JPH0578809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical bistable semiconductor laser device which is important as a logical operation/storage element in optical switching equipment, optical information processing equipment, etc.

(Prior Art) Research into ultra-high-speed logical operations and storage devices for processing large amounts of information signals at high speed is being vigorously continued. Conventionally, current mode logic, which uses a current switch as a basic block, has been known as a device for logical operation and storage of electrical signals, and in recent years, GaAsFET, high electron mobility transistor (HEMT), and Josephson junction device have been used. Research is progressing on ultra-high-speed logical operations and storage devices using, etc. However, performing high-speed digital information processing of a large amount of two-dimensional data such as image information using electrical signals has limitations in terms of calculation speed, power consumption, etc. Furthermore, in optical transmission signal exchanges and the like, there are problems such as band limitations, distortion, and loss of wavelength information due to the conversion of light into single-carrier electrical signals. For this reason, it is desired to realize an optical logic operation and storage device that can perform digital information processing and storage of optical signals as they are in the form of light, which is fast, broadband, and compatible with two-dimensional parallel information processing. Such optical logic operation and storage devices include the magazine Optical.
Engineering (Optical Engineering) Volume 19,
Considerations include an optically bistable device using a semiconductor etalon, as described in 1980, pages 463-468, and an optically bistable semiconductor laser, as described in Proceedings of the 1980 IEICE General Conference, S17-15. It will be done. Among these, optical bistable semiconductor lasers, which have their own oscillation and amplification functions, have great potential and are expected to be used. Currently, a device that performs optical logical operations or storage using this optical bistable semiconductor laser (herein referred to as an optical bistable semiconductor laser device) is published in the Proceedings of the 1985 IEICE General National Conference, S17-13. As described, it is actually used in the system as an optical memory of a time-division optical switch.

(Problems to be Solved by the Invention) However, the conventional optical bistable semiconductor laser device has a problem in that the trigger light level increases as the speed of the optical signal increases. Therefore, in conventional devices, the upper limit of the optical signal speed that can be used is thought to be about several 100 Mb/s, and there have been problems in calculating and storing optical signals at high speeds of about Gb/s or higher.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical bistable semiconductor laser device that can perform optical signal calculation and storage at high speed.

(Means for Solving the Problems) The present invention includes an optical bistable semiconductor laser having a current injection region and a current non-injection region inside a resonator, and means for applying a bias current to the current injection region. The optical bistable semiconductor laser device is characterized in that means is provided for applying bias light to the current non-injection region.

(Operation/Principle of the Invention) First, the operation of the optical bistable semiconductor laser will be explained using the drawings.

FIG. 2a is a sectional view showing a specific example of an optical bistable semiconductor laser. Its structure is almost the same as a commonly used current injection type semiconductor laser, such as a double heterojunction laser made of GaAlAs/GaAs or InGaAsP/In. However, it differs from a normal semiconductor laser in that the electrodes are not uniform and there are some parts into which current is not injected. Since the current non-injected region acts as a saturable absorber, the optically bistable semiconductor laser shown in the figure can have bistable characteristics in the injection current vs. optical output characteristic. Note that instead of making the electrode non-uniform, similar bistable characteristics can be provided by providing non-uniformity in the part of the active layer that is the light emitting region and providing a saturable absorption region in a part thereof. In these optical bistable semiconductor lasers, by appropriately selecting the injection current i, bistable characteristics can also be obtained in the characteristics of the emitted light with respect to the externally injected light. The details of such an optical bistable semiconductor laser are described in the above-mentioned Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, S17-15.

FIGS. 2b, 2c, and d are diagrams for explaining the operation of the optical bistable semiconductor laser shown in FIG. 2a. Figure 2b
is a diagram showing the relationship between the injection current i and the output light amount P _put when the incident light amount Pin=0. That is, when the injection current i is increased from i _p , the output light amount P _put increases rapidly at i = i _a , and conversely, when the injection current i is decreased from i _t , the output light amount P _put becomes i = i It shows a hysteresis characteristic that rapidly decreases at _c , and i=
Two stable points A of the output light amount P ₀ and P ₁ at i _b
and B.

