JPH03116121A - Optical logic arithmetic unit - Google Patents

Abstract

PURPOSE:To obtain a threshold value characteristic which varies in the characteristics of a light output to a light input stepwise with a small input by providing an element, which includes a laser providing the attenuation effect of oscillation by flank injection as basic structure and has an optical logic arithmetic function, with an optical amplification area or semiconductor optical amplifier which is coupled with the element. CONSTITUTION:The element which includes the laser 1 which provides the attenuation effect of oscillation by flank injection as the basic structure and also has the optical logic arithmetic function is equipped with the optical amplification area or semiconductor optical amplifier 2 which is coupled with the element. Namely, the laser 1 and an optical waveguide which is the active layer of the semiconductor optical amplifier 2 are arranged coaxially and input light P0 is made incident on the flank of the laser 1 at right angles to the optical waveguide as the active layer so as to perform optical logic arithmetic by the laser 1. Consequently, a phenomenon wherein the amplification factor is saturated when the input of the amplification area or amplifier 2 is increased is used to improve the stepwise threshold value characteristic of the output required for the optical logic arithmetic operation to the input, so that the optical logic arithmetic which does not generate malfunction becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical logic operation device widely used in fields such as optical information processing.

Efforts are being made to develop new logical operation methods and increase speed and integration for optical information processing that is more advanced than conventional technology. As a representative example of this, W, J., Grancle and C, L.
,Tang,(A7°Rice'BiPhysical Ax Letter)Appl,Phys,L-ett,Elbow(22)1
780 (1987). This is C. Focusing on the side of the semiconductor laser, that is, focusing on the direction perpendicular to the active layer optical waveguide of the semiconductor laser.Using the extinction phenomenon of oscillation light that occurs when laser light is injected, N○T, NAND and NO
This is an implementation of R's optical logic operation. The principle is as follows. As shown in FIG. 4(a), when a laser beam (intensity Pφ) independent of the oscillation mode is injected into the optical waveguide 40, which is the active layer of a semiconductor laser that is oscillating, from a direction perpendicular to the optical waveguide 40. , as the laser oscillation decays and comes to a stop, the output P1 is reduced as shown in Fig. 4(b).
changes. A force that completely stops oscillation upon input of Po11 (with only the spontaneous light emitting part Psp remaining) A conventional example of creating a logic operation element using this effect is described in the above-mentioned document. Fig. 4 (C) (↓ This shows the configuration of the device. A main laser 41 for logic operation output and two sight lasers 42 and 43 with optical waveguides orthogonal to each other.
is a structure with overlapping portions 47 and 48. When current input is applied to the two site lasers 42 and 43, the output PI3 of the main laser 41 in the oscillation state changes due to the above-mentioned effect due to the current injection. By appropriately setting the current injection conditions, NOR and NAND operations can be achieved.The problem to be solved by the invention is the via input of the power supply element, which allows logical operations even in the conventional technology.Setting the strength of the signal, etc.・There are drawbacks such as the need to perform precise adjustment, the operating range is limited, and the SN of the calculation result cannot be obtained sufficiently due to these reasons, which poses a major problem for practical use. A detailed explanation of why the above-mentioned drawbacks exist in the prior art will be provided below. The magnitude of the oscillation extinction effect due to side injection into a semiconductor laser (i.e., the density of oscillation mode photons originally existing in the active layer of the semiconductor laser in the oscillating state and the oscillation mode induced in the semiconductor laser by side injection) It is determined by the relative ratio of the density of photons unrelated to the oscillation mode, and is proportional to the ratio of the latter photon density to that of the former. It is approximately proportional to the light intensity Ps. Therefore, in order to obtain the extinction effect, it is advantageous to set the laser drive current slightly larger than the oscillation threshold and keep the laser in a state where it oscillates slightly. 8 Laser output P1 is small b ~ Natural light emission Psp in addition to laser oscillation light
The laser output P1 is this spontaneous luminescence psp
There is a limit to how small Pl can be made, since it needs to be sufficiently larger than Pl. Therefore, it is necessary to set the drive current to a certain degree higher than the threshold value and to increase Pl, and therefore it is also necessary to increase the side-injected input light necessary to stop this laser oscillation state. In addition, in the conventional example, the dependence of the output on the input is shown in Figure 4 (b
), which is a proportional relationship, and does not provide a step-like differential characteristic that is desirable for logical operations. As mentioned above, this laser 44 (
Since we use an injection laser whose waveguide is orthogonal to the injected output laser (hereinafter referred to as the main laser) and the injection laser (which is for input signals and is hereinafter referred to as the sub-laser), one of the sub-lasers (hereinafter referred to as the sub-laser) is used. For example, the optical output P1 of the main laser with respect to the current shown in 42) is It
The optical output P1 of the main laser does not decrease until the current reaches ho (~
Therefore, it has a differential characteristic as shown in the figure, and has a so-called threshold characteristic, although it is insufficient. By biasing this sub-laser with an appropriate current less than the threshold current, the input signal light to this sub-laser is If you put
Since the optical output P1 of the main laser does not decrease, similar threshold characteristics are expected. The value characteristics are not sufficient (-in any case, in order to sufficiently produce the oscillation extinction effect and stop the oscillation and perform good optical logic operations (a larger optical input is required, the logic operation The problem is that the desired stepped threshold characteristic cannot be obtained, and that the extinction ratio deteriorates due to the influence of spontaneous light emission of the laser.

