferred.

Alternatively, the substrate surface (second surface) from which light is emitted from the optical waveguide device can be made substantially cylindrical to correct astigmatism components.

Alternatively, a cylindrical lens can be arranged in the optical path of the light emitted from the optical waveguide device to correct the astigmatism component.

In the coherent light source of the present invention, when the optical waveguide device and the semiconductor laser are arranged in a concave package, if the sealing plate for sealing the concave package is also used as the second birefringent crystal, This is preferable because the number of parts can be reduced. Alternatively, a sealing plate for sealing the concave package may be used also as the cylindrical lens.

Further, by setting the distance between the light emitting end face of the semiconductor laser and the light incident end face of the optical waveguide to about several μm (for example, 0 μm or more and 10 μm or less), the incident end face can be formed by a direct coupling method without using a coupling lens. It is possible to reduce the noise due to the return light at the time.

Further, in the SHG element, it is necessary to make the wavelength of the incident light coincide with the phase matching wavelength, and a wavelength stabilizing function is required. Therefore, by using a tunable semiconductor laser such as a tunable DBR laser as the semiconductor laser, the oscillation wavelength can be fixed within the phase matching wavelength intensity of the optical waveguide type wavelength conversion device,
The functions can be integrated to achieve miniaturization and stabilization.

In the integrated unit according to the present invention, a coherent light source configured to extract light from a second surface opposite to the first surface of the substrate on which the optical waveguide according to the present invention is formed; And the container are arranged on the same surface of the submount. In the coherent light source of the present invention, the emitted light is extracted from the second surface, so that the detector can be easily integrated in the vicinity of the light emission surface, and the alignment is easy and the assembly can be performed efficiently.

When a light shield is arranged between the coherent light source and the photodetector, it is possible to prevent the stray light component from reaching the photodetector. Alternatively, the height of the photodetector surface from the submount surface may be higher than the surface on the light emission side of the coherent light source. Alternatively, a concave portion may be formed on the surface of the submount, and the coherent light source may be arranged in the concave portion.

Further, in the integrated unit of the present invention, a coherent light source configured to extract light from the first surface of the substrate on which the optical waveguide of the present invention is formed is disposed on the first surface of the submount. , The photodetector is arranged on the second surface, which is the back surface of the first surface. For this reason, it is possible to easily prevent the stray light from reaching the photodetector without providing the light shield or the concave portion as described above.

Further, when the integrated unit and the coherent light source are arranged in the concave package, a stable optical pickup optical system can be realized by using the diffraction element. Furthermore, by forming a diffraction grating on a transparent substrate that seals the concave package, it is possible to reduce the number of components of the optical pickup.

In the optical pickup device of the present invention,
Since the integrated unit of the present invention is used, the size and thickness of the device can be reduced. Furthermore, in the focusing optics, the diffraction grating is provided on the substrate surface of the optical waveguide device or on the transparent substrate that seals the concave package, so that the diffraction element that was conventionally required as an individual component can also be used. It is possible to reduce the number of parts.

In the optical pickup device of the present invention, the photodetectors of the integrated unit are divided into a first region at the center (photodetector for focusing) and second regions on both sides of the first region (photodetectors for tracking). And the third region (tracking photodetector) is divided into at least three regions, and the second region and the third region are arranged in a direction perpendicular to the lattice fringes of the diffraction grating. Signal detection becomes possible. In this case, since the diffraction grating is arranged at a position close to the light source, it is possible to provide the diffraction grating on the surface of the substrate constituting the optical waveguide device of the integrated unit. This diffraction grating divides outgoing light into three beams of 0 order and ± 1 order. Of these, 0
The next light irradiates the target track on the optical disk, and the reflected light from the optical disk irradiates the focus detector and the RF
A signal is detected. On the other hand, the ± first-order lights become sub-beams for detecting the tracking error signal, are detected by the respective tracking photodetectors, and the tracking error signal is obtained from their differential output signals.

Further, the photodetectors are arranged on both sides with respect to the coherent light source, and each of the detectors is provided with a region (focusing photodetector) divided into a central portion and a peripheral portion, and a condensing optical system and a lens are provided. A second diffractive element (hologram) having an effect may be provided. In this case, when the reflected light from the optical disk is diffracted by the second diffraction element, an unfocused light spot is formed on one of the focusing photodetectors and focused on the other focusing photodetector. An in-focus light spot is formed. Therefore, for example, a signal can be detected by a spot size detection (SSD) method.

[0083]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional optical waveguide device, an output light is obtained from the exit end face of the optical waveguide through the end face. For this reason, a coherent light source including such a conventional optical waveguide device and a semiconductor laser has the following problems.

1) The size of the module restricts miniaturization of the optical pickup.

2) The return light from the emission end face returns to the semiconductor laser to degrade the noise characteristics.

3) Output light fluctuates due to interference with an external confocal plane.

In order to solve the above-mentioned problem, in the present embodiment, an inclined surface which is obliquely inclined with respect to the optical waveguide is formed, and the guided light of the optical waveguide is totally reflected on the inclined surface, so that the light is reflected from the surface of the substrate. A configuration for extracting guided light will be described. In the present embodiment, the first surface on the substrate on which the optical waveguide is formed is S1, and the substrate surface opposite to the first surface is S2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In particular, a quasi-phase matching method (QPM) in which a periodically domain-inverted region and an optical waveguide are formed on a substrate made of a nonlinear optical crystal as an optical waveguide device.
A second harmonic generation (SHG) device will be described.
As a coherent light source, an SHG blue laser including an AlGaAs-based near-infrared semiconductor laser and a QPM-SHG device will be described. This SHG
A blue laser is promising as a light source for a high-density optical disk, and the above problem is particularly important.

(Embodiment 1) In Embodiment 1, the end face of the optical waveguide device opposite to the incident end face of the optical waveguide is obliquely inclined with respect to the optical waveguide, and the guided light of the optical waveguide is not inclined. A description will be given of a configuration in which guided light is totally reflected on the slope and is taken out from the surface S2 opposite to the surface S1 on which the optical waveguide of the substrate is formed.

FIG. 1A is a perspective view showing a schematic configuration of an optical waveguide type QPM-SHG device 100 according to the first embodiment. Here, the Mg-doped LiNbO ₃ substrate 1
A periodic domain-inverted region 2 and a proton exchange optical waveguide 3 are formed thereon, and an end face 4 of the optical waveguide 3 on the opposite side to the incident side is inclined with respect to the optical waveguide 3.

In FIG. 1A, the X-axis is directed downward from the plane of the paper, the Y-axis is directed from the input end face to the output end face of the optical waveguide, and
The direction perpendicular to the X-axis and Y-axis and on the near side with respect to the page is Z
Axis. In addition, this coordinate axis is often referred to in this specification.

The optical waveguide device 100 was manufactured as follows. Optically polished both sides 0.5mm thick
On the + X plane (S1) of the Mg-doped LiNbO ₃ substrate 1
A comb-shaped electrode made of Ta and a parallel electrode were patterned.
The period of this comb electrode is 3.2 μm, and the wavelength is 850 nm.
Are designed to be quasi-phase-matched with respect to the light. Substrate 1
On the -X surface (S2), a back electrode made of Ta was deposited on the entire surface. Then, an electric field was applied between the comb-shaped electrode and the parallel electrode, and between the comb-shaped electrode and the back electrode formed on the -X surface, respectively, to form a periodically poled region 2 (two-dimensional electric field application method). After removing these electrodes, a stripe electrode made of Ta having a thickness of 5 μm was formed in a direction perpendicular to the periodically poled region 2 and proton exchange was performed in pyrophosphoric acid. Annealing was performed after proton exchange to produce an optical waveguide type QPM-SHG device. The end face of the obtained optical waveguide type QPM-SHG device was optically polished. At this time, the light incident end face was vertically polished, and the opposite end face 4 was optically polished so as to form an angle of 45 degrees with the direction of the optical waveguide 3 (that is, the Y-axis direction). The polishing of the slope 4 was performed by ordinary optical polishing by fixing the optical waveguide type QPM-SHG device at an angle of 45 degrees to the polishing jig.
After polishing, an antireflection coating was applied to the end face. An antireflection coat for a wavelength of 850 nm, which is a fundamental wave light, was formed on the incident end face. The reflection characteristic of this antireflection coat was 0.03%. The refractive index of the Mg-doped LiNbO ₃ substrate 1 was about 2.2, and the end face (slope) 4 was totally reflected. Both surfaces of the substrate 1 (that is, the + X plane (S
An antireflection coat for blue light (425 nm) obtained by wavelength conversion was formed on the (1) and -X planes (S2)).

The thus-obtained optical waveguide type QPM
-A coherent light source 200 as shown in FIG. 2 was configured using the SHG device 100, and its characteristics were evaluated. As the fundamental wave, an AlGaAs-based tunable DBR semiconductor laser 5 (wavelength 850 nm) was used. Tunable DBR
The semiconductor laser 5 includes two electrodes, an active region 6 and a DBR region 7, and can adjust the oscillation wavelength by adjusting the injection current into the DBR region 7. Lens 8
When optical coupling was performed using
Semiconductor laser light of 45 mW with respect to 0 mW is obtained from the opposite surface (S2) of the substrate surface (S1) on which the optical waveguide 3 is formed. The waveguide loss is 1 dB, and the reflection loss (4
When the antireflection coat for 25 nm is formed (about 10%), it is considered that about 60 mW of semiconductor laser light is coupled into the optical waveguide. When a sample whose emission end face was polished vertically was measured for comparison, a semiconductor laser beam of 45 mW was obtained from the emission end face.

In a sample in which the emission end face is polished vertically as in the prior art, since the reflected light at the emission end face returns to the semiconductor laser, it is necessary to form an antireflection coat for the emission end face at 850 nm. In a wavelength tunable DBR semiconductor laser, even if the reflected return light is about 0.05%, a multi-longitudinal mode occurs when the wavelength is tuned. Therefore, strict specifications have been required in which the reflectance of the antireflection coatings on the incident and exit end faces is set to 0.02% or less, respectively. On the other hand, since the semiconductor laser light is totally reflected on the inclined surface 4 that is polished at an angle of 45 degrees to the optical waveguide as in the present embodiment, there is no reflected light returning from the inclined surface 4 and the incident end surface. You only need to consider the reflected return light from
The tolerance of the antireflection coat can be increased. Therefore, in this embodiment, since there is no return light from the slope 4, the reflectance of the antireflection coating on the incident end face is 0.03.
%, Good wavelength tunable characteristics were obtained.

Next, the oscillation wavelength of the wavelength tunable DBR semiconductor laser 5 was adjusted to the phase matching wavelength of the optical waveguide type QPM-SHG device, and blue light (wavelength 425 nm) was generated. The blue light was also totally reflected on the inclined surface 4, and 10 mW blue light was obtained from the opposite surface (S2) of the substrate surface (S1) on which the optical waveguide 3 was formed. In the optical waveguide type QPM-SHG device, the fundamental light in the guided mode and the harmonic light in the guided mode are quasi-phase-matched, so that blue light propagates through the optical waveguide 3 as a guided mode and is polished obliquely. The light was totally reflected by the slope 4 and emitted in the TEM00 mode in the direction of the S2 surface of the substrate. In the present embodiment, an anti-reflection coat is formed on the S2 surface of the substrate for harmonic light, that is, blue light (425 nm), so that blue light can be extracted from the S2 surface with high efficiency.

