JP2001264832A - Short wavelength laser light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source having prolonged reliability in which the light-emitting surface does not deteriorate with respect to the laser beam having a wavelength of that of blue or less with high power density emitted from an optical wavelength transformation element, and to enhance the coupling efficiency of a semiconductor laser and an optical waveguide. SOLUTION: The short wavelength laser light source includes the optical wavelength transformation element 12 on which the optical waveguide 3 is formed, the semiconductor laser 11 and a sub mount 13. A fundamental wave from the semiconductor laser 11 is transformed into a higher harmonic within the optical waveguide 3. By covering an emitting portion 6 of the higher harmonic from the optical wavelength transformation element 12 by resin 4, the higher harmonic is greatly widenned in the emitting part 6 of the higher harmonic from the resin. Thereby, the power density of the emitting part of the higher harmonic lowers sharply, there is no adhesion of foreign particles and an adhesive, and thus long-term stabilization can be realized.

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 and the like, and more particularly to generation of wavelengths in a blue to ultraviolet region.

[0002]

2. Description of the Related Art In the field of optical information processing, a small-sized short-wavelength laser light source is required in order to realize a high-density optical disc and a high-definition laser printer. Techniques for achieving shorter wavelengths include semiconductor lasers,
There is a method using a second harmonic generation (hereinafter, referred to as “SHG”) technology using a quasi-phase matching (hereinafter, referred to as “QPM”) type wavelength conversion device using an optical waveguide (for example, , Yamamoto, and others: Optics Letters, Vol.16, No.15,
p.1156 (1991)).

FIG. 5 shows a schematic configuration diagram of a blue light source including a wavelength conversion device having a planar optical waveguide. In the configuration of FIG. 5, a tunable semiconductor laser having a distributed Bragg reflection (hereinafter, referred to as “DBR”) region is used as the semiconductor laser 11. In the following, DB
A wavelength tunable semiconductor laser having an R region is referred to as a “DBR semiconductor laser”. The DBR semiconductor laser 11 is, for example, a 100 mW-class AlGaAs-based DBR semiconductor laser in a 0.85 μm band, and includes an active layer region and a DBR region. By changing the amount of injection current injected into the DBR region, the oscillation wavelength of the DBR semiconductor laser 11 can be changed.

On the other hand, an optical wavelength conversion element 1 using an optical waveguide
Reference numeral 2 denotes a planar optical waveguide 3 formed on an X-plate MgO-doped LiNbO ₃ substrate and a periodic domain-inverted region. The waveguide forming surface of the DBR semiconductor laser 11 and the optical wavelength conversion element 12 is fixed on the submount 13, respectively. The submount 13 is fixed to the package 10.

[0005] The laser beam obtained from the light emitting end face of the DBR semiconductor laser 11 becomes a fundamental wave P1 and is directly transmitted to the optical wavelength conversion element 1 without using a coupling optical system such as a lens.
2 is coupled to the optical waveguide 3 formed. In particular,
By adjusting the positional relationship between the DBR semiconductor laser 11 and the optical wavelength conversion element 12 in the submount 13,
With respect to a laser output of about 100 mW from the semiconductor laser 11, a laser beam of a fundamental wave P 1 of about 60 mW is coupled to the optical waveguide 3. The optical wavelength conversion element 12 is a submount 1
3 is fixed using an ultraviolet curing adhesive. Furthermore, DB
By controlling the amount of current injected into the DBR region of the R semiconductor laser 11, the oscillation wavelength of the R
2 within the wavelength tolerance of phase matching. With such a configuration, a blue harmonic P having a wavelength of 425 nm is currently used.
2 are obtained at an output of about 15 mW.

[0006]

In such a short-wavelength laser light source, short-wavelength light of blue or less is generated from the emission end of the optical waveguide, so that the light energy is high and the power density is very high. ing. For example, if 15 mW is generated from the exit surface (10 μm ² ) of the optical waveguide, 150 kW / c
the m ² as high power. For this reason, the emission end face is deteriorated, which causes a serious problem in terms of long-term reliability.

