JPH01149033A - Optical wavelength converting element - Google Patents

Abstract

PURPOSE:To eliminate fluctuation of the oscillation wavelength and to improve the emission efficiency of second higher harmonics by providing an antireflection film for fundamental wave on an incidence face crossing one face of a first substrate and providing an antireflection film for second higher harmonics on the emission face of a second substrate. CONSTITUTION:An antireflection film 4 for fundamental wave is provided on an incidence face 1c crossing one face of a first substrate 1 on which an optical waveguide is formed, and an antireflection film 7 for second higher harmonics is provided on an emission face 5b of a second substrate 5. The other face 1b opposite to one face where the optical waveguide is formed of the first substrate 1 and a face 5a crossing the emission face 5b of the second substrate 5 are put one over the other so that second higher harmonics 6 whose phase is matched to the fundamental wave propagated in the optical waveguide are taken out in the second substrate 5 and are emitted from the emission face 5b. Thus, a stable oscillation wavelength is obtained and an optical wavelength converting element having a high emission efficiency of second higher harmonics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical wavelength conversion element for a laser light source. Possible fields of application include laser application fields such as optical discs, laser printers, and facsimiles.

2. Description of the Related Art Conventionally, the optical wavelength conversion element of this plate has an equal configuration as shown in FIG. In Figure 3, 11 is the thickness 9.411
A first substrate made of lithium niobate No. 1, on its upper surface 11a, a leading waveguide 12 having a width of 1 μm and a thickness of 0.5 μm is formed over a length of 1 cIIL by an ion exchange method,
The lower surface 11b is mirror-polished and is in close contact with the mirror-polished upper surface 13m of the second substrate 13. This second substrate 13 is also made of lithium niobate, and its upper surface 138
The end faces on both sides intersecting with each other are also mirror polished and have a thickness of 25 mm. When the semiconductor laser beam 14 having a wavelength of 0.84 μm, which is a fundamental wave, is made to enter the optical waveguide 12 from the incident surface 11c of the end surface on one side that intersects the upper surface 11a of the first substrate 11,
While the fundamental wave passes straight through the leading wave path 12, phase matching occurs within the leading wave path 12, and the wavelength is 0.42.
The second harmonic wave 15 of μm has a predetermined angle, is taken out to the second substrate 13 without sensing the mirror surface, travels straight, and is emitted from the output surface 13b on the other end surface of the second substrate 13. .

Problems to be Solved by the Invention In such a conventional configuration, when the semiconductor laser beam 14 enters the optical waveguide 12, the incident surface 1 of the first substrate 11
There was a problem in that a part of the fundamental wave semiconductor laser light 14 was reflected at 1c and turned into returned light, which caused a change in the secondary mode of the semiconductor laser, causing the oscillation wavelength to fluctuate. Also, the second
When the harmonics 15 are emitted from the emitting surface 13b of the second substrate 13, a portion thereof is reflected by the emitting surface 13b, resulting in a problem in that the emitting efficiency is reduced.

The present invention is intended to solve these problems, and aims to provide an optical wavelength conversion element that can obtain a stable oscillation wavelength and has good second harmonic output efficiency.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a first substrate having an optical waveguide formed on one surface, and a reflection surface for the fundamental wave on the incident surface intersecting the one surface. an anti-reflection film for a second harmonic wave is provided on the output surface of the second substrate, the other surface of the first substrate facing the one surface on which the leading waveguide is formed; A surface of a second substrate that intersects with the output surface is superimposed, and a second harmonic that is phase-matched with the fundamental wave propagating through the optical waveguide is extracted into the second substrate, and a second harmonic wave that is phase-matched with the fundamental wave propagating through the optical waveguide is extracted from the output surface of the second substrate. It is constructed in such a way that it emits light.

Effect With the above configuration, when the semiconductor laser light enters the optical waveguide from the entrance surface of the first substrate, the second harmonic wave that is phase-matched with the fundamental wave is extracted into the second substrate and is emitted from the exit surface of the semiconductor laser beam. In this case, the incident surface of the first substrate is provided with an antireflection film, so that the reflected light does not return to the semiconductor laser, and the oscillation wavelength of this semiconductor laser is stabilized. Further, by providing an antireflection film on the output surface of the second substrate, loss due to reflection of the second harmonic on the output surface is reduced, and output efficiency of the second harmonic is increased.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a sectional view of an optical wavelength conversion element showing one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a first substrate made of lithium niobate with a thickness of 0. This first substrate 1
The upper surface 1a and the lower surface 1=b are each mirror-polished, and a Ta layer with a thickness of 3001° is applied to the upper surface 1a by sputtering.
A thin film of
After that, a pattern with a thickness of 2 μm was exposed and developed, and then T by dry etching was applied.
By forming a pattern a and treating this first substrate 1 with birophosphoric acid at 200°C for 14 minutes, a proton exchange layer with a thickness of 0.3 μm is formed on the first substrate l, and a proton exchange layer is formed on the optical waveguide 2. Configured. One end face of the first substrate 1 that intersects with the upper surface 1a is used as the incident surface IC of the semiconductor laser beam 3, and is polished to a thickness of 1400 by sputtering after mirror polishing.
5iO1i of A was formed to constitute the first antireflection film 4 for fundamental waves. The upper surface 5a of the second substrate 5 is washed and superimposed on the lower surface 1b of the substrate l of @1, and the first substrate 1 of the superposed second substrate 5
The other end surface opposite to the incident surface side and intersecting the upper surface 5a is used as the output surface 5b of the second harmonic 6, and after mirror polishing, a 5i02 film with a thickness of 700A is formed by sputtering, and the second harmonic is The second anti-reflection film 7 was constructed for the purpose of use. The optical wavelength conversion element thus obtained has a fundamental wavelength of α84.
Used for μm.