The blue light emitted from the opposite surface (S2) of the substrate surface (S1) on which the optical waveguide 3 is formed is converted into a parallel light by the collimating lens 9, and is condensed by the objective lens to be blue light. Were evaluated for light-collecting characteristics. The blue light obtained from the surface of S2 is emitted from the optical waveguide inclined surface 4, that is, the total reflection surface as a light emitting point, passes through the Mg-doped LiNbO ₃ substrate 1, and is guided to the collimating lens 9. Therefore, a spherical aberration occurs in the ordinary collimating lens. Therefore, in the present embodiment, a 0.5 mm thick Mg-doped Li
A collimator lens 9 designed to minimize aberration for blue light transmitted through the NbO ₃ substrate 1 was used.
NA = 0.06 as the numerical aperture of the collimating lens 9,
NA = 0.6 was used as the objective lens. When the converging spot was confirmed, it was 0.4 μm in full width at half maximum, and a converging spot of almost diffraction limit could be obtained.

In this embodiment, a 0.5 mm thick Mg-doped LiNbO ₃ is used as an optical waveguide device.
An optical waveguide type QPM-SHG device was manufactured on the substrate 1. However, if the thickness of the substrate is smaller than 0.3 mm, it is difficult to handle the substrate, and the yield after the process is deteriorated. In an optical waveguide device using a substrate thicker than 1.0 mm, astigmatism is largely generated at a converging spot, which is larger than the amount of aberration allowed in an optical disk system. Therefore, in a configuration in which guided light is extracted from the opposite surface S2 of the surface (S1) of the substrate on which the optical waveguide is formed, the substrate thickness is 0.3 mm or more and 1.0 mm or more.
It is preferred that:

Also, in this embodiment, the polishing is performed so that the end face is at 45 degrees to the optical waveguide. However, if the end face is formed at an angle other than 45 degrees with respect to the optical waveguide, the top face is formed at the condensed spot. Aberration occurs. In order to suppress the aberration within the amount of aberration allowed in the optical disk system, it is necessary to form a slope at 45 ° ± 1 ° with respect to the optical waveguide.

In this embodiment, an optical waveguide type QP which is a wavelength conversion device is used as an optical waveguide device.
The M-SHG device 100 is used, and harmonic light obtained by wavelength conversion is a guided mode. When the substrate is obtained in a radiation mode such as Cherenkov light, reflection occurs on the surface of the substrate when the substrate is thin, so that a certain amount of substrate thickness is required to cause total reflection by the end surface (slope). In the present embodiment, since the harmonic light is obtained in the guided mode, the thickness of the substrate can be reduced, and occurrence of astigmatism and the like can be suppressed. Further, since an oblique groove or the like can be formed on the substrate surface (S1) on which the optical waveguide 3 is formed, an end surface (slope) can be formed.
The effect of the waveguide mode is great. Details will be described in Embodiment 3.

Further, in the present embodiment, the light of the wavelength tunable DBR semiconductor laser 5 is
Bound. As described above, by forming the inclined surface 4 at approximately 45 degrees with respect to the optical waveguide, the guided light is totally reflected by the inclined surface 4, so that the reflected light returning from the inclined surface 4 does not occur. Also, by forming an anti-reflection coat on the incident end face, return light noise can be prevented.

On the other hand, in the direct coupling system using no coupling lens, the return light from the incident end face does not pose a problem. In this direct coupling method, the distance between the emitting end face of the semiconductor laser and the incident end face of the optical waveguide device is about several μm (for example, 0 μm).
(About 10 μm or less).

FIG. 3 shows a configuration of a direct coupling type light source module according to the present embodiment. In this coherent light source (SHG blue laser) 300, a wavelength tunable DB
The R semiconductor laser 5 and the optical waveguide type QPM-SHG device 100 are connected to the active region 6 of the tunable DBR semiconductor laser 5.
Side surface and optical waveguide type QPM-SHG device 10
No. 0 is mounted so that the surface on the optical waveguide 3 side is in contact with the submount 24. On the submount 24, independent electrodes (not shown) are formed to inject current into the active region 6 and the DBR region 7, respectively. The distance between the emission end face of the semiconductor laser 5 and the incidence end face of the optical waveguide is 3 μm.
m, and the optical coupling was adjusted. The adjustment in the thickness direction was performed by adjusting the thickness of the protective film 29 formed on the optical waveguide. The optical coupling efficiency at this time was almost the same as that obtained by coupling using a lens. In this direct coupling type module, the distance between the emitting end face of the semiconductor laser and the incident end face of the optical waveguide of the optical waveguide device is short, so that the reflected light from the incident end face of the optical waveguide acts as return light noise to the semiconductor laser. Instead, it works in the same way as the emission end face of the semiconductor laser. Therefore, by forming the emission end face 4 at 45 degrees as in the present embodiment, the semiconductor laser light is guided through the optical waveguide 3 and totally reflected at the end face (slope) 4.
No reflected return light from the slope 4 to the semiconductor laser is generated. As a result, the semiconductor laser light guided in the optical waveguide 3 was converted into blue light by wavelength conversion, and could be stably obtained in the TEM00 mode from the direction of the S2 surface of the substrate. Such a direct coupling type module has a particularly large practical effect.

Further, in this embodiment, since a wavelength-tunable semiconductor laser is used as the semiconductor laser, a stable harmonic light output can be obtained when the wavelength conversion device 100 is used as the optical waveguide device. . As the wavelength variable function, a reflection grating, a band pass filter, or the like can be considered. By using a wavelength tunable DBR semiconductor laser 5 having an integrated wavelength tunable function as a semiconductor laser as in the present embodiment, the module can be downsized. The effect is great when applied to applied equipment.

FIG. 4 shows a schematic configuration of an optical pickup according to the present embodiment, on which the direct coupling type optical module (coherent light source) 300 shown in FIG. 3 is mounted. In the optical pickup 400, the blue light obtained from the S2 surface direction of the substrate of the SHG blue laser integrated unit 300 is converted into parallel light by the collimating lens 9,
After passing through the polarizing beam splitter 10 (PBS) and the 波長 wavelength plate 11, the light is reflected by the rising mirror and condensed on the optical disk 95 by the objective lens 12. The reflected light from the optical disk 95 passes through the same optical path,
Is rotated by 90 degrees, and the detection lens system 13 (detection lens, cylindrical lens) and the photodetector (P
D) It is led to 14. Then, the PD 14 detects the servo signal and the reproduction signal. The coherent light source (module) using the optical waveguide device 100 according to the present embodiment can emit blue light in a direction perpendicular to the optical axis of the module, so that the configuration is more compact than the configuration shown in the conventional example. Optical pickup 400 was realized.

The optical pickup 40 according to the present embodiment
At 0, no fluctuation in the reproduction light amount on the PD 14 is observed.
This is because, in the present embodiment, the inclined surface 4 is inclined with respect to the optical waveguide 3, so that the reflected light from the inclined surface 4 is not guided onto the optical disk. However, when the disc tilt and the focus shift occur at the same time, the reflected return light from the optical disc surface returns to a position slightly shifted from the slope 4 of the optical waveguide 3. For this reason,
Return light is re-reflected on the S1 surface of the substrate 1 constituting the optical waveguide type QPM-SHG device, and an interference effect occurs with light emitted from the optical waveguide. Therefore, in the present embodiment, antireflection is performed on the S1 surface of the substrate 1 on which the optical waveguide 3 of the optical waveguide type QPM-SHG device is formed as a non-reflection portion for the second harmonic light, ie, blue light (wavelength 425 nm). Coat applied. For example, when an antireflection coat having a reflectance of about 0.1% was formed, the interference effect could be reduced to 1% or less.

Here, a modification of the present embodiment is shown in FIG. 1B. FIG. 1B shows an optical waveguide type QPM-SHG device 1.
It is sectional drawing which shows the schematic structure of 50. In the optical waveguide device 100 shown in FIG. 1A, one end face of the substrate 1 is entirely formed on an inclined surface, whereas in the optical waveguide device 150 shown in FIG. 1B, only a part of one end face of the substrate 1 is provided. Are formed on the slope.

In the optical waveguide device 150, the end face 120 of the optical waveguide 3 opposite to the incident end face 110 is inclined obliquely with respect to the optical waveguide 3 (slope 4). The reflected light is emitted from the surface S2 of the substrate 1 opposite to the surface S1 on which the optical waveguide 3 is formed.

Here, the Mg-doped LiNbO ₃ substrate 1
A periodic domain-inverted region 2 and a proton exchange optical waveguide 3 are formed thereon, and a side 120 opposite to the incident side 110 of the optical waveguide 3.
, A slope 4 is formed which is oblique to the direction of the optical waveguide 3 (Y-axis direction). The harmonic light obtained by the wavelength conversion propagates through the optical waveguide, is totally reflected on the slope 4, and emerges from the surface S2.

In this embodiment, the slope 4 and the surface S1 are 4
Makes a 5 degree angle. When the harmonic light totally reflected by the slope 4 exits from S2, the intersection line L1 between the slope 4 and the surface S1
13 including an end surface 120 and an intersection line L2 between the end surface 120 and the surface S2.
If the angle θ between 0 and the emission direction of the guided light emitted as a harmonic does not have a sufficient angle with respect to half of the spread angle θ1 of the harmonic light, the harmonic light collides with the 120 plane. Specifically, by forming the inclined surface 4 so that the divergence angle θ1 in FIG. 1B and the angle θ between the surface 130 and the emission direction satisfy the relationship of θ1 / 2 <θ, the obtained harmonic light is applied to the end surface 120. It can be extracted as a good beam without collision. It is desirable to set the width at which the intensity becomes 1 / e ² or less of the peak intensity as the divergence angle θ1.

(Embodiment 2) In Embodiment 2, in the optical waveguide device, the end face of the optical waveguide opposite to the incident end face is inclined with respect to the optical waveguide, and the guided light of the optical waveguide is A configuration in which the reflected light is totally reflected on the inclined surface and the guided light is extracted from the surface S1 of the substrate on which the optical waveguide is formed will be described.

FIG. 5 is a perspective view showing a schematic configuration of an optical waveguide type QPM-SHG device 500 according to the second embodiment. Here, the Mg-doped LiNbO ₃ substrate 15
A periodic domain-inverted region 16 and a proton exchange optical waveguide 17 are formed on the surface S1 of the optical waveguide 3, and an end face 18 of the optical waveguide 16 opposite to the incident side is inclined with respect to the optical waveguide 3. .

