JPS60260924A - Optical "and" circuit - Google Patents

Abstract

PURPOSE:To obtain an optical AND circuit by applying voltage produced in a photoelectromotive element excited by light traveling in the 2nd optical waveguide to the narrow part of the 1st optical waveguide so as to transmit light. CONSTITUTION:Two optical waveguides 11, 12 are formed on a substrate 10 of an LiNbO3 crystal. The photoelectromotive element 20 of CdTe or the like is placed on the end of the waveguide 11. The narrow part 13 where single-mode light does not travel by diffusion is formed in the waveguide 12, and electrodes 21 are placed on both sides of the part 13. Light travels in the waveguides 11, 12a, and when the photoelectromotive force produced in the element 20 is applied to the electrodes 21 through a wiring pattern 22, the refractive index of the narrow part 13 of the waveguide 12 is increased to transmit light. This light travels in the waveguide 12b and is emitted. In case where both inputted photo signals IinA and IinB are 1, Iout becomes 1 and an optical AND circuit is obtd.

Description

[Detailed description of the invention] Background of the invention The present invention relates to an optical AND 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 circuit of an optical IC, for example an 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 a first optical waveguide to which one input optical signal is input, at least one second optical waveguide to which at least one input signal is input, and a predetermined position of the first optical waveguide. The formed narrow width portion, a photovoltaic element excited by the light propagating through the second optical waveguide, and an electrode or electro-optic for applying the voltage generated by the photovoltaic element to the narrow width portion. The width of the narrow portion and the electromotive force voltage of the photovoltaic element are such that light of a predetermined mode is propagated only when a voltage is applied in the narrow portion. It is characterized by the fact that it is defined.

Only when light is propagating to the second optical waveguide, an electromotive force is generated from the photovoltaic element, and this is applied to the electrode of the narrow portion of the first optical waveguide. When the refractive index increases due to the application of voltage, light begins to propagate through the narrow portion. At this time, if light is input to the first optical waveguide, this light will propagate through the narrow part, so "1" indicates the presence of input light, and rO indicates no input light.
A positive AND logical operation with J is achieved. 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, optical AND logic will be explained.

Optical AND logic is the same as AND logic (and positive logic for <111) of electrical signals. In FIG. 1, two input optical signals are represented by l1nA and l1nB. An output optical signal output as a result of optical AND logical operation of these input optical signals is indicated by Iout. The presence of light represents the logical value ``1,'' and the absence of light represents the logical value ``10.'' Input optical signals l1nA and l1nB or “0” and r
When OJ is "1" and "10" or "0" and "11", the output optical signal Iout is "0", and the input is "11" and "11".
”, the output will be “1”.

In FIG. 2, L I N b is used as the substrate (10).
O3 crystal is used, and two optical waveguides (11) and (12) are formed on this substrate 00). The fabrication of these optical waveguides is, for example, a T
evaporate or sputter and use this Ti film to
A waveguide pattern is formed by a lift-off method, and the Ti is thermally diffused into the substrate 00) at 970° C. for 5 hours in an oxygen atmosphere. The width of the optical waveguide (11) and the optical input section (12a) and optical output section (12b) of the optical waveguide (121) is preferably about 5μ so that the propagation mode of light is single.

One optical waveguide (11) is formed from one end of the substrate (10) to near the center of the substrate (10).
A photovoltaic element 90) is fabricated on the terminal end of 11). As the photovoltaic element (20), for example, CdTe
Good. As shown in Figure 3), even if CdTe is simply vapor-deposited on the optical waveguide (11), the field distribution of light within the optical waveguide (11) extends to the photovoltaic element (20). An electromotive force is generated from the power element (2). If the generated voltage is low, the optical waveguide (
11) It is preferable to interpose an intermediate layer made of a material with a larger refractive index than the photovoltaic element 201 and the optical waveguide (11), for example, a T i O2 film. T
The iO2 film (25) is formed by sputtering, for example. Furthermore, the photovoltaic element equipment has an optical waveguide (11) of 30
It can also be formed to cross diagonally in the vertical direction at an angle of about . Furthermore, a grating may be provided on the top surface of the optical waveguide (11) at a location where it contacts the photovoltaic element (a). 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 (20) is formed at the end of the optical waveguide (11), the amount of light sensed by the photovoltaic element increases due to reflection, scattering, etc. of light at the end of the optical waveguide, and the light A higher voltage will be obtained from the electromotive force element CO).

In FIG. 2, the other optical waveguide (12) is connected to the substrate (10
) is formed from one end to the other end, and has a narrow part (131) at the center of the body.This narrow part (
A light input section (12a) and an output section (1
2b) are connected. The width of this narrow width portion Q31 is formed to be narrow enough to prevent the light propagated from the light input portion (XZa) from propagating. For example, the optical input section (x2a
The width of the narrow width portion 03) is made so that when single mode light propagates through ), the light becomes a diffuse mode.

A pair of electrodes 01 are formed on both sides of the narrow width portion 03),
Both terminals of the photovoltaic element 00) are connected to this electrode (2) 1 by a wiring pattern +221, so that the electromotive force of the element C (1) is applied to the electrode (21).

The electrode t21) and the wiring pattern (221) are produced by lifting off Aj5 into a predetermined pattern.

