JPS61241736A - Photoelectric converter formed on base board - Google Patents

Abstract

PURPOSE:To perform highly efficient photoelectric conversion by radiating the rays of light propagated through an optical wave guide in the direction of a high-refractive index layer mounted on the optical wave guide when the rays of light reach the part of the layer and causing the rays of light to be made incident on a photovoltaic element. CONSTITUTION:An input optical signal Iin is introduced to the 1st optical wave guide 11 and a reference light IinR is always inputted in the 2nd optical wave guide 12. An output optical signal Iout is obtained from the 3rd optical wave guide 13. Since no electromotive force is generated from a photovoltaic element 15 when the input optical signal Iin is '0', no voltage is applied across electrodes 14. Therefore, 100% of the rays of light propagated through the optical wave guide 12 are shifted from a directional coupler to the optical wave guide 13 and the output optical signal Iout becomes '1'. When the input optical signal Iin is '1', a voltage is generated across the photovoltaic element 15 by the rays of light propagated through the optical wave guide 11 and the voltage is applied across the electrodes 14. Therefore, the rays of light propagated through the optical wave guide 12 are not shifted from the directional coupler to the optical wave guide 13, but propagated through the optical wave guide 12. Accordingly, the output optical signal Iout becomes '0'.

Description

BACKGROUND OF THE INVENTION The present invention relates to a photoelectric conversion device formed on a substrate, and is particularly useful for optical logic circuits integrated on a substrate.
The present invention relates to a device for generating electromotive force from an optical signal.

In recent years, optoelectronic technology has made remarkable progress, and the realization of optical ICs has been raised as one of the development issues. In fact, the basic logic circuits of optical ICs, such as optical OR (
OR) circuits and optical exclusive OR circuits have been proposed. The applicant has also proposed various optical logic circuits integrated on a substrate with an electro-optic effect (for example, Japanese Patent Application No.
7552-117554 etc.). In these optical logic circuits, an optical signal is converted into an electrical quantity, and various types of light control are achieved using this electrical quantity by utilizing the electro-optic effect of the substrate. A sufficient amount of electricity, such as a sufficiently high voltage, is required to achieve the desired light control.

Summary of the Invention The present invention provides a photoelectric conversion device that effectively utilizes light propagating through an optical waveguide formed on a substrate to obtain a sufficient amount of electricity necessary for operating an optical logic circuit, etc. This is what we provide.

In the photoelectric conversion device according to the present invention, a layer made of a material having a refractive index higher than that of the optical waveguide is loaded on the surface of an optical waveguide formed on a substrate, and a photovoltaic element is placed on the high refractive index layer. It is characterized by 4.

When the light propagating through the optical waveguide reaches the part of the high refractive index layer loaded on the optical waveguide, it is radiated in the direction of this layer and enters the photovoltaic element formed on top of it, causing the light to propagate through the optical waveguide. Much of the emitted light is used to generate electromotive force, achieving highly efficient photoelectric conversion.

DESCRIPTION OF EMBODIMENTS An embodiment in which a photoelectric conversion device according to the present invention is applied to an optical NOT circuit, which is a basic element of an optical logic circuit, will be described in detail below.

First, optical NOT logic will be explained. Optical NOT logic is the same as electrical signal NOT logic. In FIG. 1, the input optical signal is represented by lin. An output optical signal output as a result of optical NOT logical operation performed on this human-powered optical signal is indicated by 1out. The light valve has a logical value of “1”
”, and the absence of light represents the logical value “0”. When the input optical signal 11n is "0", the output optical signal 1out is "1".

When the input is "1", the output is "0".

In FIG. 2, a LiNb03 crystal is used as the substrate 10, and three optical waveguides 11, 12□
and 13 are formed. These optical waveguides are manufactured by, for example, depositing or sputtering Ti on the entire surface of the substrate 10, using this T1 film to form an optical waveguide pattern of T1 by a lift-off method, and then depositing Ti on the entire surface of the substrate 10.
This is carried out by thermally diffusing into the substrate 10 at 970° C. for 5 hours in an oxygen atmosphere.

The first optical waveguide 11 is formed from one end of the substrate IO to near the center of the substrate 10 or the other end of the substrate IO, and a photovoltaic cable 15 is fabricated at the terminal end of the optical waveguide 11 or along the way. There is. For example, as the photovoltaic element 15, C
dTe is good. As shown enlarged in Figure 3,
A layer 17 of high refractive index material is formed on the surface of the optical waveguide 11, CdTe is evaporated onto this layer 17, and terminals are formed at appropriate locations (for example, on both sides of the top surface of the CdTe) to form a photovoltaic element. 15 is completed.

As shown in FIG. 4, even if CdTe is simply deposited on the optical waveguide 11, the field distribution of light within the optical waveguide ll extends to the photovoltaic element 15, so that an electromotive force is generated from the photovoltaic element 15. Occur. However, the electromotive force generated in this case is considered to be low. This is because the optical waveguide is for confining light, and the field distribution of light leaking to the outside is small. Therefore, as shown in FIG. 3, an intermediate layer 17 made of a material having a higher refractive index than the optical waveguide 11 is interposed between the photovoltaic element 15 and the optical waveguide 11. Then, the light in the optical waveguide 11 leaks into the layer 17 having a higher refractive index.