This optical waveguide device 500 was manufactured as follows. Optically polished both sides 0.5mm thick
+ X plane of Mg-doped LiNbO ₃ substrate 15 (S1)
Then, a periodically poled region 16 and a proton exchange optical waveguide 17 were formed in the same manner as in the first embodiment. The incident end face is vertically polished, and the end face 18 is
Optical polishing was performed to 5 degrees. In the optical waveguide device 100 of the first embodiment, the end surface is polished so that a vertex angle of 45 degrees is formed on the side (S2) opposite to the surface (S1) on which the optical waveguide 3 is formed. In the optical waveguide device 500 of the embodiment, the surface (S
1) The end face was polished so that a vertex angle of 45 degrees was formed on the side. Polishing of the end face 18 was performed by ordinary optical polishing by fixing the optical waveguide type QPM-SHG device 500 at an angle of 45 degrees to the polishing jig. After polishing, an antireflection coating was applied to the end face. An antireflection coat was formed on the incident end face for a wavelength of 850 nm, which is the fundamental light. The reflection characteristic of the antireflection coat was 0.02%.
The refractive index of the Mg-doped LiNbO ₃ substrate 15 is 2.
Since the total reflection was about 2 and the end face (slope) 18 was totally reflected, no coating was performed on the end face 18. On the surface (S1) of the substrate on which the optical waveguide 17 was formed, an antireflection coat was formed as a non-reflection portion for a wavelength of 850 nm, which is a fundamental wave light. In this embodiment, light is emitted from the end face 1
Since the light reaches the substrate surface (S1) immediately after the total reflection at 8, if the antireflection coat for the fundamental wave is not formed, reflection occurs on the substrate surface (S1) and the optical waveguide 1
7 is propagated. Therefore, in a configuration using a semiconductor laser as a fundamental wave, return light noise occurs and the longitudinal mode state of the semiconductor laser deteriorates.

The thus-obtained optical waveguide type QPM
-A coherent light source 600 as shown in FIG. 6 was configured using the SHG device 500, and its characteristics were evaluated. As a fundamental wave, an optical coupling was performed using a lens 22 using an AlGaAs-based tunable DBR semiconductor laser 19. As a result, for a semiconductor laser output of 100 mW, 4
Semiconductor laser light of 5 mW was obtained from the substrate surface (S1) on which the optical waveguide 17 was formed. Assuming that the waveguide loss is 1 dB and the reflection loss on the substrate surface (because the antireflection coat for 425 nm is formed) is about 10%, 60 m
It is considered that about W semiconductor laser light was coupled into the optical waveguide.

In the configuration of the present embodiment, the substrate surface S1 is formed in the same manner as in the case of the sample whose output end face is polished vertically as in the conventional case.
Since the light reflected by the substrate returns to the semiconductor laser, an antireflection coating for 850 nm was also formed on the surface of the substrate S1.
The reflectance was 0.02%. Therefore, the amount of light reflected from both surfaces can be reduced to 0.05% or less, and good wavelength tunable characteristics are obtained.

Next, the oscillation wavelength of the wavelength tunable DBR semiconductor laser 19 was adjusted to the phase matching wavelength of the optical waveguide type QPM-SHG device 500 to generate blue light. The blue light was also totally reflected by the end face 18, and 10 mW blue light was obtained from the substrate surface (S1) on which the optical waveguide 17 was formed. In the optical waveguide type QPM-SHG device 500, the fundamental light in the guided mode and the harmonic light in the guided mode are quasi-phase-matched, so that the blue light propagates in the optical waveguide 17 as a guided mode and is polished obliquely. The light was totally reflected by the output end face 18 and emitted toward the substrate surface. In the present embodiment, the substrate S1
Since an antireflection coat was formed on the surface for harmonic light, that is, blue light (425 nm), blue light could be extracted from the S1 surface with high efficiency.

The blue light emitted from the substrate surface (S1) on which the optical waveguide 17 is formed as described above is
The light was converted into a parallel light in 3 and condensed by an objective lens, and the light condensing property of blue light was evaluated. In the first embodiment, it is necessary to control the thickness of the substrate because blue light is transmitted in the thickness direction of the substrate, and the amount of occurrence of spherical aberration differs depending on the thickness of the substrate. However, as in the present embodiment, the optical waveguide 17
In the configuration in which light is emitted from the substrate surface (S1) on which
By designing the collimating lens 23 in advance, it was possible to convert blue light into parallel light without aberration, regardless of the thickness of the substrate.

In the present embodiment, since the emitted light does not pass through the substrate, the optical waveguide device 10 of the first embodiment is not used.
Coma does not occur in the condensed spot unlike 0. However, by emitting the beam vertically, optical components such as a collimating lens can be mechanically arranged,
If the light is emitted at an angle, an aberration is generated by the collimating lens or the like. Therefore, in order to suppress the aberration within the allowable amount of the optical disk system, it is preferable to form the end surface at 45 ° ± 1 ° with respect to the optical waveguide.

Note that, as in the present embodiment, the surface S
In the configuration for emitting light from No. 1, it is preferable that the harmonic light obtained by the wavelength conversion be in a guided mode. In a radiation mode other than the waveguide mode, radiation is performed in the direction of the substrate, so that the substrate needs to have a thickness and is reflected on the S2 surface of the substrate. Also, with light in the radiation mode, it is difficult to condense light up to the diffraction limit, and it is difficult to apply it to a disk reproducing device or the like.

In this embodiment, the light of the wavelength tunable semiconductor laser is coupled to the optical waveguide using the coupling lens. However, as described in Embodiment 1,
If the distance between the light emitting end face of the semiconductor laser and the light incident end face of the optical waveguide is set to about several μm (for example, 0 μm or more and 10 μm or less) and a direct coupling method without using a coupling lens is used, the return light at the incident end face No noise occurs.

FIG. 7 shows a configuration of a direct coupling type optical module 700 according to the present embodiment. In the integrated unit 700 using this coherent light source, the wavelength tunable DBR semiconductor laser 19 and the optical waveguide type QPM-SHG are used.
The device 500 was mounted such that the surface on the active region 21 side and the surface on the optical waveguide 17 side were in contact with the submount 25. On the submount 25, independent electrodes (not shown) are formed to inject current into the active region 21 and the DBR region 20, respectively. The distance between the emission end face of the semiconductor laser 19 and the incidence end face of the optical waveguide was set to 3 μm, and the optical coupling was adjusted. The adjustment in the thickness direction was performed by adjusting the thickness of a protective film (not shown) formed on the optical waveguide. The optical coupling efficiency at this time was almost the same as that obtained by coupling using a lens. In this direct coupling type module 700, since the distance between the emission end face of the semiconductor laser 19 and the incidence end face of the optical waveguide of the optical waveguide device 500 is short, the reflected light from the incidence end face of the optical waveguide returns to the semiconductor laser. It does not act as noise, but acts in the same way as the emission end face of the semiconductor laser.

In this configuration, the semiconductor laser light guided in the optical waveguide is converted into blue light by wavelength conversion and is obtained in the TEM00 mode from the direction of the S1 surface of the substrate. Therefore, by forming the extraction window 26 on the submount 25, blue light could be extracted from the S1 surface even in the direct coupling method.

Further, in this embodiment, since a wavelength-variable semiconductor laser is used as the semiconductor laser, a stable harmonic light output can be obtained when a wavelength conversion device is used as the optical waveguide device. A tunable DB in which a tunable function is integrated as in the present embodiment.
By using the R semiconductor laser 19 as a semiconductor laser, the size of the module can be reduced. Therefore, when the present invention is applied to an applied device such as an optical disk recording / reproducing device or a laser printer, the effect is large.

Also, in this embodiment, since blue light can be emitted in the direction perpendicular to the optical axis of the module, a configuration of an optical pickup that is more compact than the configuration shown in the conventional example can be realized. Was.

When the reproduction signal of the optical pickup equipped with the coherent light source of the present embodiment was evaluated in the same manner as in the first embodiment, the fluctuation of the reproduction light amount on the PD was observed. Although this variation does not cause a problem in normal reproduction, by forming the antireflection film, a better reproduction signal can be obtained. Furthermore, in the present embodiment, the optical waveguide type QPM-SHG device 500
The fundamental wave light (wavelength 850 nm) and the second harmonic light from the semiconductor laser are formed on the S1 surface on which the optical waveguide is formed.
That is, by forming an antireflection coat of a multilayer film for blue light (wavelength 425 nm), an antireflection coat having a reflectance of about 0.1% for wavelengths of 850 nm and 425 nm is obtained, and an interference effect of 1% or less is obtained. Can be reduced.

(Embodiment 3) As described above, by forming a slope having a total reflection angle on the end face of the optical waveguide of the optical waveguide device, the guided light of the optical waveguide device can be effectively extracted. Further, by forming this optical waveguide device into a module with a semiconductor laser, it is possible to reduce the size of the light source and stabilize the emitted light, and further reduce the light returned from the end face to the semiconductor laser. However, in the case where the total reflection angle is formed on the end face of the optical waveguide, a method by optical polishing is required. Therefore, there is a problem in cost reduction in a mass production process for manufacturing a large number of elements. Therefore, the present embodiment proposes a configuration of an optical waveguide device applicable to a wafer process that can be easily mass-produced.

FIG. 8 is a perspective view showing a schematic configuration of an optical waveguide device 800 according to the present embodiment. here,
An optical waveguide 31 is formed on a substrate 30 and the optical waveguide 3
1 is formed on the surface (S1) of the substrate 30 on which the recesses 32 are formed.
Are formed. The concave portion 32 is formed in a stripe shape in a direction substantially orthogonal to the optical waveguide 31, and a side surface 32a of the concave portion 32 is formed at an angle at which the guided light is totally reflected. Light propagating through the optical waveguide 31 is reflected by the side surface 32a of the concave portion 32 and is emitted from the back surface (S2) of the substrate 30.

This optical waveguide device 800 can be manufactured, for example, as follows. In order to facilitate mass production, an etching process used in a semiconductor process is used for forming the concave portion. Here, an example in which a concave portion is formed by inclined etching using an ion beam milling device will be described. As the substrate 30, L
An iNbO ₃ substrate was used. With this LiNbO ₃ substrate, a low-loss optical waveguide can be easily formed by proton exchange.

The ion beam milling apparatus using a reactive gas has high etching selectivity and one-sidedness, so that an etched cross section having an inclined surface can be formed. First, a Cr film is formed on the substrate 30.
On the concave portions 32 by photolithography.
The film is removed to form an etching mask. The substrate is etched by a reactive ion beam milling apparatus using a reactive gas using this as a mask, so that the recess 3 is formed.
2 was formed. At this time, the etching side surface (the side surface 32a of the concave portion) could be formed obliquely with respect to the substrate by inclining the substrate 30 with respect to the ion beam emission direction in the milling device. C ₃ as reactive gas
By using F ₈ , the Cr film and the LiNbO ₃ substrate 30
Of the substrate 30 (S
A recess 32 having a side surface 32a at 45 degrees to 1) could be formed. In the present embodiment, a desired concave portion can be formed by a collective process over the entire 3-inch wafer, thereby enabling mass production. Performing the recess processing by etching in this manner facilitates the wafer process, as well as the shape, position accuracy,
Precise control of the depth of the concave portion and the like becomes possible, which is effective for realizing a configuration described later.

