JPS60260925A - Optical "and" circuit - Google Patents

Abstract

PURPOSE:To obtain an optical AND circuit by applying photoelectromotive forces produced in photoelectromotive elements placed at the ends of two optical waveguides by light traveling in the waveguides to the narrow switching part of other optical waveguide into which standard light is inputted through an addition circuit so as to transmit light. CONSTITUTION:Optical waveguides 11, 12, 13 are formed on a substrate 10 of an LiNbO3 crystal. Photoelectromotive elements 21, 22 of CdTe or the like are placed at the ends of the waveguides 11, 12. A narrow part 14 where single-mode light does not travel by diffusion is formed in the waveguide 13, and electrodes 23 are placed on both sides of the part 14. When the sum of photoelectromotive forces produced in the elements 21, 22 by light traveling in the waveguides 11, 12 is applied to the electrodes 23 through a wiring pattern 24 forming an addition circuit, standard light traveling in the waveguide 13a passes through the narrow part 14, travels in the waveguide 13b, and is emitted. Only in case where both inputted signals IinA and IinB are 1, Iout becomes 1 and an optical AND gate circuit is obtd.

Description

[Detailed description of the invention] Background of the invention The present invention relates to an optical p-ND circuit.

In recent years, optoelectronic technology has made rapid progress, and the realization of optical ICs has become 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. However, although the optical AND (AND) circuit is the most basic logic circuit, there are currently no proposals or experimental reports on its structure.

Summary of the Invention The present invention provides an optical AND circuit, which is the most basic logic circuit for realizing an optical IC.

The optical AND circuit according to the present invention includes at least two first optical waveguides into which at least two input optical signals are input;
A second optical waveguide into which a reference optical signal is input; light propagating through the first optical waveguide; at least two photovoltaic elements excited respectively; , a circuit for adding the electromotive force voltage of the photovoltaic element, and an electrode for applying the added sum voltage to the switching line are formed on the substrate portion having an electro-optic effect, and The electromotive force voltage of the electromotive force element is 2 (7f-7?)
7') Photovoltaic force element , [,,,, . . . The photovoltaic element is characterized in that the propagation of light in a predetermined mode is switched depending on whether or not a sum voltage of the electromotive forces of the photovoltaic elements is applied.

Only when light is propagating through at least two first optical waveguides, all photovoltaic elements generate electromotive force, and these voltages are added. If the switching part of the second optical waveguide is a narrow part with a narrow width and the refractive index increases as a result of applying a sum voltage, this sum of the electromotive forces of all the photovoltaic elements is added. Only when a voltage is applied to the electrode, light of a predetermined mode of the reference optical signal in the second optical waveguide passes through this switching section and becomes an output optical signal. When there is no input optical signal in any one of the first optical waveguides, no electromotive force is generated from the electromotive force element corresponding to it. In this case, the voltage applied to the electrodes does not produce a sufficiently high refractive index for light of a given mode of the reference optical signal to pass through the switching section, so that light of a given mode of the reference optical signal does not pass through the switching section. Do not propagate.

Therefore, a positive AND logical operation is achieved in which the presence of light is r I J and the absence is Oj.

When the refractive index of the switching section is reduced by applying the sum voltage of the electromotive forces of all the photovoltaic elements, a NAND AND logical operation is performed. Ru.

Since the optical AND circuit according to the present invention can be created on one substrate, it can serve as one functional element for realizing an optical IC.

Description of examples First, I will explain the optical AND logic.

Optical p, ND logic is the same as AND logic (especially positive logic) of electrical signals. In FIG. 1, two input optical signals are represented by inA and I,nB. An output optical signal output as a result of optical AND logical operation of these input optical signals is shown as ■ out . The amount of light represents a logical value of "1", and the amount of light represents a logical value of "10". Input optical signals I, , A and input B are "0"
and "Q", "1" and "0", or "0" and "1", the output optical signal I. ut becomes “0” and the input is “1”.
” and “1”, the output will be “1”.

In Fig. 2, a LiNbO3 crystal is used as a substrate, and three optical waveguides are mounted on this substrate (10).
t12+ and (13) are formed. The fabrication of these optical waveguides is, for example, by depositing or sputtering Ti on the entire surface of the substrate, using this Ti film to form a waveguide pattern made of Ti by the 7-off method, and then This is carried out by thermally diffusing into the substrate (10) at 970° C. for 5 hours in an oxygen atmosphere. At least the optical input part (13a) of the optical waveguide (13)
and the light output part (13b) + Regarding this part 11]
The thickness is preferably about 5 μm so that the light propagation mode is single.

The optical waveguides (11) and (12) guide the input optical signals 1rlA and 1flB to be subjected to an AND logic operation, and these optical waveguides fil)t121 are as follows:
It is formed from one end of the substrate (10) to near the center of the substrate (10).

