JP3156444B2 - Short wavelength laser light source and method of manufacturing the same - 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 and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 10 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). The semiconductor laser 2 is placed on the incident surface 10 of the optical waveguide 2 formed on the optical wavelength conversion element 22.
The fundamental wave P1 from 1 is incident via the lenses 37a and 37b. At this time, the half-wave plate 33 sandwiched between the lenses 37a and 37b has a function of rotating the polarization direction by 90 degrees, and thereby the polarization directions are matched so that the fundamental wave P1 is guided through the optical waveguide 2. be able to. 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 its operation will be described. The harmonic generation (wavelength 0.42 μm) with respect to the fundamental wave having a wavelength of 0.84 μm will be described in detail below (T. Taniuchi and K. Yamamoto, “Second harmonic gen
eration by Cherenkov radiation in proton-exchanged
LiNbO ₃ optical waveguide ", CLEO'86, WR3, 1986,
reference).

[0003] 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 of the guided mode of the fundamental wave is equal to the effective refractive index of the higher harmonic wave is satisfied, the optical waveguide 2
, The light of the harmonic P2 is efficiently emitted 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 prior art short wavelength laser light source which is further miniaturized will be described with reference to FIG. 11 (Yamamoto, Taniuchi, Japanese Patent Application No. 63-128914, blue laser light source and optical information recording apparatus, reference). 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 formed on an X plate are fixed to a Si submount 20 and directly coupled. The output P1 of the semiconductor laser 21 is set to 10
At 0 mW, a harmonic P2 (blue laser light) of 2 mW was obtained. In this case, the conversion efficiency P2 / P1 in the light wavelength conversion element 22 is 2%. However, it was difficult to obtain a practical 10 mW in the optical information processing field using 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 blue light of 10 mW or more (K. Yamamot).
o, K. Mizuuchi, Y. Kitaoka, and M. Kato: Applied Physi
cs Letters, May 1993). Therefore, if an optical wavelength conversion element using a domain-inverted structure is directly coupled to a semiconductor laser, there is a possibility that a short wavelength light source that is compact and mass-produced can be manufactured.

Hereinafter, this optical wavelength conversion element will be described. FIG. 12 shows the configuration of the optical wavelength conversion element formed on the LiTaO ₃ Z plate. As shown in FIG. 12, 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, the principle of harmonic amplification will be described with reference to FIG. 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 3
2a, as shown in FIG. 13, the harmonic output increases in proportion to the square of the length L of the optical waveguide. 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 when the period Λ1 of the domain-inverted layer is λ / (2 (N2
ω−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]

When a high-efficiency optical wavelength conversion element having a domain-inverted structure is used in a small-sized and light-weight short-wavelength laser light source by directly coupling a semiconductor laser and an optical waveguide as described above, light wavelength conversion is performed. Since the element is formed on the Z plate, the mode guided in the optical waveguide is TM polarized light (the electric field is perpendicular to the surface on which the optical waveguide is formed), and the mode is emitted from the semiconductor laser. The polarization of the fundamental wave is T
E-polarized light (electric field is parallel to the surface on which the active layer is formed).

FIG. 14 shows (a) a semiconductor laser cut along a plane perpendicular to the traveling direction of light, (b) an optical wavelength conversion element of a Z plate,
(c) A cross-sectional view and a polarization direction of the light wavelength conversion element of the X plate are shown. As shown in FIG. 14, the output light of the semiconductor laser and Z
Since the directions of polarization of the guided light of the optical wavelength conversion element of the plate are different by 90 degrees, coupling on the same plane as in the short wavelength laser light source shown in FIG. 11 cannot be performed. When an element having a domain-inverted structure is formed on the X-plate, the polarization is the same, but the conversion efficiency of the light-wavelength conversion element on the X-plate is extremely low. The reason will be described in detail below.

[0010] The optical waveguide formed on the X plate has a surface, which is the X plane, roughened during proton exchange, so that the propagation loss is about five times that of the Z plate. Further, it is difficult to produce a domain-inverted structure in a short period. As a result, the conversion efficiency of the light wavelength conversion element becomes about 1/5 to 1/10 of that of the Z plate. For this reason, there is a problem that it is difficult to obtain a harmonic having a practical level of a short wavelength laser light source of 10 mW or more with good reproducibility and stably.

