JPS59171908A - How to create a thin film optical structure - Google Patents

Abstract

PURPOSE:To form a thin film optical structure such as an optical waveguide, a waveguide lens, or the like accurately as prescribed values by monitoring the reflected light or the transmitted light of an optical beam to detect elements of the structure which is formed and conrolling a device, which irradiates the optical beam, on a basis of this detection signal. CONSTITUTION:A luminous flux 13 is irradiated to the whole of the surface of a substrate 1 immersed in a molten liquid 2, and a part of this luminous flux is reflected and is returned to a lens 4 and is led to a detector 7 through a beam splitter 6, and the luminous flux transmitted through the substrate is condensed by a lens 5 and is made incident to a detector 8. The surface of the substrate 1 is heated locally by the luminous flux 13, and ion exchange advances to increase the refractive index near the surface, and a waveguide is formed. Since the reflection factor and the transmittivity of the luminous flux 13 on the surface of the substrate are changed when the refractive index of the surface is changed, the variance of the intensity of the reflected light or the transmitted light is observed by the detector 7 or 8 to monitor the state of the waveguide at this time. The intensity of the monitor light of the reflected or transmitted light of the optical beam at the time, when said waveguide is formed into a pescribed state, is preliminarily detected by calculation or experiment, and the signalf rom the monitor is observed to form the waveguide with accurate values.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method for producing a thin film optical structure such as an optical waveguide or a waveguide lens.

Conventionally, in order to form an optical waveguide, there is a method in which a mask is generally used to create a Pakunoi ζ, and then annealing is performed in a diffusion furnace. On the other hand, the above mask technique Ni:j'
Study on forming an optical waveguide directly on a substrate using a laser beam without using a laser beam [Hajime Mae, Yoshiaki Ikuzawa, Masayoshi Yamada,
Megumi Yamamoto-1 Kenji Abe "Experimental study on optical waveguide formation by CW laser scanning"'82 Spring Applied Physics Proceedings, 2a
-F-9,,P, 195: ] also made tail.

Controlling the refractive index of the optical waveguide portion and the thickness distribution of the optical waveguide is effective in limiting the propagation mode to a predetermined one or improving the interaction with the surface acoustic wave formed in the optical waveguide. is important. In addition, not only optical waveguides,
Controlling the refractive index and thickness distribution is also important when forming functional elements such as optical waveguide lenses.

An object of the present invention is to provide a manufacturing method that allows thin film optical structures such as the optical waveguide section or waveguide lens to be manufactured accurately to predetermined values.

The method of manufacturing a thin film optical structure according to the present invention focuses on a method of manufacturing a thin film optical structure in which the refractive index is changed by irradiating a light beam onto a substrate and ion-exchanging the irradiated portion. By monitoring the reflected or transmitted light of the light beam used to create the structure, the state of the structure being created can be detected, and based on this detection signal, for example, the device that irradiates the light beam can be controlled. It is an attempt to achieve a goal.

FIG. 1 is a diagram showing an embodiment of a thin film optical structure manufacturing apparatus using the manufacturing method according to the present invention. In FIG. 1, 1 is a substrate, 2 is a melt, 3 is a laser light source, 4 and 5
1 is a lens, 6 is a beam sinter, 17 and 8 are detectors, 9 is a container, 10 is a heater, and 11 is a window opened in the container 9 for light. The substrate 1 is made of LlNbO5rLiTaO, which is a ferroelectric crystal with excellent piezoelectricity.
S crystal or glass such as BH3 may also be used. 2 is I(
NOs, H2SO4, Mg (NOs)t6H
2O, Ce'HsCOOH.

TzNOs, AgNOs, KNOs, Na
Examples include NOs. As a light source, it is desirable to use a laser with a wavelength that has a high absorption rate for the substrate material, such as A
r, He-Ne.

Examples include YAG and CO2 lasers. A beam 12 emitted from the laser light source 3 passes through a beam splitter 6 and is expanded by a lens 4 into a beam 13 having uniform intensity. The light beam 13 is irradiated onto the entire surface of the substrate 1 immersed in the melt 2, with some of it being reflected and some of it being transmitted. The reflected light is returned to the lens 4 and guided to the detector 7 by the beam sinter 6. On the other hand, the light beam transmitted through the substrate is squeezed by the lens 5 and enters the detector 8.