The method of forming the recess 32 is as follows.
In addition, there is a dicing method, and the recess 32 can be formed by a blade that can be ground and cut. For example, if a blade having a surface roughness of # 6000 is used, a cross section close to optical polishing can be formed. Also, by processing the shape of the blade to a cross-section of 45 ° and forming a notch having a depth equal to or greater than the thickness of the optical waveguide, for example, about 5 μm in the vicinity of the surface of the optical waveguide, the formation of a concave portion that totally reflects the optical waveguide can be achieved. It becomes possible. When dicing is used, it is easy to process the side surface shape of the concave portion, but a sharp blade shape is required in order to perform accurate V-shape processing, and the blade is greatly consumed. Therefore, only the side 4
A method in which a mirror surface of 5 degrees is formed and the shape of the bottom surface is not limited is suitable. Since the optical waveguide 31 exists only about a few μm from the surface, if the dicing depth is about 10 μm, the required total reflection angle can be formed without being affected by the bottom of the concave portion 32. In the case where the reflection end face is formed by dicing in this manner, steps such as photolithography and etching are not required, so that the manufacturing process can be simplified and the time can be shortened. Further, by performing the dicing only about 10 μm, the mirror surface processing was facilitated, the consumption of the blade was small, and the processing with high yield was facilitated.

In the present embodiment, similarly to Embodiment 1, when the side surface of the concave portion is formed at an angle other than 45 degrees with respect to the optical waveguide, coma aberration occurs in the condensed spot.
In order to suppress the aberration within the allowable amount of the optical disk system, it is necessary to form the side surface of the concave portion at 45 ° ± 1 ° with respect to the optical waveguide.

Next, the case where the above configuration is applied to an optical waveguide device having an optical wavelength conversion function was examined. An optical waveguide device can be formed by forming an optical waveguide in a periodically poled structure, and a highly efficient optical wavelength conversion element is formed by using a highly nonlinear Mg-doped LiNbO ₃ substrate as a substrate. be able to. For example, when infrared light having a wavelength of 850 nm is incident as a fundamental wave, 425 nm blue light can be emitted. In order to emit this blue light, a configuration for taking out from the total reflection surface (slope) formed in the optical waveguide proposed in the present invention was used instead of the conventional configuration for taking out from the end face of the optical waveguide. The point in the configuration here is that wavelength separation of a fundamental wave and a harmonic can be performed using the total reflection surface formed in the optical waveguide.

FIG. 9A is a sectional view showing a schematic configuration of an optical waveguide device 900 having an optical wavelength conversion function according to the present embodiment. Here, an optical waveguide 35 having a periodically domain-inverted region 34 with a period of 3.2 μm is formed near the surface of the Mg-doped LiNbO ₃ substrate 33. And
A concave portion 36 is provided near the surface of the substrate on which the optical waveguide 35 is formed.
Are formed.

In this optical waveguide 35, the fundamental wave propagating as the waveguide light is the same as in the first and second embodiments.
In the same manner as described above, the light is converted into a higher harmonic that propagates as guided light. Then, the harmonic is totally reflected by the side surface 36a of the concave portion 36, so that the harmonic can be extracted from the back surface (S2) of the Mg-doped LiNbO ₃ substrate 33. Therefore, harmonics propagating as a guided mode can be efficiently output to the outside by the above configuration. Further, in this configuration, wavelength separation using the concave portion 36 becomes possible due to the difference in the profile of the waveguide mode. The fundamental wave and the harmonic wave propagating in the optical waveguide 35 have different electric field distributions due to the relationship between the wavelength and the refractive index dispersion. For example, in an optical waveguide formed by annealing a proton exchange layer, the spread in the depth direction of the fundamental mode profile (the depth t ₁ of the guided mode of the fundamental light) is about 2.5 to 3 μm.
m, and the mode profile of the harmonic generated with respect to this fundamental wave in the depth direction (the depth t ₂ of the guided mode of the second harmonic light) is about half of the fundamental wave. By utilizing this characteristic, the concave portion 36 formed in the optical waveguide 35 can be used.
This allows wavelength separation. The shape of the recess formed by etching can be precisely controlled as described above. In particular, since the method using ion beam milling has high accuracy and mass productivity, it can be effectively used for manufacturing the structure of the optical waveguide device 900 of the present embodiment. According to this method, for example, when the depth t of the concave portion 36 is formed to be t ₂ <t <t ₁ , for example, about t = 1.5 μm, harmonics can be totally reflected by the concave portion 36 and extracted to the outside. Most of the fundamental wave can pass through the concave portion 36 and propagate through the optical waveguide 35 as it is. Thus, the fundamental wave passing through the concave portion 36 can be detected outside, and the output characteristics of the fundamental wave can be monitored. Further, it becomes easy to reduce the output of the fundamental wave mixed with the emitted harmonic.

Further, as the optical waveguide structure, it is effective to use a configuration having a high refractive index cladding layer on the surface of the optical waveguide. FIG. 9B shows an optical waveguide device 950 provided with a high refractive index cladding layer. High refractive index cladding layer 46
Is formed by forming a cladding layer having a higher refractive index than the optical waveguide 35 on the optical waveguide. For example, L
Forming the optical waveguide 35 by performing proton exchange and annealing on the iNbO ₃ substrate (the refractive index becomes closer to the substrate by annealing), and forming the high refractive index cladding layer 46 by further performing proton exchange. Can be. The thickness of the cladding layer 46 satisfies the cut-off condition for the fundamental wave propagating in the optical waveguide 35 (the condition that the cladding layer becomes thinner so that it cannot be propagated in the waveguide mode and becomes a radiation mode). While the confinement of the fundamental wave in the optical waveguide is enhanced,
6 can be prevented from being trapped. As a result,
The fundamental wave is strongly confined in the optical waveguide and propagates therethrough, and the power density can be improved, so that the conversion efficiency can be improved. At the same time, by using a high-efficiency cladding layer structure, light confinement in the optical waveguide can be enhanced even for harmonics. As a result, the depth of the harmonic propagation mode is reduced to 80% or less as compared with the case where the high-efficiency cladding layer is not formed. Therefore, the depth of the concave portion formed near the substrate surface can be set smaller. Note that when forming the concave portion by etching, it is necessary to perform a deep etching of 1 μm or more, but a mask material having high selectivity is required to form a 45 ° side surface on the substrate surface over a depth of 1 μm or more. Required. further,
When deep etching is performed, roughness occurs on the etching side surface, the reflectance of the reflection surface decreases, and the fluctuation of the wavefront of the reflected light deteriorates the light-collecting characteristics of the emitted light. On the other hand, by using an optical waveguide having a high-refractive-index cladding structure, it is possible to reduce the required depth of the concave portion by 20%, thereby improving the etching characteristics and greatly reducing the side surface roughness of the concave portion. It became possible to reduce.

Here, a preferred optical waveguide device in the present embodiment will be described with reference to FIG. 9C. FIG. 9C
Is a sectional view showing a schematic configuration of an optical waveguide device 970. Here, an optical waveguide 35 and a periodic domain inversion 34 are formed on a Mg-doped LiNbO ₃ substrate 33, and a concave portion 3 is formed on the surface (S1) of the substrate on which the optical waveguide 35 is formed.
6 are formed. The concave portion 36 is formed in a stripe shape in a direction substantially perpendicular to the optical waveguide, and the side surface 3 of the concave portion 36 is formed.
6a is formed at an angle at which the guided light is totally reflected. Light propagating through the optical waveguide 35 is reflected by the side surface 36a of the concave portion,
The light is emitted from the back surface (S2) of the substrate.

In the optical waveguide device 970, the side surface 36a and the surface S1 form an angle of 45 degrees. Side 36
When the harmonic light totally reflected at a exits from S2, the slope 3
The angle θ between the intersection line L1 between the substrate 6a and the surface S1 and the surface 930 including the intersection line L2 between the end surface 920 of the substrate and the surface S2 of the substrate, and the emission direction of the harmonic light is the angle θ of the spread angle θ1 of the harmonic light. If it does not have a large enough angle to half, the harmonic light will strike end face 920. Specifically, by forming the inclined surface 36a so that the spread angle θ1 in FIG. 9C and the angle θ between the surface 930 and the emission direction satisfy the relationship of θ1 / 2 <θ, the obtained harmonic light is reflected on the end surface 920. It can be extracted as a good beam without collision. It is desirable to set the spread angle θ1 to a width where the intensity is 1 / e ² or less of the peak intensity.

FIG. 9D is a sectional view showing a schematic configuration of the optical waveguide type QPM-SHG device 980. here,
A periodically poled region 34 and a proton exchange optical waveguide 35 are formed on a Mg-doped LiNbO ₃ substrate 33, and an end surface 920 opposite to the incident end surface 910 of the optical waveguide device 980.
, The slope 94 inclined obliquely to the optical waveguide 35
0 is formed. The harmonic light obtained by the wavelength conversion propagates through the optical waveguide, is totally reflected on the slope 940, and emerges from the surface S2.

When the coherent light source composed of the optical waveguide type QPM-SHG device 980 and the wavelength tunable DBR semiconductor laser shown in FIG. 9D is applied to an optical disk recording / reproducing apparatus, the harmonic light reflected by the slope 940 and emitted from the surface S2 is used. Is converted into parallel light by a collimator lens, and then condensed on an optical disk by an objective lens. When applied to an optical disk recording / reproducing apparatus or the like, the light-collecting characteristics greatly affect the reproducing characteristics, and coherent light with small wavefront aberration is desired.

The Mg on which the periodically poled regions 34 are formed
In the doped LiNbO ₃ substrate 33, the inverted portion and the substrate have different etching rates when performing wet etching. Therefore, when forming the slope 940, there is no problem when using mechanical processing or the like, but when performing polishing, chemical etching may occur due to the abrasive, and unevenness is formed between the domain-inverted portion and the substrate portion. I will. When unevenness occurs, aberration occurs in the harmonic light reflected by the slope 940, and the light-collecting characteristics of the objective lens deteriorate.

If the periodic domain inversion is formed up to the output end face, the period of the inversion is about 3 μm, and it is difficult to adjust the non-inverted portion to the end face. 9D, the slope 940
In the vicinity, the periodically poled region 34 is not formed. Therefore, even in the polishing process, it is possible to finish the mirror surface without forming irregularities.

Next, a study was conducted for integrating the optical waveguide device with the semiconductor laser. As for a method of integrating an optical wavelength conversion element as a waveguide type optical device with a semiconductor laser, modularization by planar coupling has been conventionally studied.