FIG. 2c is a diagram showing the relationship between the amount of incident light P _io and the amount of output light P _put when the injection current i= _ib in FIG. 2b. In other words, if the incident light amount P _io is increased from 0 when the output light amount P _put = P ₀ is at the first stable point A, the output light amount P _put will increase rapidly at P _io = P _a , and thereafter the incident light amount P When decreasing from _io = P _t , the output light amount P _put hardly decreases and the output light amount P _put = P ₁
Move to the second stable point B. Points A and B in FIG. 2c represent the same points as points A and B in FIG. 2b, respectively. Figure 2d shows the injection current i and the incident light.
The operation of an optical bistable semiconductor laser with respect to P _io is shown in a table. When the injected current i is i _b and the incident light P is 0, the optical bistable semiconductor laser responds to the previously written data as shown in Fig. 2b.
It is located at one of two stable points A and B in , and maintains the output light amount P ₀ or P ₁ . In the figure b, when the optical bistable semiconductor laser maintains one stable point B (output light amount P ₁ ), the injected current i
When is once i ₀ and returned to i _b ni, the output light amount P _put is B→D
→A changes in the order, and then the other stable point A (output light amount
P ₀ ) is maintained. That is, the optical bistable semiconductor laser is reset. Furthermore, in Fig. 2c, when the optical bistable semiconductor laser maintains the stable point A (output light amount P ₀ ), if the input light amount is set to P _t and then returned to 0, the output light amount P _put changes from A→E→B. The light changes sequentially and thereafter maintains a stable point B (output light amount P ₁ ). That is, the optical bistable semiconductor laser is set.

In this way, the optical bistable semiconductor laser operates as an S-R flip-flop for optical signals and has a storage function. The operating speed of an optical bistable semiconductor laser is determined by the carrier lifetime in the saturable absorption region, and is known to depend on the injection current bias. That is, by bringing the bias current value as close as possible to _ia in FIG. 2b, the trigger light input level is reduced and the response to high-speed optical signals is improved. When actually using an optical bistable semiconductor laser, the bias current is kept close to _ia within a range that does not cause malfunctions due to current and temperature fluctuations. The effect of improving the response to high-speed optical signals by using a bias can be similarly expected by using an optical bias. In other words, if an optical bias close to P _a ni is given to the optical input P _io in Figure 2c,
The required trigger optical input level is reduced and responsiveness to high speed optical signals is further improved. The present invention is a device that utilizes such an effect to operate an optical bistable semiconductor laser by applying current and optical bias.

(Example) The present invention will be explained in detail below using the drawings.

1A to 1D are diagrams for explaining an optical bistable semiconductor laser device according to an embodiment of the present invention, and FIG. 1A is a diagram showing the configuration of the embodiment. This embodiment has a configuration in which bias light from a semi-moving laser 3 driven by a power source 4 is applied to a current non-injection region of an optical bistable semiconductor laser 1 via an optical fiber 2. The current non-injection region is formed by etching a portion without an electrode close to the active layer, and the end face of the optical fiber 2 is brought close to the etched groove portion from above.

FIGS. 1b, 1c, and d are diagrams for explaining the operation of the embodiment shown in FIG. 1a. Figure 1b shows the bias light
FIG. 7 is a diagram showing the relationship between the injection current i and the output light amount P _put when P _b exists and the incident light amount P _io =0. As in the case of FIG. 2b described above, in this embodiment, when the injection current i is increased from _i0 , i=
When the output light amount P _put increases rapidly at i _a , and conversely, when the injection current i is decreased from i _t , the output light amount P _put becomes i
It exhibits a hysteresis characteristic that rapidly decreases at = i _c and has two stable points A and B of the output light amount P ₀ and P ₁ at i = i _b . In this way, in this embodiment, the bias light P _b
The systeresis loop is shifted to the lower injection current side by the amount that exists.

