JPS63195605A - Thin film lens - Google Patents

Abstract

PURPOSE:To increase the degree of freedom for the design of lens by using a bulk single crystal or thin film of the single crystal of a semiconductor of III-V group compd. or a semiconductor of II-IV compd. and a semiconductor of IV group for a material of a dielectric constituting a thin film lens. CONSTITUTION:A material for a dielectric constituting a thin film lens comprises a bulk single crystal or thin film of the single crystal of a semiconductor of III-V group compd., II-IV compd., or IV compd. In this case, refractive indices of a lens region 2, optical waveguide layer 1, clad layer 4, and substrate 5 are expressed by nL, nW, nC, and NS respectively and materials for the lens region 2, optical waveguide layer 1, and the clad layer 4 are selected so as to satisfy the relation expressed by nL>nW>nC. By this constitution, a thin film lens wherein the shape of the lens, and the difference of the refractive index of the optical waveguide layer 1 to the lens region 2 are designated option ally, is obtd.

Description

[Detailed Description of the Invention] <Industrial Application Fields> The present invention is one of the important components when producing optical integrated circuits and optical integrated devices by T-integrating light emitting elements, light receiving elements, etc. Regarding thin film lenses.

Prior Art The effective refractive index, or mode index, of guided light propagating through a waveguide can be changed by changing the thickness of the waveguide layer, loading the cladding layer, diffusing impurities, etc.

The effective index of refraction always increases with increasing waveguide thickness and loading of cladding layers, and often with impurity diffusion. Therefore, by creating lens-shaped regions #R with different effective refractive indexes in a uniform two-dimensional waveguide, a lens action can be performed by refraction of the guided light beam at the boundary.

Figures 4 to 4 show schematic diagrams of the structure of conventionally proposed thin film lenses.
As shown in Figure 6, (for example, Applied Physics, 48, 3, (
1979) p, 241. (Reference) In FIG. 4, 18 represents a substrate, and 19 represents an optical waveguide 1t. 20 represents a loaded cladding layer, and the effective refractive index increases in the optical waveguide layer below the cladding layer. Therefore, at the boundary between the cladding layer t and the unloaded region, refraction of the 2!4 wave light rays 21 occurs, resulting in a light condensing property.

In FIG. 5, numerals 23 and 23 represent a substrate and an optical waveguide a'i, respectively. 24 represents the loaded cladding layer, the thickness of which is thicker in the center. As a result, in the optical waveguide layer below the cladding layer, a well-fitting effective refractive index distribution is generated that decreases as the thickness becomes thinner from the center of the cladding layer. Therefore, the guided light ray δ passing through the lower part of the cladding layer U is focused according to the refractive index distribution.

In FIG. 6, 26 represents a substrate, and the valleys represent optical waveguide layers. Since the refractive index is higher than that of the optical waveguide layer surrounding the impurity diffusion region, the guided light #29 is refracted and focused at the boundary of the impurity diffusion region.

As a specific row, r7: On the Lgi60S optical waveguide layer,
Aj, ! through a rectangular aperture mask held at a distance t- from the substrate. 3. Lenses with a tapered or cluttered layer deposited on the entire surface (for example, Opi, Lett, etc.)
"Q18, (1983) p. 226) and rt:
A lens with a h% high refractive area kA in which proton exchange occurs in the LtNbos optical waveguide layer (if kept, Opt, Cotmmb,
, s+oJ47. (1983) p. 248).

<Problem that the invention seeks to solve> The above-mentioned conventional technology has the following problems.

1. The material used as the cladding layer is sho.

s<, N4. All, El, , Glass, Ta! o
, etc., or organic thin films such as epoxy or polycarbonate, the refractive index exhibits l1lE inherent to the material, and this cannot be changed arbitrarily. Therefore, P
l: The parameters that control the optical characteristics of the manufactured lens are:
Only the shape of the cladding layer is determined, and the degree of freedom in lens design is small.

Impurity diffusion and proton exchange such as 2.1t usually require heat treatment such as ion exchange at high temperatures.

When the optical waveguide layer is a compound semiconductor, heat treatment may reduce the crystallinity of the optical waveguide layer or cause it to react with the ion exchange solvent, so impurity diffusion regions and proton exchange regions Txt may be formed inside the compound semiconductor. It's far away.

The present invention is intended to solve these problems, and its purpose is to use a semiconductor material containing a compound semiconductor as the constituent material of the lens, and to improve the shape of the lens and the refractive index of the optical waveguide layer and the lens region. The difference lies in providing a thin film lens that can be designed arbitrarily.