FIG. 10 is a sectional view showing a schematic configuration of a planar coupling module light source (coherent light source) 1000 using the optical waveguide device 39 in the present embodiment. Here, a wavelength tunable DBR semiconductor laser 38 and an optical waveguide device 39 are mounted on a submount 37 made of Si or the like.
And have been fixed. At this time, by bringing the optical waveguide into close contact with the surface of the submount 37 together with the wavelength-tunable DBR semiconductor laser 38 and the optical waveguide device 39,
The accuracy in the depth direction of the optical waveguide can be improved. Further, the light reflected by the side surface 40a of the concave portion 40 formed on the optical waveguide of the optical waveguide device 39 is the surface S2 of the Mg-doped LiNbO ₃ substrate 41 on the opposite side to the surface S1 on which the optical waveguide is formed, that is, The light is emitted to the upper surface of the module. When a planar module is formed in this way, a protective film 42 is indispensable on the surface of the optical waveguide. This is because the contact between the submount 37 and the optical waveguide greatly increases the propagation loss of the optical waveguide. To prevent this, a thickness of 100
A protective film of nm or more is required. Further, a protective film is required to accurately match the height direction of the active region of the semiconductor laser with the optical waveguide of the waveguide type optical device. The thickness of the protective film 42 can be controlled with an accuracy of submicron or less.

However, when the protective film 42 is deposited on the surface of the substrate and the entire concave portion, the reflectance of the concave portion decreases depending on the refractive index of the protective film. For example, recess 4
When the angle (θ) formed between the side surface 40a of the optical waveguide 0 and the optical waveguide is 45 degrees, the condition for satisfying the total reflection condition is that the effective refractive index n ₂ of the optical waveguide and the refractive index n ₁ of the protective film are: According to the law, n ₁ / n ₂ <Sin (45 degrees) ≒ 0.7. As in the present embodiment, Mg-doped L
When the iNbO ₃ substrate 41 is used, since the refractive index n ₂ of the optical waveguide is about 2.2, n ₁ is used as the protective film 42.
It is necessary to use a material having a refractive index of 1.54 or less. However, by selectively removing the protective film only in the concave portion by a photolithography method or the like, it is possible to eliminate the influence of the protective film on the total reflection surface.

Further, the protective film or the total reflection surface can be selectively formed.
The deposited film separates the guided light into fundamental light and harmonic light.
It can be separated. For example, Mg-doped LiNb
O_ThreeRefractive index nf of optical waveguide formed on substrate 41₁Is wavelength 8
It is about 2.2 for a fundamental wave of 50 nm, and the wavelength 4
For a 25 nm harmonic, the refractive index nf of the optical waveguide _TwoIs
It is about 2.4. Therefore, protection that satisfies the condition of total reflection
The refractive index of the film is nc_Two/ Nf_Two<Sin (θ) <nc₁/
nf₁Nc for the fundamental wave₁= 1.54 or less
Nc for harmonics_Two= 1.70 or less. So
Here, using a material having a refractive index of 1.54 to 1.7,
If the film thickness is set to an appropriate value, total reflection is applied only to harmonics.
A film having a refractive index satisfying the requirements can be obtained. An example
For example, Al_TwoO_ThreeAnd SiN_xUse many materials
Can be. Furthermore, if a multilayer film is used, the fundamental wave and harmonic
It is also possible to completely separate the waves.

In a coherent light source using an optical waveguide device for performing light wavelength conversion, it is important to stabilize the amount of light by monitoring the output of a fundamental wave while simultaneously extracting harmonic components effectively. Therefore, if the wavelength separation of the fundamental wave and the harmonic wave becomes possible, a mechanism for monitoring the fundamental wave can be integrated. In addition, there is an advantage that the fundamental wave component mixed with the harmonic output to the outside can be reduced, and the wavelength separation filter is not required.

Next, a case where a coherent light source (light source module) including the optical waveguide device according to the present invention and a semiconductor laser is applied will be described. When a module light source is applied to an optical disk recording / reproducing device, an optical information processing device, or the like, it is useful to integrate a function of detecting light used for information processing. For example, in a semiconductor laser used in an optical disk recording / reproducing device, a signal is read by detecting light reflected from the optical disk by a photodetector (photodetector) provided adjacent to the semiconductor laser. This integration makes it possible to simplify the optical system, increase the tolerance of assembly accuracy, reduce costs, and the like.

In the optical waveguide device according to the present invention, the emitted light can be extracted from the surface direction of the substrate.
It becomes easy to integrate the light detection function. That is,
A photodetector can be easily integrated near the light emission surface. However, in this case, a problem arises in that light leaked from the optical waveguide is input to a detector integrated around the waveguide, and signal detection characteristics are degraded. For example, in the case of an optical waveguide device having an optical wavelength conversion function,
A harmonic of about 10 mW is generated from the fundamental wave of mW. In this case, the leakage light of the fundamental wave is close to 10 mW, which is larger than the detected higher harmonic wave (light reflected from the optical disk and returned through the optical system), so that the signal detection characteristic is greatly deteriorated. In order to prevent this, it is necessary to block the light leaking from the optical waveguide from the detector.

In the optical waveguide device according to the third embodiment,
Since the light reflected by the concave portion provided in the optical waveguide is extracted from the back surface of the waveguide, the separation between the leaked light from the waveguide and the extracted light is greatly simplified. That is, leakage light can be completely blocked by covering a portion excluding the periphery of the back surface of the substrate through which light reflected by the concave portion provided on the optical waveguide is transmitted with a film that absorbs fundamental waves and harmonics. It has become possible. The inventor of the present application disclosed that after covering the back surface and the light incident end face of the portion where the concave portion of the substrate was formed with a protective resist, a light absorbing film was deposited on the entire substrate, and the protective resist covering the back surface of the concave portion and the light incident end surface. At the same time, an optical waveguide device was manufactured by removing the light absorbing film in that portion. By using this optical waveguide device, it was possible to completely prevent light leaking to the photodetector.

It is also possible to prevent light leakage by using a light-reflective film such as a metal film instead of the light-absorbing film.

Further, in this embodiment, a V-groove is formed so that the reflection surface of the concave portion and S1 (substrate surface) are obtuse (> 90 degrees).
However, a notch or the like may be formed so that the reflection surface and S1 form an acute angle. In this case, S1
, And the same effect as in the second embodiment can be obtained.

As described above, when the light source module is used in an optical system such as an optical pickup or the like, it is common to install a diffraction grating such as a hologram in the optical path of the emitted beam to detect various signals. It has been done. This specific example will be described in a fourth embodiment described later.
When the coherent light source of the present invention is applied to an optical system using a diffraction grating as described above, as shown in a coherent light source 1100 in FIG. May be provided. In this case, it is possible to realize an optical system having a smaller number of components than a conventional optical system in which a diffraction grating is installed as an individual component. In FIG. 11, reference numeral 75 denotes an optical waveguide device, 76 denotes a submount, and 77 denotes a semiconductor laser.

(Embodiment 4) In this embodiment, an integrated unit in which a coherent light source having an optical waveguide device and a semiconductor laser, a photodetector and a coherent light source are integrated on the same submount, and an integrated unit An optical pickup using the unit will be described.

FIG. 12 is a perspective view showing a schematic configuration of an optical disk pickup optical system 1200 according to the present embodiment. This optical pickup 1200 includes an integrated unit for an optical disk pickup, a hologram 53 as a condensing optical system, and an objective lens 53a. The integrated unit includes, in the embodiment, an optical waveguide device (QPM-SHG device) 50 configured to extract light from the S2 surface opposite to the substrate surface on which the optical waveguide shown in FIG. 1A is formed, and a tunable DBR semiconductor. A light source module having a laser 56 and a photodetector are arranged on the same submount 55. The diffraction grating 51 is formed on the surface S2 of the optical waveguide device 50. Light source module 5
A silicon substrate 57 is provided on both sides of the silicon substrate 57, and on each of the silicon substrates 57, a focusing photodetector 52 having a central portion and a peripheral portion, and on both sides of the focusing photodetector 52. Two tracking photodetectors 54 are arranged in a direction perpendicular to the lattice fringes of the diffraction grating 51.

In the optical pickup 1200, the light reflected on the slope of the optical waveguide is transmitted to the optical waveguide device 50.
Are divided into three beams of 0 order and ± 1 order by the diffraction grating 51 formed on the S2 plane of FIG. Of these, the zero-order light irradiates the target track on the optical disk 95, and the reflected light is received by the focusing photodetector 52 to detect the RF signal. When the reflected light from the optical disc 95 is diffracted by the hologram 53, a light spot before focusing is formed on one of the focusing photodetectors 52 by the lens action of the hologram 53, and the other focusing light is formed. Since a focused light spot is formed on the detector 52, a focus error signal can be obtained by a so-called SSD (spot size detection) method.
On the other hand, the ± first-order light generated by the diffraction grating 51 becomes a sub-beam for detecting a tracking error signal by a so-called three-beam tracking method, and is detected by the tracking light detector 54. This tracking photodetector 54
, A tracking error signal is obtained from the differential output signal.

The optical disk pickup shown in FIG. 12, which combines the signal detection by the three-beam tracking method and the SSD method, can easily detect the signal using the hologram. Therefore, the configuration of the optical disk pickup in which the integrated unit according to the present invention is effective. It is. In particular, in the three-beam tracking method, since the diffraction grating is installed at a position close to the light source, the integrated units 50, 51, 52, 54, and 5 of the present invention capable of arranging the diffraction grating on the substrate surface of the optical waveguide device.
5, 56 are effective. As another servo signal detection method effective for optical disk pickup using hologram,
There are a phase difference tracking method and a knife edge method focus detection method, and these methods are also optical disk pickups 1200 using the integrated unit described in this embodiment.
Can be used.

In this embodiment, the submount 55
Used a silicon crystal having a thickness of 500 μm. A positioning marker was previously set on the submount 55, and the optical waveguide device 50, the tunable DBR semiconductor laser 56, and the photodetectors (52, 54) were positioned and fixed under a microscope in this order. In the present embodiment, since light is taken out from the optical waveguide device 50 in the vertical direction, the tunable DBR semiconductor laser 56, the optical waveguide device 50, and the photodetectors (52, 54) are all mounted on the same submount 55. It was placed on top and could be assembled efficiently. In the optical disk pickup optical system, FIG.
It is necessary to accurately guide the reflected light spot on the photodetector divided into regions as described above, and the relative positioning accuracy between the light source and the photodetector is required. In the optical pickup of the present embodiment, in addition to being able to position both under a microscope, since the positions of the light source and the photodetector are close to each other,
The relative position change due to the change in ambient temperature is extremely small,
This also has the effect that a stable optical system can be realized. Further, an optical pickup optical system having a configuration in which a semiconductor laser light source and a photodetector are arranged on the same substrate has been conventionally proposed. However, in the optical pickup of the present embodiment, the light source includes a semiconductor laser and an optical waveguide device. Thus, it is possible to obtain an effect which cannot be obtained conventionally, in that the alignment between the two and the alignment of the photodetector can be completed on the same submount.

