JPH032735A - Apparatus for producing second harmonic wave generating element - Google Patents

Abstract

PURPOSE:To allow the easy execution of a phase matching with high accuracy by disposing the optical circuit element part of an optical circuit element holding base on an optical axis to be irradiated from an optical system. CONSTITUTION:The optical circuit element 1 is held on the optical circuit element holding base 2. The incident angle of a laser beam 5 cast through the optical system 4 is adjusted to the incident angle at which the refractive index of the laser beam 5 and the refractive index of the generated second harmonic wave coincide or the optical circuit element 1 is moved relative with the laser beam 5 from the optical system 4 and is brought to the position of the film thickness at which the refractive index of the laser beam 5 and the refractive index of the generated second harmonic wave coincide, by which the phases are matched. The second harmonic wave generating element which allows the easy phase matching of the optical waveguide and has the high matching accuracy thereof and the excellent second harmonic wave generating and converting efficiency is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a second harmonic generation method that converts the wavelength of an incident laser beam into the negative wavelength of the part by utilizing the nonlinear optical effect of an optical crystal. The present invention relates to an apparatus for manufacturing a second harmonic generating element, and more particularly, to an apparatus for manufacturing a second harmonic generating element that can easily and accurately perform phase matching when forming a channel-type leading waveguide.

[Conventional technology]

The second harmonic generation element outputs light with a negative wavelength and can quadruple the recording density, so it is used in optical disk memories, CD players, etc. because the short wavelength improves photosensitivity. It can be applied to laser printers, etc., which require high speed, and photolithography, which enables fine pattern processing by shortening the wavelength, and has a wide range of applications.

Conventionally, such a second harmonic generating element uses a high-output gas laser as a light source and uses a burr single crystal of a nonlinear optical crystal. However, in recent years there has been a strong demand for miniaturization of entire devices such as optical disk drives and laser printers, and while gas lasers require an external modulator for optical modulation, semiconductor lasers can be directly modulated. There is something ■
Semiconductor lasers have come to be mainly used instead of gas lasers because they are cheaper and easier to handle than gas lasers.

For this reason, there has been a need for an element that can obtain a high second harmonic generation output even when a low output semiconductor laser light source is used.

In this way, in order to obtain a device with a high second harmonic generation output with a low light source output, the channel type leading waveguide confines the laser light in a narrow area and increases the optical power density, thereby improving the second harmonic generation conversion. Increasing efficiency and
It is necessary to perform phase matching between the incident laser light and the second harmonic.

In other words, in order to obtain a high second harmonic generation output, it is necessary to prevent the generated second harmonic and the polarization wave induced by the nonlinear optical effect from the fundamental wavelength light from weakening each other due to interference and attenuation. To prevent this, it is necessary to match the phase velocities of both. This corresponds to matching the refractive index of the crystal for the fundamental wavelength light and the refractive index for the second harmonic.

However, this requirement is generally not met because the refractive index changes with wavelength due to the wavelength dispersion of crystalline materials. Therefore, it is necessary to match the refractive indexes for the two wavelengths by some method.

Such phase matching methods include an angle matching method, a temperature matching method, a film thickness matching method, and the like. The first method utilizes birefringence of an optical material having optical anisotropy, and the angle θ is set with respect to the crystal axis so that the refractive index of light with wavelength λ and light with wavelength λ/2 are equal. This is a method in which light of wavelength λ is incident in a direction that forms .

The second method utilizes the fact that the refractive index of an optical material changes with temperature, and by controlling such temperature, the refractive index of light with wavelength λ and light with wavelength λ/2 are matched. It is. The third method is a method in which the effective refractive indexes of light of wavelength λ and light of wavelength λ/2 are matched by controlling the film thickness using mode dispersion of guided light.