<Means for solving the problems> The thin film lens of the present invention is characterized in that the dielectric material constituting the lens is a bulk single crystal or single crystal dielectric material of a ■-V group compound semiconductor, ...-■ group compound semiconductor, and a group ■ semiconductor. It is characterized by being a membrane.

<Implementation row> The present invention will be described in detail below in accordance with the examples.

Example 1 FIG. 1 shows the schematic structure of the thin film lens of the present invention.
The illustrated embodiment is unique in that it has a lens region embedded in the leading wave layer.

In the plan view), 1 represents the optical waveguide layer, 2 represents the lens region embedded in the leading wave layer l, and #3 represents the light ray locus, showing how the light rays passing through the lens region 2 are focused. It shows.

In the cross section 7), l and 2 are optical waveguide layers, respectively.

4 represents the lens region, and cladding layer 5 is the substrate. Here, Reno's area 2. Optical waveguide layer l cladding layer 4. The refractive index of the substrate 5 is %L, 3W,
30, 38.

3r, +) nij) n.

Flu'! /l: ツζ-Todoroki-LTh&he alrs
, Leenon bmu 41ko1-2m＞→! Select the material for the θ cladding layer.

If the relationship sW ) nB is established between the materials of the optical waveguide layer and the substrate, the cladding layer 4 may not be provided.

Substrate materials include GaA4, GQF, and FL.
P, Z%Bg.

■-■ group such as Zi8, a4, Ga and IF-
A Vl group compound semiconductor single crystal substrate or a group II semiconductor single crystal substrate can be used. Also, lens area, optical waveguide layer.

The material constituting the cladding layer t is G4Aj
, Mu! Mua, GaP, In? ■-V group compound semiconductors such as , zdj and single crystal Al of these mixed crystals
■-■ group compound semiconductors such as flIK, znSLII2%B, Cd8, Z9T#.

and single crystal thin films of these mixed crystals, Bi, Gg,
Single-crystal thin films of group III semiconductors such as and mixed crystals thereof can be used. By appropriately combining the shape of the lens region and the material constituting the lens according to the wavelength of light incident on the optical waveguide layer and the lens region, a thin film lens having desired light condensing properties can be manufactured.

Table 1 shows examples of specific combinations of materials for the plate.

(Table 1) Thin film lens t of the present invention - The combination of constituent materials is not limited to the material systems shown in Table 1, but may include m-v group compound semiconductors, n-■ group compound notebooks, bulk of group II semiconductors. As mentioned above, a single crystal or a single crystal thin film can be optionally used, and any case is included in the present invention.

The thin film lens of the present invention can be easily produced by a vapor phase epitaxy method (CVD method), a metal organic vapor phase pyrolysis method (MOCVD method), a single molecular beam epitaxy method (MBIII method), or the like. A manufacturing process diagram of the thin film lens is shown in FIG. 2. A cladding layer 7 with a thickness of about 1 to several μm is formed on a substrate 6. An optical waveguide layer 8 having a thickness of about 1 to 10-odd microns is laminated.

Next, use sho or 8<1N4 as a mask material.
Thin @f: A mask 9 is formed and a desired opening is formed by photolithography and etching. Subsequently, the optical waveguide layer 8 is removed according to the shape of the mask 9 by wet chemical etching or dry vapor phase etching such as reactive ion beam etching to form an opening 1o. Thereafter, a single crystal thin film having a higher refractive index than the optical waveguide layer 8 is selectively buried and grown inside the opening 10 to form a lens region. The mask is removed by etching. If the refractive index of the mask material is smaller than that of the optical waveguide layer, the mask itself does not necessarily need to be removed because the mask itself functions as a cladding layer for the optical waveguide layer.

Types and combinations of materials that make up thin film lenses.

Alternatively, if selective filling growth is not possible only in the lens region due to the manufacturing conditions of each layer, and a deposited layer is also formed on the mask, it becomes impossible to remove the mask and the deposited layer on the mask. .

In such a case, the mask may be formed of a material whose refractive index is sufficiently smaller than that of the optical waveguide layer.

As is clear from the above manufacturing method, the shape of the thin film lens of the present invention can be arbitrarily designed using photolithography technology. In the thin film lens of the present invention, a lens having desired characteristics can be easily produced by combining the type of material constituting the lens and the shape of the lens.

Implementation row 2 FIG. 3 shows a schematic diagram of the structure of the thin film lens of the present invention.
The illustrated embodiment is characterized by a cladding layer loaded on the optical waveguide layer.

In the plan view), 12 represents a leading wave layer and 13 represents a cladding layer loaded to form a lens region. 14 represents a ray locus.

