JPH03217828A - Nonlinear optical input/output element - Google Patents

Abstract

PURPOSE:To make the nonlinear response characteristics of the element into plural kinds by combining two pieces of semiconductor lasers and two pieces of beam splitters which change optical paths by polarization directions, thereby changing control signals. CONSTITUTION:A TE wave passes a linear polarization modulator 7 and a TM wave is converted to the TE wave when this modulator is set at the TE wave to a light input signal. Only the TE wave passes the beam splitter 3 and arrives at the semiconductor laser 2. The TM wave oscillated by the laser 1 is refracted by a mirror 6 and the beam splitter 4 if prescribed currents are previously implanted to the lasers 2, 1 at this time. After this TM wave is made incident on the laser 2, the TE wave is made incident thereon. The TM wave or TE wave is oscillated by the magnitude of the influence of the TM wave in the laser 2 and is outputted through the splitter 4. The TM wave is refracted by the splitter 3 and is outputted if the modulator 7 is set at the TM wave.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a nonlinear optical input/output device.

<Summary of the Invention> The present invention relates to an optical multifunctional logic element that exhibits a nonlinear optical output response that differs depending on a control signal in response to an optical signal input.
The combination of two multifunctional semiconductor lasers that can change the function of the injection current for control, and two beam splitters that can change the optical path in the direction of linear polarization, provides more functions and is easier to use than conventional elements. The aim is to realize an optical input/output device with steeper rise and fall characteristics compared to the
By controlling multiple injection currents and modulating the linear polarization direction, various optical response outputs such as differential gain characteristics, bidirectional stability characteristics, and negative resistance characteristics are exhibited in response to optical signal input. It is designed to function as a nonlinear multifunctional optical input/output element having functions such as multiplication, optical logical sum, optical memory optical logical negation, exclusive logical sum, wavelength conversion, and wavelength filter.

<Prior Art> FIG. 7 shows the structure of a conventional optical input/output element having nonlinear characteristics such as differential gain characteristics and bistable characteristics.

The optical input/output device shown in the figure utilizes a semiconductor laser 04 having a so-called Fabry-Bello type resonator in which a medium 01 capable of amplifying light is sandwiched between two cleavage planes (/%-humirrors) 0203. and a plurality of electrodes 05.
06 are installed in series. That is, it utilizes a series electrode arrangement type semiconductor laser. The end face of the medium is a cleavage plane, which is used as a half mirror. In response to the optical signal input, a current o7 greater than or equal to a current sufficient to amplify it (referred to as dark value current r lm) is injected into one electrode 06, and a threshold current I + h is injected into the other electrode 05.
When the following current 08 is injected, the medium portion below the former electrode 07 functions as a light amplification region 09, and the latter electrode 0
The portion of the medium below 5 functions as a light absorption region old 0.

This element has optical output response characteristics as shown in FIG. 8 with respect to optical signal input.

That is, when the optical signal input increases in the order of a-1-1) - + C, most of the light is initially absorbed by the light absorption region 010, and the light output hardly increases. , only weak spontaneous emission light is emitted. However, when absorption begins to saturate at a certain point d, the half mirror 02
, 03, positive feedback occurs instantaneously: saturation of absorption → increase in light → further saturation of absorption, the optical output jumps to d 4 e, and strong stimulated emission light is generated. It will now be emitted. In other words, the light absorption at point e is completely saturated.

On the other hand, when the optical signal input decreases from f→e−+g,
Due to the strong light of the stimulated emission light, the absorption remains saturated. However, at a certain point h, when the optical signal input becomes sufficiently weak and light absorption begins, the saturated state of light absorption -> light decrease - absorption becomes even weaker, so that even more light is absorbed.
Due to positive feedback, the light output decreases instantaneously and reaches point b.
Returning to the weak natural radiation shown in .

By controlling the injected current, this element can be operated at the rising point (point d).
), the position of the falling point (point h) can be changed. For this reason, its response characteristics are not limited to those shown in Figure 8.
Optical input/output characteristics as shown in FIGS. 9 and 10 can be obtained.