The present invention makes it possible to increase the output power and stabilize the output power of harmonics by adding a new device to the structure of a short wavelength laser light source based on a semiconductor laser and an optical wavelength conversion element. . In other words, an object of the present invention is to obtain a short-wavelength laser light source that can operate stably with high output by directly coupling a semiconductor laser and an optical wavelength conversion element via a half-wave plate.

[0012]

Therefore, a short wavelength laser light source according to the present invention comprises a semiconductor laser and an optical wavelength conversion element on a submount, and an optical waveguide in which a fundamental wave of the semiconductor laser is formed in the optical wavelength conversion element. In the short-wavelength laser light source that is converted into harmonics in the semiconductor laser, the surface on which the active layer of the semiconductor laser is formed and the surface on which the optical waveguide is formed of the optical wavelength conversion element face a submount having birefringence, and the semiconductor laser A projection formed on the submount is arranged between the optical wavelength conversion element and the optical wavelength conversion element, and the fundamental wave has a means in which the polarization direction is rotated by 90 degrees by the projection and coupled to the optical waveguide.

[0013] Also, short wavelength laser light source of the present invention includes a semiconductor laser and an optical wavelength conversion element on a submount, the short-wavelength laser light source fundamental wave of the semiconductor laser is directly coupled to the optical waveguide, wherein The active layer forming surface of the semiconductor laser and the optical waveguide forming surface of the optical wavelength conversion device face the submount, and the incident surface of the optical waveguide has a polarization direction of the fundamental wave from the semiconductor laser of 90 degrees.
A film having a birefringence that rotates by an angle is formed, and has means for coupling a fundamental wave from the semiconductor laser to the optical waveguide through the film.

The method of manufacturing a short-wavelength laser light source according to the present invention is directed to a method of manufacturing a short-wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a higher harmonic in an optical waveguide formed in an optical wavelength conversion element. Forming a protrusion on the submount having birefringence, fixing the active layer forming surface of the semiconductor laser and the optical waveguide forming surface of the optical wavelength conversion element facing the submount, and Arranging the wave so as to be coupled to the optical waveguide through a protrusion formed on the submount.

The method of manufacturing a short-wavelength laser light source according to the present invention is a method of manufacturing a short-wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a harmonic in an optical waveguide formed in an optical wavelength conversion element. Forming a film having a birefringent property in which the polarization direction of the fundamental wave from the semiconductor laser rotates by 90 degrees on the incident surface of the optical waveguide; and forming the active layer of the semiconductor laser and the light guide of the optical wavelength conversion element. Fixing the waveguide so that the fundamental wave emitted from the semiconductor laser is coupled to the optical waveguide, with the wave path forming surface facing the submount.

The method of manufacturing a short-wavelength laser light source according to the present invention is a method of manufacturing a short-wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a higher harmonic in an optical waveguide formed in an optical wavelength conversion element. Forming a film having birefringence on the incident surface of the optical waveguide, forming a film having birefringence on the emission surface of the fundamental wave of the semiconductor laser, and forming the active layer of the semiconductor laser And fixing the optical waveguide forming surface of the optical wavelength conversion element so as to face the submount and couple the fundamental wave emitted from the semiconductor laser to the optical waveguide, and the birefringence formed on the incident surface of the optical waveguide. And bonding the film having birefringence formed on the emission surface of the semiconductor laser by annealing.

[0017]

According to the present invention, it is possible to use the optical wavelength conversion element formed on the Z plate by the above-mentioned means, and it is possible to increase the generated harmonics with high efficiency. Hereinafter, this will be described in detail.