Immediately Reduce the minimum input required to stop oscillation Make the threshold characteristic of the output with respect to the input a clear step-like characteristic,
Another important issue is to suppress the influence of spontaneous laser emission.

Means for Solving the Problems The present invention provides an apparatus for performing optical logic operations in which the characteristics of the optical output with respect to the optical input have a threshold characteristic that changes in a stepwise manner by a small person's power. 8. An element having an optical logic operation function whose basic structure is a laser that produces an oscillation extinction effect through side injection, and is equipped with an optical amplification region or a semiconductor optical amplifier coupled to the element.It also has an optical logic operation function. In order to suppress the influence of spontaneous light emission on the optical output of the element, a slit is provided between the coupling space between the element and the optical amplification region or semiconductor amplifier to be coupled.Furthermore, the semiconductor amplifier may be a traveling wave optical amplifier or a pseudo-optical amplifier. It uses a traveling wave optical amplifier.

Effects of the present invention (friend) An element number having an optical logic operation function whose basic structure is a laser that produces an oscillation extinction effect by side injection. Using the phenomenon of saturation of the amplification factor, the threshold characteristics of the output required for optical logic operation can be improved in a stepwise manner with respect to the human power required for optical logic operation without malfunctions. In addition, by the configuration in which a slit is provided in the space where the element having the optical logic operation function and the optical amplification region or the semiconductor amplifier are coupled, the spontaneous luminescence component of the output light emitted from the former is transferred to the latter. By suppressing or converging the combined incidence, a significant improvement in the extinction ratio in optical logic operation can be achieved.Furthermore, by using a traveling wave amplifier as the semiconductor amplifier, the amplification factor can be increased by 9, and the saturation characteristic can be steepened. Therefore, it is possible to improve the stepped threshold characteristic of the output with respect to the input.

Embodiments Before describing specific embodiments, the principle of construction of an apparatus using the problem-solving means of the present invention will be explained with reference to FIG. (
a) is a block diagram showing the configuration;

The laser 1 and the optical waveguide, which is the active layer of the semiconductor optical amplifier 2, are arranged on the same axis.
Input light P@ is side-injected into laser l. Of course, the principle is the same as in Example 1, which will be described below, by introducing another laser whose optical waveguide is orthogonal to the laser I and performing such side injection.4 (b)
As shown in the figure, the laser output P1 decreases with respect to the input light P@ due to the extinction effect, and when the intensity of the input light reaches Pos, the oscillation stops and only the laser output Pti & spontaneous emission occurs. On the other hand, the optical output hl for the optical input P1 of the semiconductor optical amplifier 2 is as shown in (c). Under an appropriate current bias (when the input reaches P+", the gain is saturated, Also, P2 is almost constant. Therefore,
The dependence of the first output of the device, that is, the output P2 of the semiconductor optical amplifier 2, on the input Pa is as shown by the dotted line in (d).
When the side injection input P- is small, the oscillation extinction effect is small and the input to the optical amplifier 2 is sufficiently large, so the optical amplifier 2 is saturated and the power is almost constant with respect to the input P@. If the input voltage is increased, the oscillation extinction is increased, and Pl is decreased, the optical amplifier 2 will be in a state below the saturation point, and the output P2 will rapidly decrease.

The optical amplifier 2 can be simply a semiconductor laser with a long cavity length (by lowering the reflectance of both end faces, it can be used as a traveling wave amplifier (or pseudo traveling wave amplifier), so that the amplification factor becomes flat with respect to the wavelength t'L). Furthermore, by providing an appropriate optical slit in the coupling space between the laser 1 and the optical amplifier 2, the far-field pattern, that is, the divergence angle, of the laser oscillation light can be improved by spontaneous emission. It is possible to suppress the spontaneous emission component of the laser from entering the optical amplifier 2. This improves the characteristics as shown by the solid line in (d).Specific examples will be described below.

