JP3129028B2 - Short wavelength laser light source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-wavelength laser light source used in the field of optical information processing or optical measurement using coherent light.

[0002]

2. Description of the Related Art FIG. 11 shows a configuration diagram of a conventional short wavelength laser. The short-wavelength laser light source shown here is a semiconductor laser 21, an optical wavelength conversion element 22, a collimator lens 37a,
The focus lens 37b and the half-wave plate 33 were basic components (T. Taniuchi and K. Yamamoto, "Minia
turized light source of coherent blue radiation ", C
LEO'87, WP6, 1987).

A fundamental wave P1 from a semiconductor laser 21 is applied to an incident surface 10 of an optical waveguide 2 formed on an optical wavelength conversion element 22.
Through the lenses 37a and 37b. On this occasion,
Half-wave plate 33 sandwiched between lenses 37a and 37b
Has a function of rotating the polarization direction by 90 degrees, whereby the polarization directions can be matched so that the fundamental wave P1 is guided in the optical waveguide 2. The optical wavelength conversion element 22 is fixed to an element mount 38. The harmonic P2 radiated into the substrate is converted into parallel light by the shaping lens 36, branched by the beam splitter 39, and partially received by the detector 27. The light wavelength conversion element 22 used here is called a Cherenkov radiation type, and this operation will be described in detail. Hereinafter, harmonic generation (wavelength 0.42 μm) of a fundamental wave having a wavelength of 0.84 μm will be described in detail (T. Taniuchi
and K. Yamamoto, "Second harmonic generation by Ch
erenkov radiation in proton-exchanged LiNbO ₃ optic
alwaveguide ", CLEO'86, WR3, 1986,).

LiNbO ₃ substrate 2 serving as an optical wavelength conversion element
When the light of the fundamental wave P1 from the semiconductor laser 21 is incident on the incident surface 10 of the buried optical waveguide 2 formed in FIG.
When the condition that the effective refractive index N1 of the fundamental wave guided mode is equal to the effective refractive index N2 of the harmonic wave is satisfied, light of the harmonic wave P2 is efficiently radiated from the optical waveguide 2 into the LiNbO ₃ substrate 22. And operates as an optical wavelength conversion element. This Cherenkov radiation type optical wavelength conversion element has excellent temperature characteristics (half-value width of 25 ° C.), but its conversion efficiency is not so high.

Next, another conventional short wavelength laser light source which is further miniaturized will be described with reference to FIG. ). In the short-wavelength laser light source, a semiconductor laser 21 having a wavelength of 0.84 μm and an optical wavelength conversion element 22 are fixed to a Si submount and directly coupled. When the output P1 of the semiconductor laser 21 is 100 mW, 2 m
A harmonic P2 of W (blue laser light) was obtained. In this case, the conversion efficiency P1 / P2 in the light wavelength conversion element 3 is 2%.
It is. However, it was difficult to obtain a practical 5 mW with the Cherenkov radiation type. In addition, it is difficult to collect light because the harmonics are radiated into the substrate.

Recently, a high-efficiency optical wavelength conversion device based on a domain-inverted structure has been trial manufactured using a Z plate of LiTaO ₃ , which can generate 10 mW blue light. Therefore, if a light wavelength conversion element using a domain-inverted structure is directly coupled to a semiconductor laser, a compact and highly productive short wavelength light source can be manufactured.