Further, an optical wavelength conversion element 1 using an optical waveguide
2, the wavelength conversion efficiency of the short wavelength laser light source is proportional to the incident power of the fundamental wave into the optical waveguide of the optical wavelength conversion element, and the obtained optical power of the harmonic P2 is equal to that of the fundamental wave P1. It is proportional to the square of the incident power. Therefore, in order to obtain a wavelength conversion device exhibiting excellent operating characteristics,
It is essential to improve the coupling efficiency of the device to the optical waveguide and to reduce the variation between samples.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and one of the objects is to provide a high-power-density laser beam having a wavelength of blue or less emitted from an optical wavelength conversion element. Another object of the present invention is to provide a reliable light source for a long time without deteriorating the emission surface. Another is to improve the coupling efficiency between the semiconductor laser and the optical waveguide.

[0009]

In order to achieve the above object, a short wavelength laser light source according to the present invention includes an optical wavelength conversion element having an optical waveguide, a semiconductor laser, and a submount. The fundamental wave from is converted into a harmonic in the optical waveguide, the emission portion of the harmonic from the optical wavelength conversion element is covered with a resin, and the harmonic is spread at the emission portion of the harmonic from the resin. And This achieves the above object. In other words, a reliable light source can be provided in which dust and adhesive do not adhere to the end face. Further, in the present invention, the coupling portion between the semiconductor laser and the optical waveguide is configured to be covered with the resin. Thereby, the divergence angle from the semiconductor laser is reduced, and coupling with the optical waveguide is facilitated. A preferable divergence angle from the semiconductor laser is usually about 30 degrees, and preferably about 20 degrees.

[0010] Further, preferred resins for use in the light emitting portion include polycarbonate, epoxy, acrylate, and the like.
Polyimide, polymethyl methacrylate (PMMA) and the like.

In the short-wavelength laser light source according to the present invention, it is preferable that the emission part of the higher harmonic wave from the resin has a flat shape.

In the short-wavelength laser light source according to the present invention, it is preferable that the emission portion of the higher harmonic wave from the resin is formed in a lens shape.

In the short-wavelength laser light source according to the present invention, it is preferable that a coupling portion between the semiconductor laser and the optical waveguide is also covered with a resin.

In the short-wavelength laser light source according to the present invention, it is preferable that the wavelength of the harmonic is 430 nm or less.

In the short-wavelength laser light source according to the present invention, the power density of harmonics propagating in the optical waveguide is 20%.
It is preferably kW / cm ² or more.

[0016]

(Embodiment 1) As described above, in a short wavelength laser light source in which a semiconductor laser and an optical wavelength conversion element having an optical waveguide are integrated, the power density at the emission end of the harmonic is Becomes extremely large. According to experiments, it has been found that when the power is as high as 150 kW / cm ^{2 at} 425 nm, the solvent in the atmosphere is adsorbed by dust and adhesives, and the output characteristics are degraded.

In the first embodiment, in order to solve the above-mentioned problem, a short-wavelength laser light source 100 corresponding to forming a resin on an emission end face of an optical wavelength conversion element will be described. FIG. 1 shows a short wavelength laser light source 10 according to this embodiment.
FIG. 2 is a cross-sectional view showing a configuration of a zero.

In this configuration, the optical waveguide 3 is formed on a substrate made of a ferroelectric material, for example, a Mg-doped LiNbO ₃ substrate. A domain-inverted layer is formed periodically in the traveling direction of the optical waveguide 3, and constitutes the optical wavelength conversion element 12. More specifically, X-plate Mg-doped LiNbO ₃
A proton exchange planar optical waveguide 3 is formed on a substrate. On the surface, a periodically domain-inverted region having a period of 3.2 μm is formed in a direction orthogonal to the proton exchange planar optical waveguide 3. Further, a protective film 5 made of SiO ₂ is formed. A resin 4 is formed around the optical waveguide 3 so as to cover the emission part of the light wavelength conversion element 12. In addition, the emission section 6 of the resin 4 has a flat shape, and no aberration occurs with respect to harmonics. When the resin 4 was cured, it was held down by a Ni stamper, peeled off after curing, and a flat shape of the emission portion 6 from the resin was realized. Polycarbonate was used as the resin 4, but if it is transparent in this wavelength range, other epoxy resins,
Acrylate, polymid, polymethyl methacrylate (PMMA) and the like can be used.

