JPS6057825A - Light wavelength converting element - Google Patents

Abstract

PURPOSE:To improve the efficiency of SHG (2nd higher harmonic generation) conversion by forming a light guide which is longer than a substrate in an X and an Y axial direction on the Z surface of nonlinear optical crystal having an X, an Y, and a Z axis. CONSTITUTION:The light guide which is 6mum wide and 4mum deep is formed by diffusing thermally Ti in the Z surface of the LiNbO3Z plate 3' which is, for example, 2cm in the X axial direction and 1cm long in the Y axial direction. Light with wavelength lambda is made incident on this light guide 4a from its incidence end part 5 and reflected by a reflecting end part 6 where a metallic film is vapor-deposited to propagate to the next light guide 4b. The light guides (a) and (b) are at a 3 deg. angle to each other. Light entering the light guide 4c similarly is projected from a projection end part 7. The overall length of the light guides is about 6cm. Then, the incident light with the wavelength lambda and light of a converted wave with wavelength lambda/2 are put in phase with each other to maximize the output power of the converted wave. In practice, semiconductor laser light which has 1.3mum wavelength and 40mW output power is converged by a lens, made incident on the incidence end part 5, and put in phase by temperature to obtain a bit over 20% conversion efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical wavelength conversion element used in the information processing field or optical applied measurement control field using laser light.

Conventional Structures and Problems Conventionally, it has been difficult for semiconductor lasers to oscillate in the short wavelength region of 0.7 μm or less, so large lasers such as gas lasers have been used, and larger lasers have been unavoidable.

For this reason, elements have been manufactured that utilize the 5HG (second harmonic generation) phenomenon to convert semiconductor laser light into half the wavelength. FIG. 1 is a perspective view showing a configuration for converting semiconductor laser light by an optical wavelength conversion element using a conventional LiN b03 optical waveguide. Light with wavelength λ emitted from semiconductor laser 1 is focused by lens 2 and becomes L iN b Oa Y
It enters an optical waveguide 4 formed in the plate 3. By satisfying the phase matching condition between the incident light of the semiconductor laser of wavelength λ and the converted light of wavelength λ/2 by a method such as changing the LzNbO3 head, a conversion of several percent can be achieved. Converted light of wavelength λ/2 was obtained with efficiency. Actually L
z N b Width 6 It m, depth 1 on O3Y plate 3
．． By fabricating four Tf diffused light waveguides 4 with a length of 5 μm and a length of 2 Cm, and inputting the light into the optical waveguide 4 of a semiconductor laser with a wavelength of 1.3 μm and an output of 40' mW, a conversion efficiency of 2% and a wavelength of 0. Converted light of 66 μm was obtained. However, the conversion efficiency is better as the aspect ratio (width to depth ratio) of the four optical wave paths 4 is closer to 1, and since the LiNb○3Y plate 3 has a large diffusion coefficient in the X-axis direction, the four optical wave paths 4 are It spreads wide and the shimeme converter becomes extremely bad. Furthermore, the conversion efficiency is proportional to the square of the length of the optical waveguide 4, but in order to increase the conversion efficiency, it is necessary to increase the length of the LiNb○3Y plate 3 in the X-axis direction, which increases the optical wavelength. The size of the conversion element is too large.

OBJECTS OF THE INVENTION An object of the present invention is to use a Z plate of nonlinear optical crystal having x, y, and z axes, to bring the aspect ratio of the optical waveguide formed in the Z-plane VC closer to 1V, and to further achieve the above-mentioned By folding or bending the optical waveguide to increase the length of the optical waveguide, a compact optical wavelength conversion element that greatly increases the conversion efficiency, which was difficult to achieve in the past. Our goal is to provide the following.

Configuration of the Invention The optical wavelength conversion element of the present invention has a configuration in which optical waveguides longer than the lengths in the x and y axis directions are provided on two surfaces of a nonlinear optical crystal having X, Y, and Z@ axes.

Furthermore, the optical wavelength conversion element of the present invention uses the above-mentioned non-linear optical crystals, such as TeLINbO12 plate and LiTa03Z plate.
c n'lJR. Further, the optical wavelength conversion element of the present invention uses a folded optical waveguide by total reflection or directional coupling, or a curved optical waveguide as the optical waveguide.
It is I.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 is a perspective view showing the structure of a first embodiment of the light wave converter according to the present invention. In Figure 21,
By applying heat waves to Ti on the Z of the L I N b Os Z plate 3' with a length of 1.5'' and 2 cm in the axial direction and 1 cm in the Y'1u11 direction, a width of 6 μm was formed. An optical waveguide 4a'ff with a depth of 4 μm was formed. Light with a wavelength λ is incident on this optical waveguide 4a from the input end 6, and this light is reflected at the reflective end 6 on which the metal film is vapor-deposited. Moving on to the next optical waveguide 4b.The optical waveguide a and the leading waveguide A are at an angle of 3 degrees.The light that enters the optical waveguide 4C through the same process is output from the output end 7.All optical waveguides The length of is approximately ecm.