Figure 1c shows that the injection current i=i _b in Figure 1b
As, the amount of incident light when bias light P _b exists
FIG. 7 is a diagram showing the relationship between P _io and the amount of emitted light P _put . If the input light amount P _io is increased from 0 when the output light amount P _put = P ₀ at the first stable point A, the output light amount P _put will be
It increases rapidly at P _io = P _a , and then when the incident light amount P _io = P _t is decreased, the output light amount P _put hardly decreases and the output light amount P _put = P ₁ reaches the second stable point, Move to B. This is also almost the same as that explained using FIG. 2, but the difference is that the amount of light P _a at the rise of hysteresis is reduced by the presence of the bias light P _b .

FIG. 1d is a table showing the operation of the embodiment of FIG. 1a with respect to the injection current i and the incident light _Pio . When the injected current i is i _b and the incident light P _io is 0, the optical bistable semiconductor laser will move to one of the two stable points A and B in Figure 1b depending on the previously written data. , and maintains the output light amount P ₀ or P ₁ . In FIG. 1b, the optical bistable semiconductor laser 1 is located at one stable point B (output light amount
When the injection current i is once i ₀ and returned to i _b while P ₁ ) is held, the output light amount P _put changes in the order of B → D → A, and after that, the other stable point A (the output light amount P ₀ ) is changed. Hold. That is, the optical bistable semiconductor laser 1 is reset. In addition, in FIG. 1c, when the optical bistable semiconductor laser 1 maintains the stable point A (output light amount P ₀ ) and the input light amount is set to P _t and then returned to 0 again, the output light amount P _{put changes} from A→E→ B, and thereafter maintains a stable point B (output light amount P ₁ ). That is, the optical bistable semiconductor laser 1 is set.

In this way, the optical bistable semiconductor laser device shown in _FIG . The amount of light can be reduced. Therefore, the response to high-speed optical signals is significantly improved. Furthermore, since the bias is applied by light and current, there is an advantage that the operating point can be set very delicately. In conventional devices, the hysteresis characteristic of an optical bistable semiconductor laser changes due to changes in temperature, etc., so control is performed externally using a Peltier device or the like to keep the temperature constant. In contrast, in this embodiment, if the change in the hysteresis characteristic due to temperature fluctuation is known in advance, it is possible to compensate for the change in the hysteresis characteristic by changing the optical bias value. Such delicate control is possible because both the optical bias and the current bias can be changed in this embodiment.

In the embodiment shown in FIG. 1a, the optical bias is applied from the top of the optical bistable semiconductor laser 1, but in the present invention, the optical bias is applied from the input end of the optical bistable semiconductor laser 1 together with the optical input signal. structure is also possible. Furthermore, the use of the optical fiber 2 is not essential, and the present invention only needs to have a structure in which an optical bias is applied. Furthermore, it is also possible to turn off the optical bias as well as the current bias when resetting the memory.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide an optical bistable semiconductor laser device that is capable of optical logical operations and storage even for very high-speed optical signals. Therefore, the present invention greatly contributes to the realization of high-speed optical switching equipment and optical information processing equipment.

[Brief explanation of the drawing]

FIG. 1a is a diagram showing the configuration of an embodiment of the present invention,
Figure b shows the relationship between the injected current and the amount of emitted light in the example, c shows the relationship between the amount of incident light and the amount of output light in the example, and d shows the relationship between the injected current and the amount of incident light. Figure 1A is a diagram showing the operation of the embodiment;
Figure 2a is a schematic cross-sectional view showing an optical bistable semiconductor laser biased only by current, Figure 2b is a diagram showing the relationship between the injection current and the output light amount of the optical bistable semiconductor laser of Figure 2a, Figure c shows the relationship between the amount of incident light and the amount of emitted light from the optical bistable semiconductor laser in Figure A, and Figure d shows the operation of the bistable semiconductor laser in Figure 2A with respect to the injection current and the amount of incident light. It is a diagram. 1... Optical bistable semiconductor laser, 2... Optical fiber, 3... Semiconductor laser, 4... Power supply.

Claims (1)

[Claims] 1. In an optical bistable semiconductor laser device comprising an optical bistable semiconductor laser having a current injection region and a current non-injection region inside a resonator, and means for applying a bias current to the current injection region, the current non-injection region An optical bistable semiconductor laser device, characterized in that it is provided with means for applying bias light to.