An optical wavelength conversion element having a Z-plate polarization inversion structure can obtain higher harmonic power than the X-plate by 5 times or more. In order to couple the high-efficiency optical wavelength conversion element with the semiconductor laser, the fundamental wave of the semiconductor laser is rotated by 90 degrees by the protrusion of the submount, and is incident on the optical waveguide with high efficiency. This is because the protrusions have birefringence, and the polarization direction can be rotated by arranging the main axis at 45 degrees with respect to the polarization direction. Therefore, a high output harmonic can be emitted even as a short wavelength laser light source.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment, a short wavelength laser light source of the present invention will be described with reference to FIG. FIG. 1 shows a structural diagram of a short wavelength laser light source according to a first embodiment of 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 Z plate LiTaO ₃ substrate is used as an optical wavelength conversion element. FIG. 1 is a sectional view of the short wavelength laser light source. FIG.
Reference numeral 20 denotes a submount made of LiNbO ₃ , 21 denotes a semiconductor laser, and 22 denotes an optical wavelength conversion element. LiNbO ₃ is a material having a large birefringence, and the difference between the extraordinary refractive index and the ordinary refractive index is 0.08.
There is also. The semiconductor laser 21 used here has a wavelength of 0.84.
μm. The light wavelength conversion element 22 is made of LiTaO ₃
In this example, a domain-inverted layer 3 and an optical waveguide 2 are formed on a substrate by proton exchange in phosphoric acid.

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 active layer 23 of the semiconductor laser 21 and the optical waveguide 2
Is coaxial and the fundamental wave P1 of the semiconductor laser 21 is the projection 1
Directly connected via the The fundamental wave P1 from the semiconductor laser generated as TE polarized light by the projection 1 is 9
The optical waveguide is rotated by 0 degrees and coincides with the TM polarized light that can be guided, and is coupled with high efficiency. In this embodiment, a copper block is used as the second submount 28 for heat radiation of the semiconductor laser 21. For this reason, all the heat of the semiconductor laser 21 escapes to the second submount 28 and is not transmitted to the submount 20 of LiNbO _{3 having} poor heat radiation.

Next, a method of manufacturing the short wavelength laser light source will be described with reference to FIG. First, in FIG. 2A, a LiNbO ₃ submount 20 is 5.4 μm wide and 10 μm deep by a normal photo process and dry etching process.
The projection 1 was formed. LiNbO ₃ used was obtained by inclining an X plate by 45 degrees in the C direction. Next, in FIG.
1 was bonded with the formation surface 24 of the active layer 23 facing the submount 20 side. 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) is bonded to the second submount 28. Next, after a current is applied to the semiconductor laser 21 to emit a fundamental wave P1 in FIG.
The optical wavelength conversion element 22 was pressed against the semiconductor laser 21 with the substrate facing the sub-mount 20 side, and was fixed. At this time, the incidence surface 10 of the optical wavelength conversion element 22 is formed on the formation surface 25 of the optical waveguide 2.
Is approximately 90 degrees. Further, the amount of light returning to the active layer 23 due to reflection on the incident surface 10 can be reduced. Al was patterned on the submount 20 in advance, and a current was able to flow by contacting the semiconductor laser. When fixed, the alignment in the direction A was performed so that the harmonic output P2 was maximized. In the direction B, an SiO ₂ protective film 17 was added to the optical waveguide 2, and the height was adjusted to the active layer 23.

The length of the manufactured element is 10 mm. Semiconductor laser light (wavelength 0.84 μm) as the fundamental wave P1
When m) was guided from the incident surface 10, it propagated in 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%. Fundamental wave 7
A harmonic of 10 mW (wavelength: 0.42 μm) was obtained at 0 mW. FIG. 3 shows the time change of the harmonic. The semiconductor laser operated stably and the fluctuation of the harmonic output was less than ± 1%. The stability is greatly improved as compared with a short wavelength light source using a conventional lens.

In multi-mode propagation with respect to the fundamental wave, the output of the higher harmonic wave is unstable and not practical. When the distance between the semiconductor laser and the light wavelength conversion element is 20 μm or more, the coupling efficiency becomes small and is not practical. However, if a material having a large birefringence is selected, the width of the protrusion can be reduced, and there is no problem.