(Example 1) FIG. 2(a) is a completed diagram of the created device. However, in order to make it easier to understand, only the main parts are shown and the details are omitted. Undoped InG with a composition of 1.3μm in bandgap wavelength expression (2g)
The aAsP quaternary layer 23 is set to 0.2. ua P type 1nP24
P-type InGaAs with a composition of 2.5μmλg-1,1μm
After sequentially growing the P layer 25 by 0.5 μm, a pitch of 400 μm is formed using normal photolithography. A first stripe 61 with a width of 2.5 μm and a second stripe 71 with a pitch of 400 μm and 10 μm perpendicular thereto. are formed by patterning and etched to obtain rich stripes that are orthogonal to each other. Etching is performed to reach the substrate 21. Afterwards, by buried growth, a high resistance InP layer 31, a P-type nGaAsP layer (2g-
1, 1μ) 51 are formed one after another to make the surface flat. 2nd
Figure (b) shows the wafer for orthogonal laser produced in this manner. The figure shows that the first waveguide 6, which is an active layer with a width of 2.5 μm, and the waveguide 7, which is an active layer with a second width of 10 μm, are buried at right angles to each other by the high-resistance InP layer 31. As shown in the figure, the portion directly above the waveguides 6 and 7 is slightly concave, so even if no particular mark is placed, it is possible to locate that position from the wafer surface, that is, the first waveguide. The first waveguide in which the second waveguides 6, 7 are embedded. The second stripe position 61.71 is found. Next, by photolithography, the second stripe 71 direction is parallel to the center line of this stripe 71 by 100 μm.
Then, patterning is performed so that the center is located on the center of the first stripe 61, and a square hole 8 with a side of 50 μm is formed by reactive ion beam etching.This hole 8 extends to the surface of the substrate 21. It's too deep to reach
The side surface of this hole 8 (the end surface of the laser cavity) is etched by precisely controlling the etching conditions so that it becomes a vertical and smooth mirror surface. Silicon (Si) and silicon monooxide (S) are applied only to the side opposite to the near side.
iO) Coating the multilayer film 111 so that the wavelength is 1.3μ
The reflectance of this side surface for light of m is set to 0.1%. After that, the P electrode pattern of each part is formed as shown in FIG. 2(C). First P electrode pattern 9 for main laser
1. P electrode pattern 92 for optical amplifier (91 for main laser)
and the optical amplifier 92 are connected at this point). Next, as shown in FIG.
A rectangular pattern (SiO2 film for insulating the P electrodes of the main laser and the sub laser) 93 is formed with a thickness of 0.00 mm.

To the end, form the sub-laser electrode pattern IO.

Next, the back surface of the substrate was polished to a thickness of approximately 100 μm. After forming an n-electrode on the back surface of the substrate, the center of the second stripe 71 was parallel to the second stripe 71 and opposite to the hole 8 with a width of 50 μm. All positions 101 35 μm from the line are pleated to form a bar shape. Of the two interwing surfaces in the direction of the second stripe 71 of each bar, a Si/SiO multilayer film is applied to the folded surface on the opposite side from the second strap side in the same manner as in the case of the side surface of the hole 8 described above. 112, and the reflectance of this surface for light with a wavelength of 1.3 μm is 0.1.
%. The distance between the first stripes 61 is 400 μm parallel to the direction of the first stripe 61 so that the first stripe 61 is located at the center.
Make a chip by folding between each fold.

In this way, the resulting force (as shown in Fig. 2(d), the orthogonal laser and the semiconductor traveling wave amplifier, in which the resonators are separated by the hole 8 and coupled with their optical axes aligned, are orthogonal to each other). In the figure, the optical waveguide 7 of the sub laser and the optical waveguide 62 of the main laser constitute an orthogonal laser, and the optical waveguide 63 of the optical amplifier constitutes a semiconductor traveling wave amplifier. Figures 2(e) and 2(f) show the characteristics of the device fabricated using this method.The threshold current of the main laser is approximately 20 mA, and the threshold current of the sub laser is ~80 mA.
It is A. (e) is the current I of the sub laser when a bias current is applied to the main laser and the output Pe2 is approximately 0.15 mW.
P+2, which is the direct output of the main laser, decreases almost proportionally when it exceeds 80mA, and even if the main laser oscillation stops at about 3000mA, the direct output of the main laser, P+2, decreases almost proportionally when it exceeds 80mA. The output P2a of the optical amplifier
l;L At first, the output did not decrease much and Io was ~180m
It rapidly decreases above A.