Semiconductor laser 11 and optical wavelength conversion element 12
Are mounted on the Si submount 13 by junction down so that the active layer (junction) surface or the formation surface of the optical waveguide 3 is in contact with the Si submount 13. The position of the laser light emitting portion of the semiconductor laser 11 and the position of the optical waveguide 3 of the optical wavelength conversion element 12 using the planar optical waveguide are each set at a height of 5 μm from the surface of the Si submount 13 after mounting. Has been adjusted. The semiconductor laser 11 is a solder, an optical wavelength conversion element 12
Was fixed on the submount 13 with an adhesive. This was fixed to the package 10.

As described above, the short-wavelength laser light source 100 having the configuration shown in FIG. 1 is manufactured.

In the configuration of the short wavelength laser light source 100 according to the first embodiment, the fundamental wave P 1 obtained from the light emitting end face of the semiconductor laser 11 is coupled to the optical waveguide 3 of the optical wavelength conversion device 12. Specifically, the fundamental wave P from the semiconductor laser 11
The laser light of 60 mW was coupled to the optical waveguide 3 with respect to the laser output of 100 mW which is 1 (coupling efficiency of 60 mW).
%). The oscillation wavelength of the semiconductor laser 11 is changed to the light wavelength conversion element 1
By fixing the phase matching within the wavelength tolerance of 2, a harmonic P2 having a wavelength of 425 nm was obtained at about 15 mW, and wavelength conversion was realized.

FIG. 2 is a graph showing the long-term stability of the output of the short-wavelength laser light source according to the first embodiment of the present invention and the conventional short-wavelength laser light source not covered with resin. The light source of this embodiment is 1
It had a life of more than 10,000 hours and no deposits were found on the end face. On the other hand, in the conventional light source, outgas from the adhesive or the like adhered to the harmonic emission portion, and the output gradually decreased. 1
When 5 mW is generated from the emission surface (10 μm ² ) of the optical waveguide, the power becomes as high as 150 kW / cm ^2. However, as in the present embodiment, the harmonic P2 is extracted from the emission portion 6 from the resin, and this emission portion is obtained. In No. 6, the harmonic P2 is spread to a radius of about 300 μm, and the power density is reduced to about 5 W / cm ² . Attraction of the particles has a strong correlation with the power density, and thus could be dealt with by devising the emission part.

[0023] Since it is hardly observed above 430 nm, it is particularly effective for use at 430 nm or less. It is considered that the gas of the ultraviolet adhesive used for fixing the light wavelength conversion element acts particularly on a wavelength shorter than blue.

(Embodiment 2) In the present embodiment, not only the optical wavelength conversion element but also the joint with the semiconductor laser are covered with the resin. Embodiment 2 will be described.
FIG. 3 is a sectional view showing the configuration of the short wavelength laser light source 100 configured according to the present embodiment.

The basic structure of the short-wavelength laser light source 100 of the present embodiment is the same as that of the first embodiment, except that the joint between the semiconductor laser 11 and the optical waveguide 3 is also covered with resin. The divergence angle from the semiconductor laser is reduced to facilitate coupling to the optical waveguide 3.

In this example, a substrate made of a ferroelectric material, L
An optical waveguide 3 is formed on an iTaO ₃ substrate. A domain-inverted layer is formed periodically in the traveling direction of the optical waveguide 3, and constitutes the optical wavelength conversion element 12. More specifically, a proton exchange planar optical waveguide 3 is formed on a LiTaO ₃ substrate. Further, a periodically domain-inverted region having a period of 3.7 μm is formed in a direction orthogonal to the proton exchange planar optical waveguide 3. Furthermore, SiO ₂
Is formed.