FIG. 4 is a structural view of a second 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. 4 is a cross-sectional view of the short wavelength laser light source. In FIG. 4, reference numeral 20 denotes a Si submount, 21 denotes a semiconductor laser, 22 denotes an optical wavelength conversion element, and 6 denotes a half-wave plate. The half-wave plate 6 was polished from the X plate LiNbO ₃ to have a thickness of 16 μm. The main axis of the half-wave plate 6 was fixed at an angle of 45 degrees with respect to the TE polarized light. This thickness is 3/2
Although it becomes a wave plate, the operation is the same as that of a half-wave plate. Since it is difficult to reduce the thickness to 5 μm by polishing, a 3/2 wavelength plate was used. 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 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 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 FIG. 4, 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 transmitted from the incident surface 10 of the optical wavelength conversion element 22 through the half-wave plate 6 to the optical waveguide 2. When coupled directly to the fundamental wave P1, the fundamental wave P1 propagates in a single mode, and the harmonic wave P having a wavelength of 0.42 μm is propagated by the wavelength converter 26 in the optical waveguide 2.
2, and the blue laser light is extracted from the emission surface 12 to the outside of the substrate.

In this short-wavelength laser light source, the semiconductor laser 21 was driven at 150 mW to obtain a harmonic P2 (wavelength 0.42 μm) of 10 mW. The conversion efficiency in this case is 7%. The rise was within 10 seconds and the harmonic output was stable. Here, the polarization direction was completely rotated by 90 degrees by the half-wave plate, and the coupling efficiency to the optical waveguide was 80%.

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.

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 0.8 μm band semiconductor laser is used as a short wavelength laser light source, and a Z plate LiNbO 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 0.86 μm.
m and an output of 100 mW. The light wavelength conversion element 22 is obtained by forming a periodically poled layer 3 and an optical waveguide 2 on a LiNbO 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 configuration of this embodiment, the surface 24 on which the active layer 23 of the semiconductor laser 21 is formed and the light wavelength conversion element 2
The formation surface 25 of the second optical waveguide 2 faces 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. Here, a birefringent film 5 serving as a half-wave plate is formed on the light wavelength conversion element 22. The wavelength converter 26 for converting a fundamental wave into a higher harmonic wave is not thermally in contact with the submount 21 because it is not in contact with the submount 21. Therefore, there is no influence of heat from the semiconductor laser 21. The semiconductor laser 21 is driven in FIG.
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 P 1 is polarized at 90 degrees by the birefringent film 5 Is rotated and propagates through the optical waveguide 2,
The light is converted into a harmonic P2 having a wavelength of 0.43 μm by the wavelength converter 26 in the optical waveguide 2 and blue laser light 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. 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 birefringent film 5 was formed on the incident surface 10 of the light wavelength conversion element 22. This will be described in detail with reference to FIG.

FIG. 6 shows an electron beam evaporation apparatus for forming a birefringent film. Forming surface 25 of optical waveguide 2 of optical wavelength conversion element
Is fixed to the jig 70 at an angle of 45 degrees. Crucible 7
The Ta ₂ O ₅ 72 placed in 1 is irradiated with an electron beam to evaporate it and obliquely deposit it on the incident surface 10. A Ta ₂ O ₅ film as a birefringent film having a thickness of 4 μm was formed. When the next step was fixed, the alignment in the direction A was performed by moving the optical wavelength conversion element 22 so that the harmonic output P2 was maximized. In a short wavelength laser light source using a conventional lens system, three of A, B, and C are used.
Axis alignment is required, but according to this configuration, A
Only alignment in the direction is sufficient. This is because the direction C is applied to the semiconductor laser, and the direction B does not require alignment because 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. It depends. In the direction B, an SiO ₂ protective film 17 was added to the optical waveguide 2, and the height was adjusted to the active layer 23. The height of the optical waveguide 2 from the surface of the submount 20 is 4 μm. The length of the optical wavelength conversion element is 8
mm.

In the short-wavelength laser light source manufactured as described above, the semiconductor laser 21 is driven at 100 mW and is driven at 20 mW.
(Wavelength 0.43 μm) was obtained. The conversion efficiency in this case is 20%. Here, the coupling efficiency was 80%, and the fundamental wave was incident on the light wavelength conversion element 22.

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.

FIG. 7 shows a configuration in which the short wavelength laser light source of the third embodiment is packaged. The 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. 52 is an optical wavelength conversion element 22 made of quartz.
This 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. In addition, by filling with nitrogen gas, deterioration of the antireflection film and the like due to oxidation in the air can be prevented, which is effective.

