JPH032736A - Method and 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 exposing and developing a photosensitive material and etching an optical waveguide surface, thereby patterning the optical waveguide route for second harmonic waves. CONSTITUTION:A photomask formed with the pattern of the channel type optical waveguide on the propagation route for the second harmonic waves is registered and is exposed by an exposing light source 7 to expose the photosensitive material applied on an optical circuit element 1. The photosensitive material is then developed to form the etching mask corresponding to the route for the second harmonic waves. The slab type optical waveguide is etched by an ion beam etching to etch the parts exclusive of the etching mask. The etching mask is removed from this optical circuit element 1 to produce the second harmonic wave generating element. 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 utilizes the nonlinear optical effect of an optical crystal to convert the wavelength of an incident laser beam to the negative wavelength of the portion thereof. The present invention relates to a device manufacturing method and an apparatus thereof, and in particular, the present invention relates to a device manufacturing method and an apparatus thereof, and in particular, when forming a channel type optical waveguide,
The present invention relates to a method and apparatus for manufacturing a second harmonic generating element that can easily perform phase matching with extremely high precision.

[Prior Art] 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. to improve photosensitivity by shortening the wavelength. The field of application is very wide, as it can be applied to laser printers, etc., which require faster speeds because of the improvement in the wavelength, and photolithography, etc., because the shorter wavelength makes it possible to process fine patterns.

Conventionally, such a second harmonic generation element uses a high-output gas laser as a light source and uses a bulk 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 laser light is confined in a narrow region using a channel type optical waveguide, and the second harmonic generation conversion is achieved by creating a high optical power density. 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 not met because the refractive index generally changes with wavelength due to wavelength dispersion of crystalline materials.Therefore, it is necessary to match the refractive index 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 wavelength λ
In this method, light with a wavelength λ is incident in a direction forming an angle θ with respect to the crystal axis so that the refractive index of the light with a wavelength λ/2 is equal to that of the light with a wavelength λ/2.

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 optical 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 not practical because it had to be controlled at about 'C, and special equipment was required when using 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 problems]

As a result of various studies on methods for solving the above-mentioned problems, the inventor of the present invention visualized the optical waveguide path of the second harmonic generated by phase matching on the surface of the optical waveguide. We have discovered a method of forming an etching mask along the harmonic optical waveguide path and etching the parts other than the etching mask to form a channel type optical waveguide, and have completed the present invention. .

That is, the present invention provides the following steps: Coating a photosensitive material on the optical waveguide of an optical circuit element having a slab-type optical waveguide made of an optical crystal thin film; Injecting a laser beam into the optical waveguide whose light input and output side end faces have been polished. a step of aligning and setting a photomask having a channel-type waveguide pattern using the second harmonic light; exposing the photosensitive material; A method for producing a second harmonic generating element, which comprises the following steps: - and a step of etching the optical waveguide surface to pattern an optical waveguide path for the second harmonic, and the basics thereof. A second harmonic generation device manufacturing apparatus comprising a wave laser light source, an optical system for converting laser light into substantially parallel beams, a movable optical circuit element holder, and an exposure light source, wherein the optical circuit element holder is , the waveguide portion of the optical circuit element is arranged so as to be aligned on the optical axis of the laser beam irradiated from the optical system, and the exposure light source is held on the optical circuit element holder. 1. An apparatus for manufacturing a second harmonic generating element, characterized in that the second harmonic generating element is disposed at a position where it can irradiate the optical circuit element.

According to the method of the present invention, it is preferable to coat a photosensitive material and a fluorescent agent on the channel-type optical waveguide of the optical circuit element, and in the apparatus of the present invention, the optical circuit element of the optical circuit element holding stand is preferably coated with a photosensitive material and a fluorescent agent. A device in which a light receiving device is disposed at the rear of the portion is suitable, and the optical circuit element holding stand includes:
It is preferable to use a rotatable stage, a stage movable in at least two axes, or a stage having a combination of these structures.

[Effect]

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

The method of manufacturing a second harmonic generating element according to the present invention is a proposal for a method of generating a second harmonic through phase matching and visualizing the optical waveguide path of the second harmonic on the surface of a slab type optical waveguide. .

The manufacturing method of the second harmonic generating element according to the present invention includes a method in which phase matching is performed by changing the incident angle of a laser beam (angle matching method) and a method in which phase matching is performed by adapting the film thickness (film thickness). thickness matching method).

When using the angle matching method, an optical circuit element having a slab waveguide made of optical crystal with a uniform film thickness is used; when using the film thickness matching method, an optical circuit element with a continuously changing film thickness is used. An optical circuit element having a slab waveguide made of crystal is used.

According to the present invention, after coating the photosensitive material on the slab type optical waveguide of the optical circuit element, when using the angle matching method,
The optical circuit element is held on a rotatable stage, and in the case of the film thickness matching method, the optical circuit element is held on an optical circuit element holder consisting of a stage movable in at least two axial directions, and the optical waveguide of the optical circuit element is irradiated with a laser from the optical system. Arrange it so that it is located on the optical axis of the light.