Hereinafter, this light wavelength conversion element will be described. FIG. 13 shows the configuration of this optical wavelength conversion element. FIG.
As shown in FIG. 1, an optical waveguide 2 is formed on a LiTaO ₃ substrate serving as an optical wavelength conversion element 22, and a layer 3 (a domain-inverted layer) having periodically inverted polarization is formed in the optical waveguide 2. By compensating for the mismatch between the propagation constant of the fundamental wave and the generated harmonic with the periodic structure of the domain-inverted layer 3 and the non-domain-inverted layer 4, it is possible to emit harmonics with high efficiency. First, FIG.
Will be used to explain the principle of harmonic amplification. In the non-polarization inversion element 31 in which the polarization has not been reversed, the polarization inversion layer is not formed and the polarization inversion direction is one direction. In the non-polarization inversion element 31, the harmonic output 31a merely increases and decreases in the traveling direction of the optical waveguide. On the other hand, in the domain-inverted wavelength conversion element (primary cycle) 32 whose polarization is periodically inverted, the output 32a has a higher harmonic in proportion to the square of the length L of the optical waveguide as shown in FIG. The output increases. However, the output of the higher harmonic wave P2 with respect to the fundamental wave P1 is obtained only during the quasi-phase matching in the polarization inversion. This quasi-phase matching is established only when the period Λ1 of the domain-inverted layer matches λ / (2 (N2ω-Nω)). Here, Nω is the effective refractive index of the fundamental wave (wavelength λ), and N2ω is the effective refractive index of the harmonic wave (wavelength λ / 2). The optical wavelength conversion element capable of increasing the output in this manner has a polarization inversion structure as a basic component. In addition, the optical wavelength conversion element has a feature that light is easily collected because harmonics are emitted from the optical waveguide.

[0008]

A 5 mW required for optical information processing and the like by using a high-efficiency optical wavelength conversion element having a domain-inverted structure in a short-wavelength laser light source that is directly and compactly reduced in size and weight as described above is used. When trying to obtain the above output, it is difficult to extract harmonics to the maximum or stably due to the narrow allowable temperature range of the optical wavelength conversion element. The reason will be described in detail below. FIG. 15 shows a temperature distribution at each point (shown in FIG. 12) of the short wavelength laser light source module. The semiconductor laser 21 converts about 70% of electric power into heat instead of light. Therefore, the semiconductor laser 21 itself becomes a heat source and a temperature distribution as shown in FIG. 15 is generated in the length direction of the light wavelength conversion element. Temperature tolerance of optical wavelength conversion element is 3 ℃
Because of this, only a part is phase-matched, and the harmonic power is greatly reduced. In addition, it took a long time of 30 minutes from turning on the semiconductor laser 21 until the temperature reached a stable state. Therefore, there is a problem in that it is difficult to obtain a harmonic having a practical level of a short wavelength laser light source of 5 mW or more with good reproducibility and stability.

According to the present invention, it is possible to increase the output power and stabilize the output power of harmonics by adding new ideas to the structure of a short wavelength laser light source based on a semiconductor laser and an optical wavelength conversion element. . That is, an object of the present invention is to obtain a short-wavelength laser light source that can be operated stably with high output by directly coupling a semiconductor laser and an optical wavelength conversion element.

[0010]

[0011]

Short-wavelength laser light source SUMMARY OF THE INVENTION Accordingly the present invention comprises a semiconductor laser and an optical wavelength conversion element on a submount, short-wavelength laser fundamental wave of the semiconductor laser is directly coupled to the optical waveguide In the light source, the surface on which the active layer of the semiconductor laser is formed and the surface on which the optical waveguide of the optical wavelength conversion element is formed face the submount, and a groove or a taper is formed in the submount immediately below the wavelength conversion section of the optical wavelength conversion element. And a means for making the submount and the wavelength converter non-contact.

[0012]

Further, the short-wavelength laser light source according to the present invention comprises a semiconductor laser and an optical wavelength conversion element on a submount, wherein a fundamental wave of the semiconductor laser is directly coupled to the optical waveguide. Means are provided such that the active layer forming surface of the laser and the optical waveguide forming surface of the optical wavelength conversion element face the submount, and the wavelength conversion section of the optical wavelength conversion element is equidistant from the semiconductor laser in the length direction.

The short-wavelength laser light source according to the present invention comprises a semiconductor laser and an optical wavelength conversion element on a submount, wherein a fundamental wave of the semiconductor laser is directly coupled to the optical waveguide. The optical wavelength conversion element is arranged at right angles to the laser, and the surface on which the active layer of the semiconductor laser is formed faces the submount.

[0015]

[0016]

According to the present invention, the harmonic power emitted from the optical wavelength conversion element can be made stable and highly efficient without transmitting the heat generated by driving the semiconductor laser to the optical wavelength conversion element. Hereinafter, this will be described in detail. When a current flows, the semiconductor laser starts generating heat simultaneously with oscillation. Although this heat is transmitted to the submount, since the wavelength conversion portion of the optical wavelength conversion element is shielded from the submount, the heat is not transmitted and the device operates at a substantially constant temperature. As a result, even if the optical wavelength conversion element has a domain-inverted structure having a temperature tolerance of 3 ° C. or less, there is no deterioration in harmonic power. Also, the rise of the harmonics is fast without being affected by the temperature rise of the submount due to the semiconductor laser lighting.