It shows how light rays passing through a lens region formed under the cladding layer are focused. In the cross-sectional view CB), 12 and 13 are the optical waveguide layer and the lens area m, respectively.
t-cladding layer loaded to form.

A lens region 11d is formed at the bottom of the cluttering layer I3 due to a change in the effective refractive index! 15 is formed.

16 represents the second cladding layer, and 17 represents the substrate.

As in Example 1, the whale ding layer 13. Optical waveguide layer 12
, second cladding layer 16. Materials for the optical waveguide layer 12 and the cladding layers 13 and 16 are selected so as to satisfy the following relationship, where the refractive index of the substrate 17 is fLLs ``H'IL'' $ne.

fLll) @B If the following relationship is established between the materials of the optical waveguide layer and the substrate, it is not necessary to provide the second cladding layer 16, and the material constituting the lens is ■- as in Implementation HJ 1.
Pulk single crystal or single l1faW[t-group (1) group compound semiconductor, n-vt group compound semiconductor (Gv2) group semiconductor, or single l1faW[t- can be used arbitrarily.

It is also true that the characteristics of the lens can be designed by combining the shape of the cladding layer 13 and the materials that make up the lens.
Same as N17. The lens can be manufactured using the same steps as in Example 1. That is, the second cladding layer 16 and the optical waveguide layer 12t are laminated on the substrate 17J, and then a mask having an opening of a desired shape is formed, and selective growth is performed in the opening to form the cladding layer 13. Finally, by removing the mask, the lens can be manufactured. Whether or not to remove the mask may be determined in the same manner as in the case of implementation column 1, and it is not necessarily necessary to remove the mask.

Actual Example 3 In Examples 1 and 2, single crystal thin films of different materials or different compositions were used to change the refractive index of the lens region, leading wave layer, and cladding layer. Without being limited to the structure, if fed, single-cell thin Ut of the same composition may be used, and the type or type of impurity added to each layer may be changed.
A configuration in which a refractive index difference is formed between the lens region, the optical waveguide layer, and the cladding layer by changing t is also included within the scope of the present invention.

The thin film lens of the present invention can be used not only as an individual optical element to condense a light beam emitted from a semiconductor laser, an optical fiber, etc., but also to be monolithically fabricated on the same substrate together with a semiconductor laser, photodiode, etc. It is also possible to apply it to integrated devices.

<Effects of the Invention> As described above, according to the present invention, in a mode index lens made of a plurality of dielectric materials having different refractive indexes, a ■-V group compound semiconductor, a ■-■ group compound semiconductor, and a ■-V group compound semiconductor are used as the dielectric materials. By using bulk crystal or single-crystal thin IT of Group III semiconductors], the shape of the lens and the refractive index difference between the optical waveguide layer and the lens region can be set arbitrarily, and by changing these parameters, arbitrary characteristics can be obtained. The Is film lens of the invention can be easily integrated with semiconductor lasers, photodiodes, etc., making it extremely important when manufacturing optical integrated circuits and optical integrated devices. I am confident that it will become a major component.

[Brief explanation of the drawing]

Fig. 1) (b) is a schematic diagram of the structure of the thin film lens of the present invention. FIG. 1(6) is a plan view, and FIG. 1(6) is a sectional view. 1. Optical waveguide layer 2. Lens region 3. Ray locus 4. Cladding layer 5. Substrate 2. (a) to 2 are manufacturing process diagrams of the thin film lens of the present invention. 6 Substrate 7 Cladding layer 8 Optical waveguide layer 9 Mask 1
Figure 3 (6) is a schematic diagram of the structure of the thin film lens of the present invention; Figure 3 (6) is a plan view; Figure 3 (b) is a sectional view. Minoru optical waveguide! 13 Cladding layer 14 Element line locus 1
5 lenses 1 Jljli 116 second cladding layer 1
7 substrates Figures 4 to 6 are schematic diagrams of the structure of conventionally proposed thin film lenses. 18 substrate 19 optical waveguide layer 21 waveguide light beam 2 substrate optical waveguide layer scrubbing layer 3 waveguide light beam 3 substrate n lead wave layer
Wing impurity diffusion region bA29 waveguide beam'
1. , t-15M sprout 1 country l left, Shinsu N! L7i\1' v3 Figure 5th Hu

Claims (1)

[Claims] 1. In a mode index lens made of multiple dielectric materials with different refractive indexes, the dielectric material is a bulk single crystal or single crystal thin film of a III-V group compound semiconductor, a II-VI group compound semiconductor, and a group IV semiconductor. A thin film lens featuring