JPH03228233A - Waveguide type optical element - Google Patents

Abstract

PURPOSE:To allow the control of a focal length and position with high accuracy by providing a condenser optical system consisting of waveguide reflecting mirrors which have the plane shape formed as a quadratic curve shape, such as ellipse, parabola and hyperbola and reflect and condense the guided light guided by the boundary part with optical waveguide layers. CONSTITUTION:The guided light 17 guided in the optical waveguide layer 13 is condensed to a prescribed position by the condenser optical system and is the condensed light by the reflection of the waveguide reflecting mirrors 14, 15. The focal position F does not depend on the refractive index, film thickness, light source wavelength, etc., of the optical waveguide layer 13. The focal position F is controlled with the high accuracy by the plane shape accuracy and position accuracy of the respective waveguide reflecting mirrors 14, 15 and since the plane shape of the waveguide reflecting mirrors in particular is formed to the quadratic curve shape, such as ellipse, parabola and hyperbola, the focal position can be freely set by the combinations thereof; in addition, any of collimated beams of guided wave, the guided light scattered from a spot light source and converging guided light is condensed to the focal position without spherical aberrations.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a waveguide type optical device used in fields such as optical integrated circuits, optical communications, and optical calculations.

Conventional technology A waveguide lens that functions for guided light propagating within a two-dimensional waveguide is an extremely important element in the construction of optical integrated circuits, etc.
・It is.

There are various types of such waveguide lenses.

First, FIG. 9 shows a mode index lens l. This is a simple two-dimensional version of the bulk lens, with the refractive index of the lens region 2 being nL and the refractive index of the surrounding area 3 being 08
In this case, the lens region 2 acts as a convex lens for the guided light 4, and a light condensing effect is obtained.

Further, FIG. 10 shows an example of the Luneburg lens 5. This has a lens portion 8 deposited on a waveguide layer 7 on a substrate 6 so as to have a rotationally symmetrical and graded effective refractive index distribution.

With this configuration, the circumference (radius S
1) Move point A above to point B on another concentric circle (radius S,)
The idea is to form a complete image on the image. Such a Luneburg lens 5 is manufactured by depositing the lens portion 8 as a layer having a thickness distribution on the waveguide layer 7 by sputtering or vapor deposition.

There is also a geodesic lens 9 as shown in FIG. This means that if the waveguide surface of a two-dimensional waveguide is curved in a certain region to create a curved surface that deviates from the original waveguide surface, the guided light beam that passes through this region will travel in a curved line according to Fermat's principle. Since the direction is changed, a suitable lens curved surface 10 as shown in FIG. 11 is used to perform the lens action. The feature of this geodesic lens 9 is that it essentially has no chromatic aberration, and since the focal length does not depend on the mode order, it functions without aberration for all modes in a multimode waveguide. Such a geodesic lens 9 is manufactured by a method of processing a substrate to form a lens curved surface (concavity), and forming a waveguide layer on the substrate surface including the concavity.

Furthermore, as shown in FIG. 12, there is also a grating lens 11 that uses diffraction to condense guided light.

By appropriately combining these lenses, various waveguide optical systems can be constructed.

Problems to be Solved by the Invention However, in the case of the mode index lens I shown in FIG. 9 and the Lunebourg lens 5 shown in FIG. In manufacturing, it is difficult to control the focus side position with high precision.

In addition, in the case of the geodesic lens 9 shown in FIG. 11 that utilizes an optical path length difference, it is difficult to fabricate a structure for providing an optical path length difference with high precision, so it is necessary to have a highly accurate focal length,
Position control is difficult.

Furthermore, in the case of the grating lens 11 shown in Fig. 2 that utilizes diffraction, the focal length can be set depending on the shape of the grating, making it easier to control the focal length than the other lenses mentioned above. However, the diffraction efficiency is not high enough.

Therefore, even if these lenses are combined, it is actually impossible to construct a highly accurate waveguide type optical system.