[0017]

FIG. 1 is a structural view of a short wavelength laser light source according to a first embodiment of the present invention. In this embodiment, a 0.8 μm band semiconductor laser is used as a short wavelength laser light source, and a LiTaO ₃ substrate is used as an optical wavelength conversion element. FIG. 1 is a sectional view of the short wavelength laser light source. In FIG. 1, 20 is a submount of Si,
21 is a semiconductor laser, 22 is an optical wavelength conversion element. The semiconductor laser 21 used here has a wavelength of 0.86 μm and an output of 100 mW. The optical wavelength conversion element 22 is one in which a periodically poled layer 3 and an optical waveguide 2 are formed on a LiTaO ₃ substrate by proton exchange in phosphoric acid. The proton exchange optical waveguide 2 used here is characterized by a large change in refractive index, good confinement of light, and high conversion efficiency to harmonics.

In the structure of this embodiment, the surface 24 on which the active layer 23 of the semiconductor laser 21 is formed and the surface 25 on which the optical waveguide 2 of the optical wavelength conversion element 22 is formed face the submount 20. The surface 24 on which the active layer 23 is formed is a surface on which the active layer 23 is epitaxially grown on the substrate of the semiconductor laser 21. The surface 25 on which the optical waveguide 2 is formed is a surface where the optical waveguide 2 is It is the formed surface.
The active layer 23 of the semiconductor laser 21 and the optical waveguide 2 are coaxial, and the fundamental wave P1 of the semiconductor laser 21 is directly coupled to the optical waveguide 2.

The wavelength converter 26 for converting a fundamental wave into a higher harmonic wave is not in contact with the submount 21 and is thermally cut off. Therefore, there is no influence of heat from the semiconductor laser 21. In FIG. 1, the fundamental wave P
When the semiconductor laser light (wavelength 0.86 μm) emitted from the active layer 23 is directly coupled to the optical waveguide 2 from the incident surface 10 of the optical wavelength conversion element 22 as the fundamental wave 1, the fundamental wave P1 propagates in a single mode, and Is converted into a harmonic P2 having a wavelength of 0.43 μm by the wavelength converter 26, and blue laser light is extracted from the emission surface 12 to the outside of the substrate.

Next, a method for manufacturing the short wavelength laser light source will be described. The semiconductor laser 21 was bonded with the formation surface 24 of the active layer 23 facing the submount 20. After a current was applied to the semiconductor laser 21 to emit the fundamental wave P1, the optical wavelength conversion element 22 was pressed against the semiconductor laser 21 with the formation surface 25 of the optical waveguide 2 facing the submount 20 and fixed. At this time, the incidence surface 10 of the optical wavelength conversion element 22 has an angle of 90 degrees or less with respect to the formation surface 25 of the optical waveguide 2, and it is not possible to break the semiconductor laser by contacting the emission surface of the semiconductor laser 21. Absent. Also, the incident surface 1
Light returning to the active layer 23 due to reflection at 0 can be reduced.

When fixed, the alignment in the X direction was performed by moving the optical wavelength conversion element 22 so that the harmonic output P2 was maximized. A short-wavelength laser light source using a conventional lens system requires alignment in three axes of X, Y, and Z. According to this configuration, alignment in only the X direction is sufficient. This is because the Z direction is applied to the semiconductor laser, and in the Y direction, the height of the active layer 23 of the semiconductor laser 21 and the height of the optical waveguide 2 of the optical wavelength conversion element 22 match, so that no alignment is required. It depends. An SiO ₂ protective film 17 was added to the optical waveguide 2 in the Y direction, and the height was adjusted to the height of the active layer 23. The height of the optical waveguide 2 from the surface of the submount 20 is 4 μm.