The surface of the substrate 1 is locally heated by the light beam 13, ion exchange progresses, the refractive index near the surface increases, and a waveguide is formed. The rate of generation of harmful gases is kept lower than when the entire melt is heated. Furthermore, as a thermal bias, it is also possible to use the heater 1o to appropriately heat the melt in advance. According to the above principle, when the refractive index of the surface 9 changes, the reflectance and transmittance of the light beam 13 on the substrate surface change, so if the detector 7 or 8 observes the fluctuation in the light intensity of the reflected light or transmitted light, , the state of the waveguide at that point can be monitored.

When the waveguide is formed in a predetermined state, if the intensity of the reflected light of the light beam or the transmitted light of the monitor light is known in advance by calculation or experiment, the intensity of the monitor light from the monitor (No. 1) can be determined by observing It is possible to create waveguides with precise values.

In the above implementation example, a waveguide was created by irradiating a light beam onto a substrate immersed in a melt, but a solid material that forms ion molecules is provided on the substrate, and the ion species are exposed to light. The invention of the present application is also effective in the case of ion exchange on the substrate surface by beam irradiation.

FIG. 2 is a diagram showing an embodiment of an apparatus for manufacturing a waveguide lens, which is an example of a thin film optical structure, using the manufacturing method according to the present invention, in which members given the same numbers as in the first section are the same. represents the kidnapping of In FIG. 2, reference numeral 14 denotes an optical scanning device, which is composed of a mechanical deflector such as a galvano mirror or a polygon mirror, and a scanning lens that focuses the beam 15 from the deflector onto the substrate. Incidentally, instead of the mechanical deflector, a physical optical deflector such as an acousto-optic deflector or an air-optical deflector may be used. It is desirable that the scanning light beam 15 entering the substrate 1 from the optical scanning device 14 is perpendicularly incident on the substrate 1. In such a case, the light beam 12 from the light source 3 is deflected at the point of action of the optical deflector, that is, the light beam 12 from the light source 3 is deflected. A so-called telecentric configuration is adopted in which the point at which the image is displayed coincides with the pupil position of the scanning lens.

It should be noted that there is no problem even if the beam is obliquely incident on the counter light east 15I'i and the substrate 1.

As shown in Fig. 2, the light beam 1 emitted from the laser light sea 3
After passing through the 2-digit beam splitter 6, the optical scanning device 14
The surface of the substrate 1 is scanned. The reflected light of the scanning light beam 15 passes through the beam splitter 6 again and enters the detector 7. On the other hand, the transmitted light of the scanning light beam 15 passes through the window 11,
Inspection.

Guided by Usufruct 8. The scanning light beam 15 is irradiated onto the optical substrate 1.
The 0 surface is locally heated, ion exchange progresses, and the refractive index near the surface increases. As the time for irradiating the substrate with the scanning light beam 15 increases, the depth at which ion exchange occurs also increases. If the refractive index and ion diffusion thickness of the light irradiation area change in this way, the reflectance and transmittance of the scanning light beam 15 on the substrate surface will change, so use the detector 7 or 8 to observe fluctuations in the light intensity. Then, the state of the light irradiated area at that point can be monitored.

In order to fabricate a Luneburg lens by utilizing the above phenomenon, the following optical scanning may be performed. As shown in FIG. 3, optical scanning is performed concentrically, and the number of scans on the same scanning trajectory 16 decreases as the lens progresses from the center to the periphery.

Further, in the portion other than the lens, a planar optical waveguide is formed by keeping the number of scans constant. When the intensity distribution of the scanning light beam is rectangular, the scanning pitch width of the scanning light beam becomes the light beam width as shown in FIG.

When the intensity distribution is Gaussian, the scanning pitch width d is determined so that the intensity distribution becomes uniform when the scanning light beams are superimposed, as shown in FIG. According to the above scanning method, as shown in FIG. 6, the distribution of the ion diffusion layer 17 in the direction perpendicular to the substrate surface is deep at the center of the lens, becomes thinner toward the periphery, and is constant in areas other than the lens. become. The thickness distribution of the above-mentioned ion diffusion layer required for a lens of a predetermined focal length can be found in the document by Southweff [J
, Opt, Soc, Am, 67, 1010 (
1977)).