In the present embodiment, an optical waveguide device having a configuration in which light is totally reflected at the end face (slope) of the optical waveguide described in Embodiment 1 and light is extracted from the S2 surface opposite to the substrate surface is used. The example in which the coherent light source and the photodetector are integrated has been described.
A coherent light source using an optical waveguide device having a configuration in which light is totally reflected in a concave portion provided near the surface of the substrate and light is extracted from the S2 surface on the opposite side of the substrate surface, as described in, is also configured as an integrated unit. It is possible to

(Embodiment 5) In this embodiment, an integrated unit having a configuration in which a stray light component incident on a photodetector is suppressed will be described.

In the configuration of the integrated unit 1200 shown in FIG. 12, the photodetector is formed on the silicon substrate 57 having a thickness of 1 mm, and is higher than the substrate surface S2 of the optical waveguide device 50 having a thickness of 500 μm from the submount 55 surface. , The signal error due to the stray light component is small. That is, the optical waveguide device 50
Is reflected from the emission surface S2 of the optical waveguide, the light that is multiple-reflected in the optical waveguide substrate and emitted from the side surface of the substrate does not reach the surface of the photodetector, and a signal error due to the stray light does not occur. Has become. The exit surface S of the optical waveguide device 50
2 is provided with an anti-reflection coating made of a multilayer film having a reflectance of 0.1% for both the fundamental wave of 850 nm and the wavelength-converted blue light of 425 nm. However, in addition to the signal light causing a light amount loss in the hologram and the diffraction grating, since the lens function of the fundamental wave light is large with respect to the blue light, slight reflected light causes large stray light. Therefore, the configuration of the optical pickup 1200 shown in FIG. 12 has an effect of effectively suppressing the stray light from reaching the photodetector surface.

A similar effect is obtained by using a submount 5 made of silicon as in the integrated unit 1300 shown in FIG.
The optical detector group 59 can be formed on the submount 58 and the location where the optical waveguide device 60 is installed on the submount 58 can be formed as a concave portion. In order to process the submount 58 into a concave shape, a method using anisotropic etching of silicon crystal is effective, and the surface accuracy of the bottom surface of the concave shape can be kept higher than that of the cutting process.

The integrated unit 140 shown in FIG.
The stray light can also be prevented from reaching the surface of the photodetector by disposing the light-shielding object 63 between the optical waveguide device 60 mounted on the submount 64 and the photodetector 62 as shown in FIG. . In this embodiment, a light-shielding object 63 is formed by applying an aluminum vapor-deposited film on the side surface of the optical waveguide device 60. For comparison, when a structure without the aluminum vapor-deposited film was fabricated, a large DC component was superimposed on the output of each photodetector, and an RF signal with a sufficient amplitude could not be detected. This light-shielding object may be a material having light reflectivity or a material having light absorbency, and the rise in temperature does not matter with a normal light amount.

In the integrated unit in which the SHG blue laser and the photodetector described in the second embodiment are integrated, like the optical pickup 1500 shown in FIG.
The optical waveguide device 60a and the photodetector 59a are arranged on opposite sides via the submount 25. As in the coherent light source 700 shown in FIG.
In the configuration of the optical waveguide device that obtains blue light from one surface, it is necessary to form the extraction window 26 in the submount 25. The blue light emitted from the extraction window 26 is converted into parallel light by the collimator lens 9 and is condensed on the optical disk 95 by the objective lens 12. In this configuration, stray light generated by multiple reflection in the optical waveguide substrate is taken out of the extraction window 2.
Blocked by 6. In the configuration of the optical pickup 1500 shown in FIG. 15, the photodetector group 59a is formed on the surface of the submount 25 where the optical waveguide device 60a is not mounted. Therefore, it is possible to prevent the influence of stray light without providing the above-described light-shielding object or the concave dug structure.

(Embodiment 6) Next, astigmatism occurring in an optical waveguide device will be described with reference to FIG.

In the optical waveguide device 100 shown in FIG. 1A in the first embodiment, an X-plate LiNbO ₃ crystal having an axial configuration as shown in FIG. 16C is used as a substrate (optical waveguide substrate) 70 constituting the optical waveguide device. Used as FIG.
The optical waveguide substrate 70 of the optical pickup 1600 shown in FIG.
, The guided light propagates as extraordinary light and has a wavelength of 850 n
The m fundamental waves are converted to harmonics having a wavelength of 425 nm. The light reflected at right angles on the end surface (slope) of the optical waveguide opposite to the incident side propagates through the optical waveguide substrate 70 as a divergent beam, and is variously reflected like a light beam Irohaniho shown in FIG. Light having various directional components. Among them, the rays a, b, and e are extraordinary lights, and the refractive index of the substrate is felt as ne, whereas the rays c and d are slightly ordinary light, and thus are felt as the refractive index no. The refractive index of the LiNbO ₃ crystal with respect to extraordinary light is about 2.2, whereas the refractive index with respect to ordinary light is as large as about 2.28. There is a delay. As a result, the light beam emitted from the optical waveguide has a wavefront shape having a larger radius of curvature in a direction parallel to the optical waveguide direction and a smaller radius of curvature in a direction perpendicular to the optical waveguide direction. Has an astigmatism component as shown in FIG.

The sealing plate 71 shown in FIG. 16A is provided for sealing the concave package 72, and has an effect of reducing the above-mentioned astigmatism. In the present embodiment, a Z plate (a substrate whose direction perpendicular to the substrate is the Z axis) LiNbO ₃ crystal is used as the sealing plate 71, and its thickness is 500 μm, which is the same as that of the optical waveguide substrate 71. Light emitted from the optical waveguide device propagates through the sealing plate 71 as a divergent beam. At this time, the optical waveguide substrate 70
Contrary to the case where light propagates through the inside, the rays a, b, and e feel the refractive index no of ordinary light, while the rays c and d slightly sense the refractive index ne of extraordinary light. Is a ray
A phase advance occurs for b and e. The phase advance cancels the phase delay in the optical waveguide substrate 70, and the sealing plate 7
The light beam passing through 1 becomes an astigmatic spherical wave from which the astigmatism component has been removed. In the experiments of the present inventors, the sealing plate 7 was used.
When a glass plate was used, astigmatism of about 15 mλ was observed, whereas when a Z-plate LiNbO ₃ substrate was used, the astigmatism component could be suppressed to a measurement limit (about 5 mλ) or less. .

Alternatively, as in the optical pickup shown in FIG. 17, a substrate having a cylindrical lens 73 shape can be used as a sealing plate to correct the astigmatism component in the same manner as in FIG. In this embodiment, Corning # 7 is used as the substrate.
059 glass was used. Since a large cost is required for polishing the cylindrical shape, the cylindrical sectional shape is approximated by a step-like sectional shape as shown in FIG. Actually, the patterning of the photoresist by photolithography and the etching by hydrofluoric acid were repeated three times to form an 8-level stepped cross-sectional shape. Even in a configuration in which a cylindrical lens is approximated by a step-shaped cross-sectional shape 73a as shown in FIG.
A good outgoing wavefront without astigmatism component was confirmed. Further, the example shown in FIG. 17 has an advantage that an inexpensive optical material such as glass or plastic can be used as the sealing plate. In particular, in the mass production process, the cost can be reduced by using the injection molded plastic substrate.

In this embodiment, in order to reduce astigmatism, a second birefringent optical crystal whose optical axis is orthogonal to the optical waveguide substrate is used as a sealing plate for sealing a package, or a cylindrical member is used. The example in which the lens shape is used has been described.
May be separately provided on the optical path of light, or the substrate surface (S2) from which light from the optical waveguide device is emitted may be processed into a substantially cylindrical shape.

The light source module having a configuration in which light is extracted from the surface (S1 surface) on which the waveguide of the optical waveguide device is formed also has a diffraction grating on a transparent sealing substrate 71 as shown in an optical pickup 1900 in FIG. 74 can be formed to reduce the number of parts. In this case, light is extracted from the back surface of the submount 76 by providing an opening in the submount 76 and the concave package 72. In this configuration, by aligning both the photodetector 78 and the optical waveguide device 75 with the opening of the submount 76, the relative positional accuracy between the optical waveguide device 75 and the photodetector 78 is ensured.

[0169]

As described in detail above, according to the present invention,
The guided light is totally reflected on the slope of the optical waveguide provided on the first surface of the substrate constituting the optical waveguide device, and can be extracted from the first surface or the second surface.
Therefore, the coherent light source of the present invention in which the optical waveguide device and the semiconductor laser are combined can reduce the return light to the semiconductor laser and improve the noise characteristics. Further, it is possible to reduce the size of the optical pickup equipped with the coherent light source, and its practical effect is very large.

If the thickness of the substrate constituting the optical waveguide device is 0.3 mm or more and 1.0 mm or less, it is easy to handle and suitable for mass production. This is preferable because the amount of aberration can be suppressed.

Further, the substrate constituting the optical waveguide device is made of a nonlinear optical material, and the fundamental wave light of the semiconductor laser incident on the optical waveguide is wavelength-converted to the second harmonic light.
When light is emitted from the first surface, the second surface is placed on the first surface side.
By providing an anti-reflection coating for harmonic light, return light can be prevented from re-reflecting on the first surface. Therefore, it is possible to prevent the signal waveform from deteriorating due to the interference between the return light re-reflected on the first surface and the light emitted from the waveguide.

Further, according to the present invention, the guided light is totally reflected on the slope of the optical waveguide provided on the first surface of the substrate constituting the optical waveguide device, and can be extracted from the first surface. Therefore, the coherent light source of the present invention in which the optical waveguide device and the semiconductor laser are combined can reduce the return light to the semiconductor laser and improve the noise characteristics. Also, it is possible to reduce the size of the optical pickup equipped with the coherent light source,
Its practical effect is very large.

Further, when the substrate constituting the optical waveguide device is made of a non-linear optical material, and the wavelength of the fundamental wave light of the semiconductor laser incident on the optical waveguide is converted to the second harmonic light, the first surface side has the fundamental wave light. By applying the anti-reflection coating, it is possible to prevent the fundamental light from re-reflecting on the first surface. Therefore, it is possible to prevent the light re-reflected on the first surface from returning to the waveguide.

In the above-mentioned optical waveguide device, it is preferable that the inclined surface of the optical waveguide is formed at an angle of approximately 45 degrees (45 degrees ± 1 degree) with respect to the optical waveguide because no coma aberration occurs in the condensed spot.

Further, when the substrate constituting the optical waveguide device is made of a non-linear optical material, and the fundamental wave light of the semiconductor laser incident on the optical waveguide is wavelength-converted into the second harmonic light, the harmonic light may be in the waveguide mode. This is preferable because the substrate can be made thinner than in the radiation mode and astigmatism and the like can be suppressed. Further, in the case of the guided mode, the first
By providing a concave portion (groove) or the like on the surface of the device, an end surface (slope) can be easily formed, and mass production can be easily performed.

In the above-described optical waveguide device, by forming a concave portion or a cut portion near the first surface so as to be substantially orthogonal to the optical waveguide, a part (for example, a side surface) of the concave portion or the cut portion is formed with the slope of the optical waveguide. You can also. In this case, the slope can be easily formed by etching or the like used in the semiconductor process, and the cost can be reduced by the mass production process.