In Fig. 2, the optical signal input is β, fixed at a point C lower than the rising point and higher than the falling point, and when a light pulse γ higher than the rising point is momentarily input to this point, the characteristic is C 4 d →e→g and changes the light output to point g
can be maintained at a high level. Conversely, if the optical input is momentarily reduced to point α, which is lower than the rising point, the optical output changes from g → h''-b → C, and the optical output can be maintained low at point C. In other words, It operates as an optical memory with point C set to high and point g set to low.In addition, when configuring an optical AND or optical OR circuit, two or more in Fig. 3 and one in Fig. 4 are used. The injected current may be controlled so that the optical output becomes high for three or more optical inputs.Furthermore, the element shown in FIG. 7 can also be used as a laser oscillation wavelength tunable laser or a wavelength tunable amplification optical filter. In this case, the light absorption region is eliminated,
One is used as a constant optical amplification region with a fixed injection current, and the other is used as a variable injection current amplification region. Furthermore, the refractive index of the optically variable amplification region, which changes due to current injection, is amplified by positive feedback, thereby making it possible to change the oscillation wavelength of the element. Furthermore, by injecting the same current into all electrodes and treating them equivalently as a single electrode, the device in Figure 7 can have threshold characteristics like a normal semiconductor laser, as shown in Figure 11. It is also possible.

In this case as well, it is possible to use an optical AND or optical OR circuit. As shown in Fig. 11, the light input/output characteristics change depending on the magnitude of the control current, but since the current is generally small, it is necessary to supplement the carriers necessary for light emission with the input light, and for this reason, the efficiency decreases, and the quantum efficiency (slope) tends to worsen.

As described above, the optical input/output element shown in FIG. 1 has various functions, and high efficiency can be achieved by controlling the transverse mode in various ways. It has the disadvantage that it is impossible to construct a logical NOT circuit and it is impossible to provide negative resistance characteristics.

On the other hand, as another optical input/output element, one shown in FIG. 6 is also known. As shown in the figure, a plurality of electrodes 011. 012 are arranged in parallel.

That is, it is a parallel electrode arrangement type semiconductor laser. This element has the negative resistance characteristic shown in FIG. 13 without using any special means to define the transverse mode. That is, electrode 0
When a current equal to or greater than the threshold value 1+h is injected into 1l and a current less than that is injected into electrode 012, the semiconductor laser initially oscillates in region 013 below electrode 1. On the other hand, when light enters the region 014 below the old electrode 2, carriers in the region 013 increase, so the first
The light output also increases as shown in region I of FIG. moreover,
When the optical input is increased, the light oscillation region changes from 013 to old 4.
Move to. At this time, the lateral confinement of the current (transverse mode control IU) becomes weaker, and the oscillation efficiency decreases.
A negative resistance portion is generated as shown in area (■) in Figure 3. After the oscillation region completely shifts to 014, the region shown in Figure 13 ■
As shown in , the optical output increases again.

With this element, it is possible to construct a logic negation circuit, etc. by using the negative resistance part in region It was difficult to set a threshold value, and it was difficult to distinguish between ON and OFF. Furthermore, since the negative resistance portion is obtained without controlling the transverse mode, it is not possible to achieve higher efficiency and higher stability of the semiconductor laser that can be obtained by controlling the transverse mode.

Further, FIG. 14 shows a combination of the optical input/output device shown in FIG. 7 and the optical input/output device shown in FIG. 12. As shown in the figure, electrode 015. By applying currents to 016 and 017, the optical input/output characteristics shown in FIGS. 8, 9, IO, and 13 can be provided. That is, electrode 015.
Series arrangement by using 016, electrodes 015, 01
By using No. 6,017, a semiconductor laser having electrodes arranged in parallel can be obtained. That is, it can be a series-parallel electrode arrangement type semiconductor laser. However, the above-mentioned drawbacks have not been resolved.

Semiconductor lasers are not only used alone, but also in
They can also be used in combination as shown in the figure. In the system shown in the figure, an optical input signal is split into orthogonal components by a beam splitter 8, one of which is refracted by a mirror 9, and the two are converted into parallel beams by semiconductor lasers 020, 020, and 20, respectively.
021. Here, the semiconductor laser 020. 021 has a different installation direction.