In the short-wavelength laser light source produced as described above, the semiconductor laser 21 was driven at 100 mW to obtain a harmonic P2 (wavelength 0.43 μm) of 7 mW. The conversion efficiency in this case is 7%. FIG. 2 shows the temperature distribution. The temperature difference in the length direction of the wavelength conversion section 26 of the optical wavelength conversion element 22 is within 1 ° C., and the efficiency does not deteriorate. In addition, the rise time is within one minute, and there is no problem when used as an apparatus. Here, the coupling efficiency was 76% and the fundamental wave was incident on the light wavelength conversion element 22. In FIG. 1, reference numeral 10 denotes an incident surface of the light wavelength conversion element 22, and SiO ₂ is formed on the incident surface 10 as an antireflection film. Thereby, the coupling efficiency of the fundamental wave P1 to the optical waveguide 2 increases by 15%. In addition, the antireflection film can prevent unstable operation of the semiconductor laser due to return light to the semiconductor laser.

The size of the short wavelength laser light source of this embodiment is 4
The size is as small as 4 × 10 mm. In addition, there is no portion causing an optical axis shift, and the structure is extremely resistant to temperature change and vibration.

Next, a short wavelength laser light source according to a second embodiment of the present invention will be described. FIG. 3 shows the configuration of the short wavelength laser light source according to the second embodiment. In this embodiment, the short wavelength laser light source of the first embodiment is enclosed in a package 50. Package 50
Was filled with nitrogen gas and shut off from outside air. The harmonic P2 is taken out of the window 51 made of coated glass. Reference numeral 51 denotes an infrared light cutoff filter that also functions as a blue light transmission filter. Reference numeral 52 denotes a support for the optical wavelength conversion element 22 made of quartz, which prevents vibration blur. The entire short wavelength laser light source was stabilized by performing temperature control of ± 1 ° C. using a Peltier. As a result, the output of the harmonic P2 hardly changed with respect to the change in the ambient temperature. FIG. 4 shows the relationship between the harmonic output and the environmental temperature. In addition, by filling with nitrogen gas, deterioration of the antireflection film and the like due to oxidation in air can be prevented.

FIG. 5 is a structural diagram of a third embodiment of the short wavelength laser light source according to the present invention. In this embodiment, a semiconductor laser of 0.8 μm band is used as a short wavelength laser light source, and a LiTaO ₃ substrate is used as an optical wavelength conversion element. FIG. 5 is a sectional view of the short wavelength laser light source. In FIG. 5, reference numeral 20 denotes a Si submount, 21 denotes a semiconductor laser, and 22 denotes an optical wavelength conversion element. The semiconductor laser 21 used here has a wavelength of 0.84 μm.
m and an output of 150 mW. The optical wavelength conversion element 22 is one in which a periodically poled layer 3 and an optical waveguide 2 are formed on a LiTaO ₃ substrate by proton exchange in phosphoric acid. In the configuration of the present embodiment, the formation surface 24 of the active layer 23 of the semiconductor laser 21 and the formation surface 25 of the optical waveguide 2 of the optical wavelength conversion element 22 face the submount 20. The active layer 23 of the semiconductor laser 21 and the optical waveguide 2 are coaxial and have a configuration in which the fundamental wave P1 of the semiconductor laser 21 is directly coupled. A groove is formed in the submount by etching. The wavelength converter 26 for converting the fundamental wave into a harmonic wave is not in contact with the submount 21 by the groove 8 and is thus thermally cut off. In FIG. 5, when the semiconductor laser 21 (wavelength 0.84 μm) emitted from the active layer 23 as the fundamental wave P1 by driving the semiconductor laser 21 is directly coupled to the optical waveguide 2 from the incident surface 10 of the optical wavelength conversion element 22, the fundamental wave P1 propagates in single mode, and the optical waveguide 2
The blue laser light is converted into a harmonic P2 having a wavelength of 0.42 μm by the wavelength conversion unit 26 and is extracted from the emission surface 12 to the outside of the substrate.