Means to solve the problem An optical waveguide layer is provided on the substrate, and the planar shape is elliptical, parabolic,
A condensing optical system is provided with at least one waveguide reflecting mirror that has a quadratic curve shape such as a hyperbola and reflects and condenses the guided light guided through the leading waveguide layer at the boundary with the optical waveguide layer. Ta.

The guided light guided through the optical waveguide layer is focused at a predetermined position by a focusing optical system, but the light is focused by reflection from at least one waveguide reflector, and its focal position is located at a predetermined position in the optical waveguide layer. It does not depend on the refractive index, film thickness, light source wavelength, etc., and the focal position can be controlled with high precision only by the planar shape accuracy and positional accuracy of each waveguide reflecting mirror. In particular, since the planar shape of the waveguide reflector is a quadratic curve shape such as an ellipse, parabola, or hyperbola, the focal position can be freely set by combining these, and it is also possible to set the focal position freely, and also to adjust the shape of parallel waveguide light or divergent waveguide light from a point light source. ,
Any type of convergent waveguide light can be condensed at the focal position without spherical aberration.

Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. First, a waveguide layer 13 is formed on a substrate 12 . A portion of the optical waveguide layer 13 is then removed by dry/wet etching, grinding, evaporation, or the like as shown in FIG. As shown in FIG. 1, a condensing optical system is formed by two waveguide reflecting mirrors I4.15.

These waveguide reflecting mirrors 14 and 15 may be formed by simply forming an aperture, or the aperture may be filled with another material having a lower refractive index than the optical waveguide layer 3.

In addition, as shown in FIG. 2(b), a metal 16 having a high reflectivity for the light source wavelength is plated, vapor-deposited,
It may be provided by sputtering or other methods.

Incidentally, these waveguide reflecting mirrors 14 and 15 are formed as concave mirrors, and for example, the incident angle of the guided light incident on the waveguide reflecting mirror 14 is set to Ol as shown in FIG. In addition, the equipolarized refractive index of the guided light in the optical waveguide layer 13 is N
1. Let the equipolarized refractive index of the part where the optical waveguide layer 13 is removed be N (if it is filled with air with the removed part, N,
= 1). Here, the structure shown in FIG. 2(a) or the structure in which the removed part is filled with another low refractive index material (however,
N, )N, maintaining the relationship), the waveguide reflection v
A14 is that in order to reflect the incident light by total internal reflection, the angle of incidence f) ifJ<Oi ≧s r n-' (N r
/N+) must be satisfied. In other words, the arrangement of the waveguide reflecting mirrors is subject to some restrictions. However, according to the structure in which the removed end face is loaded with metal 16 as shown in FIG. 2(b), total reflection is always performed, so that such restrictions on arrangement are not imposed.

Therefore, in this embodiment, the waveguide reflecting mirror 14 is used to first reflect the parallel incident light 17 guided in the waveguide layer 13.
is a concave mirror with a parabolic planar shape (hereinafter referred to as the parabolic mirror 14), and the waveguide reflecting mirror 15 that further reflects the reflected waveguide light from the parabolic mirror 14 is a concave mirror with a hyperbolic planar shape. (Hereinafter referred to as hyperbolic mirror 15).

In such a configuration, when using the parabolic mirror 14, parallel light is focused at one point (focal point F) without spherical aberration, as shown in FIG.
), the parallel incident light 17 guided through the leading wave layer 13 is reflected by the parabolic mirror 14, and then
It attempts to converge on the focal point of this parabolic mirror 14. Since the hyperbolic mirror 15 exists in the waveguide optical path of this convergent light and reflects the convergent light, a convergence effect further acts and the focal position can be changed. Here, if the two focal points of the hyperbolic mirror 15 are F, , F, as shown in FIG. It has the property of being luminous.

Therefore, the focus F of the hyperbolic mirror 15 is the focus of the parabolic mirror 14.
, and also adjust the parameters of the hyperbolic mirror 15 so that the other focal point F1 of the hyperbolic mirror 15 coincides with the desired focus, so that the parallel incident light 17 incident on the parabolic mirror 14 can be made free of spherical aberration. The light can be focused on the focal point F1.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In this example, 'T'-i? A condensing optical system is a combination of a +i elliptical waveguide reflecting mirror (elliptical mirror) 18 and a plane hyperbolic waveguide reflecting mirror (hyperbolic mirror) 19.