Semiconductor laser 11 and optical wavelength conversion element 12
In either case, the Si submount 13 is junction-down so that the active layer (junction) surface or the planar optical waveguide forming surface is in contact with the Si submount 13.
Implemented in The laser light emitting portion of the semiconductor laser 11 and the optical wavelength conversion element 1 using the planar type optical waveguide
The positions of the two optical waveguides 3 are adjusted so as to be 3 μm above the surface of the Si submount 13 after mounting. The semiconductor laser 11 was fixed on the submount 13 with solder and the light wavelength conversion element 12 was fixed with an adhesive. Further, a resin 4 is formed so as to cover the optical wavelength conversion element 12 and the coupling portion between the semiconductor laser 11 and the optical waveguide 3. Further, the emission portion 6 of the resin 4 has a flat shape, and no aberration occurs with respect to the harmonic P2. When the resin 4 was cured, it was held down by a Ni stamper, peeled off after curing, and a flat shape of the emission portion 6 from the resin was realized.

As described above, the short-wavelength laser light source 100 having the configuration shown in FIG. 3 is manufactured.

In the configuration of the short wavelength laser light source 100 according to the second embodiment, the fundamental wave P 1 obtained from the light emitting end face of the semiconductor laser 11 is coupled to the optical waveguide 3 of the optical wavelength conversion device 12. Specifically, 100 m from the semiconductor laser 11
With respect to the laser output of W, 70 mW of laser light was coupled to the optical waveguide 3 (coupling efficiency 70%). Semiconductor laser 1
1 is fixed within the tolerance of the phase matching wavelength of the optical wavelength conversion element 12, so that the harmonic P having a wavelength of 425 nm is obtained.
2 was obtained at about 15 mW, and highly efficient optical coupling and wavelength conversion were realized.

The refractive index of the resin was 1.5, whereby the spread of light in the resin was reduced, and the coupling efficiency to the optical waveguide 3 μm away was greatly improved.

(Embodiment 3) In Embodiment 3, an example will be described in which a lens is formed at an emission portion in a case where a light wavelength conversion element is covered with a resin. FIG. 4 shows a cross-sectional view of the vicinity of the emission section of this embodiment. The basic configuration is the same as in the first embodiment. Here, the emission part 6 from the resin was formed in a lens shape.

The optical waveguide 3 is formed on a substrate made of a ferroelectric material, for example, a Mg-doped LiNbO ₃ substrate.
A domain-inverted layer is formed periodically in the traveling direction of the optical waveguide 3, and constitutes the optical wavelength conversion element 12. More specifically, a proton exchange planar optical waveguide 3 is formed on an X-plate Mg-doped LiNbO ₃ substrate. Also,
On the surface of the substrate 1, a proton exchange planar optical waveguide 3
A periodic domain-inverted region is formed in a direction orthogonal to. Further, a protective film 5 made of SiO ₂ is formed. In addition, a resin 4 is formed around the optical waveguide 3 so as to cover the emission part of the light wavelength conversion element 12. Also,
The emission part 6 of the resin 4 is in the form of a lens, and the harmonic P
2 can be emitted in parallel. When the resin 4 was cured, it was held down by a Ni stamper, peeled off after curing, and the lens shape of the exit portion 6 from the resin was realized.

In the configuration of the short wavelength laser light source 100 according to the third embodiment, the fundamental wave P 1 obtained from the light emitting end face of the semiconductor laser is coupled to the optical waveguide 3 of the optical wavelength conversion device 12. Specifically, a laser beam of 25 mW was coupled to the optical waveguide 3 with respect to a laser output of 50 mW from the semiconductor laser (coupling efficiency of 50%). By fixing the oscillation wavelength of the semiconductor laser within the tolerance of the phase matching wavelength of the optical wavelength conversion element 12, a harmonic P2 having a wavelength of 405 nm was obtained at about 4 mW, and wavelength conversion was realized.