Next, a method of manufacturing the short wavelength laser light source will be described. First, a groove 8 having a width of 6 mm and a depth of 100 μm was formed in a Si submount 20 by a normal photo process and a dry etching process. Next, the semiconductor laser 21 was bonded with the formation surface 24 of the active layer 23 facing the submount 20 side. After a current was applied to the semiconductor laser 21 to emit the fundamental wave P1, the optical wavelength conversion element 22 was pressed against the semiconductor laser 21 with the formation surface 25 of the optical waveguide 2 facing the submount 20 and fixed. At this time, the incidence surface 10 of the optical wavelength conversion element 22 has an angle of 90 degrees or less with respect to the formation surface 25 of the optical waveguide 2, and it is not possible to break the semiconductor laser by contacting the emission surface of the semiconductor laser 21. Absent. Further, the amount of light returning to the active layer 23 due to reflection on the incident surface 10 can be reduced. Further, a thin film heater 15a is formed on the optical waveguide 2 by depositing a Ti film having a thickness of 300 nm, and the temperature of the wavelength conversion section 26 is kept constant by flowing a current. This temperature is constant because the groove is thermally insulated from the Si submount 20. When fixed, alignment in the X direction was performed so that the harmonic output P2 was maximized. An SiO ₂ protective film 17 was added to the optical waveguide 2 in the Y direction, and the height was adjusted to the height of the active layer 23.

In the short-wavelength laser light source manufactured as described above, the semiconductor laser 21 is driven at 150 mW and is driven at 10 mW.
(Wavelength 0.42 μm) was obtained. The conversion efficiency in this case is 7%. The rise was within 10 seconds and the harmonic output was stable. It is considered that the rise was quickened in this way because the thin film heater was added.

The size of the short wavelength laser light source of this embodiment is 3
It is as small as 3 x 12 mm. In addition, there is no portion causing an optical axis shift, and the structure is extremely resistant to temperature change and vibration. As a result, a change in the output of the harmonic P2 with respect to a change in the ambient temperature is minimized.

Although the submount is made of Si having good workability and excellent heat conductivity, the present invention is not limited to this.

As a fourth embodiment, a short wavelength laser light source according to the present invention will be described with reference to FIG. FIG. 6 shows a structural diagram of a short wavelength laser light source according to a fourth embodiment of the present invention. In this embodiment, a 0.8 μm band semiconductor laser is used as a short wavelength laser light source, and a LiNbO ₃ substrate is used as an optical wavelength conversion element. FIG. 6 is a cross-sectional view of the short wavelength laser light source. 6 in FIG.
Reference numeral 0 denotes a submount made of quartz glass, reference numeral 21 denotes a semiconductor laser, and reference numeral 22 denotes an optical wavelength conversion element. The semiconductor laser 21 used here has a wavelength of 0.84 μm. Also,
The light wavelength conversion element 22 is obtained by performing proton exchange in phosphoric acid on a LiNbO ₃ substrate to form a domain-inverted layer 3 and an optical waveguide 2. In the configuration of this embodiment, the semiconductor laser 2
The formation surface 24 of the active layer 23 and the formation surface 25 of the optical waveguide 2 of the optical wavelength conversion element 22 face the submount 20. The active layer 23 of the semiconductor laser 21 and the optical waveguide 2 are coaxial and have a configuration in which the fundamental wave P1 of the semiconductor laser 21 is directly coupled. In this embodiment, a copper block is used as the second submount 28 for heat radiation of the semiconductor laser 21. For this reason, the heat of the semiconductor laser 21 escapes to the second submount 28 and is not transmitted to the quartz submount 20 having poor heat radiation. First, the back surface 29a of the semiconductor laser 21 (the surface opposite to the surface 24 on which the active layer 23 is formed) was bonded to the second submount 28. Next, the optical wavelength conversion element 22 was fixed to the submount 20 and pressed. The length of this fabricated element is 8 mm. When a semiconductor laser beam (wavelength 0.84 μm) was guided from the incident surface 10 as the fundamental wave P1, it propagated in a single mode, and a harmonic P2 having a wavelength of 0.42 μm was extracted from the emission surface 12 to the outside of the substrate. Since the emission surface is AR-coated with respect to the fundamental wave and the harmonics, the output of the harmonics can be effectively taken out and the output can be increased by 15%. A harmonic of 5 mW at a fundamental wave of 70 mW (wavelength 0.42 μm)
m) was obtained. Also, since the reflected light was greatly reduced, the semiconductor laser operated stably, and the fluctuation of the harmonic output was ± 3.
% Or less.

In the multi-mode propagation with respect to the fundamental wave, the output of the higher harmonic wave is unstable and not practical. On the other hand, if the distance between the semiconductor laser and the optical wavelength conversion element is 30 μm or more, the coupling efficiency becomes small, which is not practical.

