WO2003077259A1

WO2003077259A1 - Very high speed optical memory method and apparatus using bistable semiconductor laser

Info

Publication number: WO2003077259A1
Application number: PCT/JP2003/002687
Authority: WO
Inventors: Hitoshi Kawaguchi
Original assignee: Japan Science And Technology Agency
Priority date: 2002-03-12
Filing date: 2003-03-07
Publication date: 2003-09-18
Also published as: JP2003337355A; JP4368573B2

Abstract

There are provided a very high speed optical memory method and apparatus using bistable semiconductor laser capable of controlling each bit and reading out information at the necessary timing. The very high speed optical memory apparatus using bistable semiconductor laser includes an array (5) having a plurality of bistable semiconductor lasers performing the AND gate operation and the memory operation, optical signal write means for writing an optical signal to the array (5), and optical signal read out means for reading out the optical signal written to the array (5). The apparatus is an entirely-optical type not converting the optical signal into an electric signal. The apparatus records a time-series optical signal to the bistable semiconductor laser bit by bit and reads out the recorded signal as a time-series signal at a necessary timing. Moreover, it is possible to transfer a recorded signal from a bistable semiconductor laser to another bistable semiconductor laser and record it there.

Description

Description Ultra-high-speed optical memory method using bistable semiconductor laser and device therefor

The present invention relates to an ultrafast optical memory method using a bistable semiconductor laser and an apparatus therefor. Background art

At present, optical fiber communication systems are being developed as communication transmission systems for the advanced information society. However, current optical fiber communication systems have not yet fully utilized the characteristics of light with a carrier frequency of 200 THz. In order to respond to the increase in the amount of information in the future, further development of ultra-high-speed optical communication systems is desired. To achieve such ultra-high speed, all-optical systems that also use light for signal processing are required. Expected. In particular, an all-optical bucket-based routing technology is needed. FIG. 1 is a schematic diagram of a conventional fiber delay line buffer memory.

In this figure, 101 is a packet input, 102 is a first optical switch, 103 is a bucket storage device, 104 is a second optical switch, and 105 is a bucket output. .

In the method using such a fiber delay line buffer memory, it was difficult to control each bit and read information at a necessary timing.

(Non-Patent Document 1)

Tamura, Yamayoshi, Kawaguchi "All-optical signal processing using ultrafast polarization bistable surface-emitting semiconductor laser" IEICE Tech., LQE 2000-42 (August 2000)

(Non-patent document 2)

Yamayoshi, Kawaguchi, "All-Optical Ultrafast DE MUX Using Polarization Bistability of Surface-Emitting Semiconductor Laser" IEICE Tech., PS 98-15 (June 1998)

(Non-Patent Document 3)

H. Kawaguc hi, B ist ab lelaserdio de s and the ir app lic at ion; St at eof the art, I EEE J. Select d. Top. Quantum E 1 ectr on., 3 (1997) 1254.

Therefore, the present inventors have provided a plurality of bistable semiconductor lasers that perform an AND gate operation and a memory operation, and convert an all-optical, time-series optical signal without converting an optical signal into an electric signal. The challenge was to develop an ultra-high-speed optical memory that could record one bit at a time on a stable semiconductor laser and read out the recorded signal as a time-series signal at the required time.

Furthermore, as will be described in detail later, as the number of bits increases, an optical spatial parallel signal converter that receives optical time-series signals for input and output and an optical time-series signal converter that receives optical parallel signals are required for the number of bits. However, there is a drawback that the equipment becomes large, and it has been an issue to solve it.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a method and an apparatus for an ultra-high-speed optical memory using a bistable semiconductor laser having a shift register function, which can read information at the required timing and control for each bit. The purpose is to provide.

The present invention, in order to achieve the above object,

[1] An ultra-high-speed optical memory method using a bistable semiconductor laser, comprising a plurality of bistable semiconductor lasers that perform an AND gate operation and a memory operation, and all light without converting optical signals into electrical signals. It is characterized in that a time-series optical signal is recorded one bit at a time in each bistable semiconductor laser, and the recorded signal is read out as a time-series signal at the required timing.

[2] In an ultra-high-speed optical memory device using a bistable semiconductor laser, an array having a plurality of bistable semiconductor lasers performing an AND gate operation and a memory operation, and an optical signal write for writing an optical signal to the array Means for reading optical signals written in the array, and optical signal reading means for reading optical signals written in the array, wherein all-optical, time-series optical signals are converted to each bistable semiconductor laser without converting the optical signals into electric signals. Recording the data bit by bit and reading the recorded signal as a time-series signal at the required timing Features.

[3] In the ultrahigh-speed optical memory device using the bistable semiconductor laser according to the above [2], the optical signal writing means includes: an optical branch to which a time-series optical signal is input; And a set light irradiating means and a reset light irradiating means for the half mirror.

[4] In the ultrahigh-speed optical memory device using the bistable semiconductor laser according to the above [2], the optical signal readout means includes a half mirror, an analyzer, an optical gate means, and a gate light pulse irradiation means. And an optical delay / merging line of the read signal light.

[5] The ultrahigh-speed optical memory device using the bistable semiconductor laser according to the above [4], wherein the optical gate means is an optical gate element.

[6] The ultrahigh-speed optical memory device using the bistable semiconductor laser according to the above [4], wherein the optical gate means is a saturable absorber.