[Problem that the invention seeks to solve]

However, when performing phase matching based on the above-mentioned angle matching method, precision is required to control the angle within about ±0.1°. Therefore, in a slab type optical waveguide in which an optical waveguide is formed over the entire surface of the substrate, the element is cut in advance so that the angle θ is almost perpendicular to the incident plane, and then the incident angle of the incident light is finely adjusted. Phase matching can be easily achieved, but in the case of channel-type guided waveguides, the optical waveguide must be created with an accuracy of about ±0.1', which requires extremely difficult technology. At the same time, high-precision manufacturing equipment was required.

In addition, when phase matching is performed using the temperature matching method, the temperature must be adjusted by ±0.1 in order to obtain a device with high second harmonic generation output.
It was impractical because it had to be controlled at about 0.degree. C. and special equipment was required to use the device.

Furthermore, when performing phase matching using the film thickness matching method, the film thickness must be controlled with an accuracy of about ±0.01 μm.
Attempting to achieve this using conventional mechanical polishing methods or dry etching processes would require extremely difficult techniques.

[Means for Solving the Problems] As a result of various studies on methods for solving the above-mentioned problems, the inventors of the present invention have determined that the optical waveguide path of the second harmonic generated by phase matching is connected to the surface of a slab type optical waveguide. We have discovered a method of forming a channel-type guide waveguide by visualizing it, forming an etching mask on the surface of this slab-type guide waveguide along the optical waveguide path of the second harmonic, and etching the parts other than the etching mask. Furthermore, they have come to invent an apparatus for carrying out this method. That is,
The present invention provides an apparatus for manufacturing a second harmonic generating element, which comprises a fundamental wave laser light source, an optical system for converting laser light into a substantially parallel beam, and a movable optical circuit element holding table, the apparatus comprising: An apparatus for manufacturing a second harmonic generation element, characterized in that an optical circuit element portion of the stand is disposed on an optical axis irradiated from the optical system.

It is preferable to use a device in which a light receiving device is disposed behind the optical circuit element portion of the optical circuit element holder, and the optical circuit element holder includes a rotatable stage, movable in at least two axes. It is preferable to use a stage that has a similar structure or a stage that has both of these structures.

[Function] The second harmonic generation device manufacturing device according to the present invention is a device that generates a second harmonic through phase matching and visualizes the optical waveguide path of the second harmonic on the surface of a slab type optical waveguide. It's a suggestion.

That is, the second harmonic generation element manufacturing apparatus according to the present invention includes a fundamental wave laser light source, an optical system for making the laser beam into a substantially parallel beam, and a movable optical circuit element holding stand, which are connected to the optical circuit element. This is a device in which the optical circuit element portion of the holder is positioned on the optical axis of the laser beam irradiated from the optical system.

Hereinafter, the apparatus of the present invention will be explained with reference to FIG.

According to the apparatus of the present invention, an optical circuit element (1) is held on an optical circuit element holder (2), and a laser beam ( 5) so that the refractive index of the laser beam (5) matches the refractive index of the second harmonic to be generated, or alternatively, the optical circuit element (1) is connected to the optical system (
The phase is matched by moving it relative to the laser beam (5) from 4) to a position where the film thickness matches the refractive index of the laser beam (5) and the refractive index of the second harmonic to be generated. be able to. Due to such phase matching, a second harmonic having a half wavelength of the incident laser beam is output.

The second harmonic propagates linearly within the slab type optical waveguide, but scattered light generated along the path leaks from the top of the element. This is used to expose the photosensitive material along the optical waveguide path. Therefore, an optical waveguide path for the second harmonic generated by phase matching can be realized on the slab-type leading waveguide.

The wavelength of the fundamental laser light source (3) used in the above process may be appropriately selected depending on the desired wavelength of the second harmonic.

According to the device of the present invention, a device in which a light receiving device (6) is disposed behind the optical circuit device (1) portion of the optical circuit device holder (2) is suitable. The reason for this is that by arranging the light receiving device (6) behind the optical circuit element (1) portion of the optical circuit element holder (2), the second harmonic from the output end face of the optical circuit element (1) can be detected. This is because phase matching can be confirmed by measuring the waves.