Next, a description will be given of a method of manufacturing a short wavelength laser light source according to a fourth embodiment of the present invention. Configuration is Example 3
Is the same as LiTaO ₃ was used as a substrate. In the present embodiment, the emission surface of the semiconductor laser and the incidence surface of the optical waveguide are WO
A birefringent film of ₃ was formed and bonded by annealing. FIG. 8 shows the manufacturing process. First, a birefringent film 5a is deposited on the emission surface of the semiconductor laser 21 by 2.5 μm. Next, an optical wavelength conversion element is manufactured. 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. After a Ta film having a thickness of 20 nm is sputter-deposited on a LiTaO ₃ substrate, the Ta film is periodically patterned using a normal photo process and dry etching. LiTaO ₃ substrate patterned with Ta
C., immersion 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. In order to further form the optical waveguide 2, in pyrophosphoric acid
Proton exchange is performed at 260 ° C. for 12 minutes to form a 0.5 μm-thick proton exchange layer immediately below the slit, and then heat-treated at 420 ° C. for 1 minute. Next, a film of Ta ₂ O ₅ is formed with a thickness of 300 nm. Next, an input / output surface is formed by polishing. The optical waveguide 2 has a thickness of 1.9 μm and a length of 5 mm. Finally, FIG.
As shown in (b), a birefringent film 5b made of WO _{3 which} is the same as that applied to a semiconductor laser by electron beam evaporation is formed on a 2.5 μm incident surface. Next, as shown in FIG. 3C, the active layer 2 of the semiconductor laser 21 is placed on a submount 20 made of Si having a length of 7 mm.
Bonding with the 3 side down. 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. Thereafter, annealing is performed at 200 ° C. for one hour to bond the birefringent films 5a and 5b. Thereby, reflection loss due to the air layer can be prevented.
Through the above steps, a compact short-wavelength laser light source was manufactured. A harmonic of 8 mW (wavelength 0.42 μm) was obtained at an incident fundamental wave of 50 mW. The short-wavelength laser light source 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 is also applicable to ferroelectric materials such as KTP (KTiOPO ₄ ) and KNbO ₃ and organic nonlinear materials such as MNA. LiNbO ₃ , Ta ₂ O ₅ , WO ₃
However, a dielectric such as Ti ₂ O ₅ , ZrO ₂ , Bi ₂ O ₃ , or CeO ₂ may be used.

Next, as a fifth embodiment, an example in which the short-wavelength laser light source of the present invention is incorporated in an optical information recording device and applied to reading and writing 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 incident on the light wavelength conversion element 22 via the birefringent film 5, and is turned on.
And is radiated to the outside as blue laser light, which is the harmonic P2. This blue laser light P2 is converted into parallel light by the lens 40. After passing through the polarization beam splitter 41, the harmonic P2 converted into parallel light is condensed by the focusing lens 42 and is collected on the optical disk 43 by 0.6 μm.
m spots. The reflected signal again passes through the polarizing 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.

When the domain-inverted structure is used, high-efficiency, high-output short-wavelength light can be generated as shown in the embodiment.

As described above, by using the short wavelength laser light source of the present invention, a 0.8 μm band semiconductor laser conventionally used was used.
As compared with the reading system of the optical information recording apparatus using the laser, the spot can be narrowed to half, and the recording density of the optical information recording apparatus can be improved to four times that of the conventional one.

[0040]

As described above, according to the short-wavelength laser light source of the present invention, the coupling efficiency is greatly improved by directly coupling the semiconductor laser and the high-efficiency optical wavelength conversion element using the Z plate without using a lens. At that time, the polarized light from the semiconductor laser is rotated by a birefringent projection or plate or film, and is incident on the optical waveguide formed on the optical wavelength conversion element with high efficiency, and the output of the short wavelength laser light source is significantly increased. improves. Further, the present invention can provide a short-wavelength laser light source which is compact and easily mass-produced, and has an extremely large industrial value.

[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 manufacturing process diagram of a first embodiment of the short wavelength laser light source according to the present invention.

FIG. 3 is a diagram showing the time dependence of the harmonic output of the short wavelength laser light source of the present invention.

FIG. 4 is a structural diagram of a second embodiment of the short wavelength laser light source according to 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 diagram showing a method for depositing a birefringent film according to a third embodiment of the short wavelength laser light source of the present invention.