Next, a laser beam is introduced into the optical waveguide from the light-incidence side end face of the polished slab-type optical waveguide of the optical circuit element, and then the optical circuit element is phase-matched by relatively moving to produce a second harmonic. A photomask having a channel waveguide pattern is aligned and set using its second harmonic, and then the photosensitive material is exposed and developed. Note that this photosensitive material is
If the photosensitive material does not have the function of a resist during etching, the surface of the photosensitive material may be further coated with an etching mask.

A second harmonic generation element is manufactured by etching the surface of the slab type optical waveguide.

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. The coating film of such a photosensitive material has a thickness of 0.1 to 100 μm, preferably 1 to 2 μm.
0 μm2, particularly preferably 2 μm.

According to the present invention, it is preferable to apply a fluorescent agent together with a photosensitive material on the optical waveguide of the optical circuit element.The reason for this is that the conversion efficiency to second harmonic light is low or the waveguide surface is smooth. This is because confirmation can be made easier when the scattering loss is small. The fluorescent agent may be applied either above or below the photosensitive material, but if necessary, it can be mixed with the photosensitive material and applied.

The photosensitive agent is one that is excited by second harmonic light and has a wavelength (0°6 to 0.8μ) that does not sensitize the photosensitive material.
Advantageously, it emits fluorescence in the visible light (yellow to red) of m).

Optical crystals for optical waveguides in the present invention include, for example, LiNbO5 in which Ti is thermally diffused and LiNbOi in which protons are exchanged.

MgO solid solution LiNbO5, LiTaO5゜KT I O
P Oa , KN b Os .

Bag NaNb5 Ots, Bag L i NbO
5Ots.

Ks Li* Nbs Ots, β-BaBtO
,.

α-quartz, KH, PO4, KD, PO,.

CsDg As1a, C5Hz ASO4.

C5Dt As1a, RbHt POa.

RbHt ASO4, Be5On -4Hz O.

L I Cll0a 3 Hz O, L t IOi
and organic nonlinear optical materials such as 2-methyl-4-nitroaniline, 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 five optical waveguides 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 path is such that the etching process directly affects the dimensions of the channel type optical waveguide and prevents optical loss due to scattering of laser light within the channel type optical waveguide. Since it is important for producing high power density, high precision is required in the etching process. Examples of methods that meet such requirements include ion beam etching,
Methods include reactive ion etching, plasma etching, and laser etching.

Next, an apparatus for manufacturing a second harmonic generating element according to the present invention will be explained.

The second harmonic generation device manufacturing apparatus according to the present invention generates the second harmonic by phase matching the second harmonic optical waveguide on the surface of the slab type optical waveguide. This is a proposal for a device that visualizes the image on the surface of a slab-type optical waveguide.

That is, the second harmonic generation device manufacturing apparatus according to the present invention includes a fundamental wave laser light source, an optical system for converting laser light into substantially parallel light beams, a movable optical circuit element holder, and an exposure light source. A second harmonic generation device manufacturing apparatus, wherein the optical circuit device holder is arranged so that the waveguide portion of the optical circuit device can be aligned on the optical axis of the laser beam irradiated from the optical system. and the exposure light source is disposed at a position where it can irradiate the optical circuit element held on the optical circuit element holder. It is a device.

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

According to the device of the present invention, the optical circuit element (1) is held on the optical circuit element holder (2), and the fundamental wave laser light source (3)
The incident angle of the laser beam (5) generated in the laser beam (5) and irradiated through the optical system (4) is adjusted.
) and the refractive index of the second harmonic to be generated, or by moving the optical circuit element (1) relative to the laser beam (5) from the optical system (4). ,
By setting the film thickness at a position where the refractive index of the laser beam (5) and the refractive index of the second harmonic to be generated match, the phases can be matched. With 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. Utilizing this, the photomask (6) is aligned along the optical waveguide path of the photosensitive material, and then the photosensitive material coated on the surface of the optical circuit element (1) is exposed by the exposure light source (7). It is. Therefore, the optical waveguide path of the second harmonic generated by phase matching can be realized on the slab type optical 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 (8) 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 (8) behind the optical circuit element (1) portion of the optical circuit element holder (2), the second harmonic from the output end face of the circuit element can be measured. This is because phase matching can be confirmed by this.

The optical circuit element holder (2) of the apparatus of the present invention is preferably a rotatable stage or a stage movable in at least two axes, and a stage having both of these functions is particularly preferred.

[Example] The present invention will be explained below using examples.