When the first surface side of the substrate on which the optical waveguide is formed is arranged on the submount, the first surface of the substrate except for the concave portion is provided.
If a protective layer is provided on the surface of, the refractive index of the protective layer can be prevented from affecting the total reflection surface.

When a protective layer is provided on the first surface of the substrate,
The refractive index n ₁ of the protective layer, the effective refractive index n ₂ of the optical waveguide with respect to the light guided through the optical waveguide, and the angle θ between the first surface and the normal to the side surface (slope) of the concave portion are represented by Sin (θ If the relationship of n ₁ / n ₂ is satisfied, the concave side surface (the slope of the optical waveguide)
Satisfies the total reflection condition.

Further, the depth t ₁ of the guided mode of the fundamental wave light guided in the optical waveguide, the depth t ₂ of the guided mode of the second harmonic light guided in the optical waveguide, and the depth t of the concave portion. When the relationship of t ₂ <t <t ₁ is satisfied, the harmonics are totally reflected in the concave portion and the fundamental wave passes through the concave portion, so that the wavelength of the harmonic and the fundamental wave can be separated. it can. Alternatively, the refractive index nc ₁ of the protective layer for fundamental light, the refractive index nc ₂ of the protective layer for second harmonic light, the refractive index nf ₁ of the optical waveguide for fundamental light, and the refractive index of the optical waveguide for second harmonic light and nf _2, the first surface and the theta normal angle of said recess side surfaces _{nc 2 / nf 2 <Sin (} θ) < film using a protective film that satisfies the relationship of nc ₁ / nf ₁ If the thickness is set appropriately, the condition for total reflection is satisfied only for harmonics, and thus wavelength separation becomes possible. Therefore, the output of the fundamental wave mixed with the output of the harmonic can be easily reduced,
Further, the fundamental wave output characteristic can be monitored by detecting the fundamental wave that has passed through the concave portion.

In the case where light is extracted from the second surface of the substrate on which the optical waveguide is formed, opposite to the first surface, a component is formed by forming a diffraction grating on the second surface. Points can be reduced.

When light is extracted from the second surface of the substrate constituting the optical waveguide device, the birefringent optical crystal constituting the substrate has an optical axis orthogonal to the diverging optical path of the light emitted from the optical waveguide device. It is preferable to dispose a second birefringent optical crystal to correct astigmatism. Alternatively, the substrate surface (second surface) from which light is emitted from the optical waveguide device
May have a substantially cylindrical shape, or a cylindrical lens may be arranged in the optical path of light emitted from the optical waveguide device.

According to the coherent light source of the present invention, since the optical waveguide device of the present invention and the semiconductor laser are provided, the return light to the semiconductor laser can be reduced and the noise characteristics can be improved. Further, it is possible to realize a miniaturized optical pickup equipped with the coherent light source. Furthermore, when an integrated unit is configured in combination with a photodetector, the alignment between the optical waveguide device and the semiconductor laser is not required, and the apparatus can be easily and accurately adjusted only with the alignment between the coherent light source and the photodetector. Can be configured.

Further, by using a wavelength-tunable semiconductor laser, the oscillation wavelength can be fixed within the phase matching wavelength intensity of the optical waveguide type wavelength conversion device, so that a large conversion efficiency can be obtained.

Further, the distance between the light emitting end face of the semiconductor laser and the light incident end face of the optical waveguide is about several μm (for example, 0 μm).
(Not more than 10 μm) and using a direct coupling method without using a coupling lens, it is possible to prevent return light at the incident end face and improve noise characteristics.

In the coherent light source of the present invention, when the optical waveguide device and the semiconductor laser are arranged in a concave package, a sealing plate for sealing the concave package is made of the second birefringent crystal or the cylindrical plate. By using a lens, the number of components can be reduced, and the cost can be further reduced.

According to the integrated unit of the present invention, the coherent light source for extracting light from the second surface opposite to the first surface of the substrate on which the optical waveguide is formed and the photodetector are on the same surface of the submount. Since they are arranged, the photodetector can be easily integrated near the light emission surface. In addition, the photodetector and the coherent light source can be easily and accurately aligned, and an integrated unit can be efficiently assembled.

When light is extracted from the second surface opposite to the first surface of the substrate on which the optical waveguide is formed, a stray light is disposed between the coherent light source and the photodetector, and stray light is transmitted to the photodetector. If it does not reach, signal errors due to stray light components can be reduced. Further, the height of the photodetector surface from the submount surface may be higher than the surface on the light emission side of the coherent light source, or a concave portion may be formed in the submount surface, and the coherent light source may be disposed in the concave portion.

According to the integrated unit of the present invention,
The coherent light source from which light is extracted from the first surface of the substrate on which the optical waveguide is formed is formed on the first surface of the submount, and the detector is formed on the second surface of the submount. It is possible to easily prevent stray light from reaching the photodetector without providing a light-shielding body or a concave portion.

Further, when the integrated unit and the coherent light source are arranged in a concave package, the number of components can be reduced by forming a diffraction grating on a transparent substrate for sealing the concave package. it can.

According to the optical pickup device of the present invention, it is possible to reduce the size and thickness of the device by using the integrated unit of the present invention. Further, since the diffraction grating is provided on the substrate surface of the optical waveguide device or on the transparent substrate for sealing the concave package in the condensing optical system, a stable optical system can be realized.

The photodetector of the integrated unit is divided into a first region (focusing photodetector) at the center, a second region (tracking photodetector) on both sides of the first region, and a third region (tracking photodetector). By dividing the second region and the third region in a direction perpendicular to the lattice fringes of the diffraction grating by dividing into at least three regions of the photodetector, signal detection can be performed by, for example, a three-beam tracking method. it can. In this case, since the diffraction grating is arranged at a position close to the light source, it is effective to provide the diffraction grating on the surface of the substrate constituting the optical waveguide device of the integrated unit.

Further, the photodetectors are arranged on both sides with respect to the coherent light source, and each of the detectors is provided with a region (focusing photodetector) divided into a central portion and a peripheral portion, and a condensing optical system and a lens are provided. By providing the second diffraction element (hologram) having the function, signal detection can be performed by, for example, a spot size detection (SSD) method. In an optical pickup based on a combination of the SSD method and the three-beam tracking method, signal detection using a hologram is easy, and the integrated unit of the present invention is effective.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a schematic configuration of an optical waveguide device according to a first embodiment in which an end face is formed obliquely to an optical waveguide.

FIG. 1B is a cross-sectional view showing a schematic configuration of an optical waveguide device according to a modification of the first embodiment, in which a part of an end face of the optical waveguide device is formed obliquely together with the optical waveguide.

FIG. 2 shows an optical waveguide device in which an end face is formed obliquely to an optical waveguide and a wavelength-variable DBR in the first embodiment.
FIG. 3 is a cross-sectional view for explaining a method of performing wavelength conversion using a coherent light source including a semiconductor laser.

FIG. 3 is a diagram illustrating an optical waveguide device having an end face formed obliquely to an optical waveguide and a wavelength tunable DBR according to the first embodiment.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of a coherent light source (SHG blue laser) including a semiconductor laser.

FIG. 4 is a diagram showing a schematic configuration of an optical pickup on which the SHG blue laser of the first embodiment is mounted.

FIG. 5 is a cross-sectional view illustrating a schematic configuration of an optical waveguide device according to a second embodiment in which an end surface is formed obliquely with respect to the optical waveguide.

FIG. 6 is a diagram illustrating an optical waveguide device in which an end face is formed obliquely to an optical waveguide and a wavelength tunable DBR according to the second embodiment.
FIG. 3 is a cross-sectional view for explaining a method of performing wavelength conversion using a coherent light source including a semiconductor laser.

FIG. 7 is a diagram illustrating an optical waveguide device having an end face formed obliquely to an optical waveguide and a wavelength-tunable DBR according to the second embodiment.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of a coherent light source (SHG blue laser) including a semiconductor laser.

FIG. 8 is a perspective view showing a schematic configuration of an optical waveguide device according to a third embodiment in which a concave portion is formed on an optical waveguide.

FIG. 9A is a cross-sectional view illustrating a schematic configuration of an optical waveguide device in which a concave portion is formed on an optical waveguide according to a third embodiment.

FIG. 9B is a cross-sectional view illustrating a schematic configuration of an optical waveguide device according to Embodiment 3 in which a concave portion is formed on an optical waveguide and a high refractive index cladding layer is provided.

FIG. 9C is a cross-sectional view showing a schematic configuration of the optical waveguide device for describing a preferred positional relationship between the concave portion and the optical waveguide device in the third embodiment.

FIG. 9D is a sectional view showing a schematic configuration of an optical waveguide device in which a concave portion is formed on an optical waveguide in another example of the third embodiment.

FIG. 10 is a cross-sectional view showing a schematic configuration of a coherent light source (SHG blue laser) including an optical waveguide device in which a concave portion is formed on an optical waveguide and a tunable DBR semiconductor laser according to a third embodiment.

FIG. 11 is a cross-sectional view illustrating a configuration in which a diffraction grating is provided on a sealing plate for sealing a concave package in which a coherent light source is arranged according to the third embodiment.

FIG. 12 shows a schematic configuration of an optical pickup according to a fourth embodiment in which the coherent light source and the photodetector according to the first embodiment are integrated on the same surface of a submount, and further provided with a condensing optical system. It is a perspective view.

FIG. 13 is a perspective view showing a schematic configuration of an integrated unit in which a coherent light source and a photodetector according to the first embodiment are integrated on the same surface of a submount in the fifth embodiment.

FIG. 14 is a perspective view illustrating a schematic configuration of an integrated unit according to a fifth embodiment in which the coherent light source and the photodetector according to the first embodiment are integrated on the same surface of a submount.

FIG. 15 shows the coherent light source of the second embodiment arranged on one surface of the submount in the fifth embodiment;
It is a perspective view which shows schematic structure of the optical pickup by which the photodetector was arrange | positioned on the other surface.

FIG. 16A is a perspective view showing a configuration in which a concave package in which a coherent light source is arranged is sealed with a birefringent sealing plate according to the sixth embodiment, and FIG. 16B is a birefringent sealing plate. FIG. 3C is a diagram showing a refractive index ellipsoid of the optical waveguide substrate, and FIG.

FIG. 17 is a perspective view showing a configuration in Embodiment 6 in which a concave package in which a coherent light source is arranged is sealed with a cylindrical lens.

FIG. 18 is a sectional view showing a sectional shape of a cylindrical lens.

FIG. 19 is a cross-sectional view illustrating a configuration in which a diffraction grating is provided on a sealing plate for sealing a concave package in which a coherent light source is arranged according to the sixth embodiment.

FIG. 20 is a cross-sectional view illustrating a configuration of a conventional SHG blue laser.

FIG. 21 is a diagram showing a configuration of an optical pickup on which a conventional SHG blue laser is mounted.