This means that the propagation modes of semiconductor lasers include a TE mode in which the electric field vector is parallel to the heterointerface, and the magnetic field vector is perpendicular to the propagation direction and the heterointerface. TM whose electric field vector has a component perpendicular to the direction of propagation and the direction perpendicular to the heterointerface.
mode, therefore the semiconductor laser has TE. Although it is possible to oscillate in both TM modes, in reality there is a tendency for oscillation to occur more easily in the TE mode. Therefore, when the input light has TM polarization, the polarization of the input light is not preserved unless strong input light is used that cancels out the difference in reflectance. Therefore, in FIG. 15, the beam splitter 01
T. at 8. Since the E and TM polarized waves are separated and input to the semiconductor lasers 020 and 021 installed in directions perpendicular to each other, the polarized waves can be maintained. Semiconductor laser 020. The polarized waves separately amplified at 021 are combined again at a mirror 023 and a beam splitter 022. The reason why semiconductor lasers actually tend to oscillate more easily in the TE mode is that the cleavage plane used as a mirror in the Fabry-Bello resonator has a higher T mode than in the TM mode.
This is because it reflects E mode well.

<Problem to be solved by the invention> The present invention has been made in view of the above-mentioned prior art,
The purpose is to provide a nonlinear multifunctional optical input/output device that allows optical output to have multiple types of nonlinear response characteristics to optical input by changing a control signal.

<Means for Solving the Problem> The configuration of the present invention to solve the above object includes two semiconductor lasers, two beam splitters that change the optical path depending on the polarization direction, and a linearly polarized wave input optical signal. The linear polarization modulator converts the polarization direction of an input optical signal into a TE or TM wave, and then converts the optical path of the input optical signal into a first wave. The oscillated light from the first semiconductor laser is input to the first semiconductor laser in the case of TM waves and the second semiconductor laser in the case of TE waves, and the oscillation light from the first semiconductor laser is input to the second semiconductor laser. The output from the second semiconductor laser is passed through the first beam splitter in the case of a TM wave, and the second beam splitter in the case of a TE wave. It is characterized by obtaining.

Further, as the semiconductor laser, a series electrode arrangement type semiconductor laser having a plurality of electrodes in the series direction of the laser resonator, or a series-parallel electrode arrangement type semiconductor laser having a plurality of electrodes in the series direction and parallel direction of the laser resonator may be used. It is desirable to use two.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

Figure 1 shows a first embodiment of the present invention. As shown in the figure, single-electrode semiconductor lasers 1 and 2 are installed in directions orthogonal to each other. Single electrode semiconductor laser 1,
2 is similar to that shown in FIG. The beam splitters 3 and 4 convert the optical input signal into TE depending on the polarization direction.
It separates into polarized waves and TMW waves and combines them. The mirrors 5 and 6 convert the separated TE polarized light and TM polarized light into parallel light, and conversely refract them in orthogonal directions in order to combine them. The linear polarization modulator 7 changes the linear polarization of the input optical signal, and uses, for example, a modulator that utilizes the magneto-optic effect or the acousto-optic effect.

Therefore, if the linear polarization modulator 7 is set to the TE wave for the optical input signal, the TE wave will pass through as is, and the TM wave will be the T wave.
Only the TE wave is converted into an E wave and input to the beam sweeper 3. The TE wave then passes through the beam sweeper 3 and is guided to the semiconductor laser 2 as shown by the thick arrow in FIG. At this time, the semiconductor laser 1 has a threshold value T l
When a current of k or more is injected in advance into the semiconductor laser 2 and a current of less than that is injected into the semiconductor laser 2, the TM wave oscillated by the semiconductor laser 1 is refracted by the mirror 6 and the beam splitter 4 and is initially incident on the semiconductor laser 2. After that, TE is used as the optical input signal.
waves will be incident. In the semiconductor laser 2, when the former influence is stronger than the latter influence, a TM wave is oscillated, and in the opposite case, a TE wave is oscillated, passes through the beam splitter 4, and is output. There will now be switching points as shown in Figure 3. This is steeper than the characteristic of the normal semiconductor laser shown in FIG. 11 described above, and can be used as a device having excellent optical AND and optical OR functions.