A photovoltaic element t2]) (2a) is fabricated on the terminal end of the optical waveguide fil+ t12). For example, CdTe is suitable as the photovoltaic element (21) f22+. As shown in FIG. 1. Optical waveguide (1
1) Even if you just deposit CdTe on top of the car, you can create an optical waveguide (
Since the field distribution of light in 11) also extends to the photovoltaic element c11), an electromotive force is generated from the photovoltaic element 01). When the generated voltage is low, as shown in FIG.
1) and the optical waveguide (11). The TiO2 film 051 is formed, for example, by spucking. Furthermore, the photovoltaic element (21) is connected to the optical waveguide (
11) can be formed so as to diagonally cross downward at an angle of about 30''. In addition, the optical waveguide 1111
A grating may be provided at a portion of the surface that is in contact with the photovoltaic element (21). In any case, as described later, sufficient electromotive force should be generated to increase the equivalent refractive index to a desired value. Since the photovoltaic element (21) is formed at the end of the optical waveguide (11), the photovoltaic element (21)
The amount of light sensed by the photovoltaic element (21) will increase and a higher voltage will be obtained from the photovoltaic element (21). The above points also apply to the photovoltaic element (22).

In Fig. 2, the optical waveguide (13) is the reference light input ■in
Output light ■ that constantly introduces R and represents the AND logical operation result. This outputs ut.

This optical waveguide (13) is formed from one end of the substrate (10) to the other end, and has a narrow portion (j4) across the center. A light input section (13a,) and an output section (13b) are connected to both ends of the narrow width section (14). The width of this narrow portion (14) is the width of the optical input portion (14).
It is formed so narrowly that it does not allow the light propagating from 3a) to propagate. For example, when single-mode light propagates through the light input section (13a), the width of the narrow portion (14) is designed so that the light becomes a diffuse mode.

A pair of electrodes (23) are formed on both sides of the narrow mountain portion (14). Wiring pattern C4) 1 connects both photovoltaic elements (21) and the pixel element (2+) in series.
The sum of the electromotive forces of and @ is applied to the electrode reed. The electrode (231) and wiring pattern (24) are AI!
It is manufactured by lift-off in a predetermined pattern.

Since LiNbO3 is a crystal with an electro-optic effect, when an electric field is applied to this crystal, its refractive index changes. For example, when an electric field E is applied in the C-axis direction 3 of a L i N b O3 crystal, the refractive index becomes Δ”eo ”'--
Fist γ33・E Change. Here, n is LiNbO3
The refractive index is 2.200. γ33 is an electro-optical constant of 30
, sx 10'''m/V. Optical waveguide (13)
The narrow part of the electrode (23) has a width that does not allow light to propagate as described above, but when a voltage is applied between the electrodes (23),
The higher the refractive index, the more light will propagate. This will be explained using FIG. 4.

FIG. 4 shows the relationship between the mode of light that can propagate in the optical waveguide and its isolateral refractive index for the normalized optical waveguide section.

The input part (13a) or the output part (1) of the optical waveguide (13)
3b) is D□, and the width of the narrow mountain portion +141 is D2, then the normalized optical waveguide in these optical waveguide portions is k@D1. convex) *Jn*n-1k
・Given by 25 D, k, Dl, 7'i-5) k@D
2A/Seal p*Jnen-. Here k is the wave number, Δn
is the difference in refractive index between the optical waveguide part and the substrate 6, Figure 4°
' Show 8. tLTl, N, BJ1. U°'・Optical waveguide 0°
Input part (13a) and output part (13b) of l j :
The width D□ is determined so as to propagate single-fist mode light (see point (F'l)).The narrow part (14) is designed to prevent single-fist mode light from propagating [
In other words, the width D2 is determined like a ring in the dissipation mode (see point (El). This is the electrode (support)).
This is the case when no voltage is applied to. Therefore, the electrode (2
3), when no voltage is applied to the input section (13
The light in a) does not propagate through the narrow mountain portion (141) and leaks, so that no light is obtained at the output portion (13b).

Suppose that when the voltage generated in either one of the photovoltaic elements Ol) or (22) is applied to the electrode (23), the refractive index of the narrow portion (14) increases by Δn. Then, the normalized optical waveguide “1” in the narrow 1] part (14)
] increases and becomes k@D2J ding 廼−了75 ding 7 (4th
(See figure, point (Eo□)). However, even in this leading wavepath, the single fist mode light does not propagate through the narrow width part +14).

If the output voltages of both photovoltaic elements 21) and 23) are added and this sum voltage is applied to the electrode [23+1], the applied voltage will be twice the G of the above case.
14) The refractive index at + increases further.

Then, the normalized optical waveguide inside the narrow part +14+1 becomes -D2f'υn-Jn,)n (see point (Eo2) in Figure 4), and the input and output parts (i3a) (
13b), and the light propagates in a single mode. Therefore, the single mode light from the optical input section (13a) passes through the narrow width section (141) and is obtained from the optical output section (13b).

Now, returning to FIG. 2, the operation of this optical AND circuit will be explained in a unified manner.

Both the input optical signal ■inA and the input optical signal 1IIB have the logical value "
0'' (photothermal), photovoltaic elements (21) (2
Since no electromotive force is generated from either of 2), the base light I
, nR do not pass through the narrow width part 04), and the output optical signal Iout
is also "0".