As a fifth embodiment, a short wavelength laser light source according to the present invention will be described with reference to the drawings. FIG. 7 shows a structural diagram of a short wavelength laser light source according to a fifth embodiment of the present invention. In this embodiment, a semiconductor laser having a wavelength of 0.79 μm is used as a short wavelength laser light source, and a KTP (KTiOPO ₄ ) substrate is used as an optical wavelength conversion element. FIG. 7 is a sectional view of the short wavelength laser light source. KTP is characterized by being resistant to optical damage. In FIG. 7, reference numeral 20 denotes a Si submount, 21 denotes a semiconductor laser,
Is an optical wavelength conversion element. The incident surface 10 of the light wavelength conversion element 22 is formed at an angle of 45 degrees by polishing. The light wavelength conversion element 22 is arranged perpendicular to the semiconductor laser 21. The optical wavelength conversion element 22 is obtained by performing ion exchange on a KTP substrate to form a domain-inverted layer 3 and an optical waveguide 2. The fundamental wave P1 emitted from the semiconductor laser 21 is totally reflected by the incident surface 10 and enters the optical waveguide 2. The wavelength converter 26 that converts the fundamental wave into a harmonic wave is not in contact with the submount 21 and is thermally cut off. The semiconductor laser 21 (wavelength 0.79 μm) emitted from the active layer 23 as the fundamental wave P1 by driving the semiconductor laser 21
m) from the incident surface 10 of the optical wavelength conversion element 22 to the optical waveguide 2
When coupled directly, the fundamental wave P1 propagates in a single mode, and the wavelength conversion section 26 in the optical waveguide 2 has a wavelength of 0.395 μm.
The light is converted into an ultraviolet harmonic P2 of m and is extracted from the emission surface 12 to the outside of the substrate.

Next, the configuration of a laser light source according to the present invention, which is a sixth embodiment, will be described with reference to FIG. FIG. 8 shows a configuration diagram of the short wavelength laser light source of the present invention. The laser light source basically includes a Si submount 20, a semiconductor laser 21, and an optical wavelength conversion element 22 in which an optical waveguide is formed. A grating 7 of Ta ₂ O ₅ is formed on the optical waveguide 2 of the optical wavelength conversion element 22. Submount 2
Light P1 emitted from the semiconductor laser 21 fixed to 0
Is directly introduced into the optical waveguide 2. A tapered optical waveguide 9 is formed in the input section to improve the likelihood of alignment. The Si submount is slanted for heat dissipation. Thereby, heat is not transmitted to the wavelength conversion unit 26.

The fundamental wave P1 entering the optical waveguide 2 is partially reflected by the grating 7 and is returned to the semiconductor laser. Therefore, the semiconductor laser oscillates at a wavelength determined by the period of the grating 7 and the refractive index of the substrate.

The optical waveguide 2 was manufactured by proton exchange in pyrophosphoric acid. Hereinafter, a method for producing a domain-inverted layer, an optical waveguide, and a grating on a substrate will be described. First, the domain-inverted layer 3 is formed. 20nm thick Ta on LiTaO ₃ substrate,
After sputter deposition, Ta is patterned in a periodic manner using a normal photo process and dry etching. LiTaO ₃ substrate patterned with Ta
Immersion at 0 ° C. for 20 minutes to perform proton exchange to form a proton exchange layer. Thereafter, heat treatment is performed at a temperature of 540 ° C. for 20 seconds. As a result, a periodic domain-inverted layer having a thickness of 2 μm is formed. Next, the tapered optical waveguide 9 is formed. After Ta is sputter-deposited on a LiTaO ₃ substrate to a thickness of 20 nm, the Ta is patterned using a normal photo process and dry etching. To form a tapered optical waveguide, a part of the LiTaO ₃ substrate on which a pattern of Ta was formed was heated at 260 ° C and 5 ° C in pyrophosphoric acid.
Soak for 0 minutes, perform proton exchange, and place
A proton exchange layer serving as a 1.2 μm tapered optical waveguide is formed. Thereafter, heat treatment is performed at a temperature of 420 ° C. for 20 minutes. Thereby, a 5 μm-thick tapered optical waveguide is formed. Further, in order to form the optical waveguide 2, 260 ° C.
Proton exchange for 2 minutes, 0.5μm thickness just under the slit
After forming the proton exchange layer, heat treatment is performed at 420 ° C. for 1 minute. Next, a film of Ta ₂ O ₅ is formed with a thickness of 30 nm. Next, using photolithography and dry etching, Ta ₂ O ₅
Is formed. This is grating 7
Becomes The grating period is 0.8 μm, which is four times the primary period of 0.2 μm. Thus, the period is 1
Any integer multiple of the next period can be used. Finally, an incoming / outgoing surface is formed by polishing. The optical waveguide 2 has a thickness of 1.9
μm, and the length is 5 mm. The reflectivity of the grating is 10%. With this amount of reflection, the wavelength can be sufficiently stabilized.