FIG. 22 is a perspective view showing a configuration of a conventional optical waveguide device having a notch.

[Explanation of symbols]

1, 15, 33, 41 Mg-doped LiNbO ₃ substrate 2, 16, 34, 85 Periodically domain-inverted region _3, 17, 31, 35, 84, 93 Optical waveguide 4, 18 End face (slope) 5, 19, 38, 56, 80 Tunable DBR semiconductor laser 6, 21, 81 Active region 7, 20, 82 DBR region 8, 22 Lens 9, 23, 86 Collimating lens 10, 87 Polarizing beam splitter 11, 88 Quarter-wave plate 12, 53a , 89 Objective lens 13, 90 Detection lens system 14, 91 Photodetector 24, 25, 37, 55, 58, 64 Submount 26 Extraction window 30 Substrate 32a, 36a, 40a Side surface of concave portion 32, 36, 40 concave portion 39, 50, 60, 60a, 75 Optical waveguide device 42 Protective film 46 Cladding layer 51, 74 Diffraction grating 52 Focus Photodetector 53 Hologram 54 Tracking photodetector 57 Silicon substrate 58, 76 Submount 59, 59a, 62, 78 Photodetector (group) 63 Shielding object 70 Optical waveguide substrate 71 Sealing plate 72 Concave package 73 Cylindrical Lens 73a Stepped cross-sectional shape of cylindrical lens 77 Semiconductor laser 83 Optical waveguide type wavelength conversion device 92 Glass substrate 94 Cut 95 Disk 100, 150, 500, 800, 900, 950, 9
70,980 Optical waveguide device 110,910 Incident end face 200,300,600,700,1000,110
0, 2000 Coherent light source 400, 1200, 1500, 1600, 1700, 1
900, 2000 Optical pickup 940 Slope 1300, 1400 Integrated unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/135 H01S 5/026 H01S 5/022 G02B 6/12 A 5/026 HB (72) Inventor Kosuke Mizuuchi 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture (72) Kazuhisa Yamamoto Kazuhisa Yamamoto 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (45)

[Claims] 1. A substrate having a first surface and a second surface, and an optical waveguide formed on the first surface of the substrate, wherein the optical waveguide is a light incident end face and a light guide. An optical waveguide having an inclined surface that is obliquely inclined, and a waveguide light incident on the optical waveguide from the light incident end face is totally reflected on the inclined surface, and the first surface of the substrate or the first surface of the substrate. An optical waveguide device from which guided light is emitted from the second surface. 2. The optical waveguide device according to claim 1, wherein the guided light is emitted from a first surface of the substrate. 3. The optical waveguide device according to claim 1, wherein the guided light is emitted from a second surface of the substrate. 4. The optical waveguide device according to claim 1, wherein the substrate is made of a non-linear optical material, and the guided light incident on the optical waveguide as a fundamental light is wavelength-converted into a second harmonic light and emitted. . 5. The optical waveguide device according to claim 4, wherein said second harmonic light is emitted from a second surface of said substrate. 6. The thickness of the substrate is 0.3 mm or more,
The optical waveguide device according to claim 5, which is 1.0 mm or less. 7. The optical waveguide device according to claim 5, wherein a non-reflection portion that does not reflect the second harmonic light is provided on the first surface of the substrate. 8. The optical waveguide device according to claim 7, wherein the non-reflection portion is formed by an anti-reflection coating. 9. The optical waveguide device according to claim 4, wherein said second harmonic light is emitted from a first surface of said substrate. 10. The optical waveguide device according to claim 9, wherein a non-reflection portion that does not reflect the fundamental wave is provided on the first surface of the substrate. 11. The optical waveguide device according to claim 10, wherein the non-reflection portion is formed by an anti-reflection coating. 12. The optical waveguide device according to claim 1, wherein an angle between the inclined surface of the optical waveguide and the optical waveguide is 45 ± 1 degrees. 13. The optical waveguide device according to claim 4, wherein said second harmonic light is in a guided mode. 14. The optical waveguide device according to claim 1, wherein an entire surface of the substrate corresponding to a slope of the optical waveguide is inclined with respect to the optical waveguide. 15. The optical waveguide device according to claim 1, wherein the slope of the optical waveguide is formed by a cut portion formed near the first surface of the substrate and substantially orthogonal to the optical waveguide. 16. The optical waveguide device according to claim 1, wherein the slope of the optical waveguide is formed by a concave portion formed near the first surface of the substrate and substantially perpendicular to the optical waveguide. 17. The optical waveguide device according to claim 16, further comprising a protective layer on at least the first surface of the substrate except for the concave portion. 18. The optical waveguide device according to claim 16, further comprising a protective layer on the first surface of the substrate. 19. The refractive index n _{1 of the} protective layer and the effective refractive index n of the optical waveguide with respect to light guided through the optical waveguide.
19. The optical waveguide device according to claim 18, wherein ₂ and an angle θ formed by a normal of the first surface of the substrate and a side surface of the concave portion satisfy a relationship of Sin (θ)> n ₁ / n ₂ . 20. The slope of the optical waveguide is formed by a concave portion formed near the first surface of the substrate and substantially orthogonal to the optical waveguide, and guides a fundamental wave light guided through the optical waveguide. Mode depth t ₁
5. The depth t ₂ of the waveguide mode of the second harmonic light guided through the optical waveguide and the depth t of the concave portion satisfy a relationship of t ₂ <t <t _1. The optical waveguide device according to any one of the preceding claims. 21. A substrate further comprising a protective layer on a first surface of the substrate, wherein the slope of the optical waveguide is formed near the first surface of the substrate and formed substantially orthogonal to the optical waveguide. The refractive index nc ₁ of the fundamental wave light guided through the optical waveguide with respect to the protective layer, the refractive index nc _{2 of} the second harmonic light guided through the optical waveguide with respect to the protective layer, and the refractive index of the optical waveguide The refractive index nf ₁ for the fundamental wave light, the refractive index nf ₂ for the second harmonic light of the optical waveguide, and the angle θ between the first surface and the normal to the side surface of the concave portion are nc ₂ / nf ₂ <Sin ( theta) satisfies the relation <nc ₁ / nf _1, an optical waveguide device according to claim 4. 22. The optical waveguide device according to claim 5, wherein a diffraction grating is formed on the second surface of the substrate. 23. The optical waveguide device according to claim 1, wherein said substrate is made of a first birefringent optical crystal. 24. The optical device according to claim 2, further comprising a second birefringent optical crystal arranged in an optical path of the emitted guided light and having an optical axis orthogonal to the first birefringent optical crystal of the substrate.
4. The optical waveguide device according to 3. 25. The optical waveguide device according to claim 1, wherein a surface from which the guided light is emitted has a substantially cylindrical shape. 26. The apparatus according to claim 26, further comprising a cylindrical lens disposed in an optical path of guided light emitted from the optical waveguide device.
The optical waveguide device according to claim 1. 27. The optical waveguide device according to claim 24, further comprising a concave package in which the optical waveguide device is disposed, wherein the second birefringent crystal seals the concave package. 28. The optical waveguide device according to claim 26, further comprising a concave package in which the optical waveguide device is disposed, wherein the cylindrical lens seals the concave package. 29. The substrate has a first end face including a light incident end face of the optical waveguide, and a second end face facing the first end face, wherein the slope and the first end face of the substrate are provided. The angle between the line of intersection with the surface, the plane including the line of intersection of the second end surface of the substrate with the second surface of the substrate, and the direction in which the guided light is emitted is defined by the angle of the substrate. The optical waveguide device according to claim 1, wherein the optical waveguide device is larger than a half of a spread angle of the guided light emitted from the second surface. 30. A surface including a line of intersection between the slope and the first surface of the substrate, a surface including a line of intersection between the second end surface and the second surface of the substrate, and the guided light is emitted. 30. The optical waveguide device according to claim 29, wherein an angle θ between the direction and the spread angle θ1 of the guided light extracted from the second surface of the substrate satisfies a relationship of θ1 / 2 <θ. 31. The optical waveguide device according to claim 1, further comprising a periodically poled region formed on a first surface of the substrate. 32. The optical waveguide device according to claim 31, wherein the periodically poled region is not formed near the slope of the optical waveguide. 33. A coherent light source, comprising: a semiconductor laser; and the optical waveguide device according to claim 1. 34. The coherent light source according to claim 33, wherein the semiconductor laser is a tunable semiconductor laser. 35. The distance between the light emitting end face of the semiconductor laser and the light incident end face of the optical waveguide is 0 μm or more and 10 μm or more.
34. The coherent light source according to claim 33, which is less than or equal to μm. 36. A coherent light source having a semiconductor laser and the optical waveguide device according to claim 3, into which light from the semiconductor laser is incident; and a light associated with light emitted from the optical waveguide device. An integrated unit comprising: a photodetector for detection; and a submount on which the coherent light source and the detector are arranged on the same plane. 37. The integrated unit according to claim 36, further comprising a light shield disposed between the coherent light source and the light detector. 38. The integrated unit according to claim 36, wherein a height of the photodetector surface from the submount surface is higher than a surface on the light emission side of the coherent light source. 39. The integrated unit according to claim 36, wherein a recess is formed in the surface of the submount, and the coherent light source is disposed in the recess. 40. A coherent light source comprising: a semiconductor laser; and the optical waveguide device according to claim 2, into which light from the semiconductor laser is incident; and light associated with light emitted from the optical waveguide device. A submount having a photodetector to be detected, a first surface, and a second surface that is a back surface of the first surface, wherein the coherent light source is disposed on a first surface of the submount. And a submount, wherein the photodetector is disposed on the second surface. 41. The coherent light source according to claim 33, a concave package in which the coherent light source is disposed, and a transparent substrate sealing the concave package and having a diffraction grating formed on the surface. , Comprising an integrated unit. 42. An integrated unit according to claim 36, and a condensing optical system for condensing the light emitted from the integrated unit, wherein the light guided from the optical waveguide device of the integrated unit is provided. An optical pickup device, wherein a diffraction grating is formed on a surface from which light is emitted. 43. An optical pickup device comprising: the integrated unit according to claim 41; and a condensing optical system that condenses light emitted from the integrated unit. 44. The photodetector of the integrated unit is divided into a central first region, and at least three regions, a second region and a third region on both sides of the first region, 43. The optical pickup device according to claim 42, wherein the second region and the third region with respect to a region are arranged in a direction perpendicular to a lattice fringe of the diffraction grating. 45. A semiconductor laser, and the optical waveguide device according to claim 1, wherein light from the semiconductor laser is incident, and two light detectors for detecting light related to light emitted from the optical waveguide device. A submount on which the coherent light source and the detector are disposed; a condenser optical system for condensing light emitted from the optical waveguide device; and a lens function disposed in the condenser optical system. A diffractive element comprising: a light diffusing element, wherein the two photodetectors are positioned to face the optical waveguide device, and each of the two photodetectors has at least a region divided into a central portion and a peripheral portion. An optical pickup device, wherein the light diffracted by the diffraction element irradiates each of the two detectors.