Furthermore, the scanning method is not limited to concentric scanning, but may also be linear scanning as shown in FIG. Reference numeral 18 denotes a trajectory of a scanning light beam, which scans parts other than the lens at a constant speed, and changes the scanning speed to the inside of the lens depending on the required thickness of the ion diffusion layer. As a result, the thickness distribution of the ion diffusion layer as shown in FIG. 6 may be formed.

An optical waveguide lens having a distribution of ion diffusion layers as shown in FIG. 6 becomes a convex lens. However, according to the method of the present invention, an optical waveguide lens that acts as a concave lens can also be easily created. Figure 8 shows the thickness distribution 19 of the ion diffusion layer of a mode index type optical waveguide lens that acts as a concave lens.The thickness of the ion diffusion layer is thin at the center of the lens, and becomes thicker toward the periphery of the lens. It remains constant for parts other than the lens.

As in the case of the convex lens described above, the optical scanning method for creating the optical waveguide lens that acts as a concave lens can be either concentric circular or linear scanning, and can be achieved by appropriately adjusting the number of scans and the scanning speed. The thickness distribution of the ion diffusion layer shown in FIG. 8 is obtained.

In the above embodiment, the case where the light beam that irradiates the substrate is irradiated from above is shown. However, depending on the melt, a desired gas may be generated by the light beam, and in such a case, the container 9 may require a lid to close off the gas. In such a case, a transparent window can be provided on the lid to allow the light beam to enter. However, if the lid is fogged due to the undesired gas, the light beam can be directed to the side of the container 9 or It is desirable that the light enters through a transparent window provided on the bottom.

As described above, in the fabrication method according to the present invention, the state of the thin film optical structure being fabricated can be monitored in real time, so for example, when fabricating an optical waveguide, the number of modes to be excited can be controlled. In addition, it is possible to control the waveguide thickness to strengthen the interaction with surface acoustic waves.

Furthermore, in the manufacturing method according to the present invention, in the case of optical waveguide lenses formed by multiple optical scanning methods, it is difficult to monitor using a light beam other than the light beam for creating the waveguide lenses. It is difficult to accurately monitor the position scanned by the light beam, and it is also difficult to monitor in real time. Therefore, it is effective to use the reflected light or transmitted light of the scanning light beam as monitor light as in the present invention.

Furthermore, in the manufacturing method according to the present invention, the depth of the ion diffusion layer can be freely controlled, so the numerical aperture of the waveguide lens can be selected from a wide range of values. It is.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are a diagram showing an embodiment of a manufacturing apparatus for a thin film optical structure using the manufacturing method according to the present invention, and FIG.
The figure shows an example of optical scanning when forming a waveguide lens using the apparatus shown in FIG. 2, and FIGS. 4 and 5 respectively.
In the apparatus shown in Fig. 2, a diagram for explaining the pitch width of the scanning line, Fig. 6 is a diagram showing the cross-sectional shape of a waveguide lens having a positive refractive index, and Fig. 7 is a diagram for explaining the pitch width of the scanning line. A diagram showing another example of optical scanning when forming a waveguide lens with the apparatus shown in FIG.
FIG. 8 is a diagram showing the cross-sectional shape of a waveguide lens having a negative refractive index. 1... Substrate, 2. Melt, 3... Laser light source, 4.
5...Lens, 6...Beams fritter-17, 8...
・Photodetector, 9... Container, 10... Heater, 11
...Window, 12.13...Light flux, 14...Light scanning device, 15...Scanning light flux. Applicant: Canon Corporation? -3 B L2 4 83 Hard A 6 Fourth, Foil 50

Claims (1)

[Claims] (1) In the method of creating a thin film optical structure such as an optical waveguide or a waveguide lens by irradiating an original beam onto a substrate and changing the refractive index by ion-exchanging the substrate portion irradiated with the beam, A method for producing a thin film optical structure, comprising monitoring the reflected or transmitted light flux of a light beam irradiated onto a substrate, and controlling the configuration of the thin film optical structure produced on the substrate based on the monitored information.