The input optical signals ■1tlA, l1nB have the logical value rlJ, "0
'' or in the case of logical values ``0'' and ``1'', the electromotive force is generated from only one photovoltaic element, so the refractive index of the narrow circle is the input light . It does not increase enough to propagate R. Therefore, the input part (13) of the optical waveguide (13)
The light in a) leaks at the narrow part (14), resulting in an output optical fiber type. ut is "0".

When the input optical signals ■inA and l1TIB are both "1", a voltage is generated in both photovoltaic elements f2]) (22) + by the light propagating through the leading waveguide +Ill f121, and the sum voltage of these is applied to the electrode (23). Therefore, the optical input section (13a) of the leading waveguide (13)
The light propagates through the Sayama part 04) to the light output part (13b), so it is an output light beam type. ut becomes rlJ.

Applying a voltage to the electrode (c) [Thus, if the refractive index decreases, NAND AND logic is performed.

In this case, it is not necessary to make the width of the optical waveguide (131 portion (14) narrow).When no voltage is applied to the electrode (23H), and when only the voltage of one photovoltaic element is applied Input light Ii.R is transmitted through this optical waveguide (13
) and output as output light Iout. When the sum of the output voltages of both photovoltaic elements is applied to the electrode f231, the input light l
It is sufficient to prevent 1nR from passing through the portion (141).

As a result, the output optical fiber type is output only when the input optical signal Iin As ``in B'' is ``L''. Straight is 10
”. In this invention, it is included in the concept of such NAND AND logic.

This invention enables not only single-mode light but also multi-mode light.
It can also be applied to optical AND or NAND logical operations of modes. In this case, focusing on the light of a certain higher mode, the logical value "1" is determined depending on the presence or absence of light in that mode.
, it is better to set "0".

Further, the present invention provides an AND or an N of two input optical signals.
It is applicable not only to AND logical operations but also to AND or NAND' logical operations of three or more input optical signals. For example, if there are three input optical signals, yet another optical waveguide and a photovoltaic element are provided.

Then, the sum of the electromotive forces of these three photovoltaic elements is applied to the electrode (23+) of the narrow part (I4), and the width of the narrow part (14) is determined by the electromotive force of the three photovoltaic elements. The setting is such that the propagation of light can be achieved only when a voltage equal to the sum of the voltages is applied ((in the case of AND logic)).

Also in the configuration shown in FIG. 2, it is possible to perform an AND logic operation on three input optical signals. In this case, instead of the reference optical signal l1nRi, the third input optical signal ■i may be input to the iDC optical waveguide (13).

The substrate (10) may be of any material as long as it has an electro-optic effect in which its refractive index changes upon application of an electric field. Therefore, each optical waveguide (Ill (12++13
1 can also be manufactured using various techniques and abrasive materials depending on the type of substrate other than thermal diffusion of Ti. The electrode (23) is an optical waveguide (
Since it is for applying voltage to the narrow RJ section 04) of the section 13), it may be placed on the section 14, and may take various shapes other than those shown. Photovoltaic element CI! 11
E is also a-8 produced by plasma CVD method.
It can be realized using various materials such as Ti, and the electrode (23) and wiring pattern Q4) can also be realized using materials such as Ti.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram showing an AND logic operation, Fig. 2 is a perspective view showing an embodiment of the present invention, Fig. 3 is a cross-sectional view showing a state in which a photovoltaic element is manufactured, and Fig. 4 is a normalization 3 is a graph showing the relationship between the mode of light propagating in the guided wave path and the mode of light propagating therein. (10)... Board, fill f+21 (13)
... Optical waveguide, 14) , Narrow [1] part (switching part), (2] H'2) ... Photovoltaic element, +23
+--electrode, +24+-10 wiring pattern (addition circuit). Figure 1 0 1 0 1 0 0 1 1 001 - Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] +1. l At least two first optical waveguides into which at least two input optical signals are input, a second optical waveguide into which a reference optical signal is input, at least two optical waveguides each excited by the light propagating through the first optical waveguide. A photovoltaic element, a switching section located at a required location of the second optical waveguide, a circuit for adding up the electromotive force voltage of the photovoltaic element, and an electrode for applying the added sum voltage to the switching line are electro-optical. A part of the substrate having an effect is formed, and the electromotive force voltage in the switching part and in the photovoltaic element is
In the switching line, the tm of light in a predetermined mode depends on whether a sum voltage of the electromotive forces of all photovoltaic elements is applied or not.
An optical AND circuit designed to switch. (2) The switching part has a narrow width part, and propagates light of a predetermined mode when the refractive index increases due to the rigid force I of the sum voltage of the electromotive forces of all the photovoltaic elements, An optical AND circuit according to claim (1). (3) When the refractive index of the switching section is reduced by applying the sum voltage of the electromotive forces of all the photovoltaic elements, light in a predetermined mode does not propagate, claim (1) f.
The optical AND circuit described here. (4) The optical AND circuit according to claim (1), wherein the third input optical signal is input to the second optical waveguide instead of the reference optical signal.