FIG. 7 is a view showing a packaged structure of a third embodiment of the short wavelength laser light source according to the present invention;

FIG. 8 is a manufacturing process diagram of a fourth embodiment of the short wavelength laser light source according to the present invention.

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

FIG. 10 is a configuration diagram of a conventional short wavelength laser light source.

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

FIG. 12 is a configuration diagram of a conventional optical wavelength conversion element.

FIG. 13 is a diagram illustrating the principle of harmonic amplification.

FIG. 14 is a diagram showing a cross-sectional view and a polarization direction of a semiconductor laser and an optical wavelength conversion element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection 2 Optical waveguide 3 Polarization inversion layer 4 Non-polarization inversion layer 5 Birefringent film 6 Half-wave plate 10 Incident surface 12 Emission surface 17 Protective film 20 Submount 21 Semiconductor laser 22 Optical wavelength conversion element 23 Active layer 26 Wavelength conversion part 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-2-262385 (JP, A) JP-A-3-138992 (JP, A) JP-A-64-32206 (JP, A) JP-A-6-283791 (JP) JP-A-5-257184 (JP, A) JP-A-5-297429 (JP, A) JP-A-4-507299 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01S 3/094-3/0947 H01S 3/109 G02B 6/12-6/138 G02F 1/37-1/383

Claims (8)

(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 converted into a harmonic in an optical waveguide formed in the optical wavelength conversion element. Wherein the surface on which the active layer of the semiconductor laser is formed and the surface on which the optical waveguide is formed of the optical wavelength conversion element face a submount having birefringence, and the submount is provided between the semiconductor laser and the optical wavelength conversion element. A short-wavelength laser light source, wherein a polarization direction of the fundamental wave is rotated by 90 degrees by the projection and the fundamental wave is coupled to the optical waveguide. 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 the optical waveguide. The optical waveguide forming surface of the wavelength conversion element faces the submount, and the incident surface of the optical waveguide is formed with a film having birefringence in which the polarization direction of the fundamental wave from the semiconductor laser rotates 90 degrees, A short wavelength laser light source, wherein a fundamental wave from a semiconductor laser is coupled to an optical waveguide through the film. 3. A method for manufacturing a short wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a higher harmonic wave in an optical waveguide formed in an optical wavelength conversion element, wherein a projection is formed on a submount having birefringence. And fixing the surface on which the active layer of the semiconductor laser is formed and the optical waveguide forming surface of the optical wavelength conversion element facing the submount, and the fundamental wave from the semiconductor laser is formed on the submount. Arranging the short-wavelength laser light source so as to be coupled to the optical waveguide through the light source. 4. A method of manufacturing a short wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a higher harmonic wave in an optical waveguide formed in an optical wavelength conversion element. Forming a film having a birefringence in which the polarization direction of the fundamental wave rotates by 90 degrees, and facing the submount with the formation surface of the active layer of the semiconductor laser and the formation surface of the optical waveguide of the optical wavelength conversion element. Fixing the fundamental wave emitted from the laser beam so as to be coupled to the optical waveguide. 5. A method for manufacturing a short-wavelength laser light source in which a fundamental wave of a semiconductor laser is converted into a higher harmonic wave in an optical waveguide formed in an optical wavelength conversion element, wherein the incident surface of the optical waveguide has birefringence. Forming a film having a birefringence on an emission surface of the fundamental wave of the semiconductor laser, and forming a surface on which an active layer of the semiconductor laser is formed and an optical waveguide forming surface of an optical wavelength conversion element. A step of fixing the fundamental wave emitted from the semiconductor laser facing the submount so as to be coupled to the optical waveguide; and forming a birefringent film formed on the incident surface of the optical waveguide and the emission surface of the semiconductor laser. Bonding the formed film having birefringence by annealing. 6. The method for manufacturing a short wavelength laser light source according to claim 3, wherein the light wavelength conversion element has a domain-inverted structure. 7. A LiNb _x Ta _{1 -x} O as an optical wavelength conversion element.
6. The method of manufacturing a short wavelength laser light source according to claim _{3, wherein a} (0 ≦ X ≦ 1) substrate is used. 8. The method according to claim 7 , wherein a Z-plate is used as the substrate.