Here, the output power of the converted wave can be maximized by matching the phases of the incident light having the wavelength λ and the wavelength λ/2 converted wave using temperature or the like. Actually wavelength 1
．． A conversion efficiency of over 20% was obtained by condensing a semiconductor laser beam of 3 μm and output power of 4 c) mW with a lens, making it incident through the input end 5, and adjusting the position depending on the temperature.

FIG. 3 is a perspective view showing a second embodiment of the optical wavelength conversion element according to the present invention. L I N b O3Z board 3'
The optical waveguides 4a and 4b, 4b and 4c provided in the optical waveguides 4a and 4b are coupled to each other in the same way as in the first embodiment except that the coupling is performed by directional coupling with a perfect coupling length.

s A Ill ++ Thick day day W F Z, -W-
? rl! ↓L 亦'、! $2i'-77)4'ff
It is a perspective view showing an example of Q. In this embodiment, instead of using a folded waveguide, a spiral optical waveguide 4 was used as a curved optical waveguide to construct a wavelength conversion element. LiNb
○In a 3Y plate, the propagation constant changes due to bending, and the phase matching conditions differ depending on the location, but L x N b
Since the Os Z plate is used, the propagation constant does not change, so the phase matching conditions do not differ depending on the location. The optical waveguide 4 has a total length of 5 cm. This optical waveguide 4' has a wavelength of 0.8 μm.
When all of the semiconductor laser light with an output power of 30 mW was made incident and the phase was matched by temperature, converted light with a wavelength of 0.4 μm was obtained with a conversion efficiency of 15%.

In the above embodiments, an L z N b O12 plate was used as the crystal, but any other nonlinear optical crystal having x, y, and z axes, such as L f Ta Os, may be used. In addition, in the example, Hx
Although an optical waveguide having a length several times the length of the nonlinear optical crystal in the X-axis direction was used, it is also possible to further increase the conversion efficiency by increasing the total length of the optical waveguide by increasing the number of turns. =! Although the description has been given using a spiral optical waveguide as a four-wave path for curved light, the waveguide is not limited to a U-shape, an S-shape, etc. Further, in this embodiment, the SHG has been explained, but it can also be used for optical parametric amplification, sum frequency, difference frequency, etc.

As described in detail of the invention, in the light wave converting element of the present invention, the length of the substrate in the X, Y axis directions is formed on two surfaces of the nonlinear optical crystal having In order to fully fabricate a long optical waveguide: the conventional X.

It is possible to exhibit an excellent effect of increasing the SHG conversion efficiency by several times compared to an optical waveguide fabricated in the Y plane.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a device for converting semiconductor laser light by an optical wavelength conversion element using a conventional L I N b 03 optical waveguide, and FIG. 2 is a first embodiment of the optical wavelength conversion element according to the present invention. FIG. 3 is a schematic perspective view showing a second embodiment of the optical wavelength conversion element according to the present invention, and FIG. 4 is a schematic perspective view showing the entire configuration of the optical wavelength conversion element according to the present invention.
FIG. 2 is a schematic perspective view showing an embodiment of the invention. 1... Semiconductor laser, 2... Lens, 3
・・・・・・L I N b Os Y board, 4a, 4
b, 4c, 4' -=-・Optical waveguide, 3'...Pa・
...L I N b O12 plate, 6...Incidence end, 6...Reflection end, 7...Output end. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 4'

Claims (4)

[Claims] (1) An optical wavelength conversion element characterized in that an optical waveguide which is longer than the length in the X and Y axes directions is provided on two surfaces of a nonlinear optical crystal having each of the X, Y, and Z axes. (2) L as a nonlinear biocrystal with X, Y, and Z axes
The optical wavelength conversion element according to claim 1, characterized in that an iNb0 Z plate or a L I T a Os Z plate is used. (3) The optical wavelength conversion element according to claim 1, characterized in that a folded optical waveguide is provided as the optical waveguide which is longer than the length in the X and Y1111 directions. (4) As an optical waveguide that is longer than the length in the X and Y axis directions,
2. The optical wavelength conversion element according to claim 1, further comprising a folded optical waveguide by directional coupling. (ei) The Q optical wavelength conversion element according to claim 1, characterized in that a curved optical waveguide is provided as the optical waveguide which is longer than the length in the x and y axis directions.