Since L I N b 03 is a crystal with an electro-optic effect, when an electric field is applied to this crystal, its refractive index changes. For example, the C-axis direction γ33 of L I N b Oa crystal
・E changes. Here, n is the refractive index of L I N bO3, which is 2.200, and γ33 is the electro-optical constant, which is 308XIO.
"' m/V. The narrow part of the optical waveguide (121 (13
) has a width that does not allow light to propagate as described above, but when a voltage is applied between the electrodes (21) and its refractive index increases, it allows light to propagate. This will be explained using FIG. 4.

FIG. 4 shows the relationship between the mode of light that can propagate through the normalized optical waveguide and its equivalent refractive index.

The input part (t2a) or the output part (1) of the optical waveguide (12)
2b) is the width D], and rlj of the narrow width part 03) is D2, the normalized optical waveguide in these optical waveguide parts is 1(・D
It is given by IID2j〒T7cho77, and klID1j clove7n1In>k@D2jchoeJn*n. Here I
(is the wave number, and Δn is the difference in refractive index between the optical waveguide portion and the substrate. As shown in FIG. 4, the optical waveguide (12)
The width D□ of the input section (IZa) and the output section (12b) is determined so as to propagate single mode light (see point (F)). Further, the width D2 of the narrow width portion [31 is determined so that single mode light is not propagated, that is, the light is in a diffuse mode (see point (E)). This is the case when no electric current is applied to the electrode (21). Therefore, when no voltage is applied to the electrode 011, the light from the input part (12a) is transmitted to the narrow part 0.
3) is not propagated and leaks, and the output part (12b)
can't get any light.

When the voltage generated by the photovoltaic element (20+) is applied to the electrode (21), the refractive index of the narrow part (13) becomes Δne
The theory is that there has been an increase. Then, the normalized optical waveguide in the narrow part 0J is D 2i〒Jn,)
n-()k * D2u d) (Figure 4, the point is also (
(see Ee)), the input and output parts (12a) (12b) approach it, and single mode light begins to propagate. Therefore, the 1 single mode light from the optical input section (12a) passes through the narrow section α3) and the optical output is all 0.
2b). Now, returning to FIG. 2, we will explain the operation of this optical AND circuit in a unified manner. The optical waveguide (11) and the optical waveguide each input light into the input section (12a) of the waveguide (12).
are input optical signals l1nA and l1nB.

Further, the output optical signal obtained from the output part (12b) of the optical waveguide (121) is Iout. Both the optical input optical signals l1nA and l1nB have the logical value "0".
(light heat), the output signal IouL is also "0".
It is.

If the input optical signal ■inA has a logical value of "1" and the input optical signal l1nB is "10", the output signal Iou is "0".
”.

When the input optical signal l1nA is "0", l1nB, or "," no electromotive force is generated from the photovoltaic element (20), so no voltage is applied to the electrode (21+).

Therefore, the light at the input part (IZa) of the optical waveguide (12) leaks at the peak 03) and does not propagate to the output part (12b), so the output optical signal Iou L is "0".

Both input optical signals l1BA and l1nB are r I J l
,.

In this case, the light propagating through the leading waveguide (11) generates a voltage in the electromotive force element (support), which is applied to the electrode 011. Therefore, the optical input part of the optical waveguide (121)
The light from 12a) passes through the narrow lJ part [131] and enters the light output part (1
2b), the output optical signal Iout becomes "1".

This invention enables not only single-mode light but also multi-mode light.
It can also be applied to A N D b calculations of mode light. In this case, we focus only on light in a certain higher order mode,
The logical value "1" or "0" may be determined depending on the presence or absence of light in that mode.

Furthermore, the present invention is applicable not only to AND logical operations of two input optical signals but also to AND logical operations of three or more input optical signals. For example, if there are three input optical signals, one of them is input to the input optical signal l1nB in Fig. 2.
, and is input to the leading waveguide (121) having a narrow width part (131) and an output part (12b).The sum of the electromotive forces of these photovoltaic elements to which the other two input optical signals are input is The voltage is applied to the electrode (211 of the narrow part 03).
Any material may be used as long as it has an electro-optical effect that allows light to propagate only when a voltage equal to the sum of the electromotive forces of two photovoltaic elements is applied to the width of 31. Therefore, each optical waveguide (Ill f12) can also be manufactured using various techniques and materials depending on the type of substrate other than thermal diffusion of Ti. The electrode (21) is connected to the optical waveguide (1
Since it is for applying a voltage to the narrow mountain portion 03) of 2), it may be placed over the portion (13) and may take various shapes other than those shown. The photovoltaic element 20+ can also be realized with various materials such as a-8t manufactured by plasma CVD method, and the electrode I21) and wiring pattern can also be made of Ti.
This can be achieved using materials such as

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram showing an optical AND logical 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 normal 3 is a graph showing the relationship between the mode of light propagating in an optical waveguide that has been fIO+-- one board, (]1) f121 ''' optical waveguide, (12a,)・e・light input part, (12b)... light output part, (13)... narrow width part, (20) ... Photovoltaic element, (21) ... Electrode. Other 4 people 0 1 0 1 0 0 1 1 0 0 0 1

Claims (1)

[Claims] A first optical waveguide to which one input optical signal is input; at least one second optical waveguide to which at least one input signal is input; formed at a required location of the first optical waveguide; A narrow part with a narrow width, a photovoltaic element excited by light propagating through the second optical waveguide, and an electrode for applying a voltage generated by the photovoltaic element to the narrow part, have an electro-optic effect. The width of the narrow width portion and the electromotive force voltage of the photovoltaic element are such that light of a predetermined mode is propagated in the narrow width portion only when a voltage is applied. Optical AND circuit defined in .