On the other hand, when the linear polarization modulator 7 is set to the TM wave for the optical input signal, the TM wave passes through as is, and the TE wave passes through the TM wave.
The TM waves are converted into waves and only the TM waves are input to the beam splitter 3. The TM wave is then refracted by the beam sweeper 3 as shown by the thick arrow in FIG. At this time, if the semiconductor laser 2 is oscillated in advance (normally it oscillates with a TE wave), the TE wave passes through the beam splitter 4 and is output. As shown in , the TM wave refracted by the mirror 6 and the beam splitter 4 is incident on the semiconductor laser 2, and at the same time, the oscillation light of the semiconductor laser 2 is converted into a TM wave. In other words,
The output through the beam splitter 4 disappears, and the TM wave is observed as an output that is refracted by the beam splitter 3. Therefore, it is possible to construct an optical logic NOT circuit as shown in FIG.

In this way, the nonlinear optical input/output device of this example not only has clear rise and fall characteristics compared to conventional devices, but also has parallel electrode arrangement type semiconductor lasers shown in FIGS. 12 and 14. Since it is not used, it is possible to reliably take measures to control the transverse mode, such as making it a refractive index waveguide type using an embedded structure, and it is possible to achieve high efficiency and high stability.

A second embodiment of the present invention is shown in FIG. 16. In this example, the single-electrode semiconductor laser l. used in the first example described above is used. Series and parallel electrode arrangement type semiconductor lasers 8 and 9 in place of 2
is used. The series electrode arrangement type semiconductor laser has the configuration shown in FIG. 7, as described above. The other configurations are similar to the first embodiment.

Therefore, if the linear polarization modulator 7 is set to the TE wave for the optical input signal, the TE wave will pass through as is, and the TM wave will be the T wave.
Only the TE wave is converted into an E wave and input to the beam splitter 3. Here, the semiconductor laser 9 is shown in FIGS.
By functioning as shown in FIGS. 1 and 2, the beam splitter 4 outputs the optical outputs of the optical memory, optical AND, and optical OR. Further, at this time, by causing the semiconductor laser 8 to oscillate with a TM wave, it is also possible to make the rising point steeper.

On the other hand, when the linear polarization modulator 7 is set to the TM wave for the optical input signal, the TM wave passes through as is, and the TE wave passes through the TM wave.
The TM waves are converted into waves and only the TM waves are input to the beam spreader 3. The TM wave is then refracted by the beam splitter 3, as shown by the thick arrow in FIG. 4, and further refracted by the mirror 5, and guided to the semiconductor laser 8. At this time, if the semiconductor laser 9 is oscillated in advance (usually oscillated with TE waves)
, the TE wave passes through the beam splitter 4 and is output, but the TM wave passes through the semiconductor laser 9 and is refracted by the mirror 6 and the beam splitter 4, as shown by the thick arrow in FIG. 4, and enters the semiconductor laser 9. At the same time, the semiconductor laser 9
The oscillated light will be converted into a TM wave. Therefore, it becomes possible to construct an optical logic NOT circuit as shown in FIG.

As described above, the nonlinear optical input/output device of this embodiment has clear rise and fall characteristics compared to conventional devices, and it can be seen from the parallel electrode arrangement type semiconductor laser shown in FIGS. 12 and 14. Since the transverse mode is not used, it is possible to reliably take other means to control the transverse mode, such as using a refractive index waveguide type with an embedded structure, and it is possible to achieve high efficiency and high stability. Furthermore, there is a feature of having an optical memory function which is not possible in the first embodiment.

sj6i f'i+1 3 FIG. 17 shows a third embodiment of the present invention. In this embodiment, a series-parallel electrode arrangement type semiconductor laser 10 is used instead of the single-electrode semiconductor lasers 1 and 2 used in the first embodiment described above.
．． 11 is used. The series-parallel electrode arrangement type semiconductor laser has the configuration shown in FIG. 14, as described above. The other configurations are similar to the first embodiment.

Therefore, if the linear polarization modulator 7 is set to the TE wave for the optical input signal, the TE wave will pass through as is, and the TM wave will be the T wave.
Only the TE wave is converted into an E wave and input to the beam splitter 3. Here, by operating the semiconductor laser 1l as shown in FIGS. 8, 9, and 10, the optical outputs of the optical memory, optical AND, and optical OR are adjusted to the beam splitter 4.
It is output from Also, at this time, the semiconductor laser lO is
By oscillating with M waves, it is also possible to make the rising point steeper.