In the case of the elliptical mirror 18 in such a configuration, if there is a point light source at one focal point [P] as shown in FIG. has the property of condensing light onto the other focal point I/4 without spherical aberration. Therefore, if there is a point light source at the position of point [Pa 3 in FIG. It will focus the light. Since a hyperbolic mirror 19 is further arranged in the optical path of this reflected guided wave light, it is reflected again and focused at 1.
The light is focused and guided at the position. That is, as described above, the hyperbolic mirror 19 has the property of condensing the light beam directed toward one focal point onto the other focal point by reflection, so that the focal point F of the elliptical mirror 18
4 and desired focal point F.

By determining the hyperbolic parameters of the hyperbolic mirror 19 so as to have two focal points, it is possible to condense and guide the emitted light 20 from the focal point F to the desired focal point F without any spherical aberration.

Incidentally, in this embodiment, if a point light source is placed at the focal point F, and the hyperbolic mirror 19 and the elliptical mirror 18 are used to reflect and guide the light in this order, the light can be focused at the focal point F1. have.

Furthermore, a third embodiment of the present invention will be explained with reference to FIG. In this embodiment, a waveguide reflecting mirror M (hyperbolic mirror) 21 having a plane hyperbolic shape and a waveguide reflecting mirror (hyperbolic mirror) having a plane hyperbolic shape are used.
This is a condensing optical system that combines 22 and 22.

In such a configuration, the slightly convergent light beam 23 to be focused on one point F is sequentially reflected and guided by the two hyperbolas &'t21 and 22, and is focused on the focal point F. At this time, as described in FIG. 1.゛, the reflected light can be focused on the other focal point. Next, by setting this focus as one focus of the hyperbolic mirror 22 and adjusting the hyperbolic parameters so that the other focus coincides with the desired point F,
The light beam 23 to be focused on point F can be focused on the focal point F without any spherical aberration.

Effects of the Invention The present invention is configured as described above, and the guided light is focused by reflection from at least one waveguide reflecting mirror, so that the focal position is determined by the refractive index of the leading wave layer, the film thickness, and the light source. It does not depend on wavelength, etc., and the focal position can be controlled with high precision only by the planar shape accuracy and positional accuracy of each waveguide reflector. In particular, when the planar shape of the waveguide reflector is an ellipse, parabola, hyperbola, etc. Because it has a quadratic curve shape, the focal position can be set freely by combining these, and the focal position is free from spherical aberration regardless of whether it is parallel waveguide light, divergent waveguide light from a point light source, or convergent waveguide light. It can also be used to focus light.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention, in which FIG. 1 is a schematic plan view, FIG. 2 is a schematic sectional view, FIGS. 3 to 5 are reflection characteristic diagrams, and FIG. 6 is a schematic plan view showing the second embodiment of the present invention, FIG. 7 is a reflection characteristic diagram, FIG. 8 is a schematic plan view showing the third embodiment of the present invention, and FIG. 9 is a schematic plan view showing the first embodiment. 10 is a sectional view and a plan view showing a second conventional example, FIG. 11 is a perspective view and a plan view showing a third conventional example, and FIG. 12 is a fourth conventional example. FIG. 3 is a plan view showing an example. 12... Substrate, 13... Optical waveguide layer, 14.15...
・Waveguide reflecting mirror, 17... Waveguide light, 18.19...
Waveguide reflector, 20... Waveguide light, 21. 22... Waveguide reflector, 23... Waveguide light Applicant: Rico Co., Ltd. Managing Director: Akira Aiki” Figure (-NoN)

Claims (1)

[Claims] The optical waveguide layer formed on the substrate has a planar shape of a quadratic curve such as an ellipse, a parabola, or a hyperbola, and the guided light guided through the optical waveguide layer is reflected by the boundary between the optical waveguide layer and the optical waveguide layer. 1. A waveguide type optical element comprising a condensing optical system including at least one waveguide reflecting mirror that condenses light.