JPH02120704A - Method for forming equivalent refractive index distribution - Google Patents

Abstract

PURPOSE:To attain the highly efficient incidence and emission of a light guide by sticking a UV curing resin having the refractive index slightly different from the refractive index of a substrate material to a substrate material so as to have a thickness distribution to form the distribution region of equiv. refractive indices at the time of curing. CONSTITUTION:The glass substrate 100 is placed on a base 125 movable in a vertical direction (Z direction) and immersed into the liquid UV curing resin 110 in such a manner that the surface of the substrate 100 is slightly below the liquid surface. The light of a laser 115 is then focused onto the surface of the substrate 100 by a lens 105. The light is focused by a rectangular aperture 135 to the rectangular beam which is equal to the waveguide width in the Y direction. A thin cured layer 130 is formed by scanning the laser 120 in the X direction. The base 125 is then lowered and the curing is started at a distance from the end part of the substrate according to a taper shape. The uncured resin 110 is removed by an org. solvent after the production by repeating the above-mentioned operations, by which the waveguide and the equiv. refractive index distribution region are formed. The efficient emission of light is enabled by adequately selecting the distribution shape of the equiv. refractive indices.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for generating equipolarized refractive indexes that form highly efficient light input/output portions of optical devices.

[Prior art] Conventionally, in order to input and output light to and from an optical element, as shown in Figure 4, a region with a high refractive index is made partially using an optical material that has high transmittance at the wavelength used, and thereby the surrounding substrate is It is used as an optical waveguide 500 that confines light in a portion having a higher refractive index than 510. In the figure, this is shown by a broken line, and the end face is polished and the light is focused and incident directly on the optical waveguide 500 using a condensing means 520 such as a lens. Prism coupling is performed using a prism 530 made of a material with a high refractive index, and a waveguide 550 is formed by gradually changing the thickness of the waveguide as shown in FIG.
A portion of the light is transmitted through the boundary between the substrate 540 and the substrate 540, and is emitted to the substrate.
A taper coupling was used that utilizes the fact that the amount of transmission increases as it advances toward the tip of the taper 560.

[Issue 8 to be solved by the invention] However, in end-face coupling, it is necessary to externally adjust the position of the optical waveguide with a size of about 2 to 5 μm using a μm hoarder, and also to align the beam. A process called edge polishing was required. Furthermore, although prism coupling can be achieved relatively easily, it requires an extra component called a prism, which increases costs. Furthermore, in a taper coupler, the thickness of the waveguide is reduced in a tapered manner, and the light is emitted to the substrate side using a cutoff that prevents the waveguide from confining the radiation and light due to changes in the propagating boundary distribution. It was difficult to create a taper.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems, and uses an ultraviolet curing resin as a material for an optical waveguide that guides light, and it is made to have a thickness distribution. It is characterized by being attached so that it has a distribution region of equipolarized refractive index, thereby realizing highly efficient light input and output from the optical waveguide.

[Means for Solving the Problems] In order to achieve this objective, the method for generating an equal polarized refractive index distribution of the present invention is to use a substrate material, an ultraviolet curable resin whose refractive index is slightly different from the ultraviolet curable resin at the time of curing, It requires a source of ultraviolet light that can be focused to layer-cure arbitrary portions of the cured resin.

[Operation] In the present invention having the above configuration, the substrate is immersed in a liquid ultraviolet curable resin, the waveguide and the equivalent open refractive index distribution region are cured by an ultraviolet light source, and the remaining liquid ultraviolet curable resin is removed. As a result, the propagation constant of the guided light propagating through this equivalent open refractive index distribution region decreases in the propagation direction, so that the light is radiated toward the substrate side. At this time, light can be efficiently emitted by appropriately selecting the distribution shape of the equipolarized refractive index. It goes without saying that light can be incident due to the plasticity of light.

[Example] The details will be explained below with reference to the drawings.