Example 1 An optical circuit element having a slab type optical waveguide was created by forming a 2-methyl-4-nitroaniline single crystal thin film on a 0.5 mm thick Sin single crystal substrate. A photosensitive material was applied to a thickness of lIIm on the slab type 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.
An e-Ne laser beam 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 0.3
A second harmonic of 16 μm was generated, and the propagation path of the second harmonic in the slab optical waveguide was visualized by scattered light generated when the second harmonic propagated within the slab optical waveguide. A photomask with a channel-type optical waveguide pattern formed thereon was aligned over this propagation path, and exposed with an exposure light source to expose the photosensitive material coated on the optical circuit element.

This photosensitive material 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 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 the light source, the efficiency was ■×10 −4, which was 2×10 −′ for the conventional element, while a high efficiency was obtained.

Example 2 A LiN b Os thin film was formed on an X-cut LiTaO5 single crystal substrate with a thickness of 0.5 mm by the LPE method,
An optical circuit element using this t, tNbozfMiJBi as a slab type optical waveguide was fabricated.

The surface of the 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 the film thickness change to allow light to enter and exit. It was made into a side end surface.

The end faces of the input and output sides of this optical waveguide were mirror-polished by vibrating puff polishing.

On the surface of this optical waveguide, a photoresist was applied to a thickness of 1IJm 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 to enter the optical 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. A second harmonic with a wavelength of 0.42 μm is generated by this phase matching, and the propagation path of the second harmonic in the slab optical waveguide is changed by the scattered light generated when this second harmonic propagates through the slab optical waveguide. was visualized. A photomask with a channel-type optical waveguide pattern formed thereon was aligned over this propagation path, and exposed with an exposure light source to expose the photosensitive material coated on the optical circuit element.

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

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

Example 3 An optical circuit element having a slab type optical waveguide was created by forming a C-axis oriented polycrystalline thin film of ZnO on a glass substrate with a thickness of 1.0 mm by RF sputtering method. A photosensitive material is coated to a thickness of 1 μm on the slab-type optical waveguide of the device, and a layer of 2 μm thick absorbs light with a wavelength of 1.06 μm to generate visible light fluorescence. coated with a fluorescent material that generates

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.
d: A YAG' laser beam was introduced into the optical waveguide.

Then, phase matching was performed by rotating the optical circuit element stand by a minute angle. Due to such phase matching, wavelength 0
．． The second harmonic of 532 μm is generated, and this phase matching is achieved by a light receiving device placed behind the optical circuit element.
This was done by checking the harmonics.

In this case, the fluorescent agent emits light due to the upward scattered light of the fundamental wave (Nd:YAG) laser beam propagating along the same path as the second harmonic, and the propagation path of the second harmonic in the slab optical waveguide is changed. visualized. A photomask with a channel-type optical waveguide pattern formed thereon was aligned over this propagation path, and exposed with an exposure light source to expose the photosensitive material coated on the optical circuit element.

This photosensitive material 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, we found that the Nd:Y
When an AG laser was used as a light source, a high efficiency was obtained, which was 5XIO-', compared to 2X10-' in the conventional element.

〔effect〕

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 optical waveguide, and the matching accuracy is high, and the second harmonic is generated. It is possible to manufacture a second harmonic generation element with excellent conversion efficiency.

[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. 1... Optical circuit element, 2... Optical circuit element stand, 3...
- Fundamental laser light source, 4... Optical system, 5... Laser beam, 6... Photomask, 7... Exposure light source, 8... Light receiving device, 9... Mask alignment device,

Claims (1)

[Claims] 1. A step of applying a photosensitive material onto the optical waveguide of an optical circuit element having a slab-type optical waveguide made of an optical crystal thin film; A step of inputting and phase-matching a laser beam to generate second harmonic light; A step of aligning and setting a photomask having a channel-type waveguide pattern using the second harmonic light; A method for manufacturing a second harmonic generating element, comprising: exposing and developing a material; and etching the optical waveguide surface to pattern an optical waveguide path for the second harmonic. . 2. The method for manufacturing a second harmonic generating element according to claim 1, wherein a photosensitive material and a fluorescent agent are applied on the optical waveguide of the optical circuit element. 3. A second harmonic generation device manufacturing device comprising a fundamental wave laser light source, an optical system for converting laser light into a substantially parallel beam, a movable optical circuit device holder, and an exposure light source,
The optical circuit element holder is disposed such that the waveguide portion of the optical circuit element can be aligned on the optical axis of the laser beam irradiated from the optical system, and the exposure light source is 1. An apparatus for manufacturing a second harmonic generating element, characterized in that the apparatus is disposed at a position where an optical circuit element held on an optical circuit element holder can be irradiated. 4. The apparatus for manufacturing a second harmonic generating element according to claim 3, wherein a light receiving device is disposed behind the optical circuit element portion of the optical circuit element holder. 5. The second harmonic generation element manufacturing apparatus according to claim 3, wherein the optical circuit element holder is a rotatable stage. 6. The second harmonic generation device manufacturing apparatus according to claim 3, wherein the optical circuit device holder is a stage movable in at least two axes.