Furthermore, in (f), the bias current is 75m for the sub laser.
A is applied, and a single fiber (SMF) module is used to inject light with a wavelength almost equal to the oscillation wavelength of the sub laser to the end face of the sub laser, and the dependence of this input light intensity is investigated (e). Similarly, when we measured the output of the main laser and the output of the optical amplifier, we found that the output was close to 0 with approximately 8 mW of manual power. ) to quantitatively determine the threshold characteristic and calculate the amount of input change △P11 required for the output to change from 20% to 80%.If the output is the direct output PI2 of the main laser, △ P@ is 5
In the case of mW optical amplifier output P22, △h is 2 mW,
An improvement of 150% can be seen in the threshold characteristic.

(Example 2) This will be explained with reference to FIG. Using the chip shown in Example 1 as it is, gold is deposited to a thickness of 1 μm or more on a 440 μm square quartz 80, and then etched to leave a gold thin film 84 on only one surface. After that, a pinhole 82 with a diameter of 5 μm was formed in that area, and a LS102 film 85 was coated to produce the fabrication shown in FIG. 3(a).
This is a slit component 81 shown in FIG. This is inserted into the 50A1m square hole 8 of the chip shown in Example 1. An enlarged view is shown in (b). The characteristics of the device in which a slit is inserted in the coupling space between the main laser and the optical amplifier in this manner are shown in FIG. 3(C). When the sub laser output is 0 and there is no optical output to the main laser, the optical output from the optical amplifier is reduced to about 175. The optical output of the amplifier (the optical output of the amplifier has decreased further than this). The extinction ratio of the buried plate has improved. This is also due to the fact that the radiation angle of the laser oscillation light is smaller than that of natural light emission. It goes without saying that this extinction ratio is important when applied to logical operations, and inserting a slit in the coupling space between the main laser and the optical amplifier to prevent spontaneous light emission can greatly improve the characteristics. There is an effect on

Effects of the Invention The present invention (as shown in Fig. 2) is a threshold for the intensity dependence of the output signal on the input signal, which is necessary in optical logic operations such as NAND and NOR, which are performed using the oscillation extinction effect that occurs when light is injected from the side of the laser. It has the effect of significantly improving the value characteristics.More E.

It is also possible to simply use a semiconductor laser as an optical amplifier, even if it produces the effect of improving the extinction ratio in the threshold characteristic. It is more effective if you use it).

[Brief explanation of drawings]

FIGS. 1(a), (b), (c), and (d) respectively show (a) the configuration El (
b) Characteristic diagram showing output change due to side injection of laser (c)
Characteristics EC (1) Input/output characteristics of the optical logic operation device showing the input/output dependence of the optical amplifier are as follows.
Figures 2(e) and (f) show the optical output of the main laser at O
', the characteristics showing the change in the main laser output and the change in the optical output of the optical amplifier with respect to the sub laser current when 15 mW are
Characteristic diagrams showing the dependence of the main laser output and the input signal light intensity on the sub-laser of the optical amplifier. A plate showing how it is inserted into the element of the first embodiment. Figure 3(c) shows the state when the input signal light is input to the element with the slit inserted and the sub laser of the element of the first embodiment. Figure 4 (a), (b) Characteristics showing optical amplifier output changes
, (c), and (d) are respectively (a) a synonym for explaining the principle used in the prior art (b) human power-output characteristics @ (C)
FIG. 3D is a characteristic diagram of a conventional device; FIG. 1... Laser for optical logic operation, 2... Optical amplifier 6... First light guide pickup 7... Second optical waveguide 8... Square hole, 61... ...First stripe, 71...Second stripe, 81...Slit section 82...Pinho/k 62...Main laser light guide extraction 63...・Optical waveguide of optical amplifier 11
1,112...Si/SiO multilayer wind

Claims (3)

[Claims] (1) In an optical semiconductor device having a structure that allows light to enter an optical waveguide, which is an active layer of a semiconductor laser, from a direction perpendicular to the axial direction of the optical waveguide, a region having an optical amplification function to be coupled with the laser. An optical logic operation device characterized by having at least one. (2) An optical semiconductor device according to claim 1, characterized in that a slit is provided on the optical axis of a coupling space between the laser and a region having an optical amplification function coupled thereto. Computing device. (3) An optical logic operation device according to claim 1, characterized in that an insulating multilayer film is attached to the end face of the input side end face of the region having an optical amplification function in order to reduce the reflectance of the end face. . (4) The optical logic operation device according to claim 1, wherein a traveling wave optical amplifier or a pseudo traveling wave optical amplifier is used as the region having an optical amplification function.