The photovoltaic element 15 senses this leaked light and generates photovoltaic force. The amount of leaking light increases as the refractive index of the high refractive index layer 17 increases and as the length of the optical waveguide ti of the high refractive index layer 17 increases. Since the extraordinary refractive index of the substrate 10 is 2.200, the material for the high refractive index layer 17 has an ordinary refractive index of 2.58.
It is better to use 4 TlO2. Tl by lift-off method
After producing O2, by sputtering CdTe, the photovoltaic cable 15 can be accurately produced on the high refractive index layer 17. In addition to TlO2, materials for the high refractive index layer 17 include T e Oa with a refractive index of 2.27 and AS23 with a refractive index of 2.46.
3 etc. may also be used.

The light that did not enter the photovoltaic element 15 may further propagate through the optical waveguide 11 and be used for other purposes, or if there is no other use, the position of the photovoltaic element 15 may be changed to the optical waveguide 11. It is considered to be the end of In this case, the optical waveguide 11
A portion of the light reflected at the end face of the photovoltaic element 15 will also be incident on the photovoltaic element 15.

In FIG. 2, the second optical waveguide 12 is formed from one end of the substrate 10 to the other end. One end of the third optical waveguide 13 is close to a part of the second optical waveguide 12, and the other part is away from the second optical waveguide 12.

Portions of the second optical waveguide 12 and the third optical waveguide 3 that are close to each other constitute a directional coupler. A pair of electrodes 14 are provided on the optical waveguide portion constituting this directional coupler.

Both terminals of a photovoltaic element 15 are connected to this electrode 14 by a wiring pattern 1B, and the electromotive force of the element 15 is transferred to the electrode 14.
It is designed to be applied between 4 and 4 hours. The electrode 14° wiring pattern 16 and the terminal of the photovoltaic element 15 are fabricated by lifting off A0 into a predetermined pattern.

A directional coupler causes optical power to be exchanged between two parallel optical waveguides that are close to each other.

A directional coupler constituted by portions of optical waveguides 12 and 13 that are close to each other has an interaction length such that 100% of the power of light propagating through one optical waveguide 12 is transferred to the other optical waveguide 13. , a coupling coefficient, a phase constant, etc. are set.

This is because LiNb03 is a crystal with an electro-optic effect.

When an electric field is applied to this crystal, its refractive index changes. When a voltage generated from the photovoltaic element 15 is applied to the electrode 14, the refractive index of the optical waveguide 12.13 directly below the electrode changes, and the phase constant in these parts of the optical waveguide 12.13 changes (Z-cut). (in the case of LiNb03), or the strength of the coupling changes by changing the refractive index between these optical waveguide sections in the optical waveguide 12.13 (
In the case of Y-cut LxNbOa). Due to such a change in coupling strength and phase matching, no optical power shift occurs in the directional coupler formed by the adjacent portions of the optical waveguides 12 and 13.

Now, the operation of the optical NOT circuit shown in FIG. 2 will be explained in a unified manner. The input optical signal 11n is introduced into the first optical waveguide 11. The second optical waveguide ■2 has a reference light of 1 inR
is always manned. The output optical signal 1out is obtained from the third optical waveguide 13.

When the human power optical signal Inn is "0", the photovoltaic element 1
Since no electromotive force is generated from the electrode 5, no voltage is applied between the electrodes 14. Therefore, 100% of the light propagating through the optical waveguide 12 is transferred from the directional coupler to the optical waveguide 13, and the output optical signal 1out becomes "1".

When the human-powered optical signal 1fn is rlJ, a voltage is generated in the photovoltaic element 15 by the light propagating through the optical waveguide 11,
This is applied between the electrodes 14. Therefore, the light propagating through the optical waveguide 12 continues to propagate through the optical waveguide 12 without transferring from the directional coupler to the optical waveguide 13. For this reason,
The output optical signal 1out becomes "0".

In the above explanation, the amount of power transfer in the directional coupler is ideally 100%, but of course it is 100%.
It doesn't need to be 0%. This is because the logical values rlJ and rOJ can be determined by level-discriminating the power of the optical signal 1out output from the optical waveguide [3.

In any case, since the photovoltaic element 15 is formed on the high refractive index layer 17 formed on the upper surface of the optical waveguide 11,
Most of the light that has propagated through the optical waveguide 11 reaches the photovoltaic element 1
5 to be used. therefore.

It has high efficiency and a large electromotive force, and can be applied to control optical signals using the electro-optic effect as described above.

It goes without saying that the optical logic circuit to which this invention is applied is not limited to the above-mentioned optical NOT circuit, and the invention can be applied to elements formed on a substrate other than optical logic circuits.

Photovoltaic elements are not limited to CdTe, but also plasma CVD
This can be realized with various products such as a-9i produced by the method.

[Brief explanation of drawings]

Fig. 1 is a waveform diagram showing an optical NOT logic operation, Fig. 2 is a perspective view showing an embodiment in which the present invention is applied to an optical NOT circuit, and Fig. 3 is an enlarged sectional view taken along the line ■-■ in Fig. 2. , FIG. 4 is a cross-sectional view corresponding to FIG. 3 in the case where no high refractive index layer is provided. 10...Substrate, 11.12.13...
optical waveguide. 15... Photovoltaic element, 17... High refractive index layer. that's all

Claims (1)

[Claims] A layer made of a material with a refractive index higher than the refractive index of the optical waveguide is loaded on the surface of the optical waveguide formed on the substrate, and a photovoltaic element is formed on the high refractive index layer. photoelectric conversion device.