Next, bonding is performed on a submount 20 made of Si having a length of 10 mm with the active layer 23 side of the semiconductor laser 21 facing down. The submount 20 is partially tapered by polishing. While the semiconductor laser is illuminated with the lead wire, the optical wavelength conversion element 22 having the optical waveguide formed thereon is bonded at a position where the fundamental wave P1 emitted from the optical waveguide is maximized. Through the above steps, a compact short-wavelength laser light source was manufactured. 5m with 50mW fundamental wave
A harmonic of W (wavelength 0.42 μm) was obtained. Further, since the wavelength of the semiconductor laser was locked by the grating, the semiconductor laser operated stably and the fluctuation of the harmonic output was ± 1% or less.

The light incident method may be a structure via a lens other than the direct coupling. Further, although Si is used as the submount, any other material having good thermal conductivity such as Cu or C may be used. In the examples, LiNbO ₃ and
Although LiTaO ₃ is used, the present invention can be applied to a ferroelectric material such as KNbO _{3 and} an organic nonlinear material such as MNA.

Next, as a seventh embodiment, an example in which the short-wavelength laser light source of the present invention is incorporated in an optical information recording apparatus and applied to reading of an optical disk will be described. FIG. 9 shows the configuration. In the present embodiment, the optical information recording device includes a short wavelength laser light source, a lens, a polarizing beam splitter, and a light receiver. The fundamental wave P1 emitted from the semiconductor laser 21 in the short-wavelength laser light source 60 is converted into a higher harmonic P2 by the light wavelength conversion element 22, and emitted to the outside as blue laser light, which is the higher harmonic P2. This blue laser light P2 is
To make parallel light. After passing through the polarization beam splitter 41, the harmonic P2 converted into parallel light is condensed by the focusing lens 42 and forms a 0.6 μm spot on the optical disk 43. The reflected signal again passes through the polarization beam splitter 41 and then enters the light receiver 45. The short-wavelength laser light source 60 emitted blue laser light P2 of 2 mW, which was used for reading an optical disk. The drive current was increased and writing was performed with a 10 mW blue laser beam. Here, the short-wavelength laser light source was stable against vibration and temperature change and operated stably.

As an eighth embodiment, a short wavelength laser light source according to the present invention will be described with reference to FIG. FIG. 10 shows a structural diagram of a short wavelength laser light source according to an eighth embodiment of the present invention. In this embodiment, a 0.8 μm band semiconductor laser is used as a short wavelength laser light source, and a LiTaO ₃ substrate is used as an optical wavelength conversion element. FIG. 10 shows the center of the optical waveguide of the short wavelength laser light source parallel to the optical waveguide forming surface. FIG. 21 is a semiconductor laser, 22 is an optical wavelength conversion element, 2 is an optical waveguide, 2
Reference numeral 6 denotes a wavelength converter. The wavelength converter 26 is formed of a bent optical waveguide, and is concentric with the semiconductor laser 21 as a heat source and has a constant temperature. Therefore, conversion to harmonics can be performed stably.

When a domain-inverted structure is used, high-efficiency, high-output short-wavelength light can be generated as shown in the embodiment. The disadvantage of the narrow allowable temperature range can be solved by thermal isolation from the semiconductor laser as in the present invention.

As described above, by using the short wavelength laser light source of the present invention, it is possible to narrow the spot to half of the reading system of an optical information recording apparatus using a 0.8 μm band semiconductor laser conventionally used. The recording density of the optical information recording device can be improved to four times the conventional value.