On the other hand, when the linear polarization modulator 7 is set to the TM wave for the optical input signal, the TM wave passes through as is, and the TE wave passes through the TM wave.
Only the TM waves are converted into waves and input to the beam sweeper 3. Then, the TM wave is refracted by the beam sweeper 3 as shown by the thick arrow in FIG. 4, and further refracted by the mirror 5 and guided to the semiconductor laser 10. At this time, if the semiconductor laser 2 is oscillated in advance (normally it oscillates as a TE wave), the TE wave passes through the beam splitter 4 and is output. TM refracted by mirror 6 and beam splitter 4 as shown in
At the same time that the wave is incident on the semiconductor laser 11, the oscillation light of the semiconductor laser 1l is converted into a TM wave. Therefore, it becomes possible to construct an optical logic NOT circuit as shown in FIG. Further, the semiconductor laser 10 is provided with the negative resistance characteristic shown in FIG. 13, and the semiconductor laser 11 is provided with a
If the optical input/output characteristics shown in the figure are provided, it becomes possible to configure the optical exclusive OR circuit shown in FIG. 6 from the beam splitter 3.

As described above, the nonlinear optical input/output device of this embodiment not only has a negative resistance characteristic with a clear falling edge compared to the conventional device, but also has a negative resistance characteristic with a clear falling edge compared to the conventional device. , it is possible to construct an optical exclusive OR circuit. Further, since the output from the beam splitter 3 is used at this time, the transverse mode cannot be actively controlled, so the efficiency of the above-mentioned embodiment is better.

<Effects of the Invention> As described above in detail based on the embodiments, according to the present invention, optical AND, optical OR,
A nonlinear multifunctional optical input/output element having functions such as optical memory, optical exclusive OR, wavelength conversion, and wavelength filtering can be realized.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, FIG. 2 is an explanatory diagram showing the optical path of the TE wave in the first embodiment of the present invention,
FIG. 3 is a graph showing the characteristics of optical logical product and logical sum, FIG. 4 is an explanatory diagram showing the optical path of the TM wave in the first embodiment of the present invention, and FIG. 5 is a graph showing the characteristics of optical logical negation. , Fig. 6 is a graph showing the characteristics of exclusive OR, Fig. 7 is a configuration diagram of a conventional nonlinear optical input/output element, Fig. 8 is a graph showing the optical memory effect, and Fig. 9 is a graph showing the characteristics of optical AND. Graphs showing characteristics,
Figure 10 is a graph showing the characteristics of optical OR, Figure 11 is a graph showing the characteristics of a normal semiconductor laser, Figure 12 is a configuration diagram of a conventional nonlinear optical input/output element, and Figure 13 is a graph showing optical negativity. A graph showing the resistance characteristics, Fig. 14 is a block diagram of a conventional nonlinear optical input/output element, Fig. 15 is a block diagram showing an example of a combination of conventional semiconductor lasers, and Fig. 16 is a block diagram of a second embodiment of the present invention. An example configuration diagram, FIG. 17, is a configuration diagram of a third embodiment of the present invention. In the drawing, 1 and 2 are single-electrode semiconductor devices, 3 and 4 are beam splitters, 5 and 6 are mirrors 7 are linear polarization modulators, 8 and 9 are semiconductor lasers with series electrodes, and 10 and 11 are series-parallel devices. This is an electrode arrangement semiconductor laser.

Claims (3)

[Claims] (1) Equipped with two semiconductor lasers, two beam splitters that change the optical path depending on the polarization direction, and a linear polarization modulator that changes the linear polarization of the optical signal input. , the polarization direction is set to T by the linear polarization modulator.
After converting into E or TM waves, the optical path of the optical signal input is changed by a first beam splitter, and in the case of TM waves, it is sent to the first semiconductor laser, and in the case of TE waves, it is sent to the second semiconductor laser. Furthermore, the oscillation light from the first semiconductor laser is made to enter the second semiconductor laser via a second beam splitter, and the output from the second semiconductor laser is the TM wave. A nonlinear optical input/output element characterized in that the TE wave is obtained through the first beam splitter and the second beam splitter. (2) The nonlinear optical input/output device according to claim (1), characterized in that two semiconductor lasers of a series electrode arrangement type having a plurality of electrodes in the series direction of the laser resonator are used as the semiconductor lasers. (3) As the semiconductor laser, two series-parallel electrode arrangement type semiconductor lasers having a plurality of electrodes in a series direction and a parallel direction of a laser resonator are used.
) nonlinear optical input/output device.