Next, a method for manufacturing a second harmonic generating element using the apparatus of the present invention will be described.

When phase matching is performed by changing the incident angle of the laser beam (angle matching method), an optical circuit element having a slab waveguide made of optical crystal with a uniform film thickness is used, and the phase matching is performed by changing the film thickness. When performing this by adapting (thickness matching method), an optical circuit element having a slab-type waveguide made of an optical crystal whose film thickness changes continuously is used.

After coating the photosensitive material on the slab-type optical waveguide of the optical circuit element, it is applied to a rotatable stage when using the angle matching method, or from a stage movable in at least two axes when using the film thickness matching method. The optical circuit element is held on an optical circuit element holding stand, and arranged so that the slab-type leading waveguide of the optical circuit element is located on the optical axis of the laser beam irradiated from the optical system.

Next, a laser beam is introduced into the optical waveguide from the light incident side end face of the polished slab type optical waveguide of the optical circuit element, and then the optical circuit element is moved to perform phase matching, and the second harmonic generated After exposing the photosensitive material along the optical waveguide, the photosensitive material is developed. Note that if this photosensitive material does not have the function of a resist during etching processing, the surface of the photosensitive material may be further coated with an etching mask.

Furthermore, a second harmonic generation element can be manufactured by etching the waveguide road surface.

The photosensitive material and etching mask are removed if necessary.

The photosensitive material used in the process of coating the photosensitive material on the slab type optical waveguide has the following functions in addition to its function as a photosensitive material that has excellent sensitivity to the generated second harmonic:
It is advantageous that the material has the function of a resist during etching processing. Incidentally, the coating film of such a photosensitive material has a 0°11-1O0II, more preferably 1 to
20 μm, particularly preferably 2 μm.

Furthermore, as optical crystals for optical waveguides, for example, TI
LiNb0. , proton-exchanged LiN
b0. , MgO solid solution LiNbO5゜LiTaO5KTI
OPO,,KNbO,.

Bat NaNb5 O+s, Bat L 1Nbos
0+5゜Ks L l t N bs O+s,
β-BaBxOnα-quartz, KH, PO,, KD! P
O4, C5Dt ASO4, C5H! ASO4.

CsD, As1a, RbHz Po4RbHx
ASO4, Be5On 4HxO.

LiCl! , 043H-0, Lr 10s or other inorganic nonlinear optical crystals or 2-methyl-4-nitroaniline,
Examples include organic nonlinear optical materials such as urea and methyl (2,4-dinitrophenyl)-aminopropanate.

The wavelength of the laser beam used in the above process may be appropriately selected depending on the desired wavelength of the second harmonic.

Further, it is advantageous to polish the input and output side end faces of the optical waveguide in order to prevent diffuse reflection at the end faces and increase the power density of the incident laser beam and the output second harmonic. Examples of such end face polishing methods include puff polishing using alumina abrasive grains, a method using a lapping plate, and a method using a lapping film.

The etching method used in the process of patterning the second harmonic optical waveguide is such that the etching process directly affects the dimensions of the channel-shaped guide waveguide and prevents the loss of light tJl due to scattering of the laser light in the channel-type guide waveguide. Because it is important for producing high power density,
Enching processing requires high precision. Examples of methods that meet this requirement include ion beam etching, reactive ion etching, plasma etching, and radiation etching.

〔Example〕

Hereinafter, an example in which a second harmonic generating element was manufactured using the apparatus of the present invention will be described.

Example 1 A single crystal thin film of 2-methyl-4-nitroaniline was formed on a StO single crystal substrate with a thickness of 0.5 mm to create an optical circuit element having a slab-type guided waveguide. A photosensitive material was applied to a thickness of 1 μm on the optical waveguide of the optical circuit element.