In the above configuration, when the semiconductor laser light 3 having a wavelength α of 84 μm, which is the fundamental wave, enters the optical waveguide 2 from the incident surface 1c of the first substrate l through the first antireflection film 4, the semiconductor laser light 30 fundamental wave is transmitted to the leading waveguide. 2, phase matching occurs, and the second harmonic 6 has an inclination angle θ with respect to the incident light.
=16°, and is taken out into the second substrate 5, and is emitted from the output surface 5b through the second antireflection film 7. At this time, the first anti-reflection film 4 eliminates light returning to the semiconductor laser at the incident surface 1C, eliminating fluctuations in the oscillation wavelength. In addition, the second anti-reflection film 7 protects the output surface 5.
The loss due to reflection at b is reduced, and the second harmonic 6
For example, when the output efficiency of the semiconductor laser beam 3 is 43 mW, -power i:s+omw.
The second harmonic 6 of is obtained.

In addition, although lithium niobate was used as the first substrate 1 in the above embodiment, lithium tantalate may also be used. In addition, in the above embodiment, the antireflection film 4.7 was formed using sputtering.
It may also be formed using vacuum deposition. Furthermore, although birophosphoric acid is used in the proton exchange treatment during the formation of the optical waveguide in the above embodiments, benzoic acid may also be used.

FIG. 2 shows the relationship between 5i02 film thickness and reflectance. There is a relationship between reflectance and film thickness. However, nl: refractive index of 5i01 nx: refractive index of LiNbos λ: wavelength of incident wave d: film thickness. As shown in Figure 2, the film thickness is 0^
That is, the reflectance is maximum when no antireflection film is applied, and the reflectance is minimum when the film thickness is 700A.

This point is greatly different from the conventional example. By providing a 700A antireflection film on the output surface 5b of the second substrate 5, the output efficiency of the second harmonic 6 output from the output surface 5b is approximately 3096. Garu.

Effects of the Invention As described above, according to the present invention, an anti-reflection film for the fundamental wave is provided on the incident surface intersecting the one surface of the first substrate having a guiding waveguide formed on one surface, and A second
An anti-reflection film for harmonics is provided, and the other surface of the first substrate opposite to the one surface on which the leading wavepath is formed is overlapped with the surface of the second substrate that intersects with the output surface. ,
By extracting the second harmonic phase-matched with the fundamental wave propagating through the optical waveguide into the second substrate and emitting it from the emission surface, the second harmonic wave is extracted from the emission surface of the second substrate. At the same time, the output efficiency of the second harmonic is greatly increased, and at the same time, there is no light returning to the semiconductor laser, and the oscillation wavelength does not fluctuate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an optical wavelength conversion element according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a SiO
□ is a relationship diagram between film thickness and reflectance, and FIG. 3 is a cross-sectional view showing a conventional optical wavelength conversion element. l...first substrate, 1a...upper surface of first substrate, l
b... Lower surface of the first substrate, 1c... Incident surface of the first substrate, 2... Guide waveguide, 3... Semiconductor laser light, 4
...first anti-reflection film, 5...second substrate, 5a.
...Top surface of second substrate, 5b... Outgoing surface of second substrate, 6... Second harmonic, 7... Second anti-reflection film.

Claims (1)

[Claims] 1. An anti-reflection film for fundamental waves is provided on the incident surface intersecting the one surface of the first substrate having an optical waveguide formed on one surface, and the output surface of the second substrate is provided with an anti-reflection film for the fundamental wave. an anti-reflection film for second harmonics is provided on the second harmonic, the other surface of the first substrate opposite to the one surface on which the optical waveguide is formed, and the surface of the second substrate that intersects with the emission surface. An optical wavelength conversion element configured to superimpose two harmonics, extract a second harmonic wave phase-matched with the fundamental wave propagating through the optical waveguide into the second substrate, and output the second harmonic wave from the output surface. 2. Claim 1 in which the antireflection film is SiO_2
The optical wavelength conversion element described in . 3. The optical wavelength conversion element according to claim 1, wherein the thickness of the antireflection film for the second harmonic is 1/2 of the thickness of the antireflection film for the fundamental wave. 4. LiNb_1_-_xTaxO_ as the first substrate
3 (0≦x≦1). 5. The optical wavelength conversion element according to claim 1, wherein the optical waveguide is formed by a proton exchange method.