[0042]

As described above, according to the short wavelength laser light source of the present invention, the coupling efficiency can be greatly improved by directly coupling the semiconductor laser and the high-efficiency optical wavelength conversion element without using a lens. Heat generated from the semiconductor laser is prevented from being transmitted to the wavelength conversion section of the optical wavelength conversion element, and the output and stability of the short wavelength laser light source are greatly improved. Furthermore, the rising characteristics are also excellent, and the industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a first embodiment of a short wavelength laser light source according to the present invention.

FIG. 2 is a temperature distribution diagram of the short wavelength laser light source of the present invention.

FIG. 3 is a structural diagram of a second embodiment of the short wavelength laser light source according to the present invention.

FIG. 4 is a characteristic diagram of the ambient temperature and the harmonic output of the short wavelength laser light source of the present invention.

FIG. 5 is a structural diagram of a third embodiment of the short wavelength laser light source according to the present invention.

FIG. 6 is a structural view of a short-wavelength laser light source according to a fourth embodiment of the present invention.

FIG. 7 is a structural view of a short-wavelength laser light source according to a fifth embodiment of the present invention.

FIG. 8 is a structural view of a short wavelength laser light source according to a sixth embodiment of the present invention.

FIG. 9 is a configuration diagram of an optical information processing apparatus according to a seventh embodiment of the present invention.

FIG. 10 is a structural diagram of an eighth embodiment of the short wavelength laser light source according to the present invention.

FIG. 11 is a configuration diagram of a conventional short wavelength laser light source.

FIG. 12 is a configuration diagram of a conventional short wavelength laser light source.

FIG. 13 is a configuration diagram of a conventional optical wavelength conversion element.

FIG. 14 is a diagram illustrating the principle of harmonic amplification.

FIG. 15 is a temperature distribution diagram of a conventional short wavelength laser light source.

[Explanation of symbols]

 Reference Signs List 2 optical waveguide 3 domain-inverted layer 4 non-domain-inverted layer 7 grating 8 groove 9 tapered optical waveguide 10 incident surface 12 emission surface 15 electrode 15a thin-film heater 17 protective film 20 submount 21 semiconductor laser 22 optical wavelength conversion element 23 active layer 26 wavelength Conversion unit 40, 42, 44 Lens 41 Beam splitter 45 Si detector 50 Package 51 Window 60 Short wavelength laser light source

Continuation of the front page (56) References JP-A-63-301582 (JP, A) JP-A-50-29282 (JP, A) JP-A-4-181928 (JP, A) JP-A-1-297632 (JP) JP-A-64-32206 (JP, A) JP-A-4-84481 (JP, A) JP-A-4-9830 (JP, A) JP-A-5-127208 (JP, A) 5-19310 (JP, A) JP-A-2-101438 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (3)

(57) [Claims] 1. A short wavelength laser light source comprising a semiconductor laser and an optical wavelength conversion element on a submount, wherein a fundamental wave of the semiconductor laser is directly coupled to an optical waveguide of the optical wavelength conversion element. The formation surface and the optical waveguide formation surface of the optical wavelength conversion element face the submount, and a groove or a tapered part is formed in the submount immediately below the wavelength conversion part of the optical wavelength conversion element. A non-contact short-wavelength laser light source. 2. A short wavelength laser light source comprising a semiconductor laser and an optical wavelength conversion element on a submount, wherein a fundamental wave of the semiconductor laser is directly coupled to an optical waveguide of the optical wavelength conversion element. A short-wavelength laser light source, wherein the surface on which the optical wavelength conversion element is formed and the optical waveguide formation surface of the optical wavelength conversion element face the submount, and the wavelength conversion section of the optical wavelength conversion element is equidistant from the semiconductor laser in the length direction. . 3. A short wavelength laser light source comprising a semiconductor laser and an optical wavelength conversion element on a submount, wherein a fundamental wave of the semiconductor laser is directly coupled to an optical waveguide of the optical wavelength conversion element. A short-wavelength laser light source, wherein an optical wavelength conversion element is disposed at a right angle, and a surface on which an active layer of the semiconductor laser is formed faces a submount.