After mirror-polishing the input and output side end faces of this optical circuit element by vibrating puff polishing, it was held on an optical circuit element holder that was horizontally rotatable around a vertical axis, and a He-Ne laser beam with a wavelength of 0.633 μm was applied. was introduced into the optical waveguide. Then, phase matching was performed by rotating the optical circuit element stand by a minute angle. By such phase matching, wavelength 0.
A second harmonic of 316 μm is generated, and the scattered light generated when this second harmonic propagates through the optical waveguide causes the photosensitive material applied to the surface of the slab-type leading waveguide to form a pattern that is the same as the path of the second harmonic. was exposed to light.

This photosensitive material was then developed to form an etching mask corresponding to the path of the second harmonic.

Next, the slab type guide waveguide was etched by ion beam etching to etch the portions other than the etching mask. Then, the etching mask was removed from this optical circuit element, and a second harmonic generation element was manufactured.

When the second harmonic generation conversion efficiency of this second harmonic generation element was measured, it was found that He-N with a wavelength of 0.633 μm and 1 mW
When an e-laser was used as a light source, the efficiency was 1 x 10-4, which was 2 x 10-' for the conventional element, while a high efficiency was obtained.

Example 2 A L i N b Oz thin film was formed on an X-cut LiTaO5 single crystal substrate with a thickness of 0.5 mm by the LPE method, and an optical circuit element using this LiNbO5 thin film as a slab type optical waveguide was created.

The surface of the slab-type optical waveguide of the optical circuit element is polished on a surface plate to form a slab-type optical waveguide with a continuously changing film thickness, and then cut along the direction of this film thickness change to form a light beam.・
The output side end face was used as the end face.

The input and output side end faces of this slab-type optical waveguide were mirror-polished by vibrating puff polishing.

On the surface of this slab type optical waveguide, a photoresist was applied to a thickness of 1 μm using a spin coater.

This optical circuit element was held on an optical circuit element holder that was movable in parallel on a horizontal plane, and a semiconductor laser beam with a wavelength of 0.84 μm was made incident into the leading waveguide.

Then, by moving the optical circuit element stand in parallel, a film thickness at which phase matching could be achieved was determined, and phase matching was performed. This phase matching generates a second harmonic wave with a wavelength of 0.42 μm, and the scattered light generated when this second harmonic wave propagates within the optical waveguide causes the photosensitive material applied to the surface of the slab-type leading waveguide to become a second harmonic wave. It was exposed to the same pattern as the harmonic path.

This photoresist was then developed to form an etching mask corresponding to the path of the second harmonic.

Next, the slab type optical waveguide was subjected to etching treatment by ion beam etching to etch the portions other than the etching mask. Then, the etching mask was removed from this optical circuit element, and a second harmonic generation element was manufactured.

When we measured the second harmonic generation conversion efficiency of this second harmonic generation element, it was 1.0% when a semiconductor laser with a wavelength of 0.84 μm and 30 mW was used as the light source, and 0.1% for the conventional element. However, higher efficiency was obtained compared to the previous method.

[Effects] As explained above, according to the device of the present invention, it is extremely easy to actually generate the second harmonic and phase match the target leading wavepath, and the matching accuracy is high.
A second harmonic generation element with excellent harmonic generation conversion efficiency can be manufactured.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a manufacturing apparatus for a second harmonic generating element according to the present invention.

Claims (1)

[Scope of Claims] 1. A second harmonic generation device manufacturing apparatus comprising a fundamental wave laser light source, an optical system for converting laser light into substantially parallel light beams, and a movable optical circuit device holder, which comprises: An apparatus for manufacturing a second harmonic generating element, characterized in that an optical circuit element portion of an optical circuit element holding stand is disposed on an optical axis irradiated from the optical system. 2. The apparatus for manufacturing a second harmonic generating element according to claim 1, wherein a light receiving device is disposed behind the optical circuit element portion of the optical circuit element holder. 3. The second harmonic generation element manufacturing apparatus according to claim 1, wherein the optical circuit element holding table is a rotatable stage. 4. The second harmonic generation element manufacturing apparatus according to claim 1, wherein the optical circuit element holder is a stage movable in at least two axes.