FIG. 1(a) is a block diagram of an embodiment of the present invention. - As an example, a glass substrate 100 with a refractive index of 1.457 is placed on a table 125 that is movable in the vertical direction (Z direction), and the whole is 150
Power of mW/c-2 at wavelength of 300-400 nm
A substrate 1 is placed in an ultraviolet curing resin 110 (hereinafter abbreviated as resin) that hardens with a refractive index of 1.46 when irradiated with ultraviolet light for 0 seconds.
Place it so that the 00 surface is slightly below the liquid level. 32
The light from the 5 nm He-Cd laser 115 is focused onto the surface of the substrate 100 by the lens 105. At this time, the light becomes a rectangular beam with the y direction equal to the waveguide width due to the rectangular aperture 135. A method for generating equipolarized refractive indices from the above configuration is shown in FIGS. 1(b) to 1(e). Figure 1 (b
), (C), by placing the substrate 100 slightly below the surface of the resin 110 and scanning the focused He-Cd laser beam 120 in the X direction, a cured layer 130 with a thin beam width in the y direction is formed. Ru. Next, lower the stand 125 as shown in Figure 1 (d).
), in the tapered part 140, curing is started at a distance from the edge of the substrate according to the taper shape, and this is repeated.
After fabrication, the uncured resin 110 is removed with an organic solvent and the first
A waveguide and an equivalent open refractive index distribution region as shown in Figure (e) can be formed.

Figure 2 is an example of the film thickness distribution of ultraviolet curing resin;
The figure shows the distribution of equipolar refractive index in the case of FIG. Already in the literature (Takeda, Miyazaki, “Special light focusing of tapered waveguide for integrated optical disk head” Confucian Edane MW87-112.198
As shown in 8), when the equipolarized refractive index decreases, light is emitted from the waveguide toward the substrate side, and by changing the distribution of the equipolarized refractive index, the intensity distribution of the emitted light can be changed. This makes it possible to combine with high efficiency. Furthermore, from the nature of light, it is clear that this method can be used not only for outputting light but also for inputting light into an optical element.

In addition, in this example, the equipolarized refractive index was changed by changing the thickness of the optical waveguide layer, but the waveguide was set to have a constant thickness, and an optical material with a thickness distribution was placed on top of it in a similar manner. It is also possible to create one. In addition, when generating the equipolarized refractive index, in this embodiment, the substrate 100 was submerged in the resin 110, but the resin 110 was submerged in the substrate 100 by a method such as a spin cord.
It may be applied to 0.

[Effects of the Invention] As is clear from the above detailed description, according to the present invention, an input/output coupler for an optical element having a distribution in the equivalent open refractive index can be constructed by a simple method.

[Brief explanation of drawings]

1 to 3 show embodiments embodying the present invention, FIGS. 1(a) to 3(e) are detailed explanatory diagrams of the present invention, and FIG. 2 is a diagram showing the thickness distribution. An explanatory diagram, FIG. 3 is an explanatory diagram of the distribution of the equivalent spread refractive index corresponding to FIG. 2, FIGS. 4 to 6 are diagrams showing conventional examples, and FIG. 4 is an explanatory diagram of end face bonding. , FIG. 5 is an explanatory diagram of a prism coupling, and FIG. 6 is an explanatory diagram of a taper coupler. In the figure, 100 is a substrate, 110 is an ultraviolet curing resin, 120 is
1 is an ultraviolet light, and 130 is an ultraviolet curing resin curing portion.

Claims (1)

[Claims] 1. In a method for generating an equivalent refractive index distribution at the input/output part of an optical element having an optical waveguide, an ultraviolet curing resin is laminated on an optical material having high transmittance for a target wavelength. A method for generating an equivalent refractive index distribution characterized by providing a thickness distribution in the curing stage and giving a gradient to the equivalent refractive index. 2. A method for generating an equivalent refractive index distribution according to claim 1, characterized in that an excimer, argon, or other laser is used as a means for curing the ultraviolet curable resin.