By forming the lens shape by solidifying the resin, a function of simultaneously emitting parallel light is provided. The resin not only protects the end face, but also easily forms a lens and the like, thus making it possible to constitute an integrated optical module. In this embodiment, a lens is configured, but a diffractive element or the like may be used.

405 nm wavelength has high energy and 4 m
When W is generated from the exit surface (10 μm ² ) of the optical waveguide, 4
Although the power is as high as 0 kW / cm ² , as in the present embodiment, the harmonic P2 is extracted from the emission part 6 from the resin, and the emission part 6 has the harmonic P2 having a radius of about 1 mm.
Are spread, and the power density is reduced to about 1 W / cm ² . Attraction of the particles has a strong correlation with the power density, and thus could be dealt with by devising the emission part.

At a wavelength of 430 nm, 20 k
It was confirmed that the present invention was effective at W / cm ² or more.
That is, the power density of harmonics propagating in the optical waveguide is 20
In the case of kW / cm ² or more, the reliability is particularly remarkably improved and the effect is remarkable.

[0037]

As described above, according to the present invention, one of the reasons is that a stable short-wavelength laser light source free of dust and adhesive can be constituted. That is, when the harmonics are emitted from the emission surface of the optical waveguide, the power density becomes high. However, as in the present invention, the harmonics are extracted from the emission portion from the resin, and the harmonics are spread at the emission portion, and the power is increased. Density is decreasing. Attraction of the particles has a strong correlation with the power density, and thus could be dealt with by devising the emission part.
The other is to cover the coupling portion between the semiconductor laser and the optical waveguide with a resin so as to reduce the divergence angle from the semiconductor laser and facilitate coupling to the optical waveguide. As a result, highly efficient short-wavelength laser light can be stably extracted, and the effect is extremely large.

Further, according to the present invention, a lens and the like can be easily formed at the same time, and an integrated optical module can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a short wavelength laser light source according to a first embodiment of the present invention.

FIG. 2 is a graph showing long-term stability of the short-wavelength laser light source according to the first embodiment of the present invention and a conventional short-wavelength laser light source.

FIG. 3 is a sectional view showing a configuration of a short wavelength laser light source according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a short wavelength laser light source according to a third embodiment of the present invention.

FIG. 5 schematically shows an example of a conventional short wavelength laser light source.

[Explanation of symbols]

 Reference Signs List 3 optical waveguide 4 resin 5 protective film 6 resin emitting section 9 window 10 package 11 semiconductor laser 12 optical wavelength conversion element 13 submount 100 short wavelength laser light source P1 fundamental wave P2 harmonic

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshifumi Yokoyama 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 2K002 AB27 CA03 EA01 EA04 FA26 HA20 5F073 AB23 BA09 FA13 FA30

Claims (6)

[Claims] An optical wavelength conversion element having an optical waveguide formed therein;
A semiconductor laser, including a submount, a fundamental wave from the semiconductor laser is converted into a harmonic in the optical waveguide, and an emission portion of the harmonic from the optical wavelength conversion element is covered with a resin, A short-wavelength laser light source characterized in that harmonics are spread at an emission portion from a resin. 2. The short-wavelength laser light source according to claim 1, wherein an emission portion of the higher harmonic from the resin has a flat shape. 3. The short-wavelength laser light source according to claim 1, wherein an emission portion of the higher harmonic wave from the resin has a lens shape. 4. The short-wavelength laser light source according to claim 1, wherein a coupling portion between the semiconductor laser and the optical waveguide is also covered with a resin. 5. The short wavelength laser light source according to claim 1, wherein the wavelength of the harmonic is 430 nm or less. 6. The short-wavelength laser light source according to claim 5, wherein the power density of the harmonic propagating in the optical waveguide is 20 kW / cm ² or more.