[7] Equipped with a plurality of bistable semiconductor lasers that perform AND gate operation and memory operation. All bistable semiconductor lasers convert optical signals into time-series optical signals without converting optical signals into electrical signals. An ultra-high-speed optical memory device that records one bit at a time on a laser and can read out the recording signal as a time-series signal at the required timing. The recording signal is recorded from one bistable semiconductor laser to another bistable semiconductor. It has a shift register function for transferring and recording to a laser. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a conventional fiber delay line buffer memory.

FIG. 2 is a schematic diagram of an ultrafast optical memory device using a bistable semiconductor laser showing a first embodiment of the present invention (a conceptual diagram of a shift register using a two-dimensionally polarized bistable surface emitting semiconductor laser array). is there.

FIG. 3 is a schematic diagram for explaining signal writing to an ultrafast optical memory using a bistable semiconductor laser according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating reading of a signal from ultrafast optical memory using a bistable semiconductor laser according to a first embodiment of the present invention. FIG. 5 is a diagram showing a simulation result of an ultra-high-speed optical memory using a bistable semiconductor laser according to the first embodiment of the present invention.

FIG. 6 is a schematic view of an ultrafast optical memory device using a bistable semiconductor laser according to a second embodiment of the present invention.

FIG. 7 shows a surface emitting semiconductor laser A, B, C! Of an optical signal according to a second embodiment of the present invention. , D, is a schematic diagram showing the arrangement in more detail for one column.

FIG. 8 is a timing chart showing recording of the optical signal of the surface emitting semiconductor lasers A 1 to A _{N according} to the second embodiment of the present invention.

FIG. 9 is a timing chart showing a state of transfer and recording of a signal from a surface emitting semiconductor laser A, to B B, B> to C,, C, to D, of an optical signal according to a second embodiment of the present invention. It is a chart. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail.

FIG. 2 is a schematic view of an ultrafast optical memory device using a bistable semiconductor laser according to a first embodiment of the present invention.

In this figure, 1 is an ultra-high-speed optical signal (input signal), 1 A is a header, 2 is an optical time-series signal / optical spatial parallel signal converter, 3, 4, and 13 are half mirrors, 1 is one-dimensional or two-dimensional. Dimensional polarization bistable surface emitting semiconductor laser (VCSEL) array, 6 is set light, 7 is reset light, 11 is analyzer (transmits 0 ° polarized light), 12 is optical gate element, 14 is optical gate element A gate optical pulse, 15 is an optical spatial parallel signal / optical time-series signal converter, and 16 is an ultra-high-speed optical signal (output signal).

In the following, detailed description will be made separately for writing a signal to the ultra-high-speed optical memory using a bistable semiconductor laser and reading a signal from the ultra-high-speed optical memory using the bistable semiconductor laser.

FIG. 3 shows a first embodiment of the present invention in which an optical spatial parallel signal is converted into an optical time-series signal by using an optical branching / delay line. It is a schematic diagram explaining writing.

In this figure, 11 is an ultra-high-speed optical signal (input signal), 21 A is a header, 2 2 Is a delay line, 22A is an input port, 22B is an output port, 23 is a half mirror, 14 is a one-dimensional or two-dimensional polarization bistable surface emitting semiconductor laser (VCSEL) array, 25 is a set light, 26 is a reset light.

Here, the operating principle of the VC SEL element will be described.

In a surface emitting semiconductor laser in which the optical waveguide has a square cross section, there are two eigenmodes whose electric field direction is along a square side. Here, they are called 0 ° mode and 90 ° mode. The optical gain of a surface-emitting semiconductor laser is almost equal to one laser oscillation mode, and the two modes are strongly coupled through gain saturation, resulting in bistability. When a short light pulse is incident from the outside, the polarization is switched to the same polarization mode as that of the incident pulse light, and the polarization after switching is maintained even if the incident pulse disappears. Therefore, a polarization bistable optical memory can be realized. The speed of polarization switching is as fast as 7 ps, making it the world's fastest switching speed for optical bistable devices. Applications such as optical demultiplexing (optical DEMUX) in ultra-high-speed optical communications and direct conversion of optical RZ signals to optical NRZ signals are expected to be applied to ultra-high-speed optical functional devices.

Next, the signal writing to the polarization bistable surface emitting semiconductor laser (VCSEL) array 24 will be described with reference to FIG.

First, an oscillating polarization of each polarization bistable surface emitting semiconductor laser (VCSEL) array 24 is perpendicular to the paper (90 °) by applying a reset light 26 having an electric field perpendicular to the paper (called 90 ° light). Light).

As shown in FIG. 3, header 11-1A is added to the ultra-high-speed time-series optical signal. The optical signal polarized in the plane of the paper (referred to as 0 ° light) enters from the input port 2 A of the optical branching / delay line 22, is branched, is delayed by a bit interval, and is output from each output port 22 B. The light is emitted and injected into the VCSEL array 14 via the half mirror 23.

Then, when the optical signal delayed most by the optical branching delay line 22 reaches the VCSEL array 24, the set light 25 of 0 ° polarization is transmitted to the VCSEL array 14 by the signal from the header 21A. Incident. Although the polarization of the VCSEL array 24 is not switched only by the signal light, when the set light 25 and the signal light are simultaneously incident, the light switches from 90 ° light to 0 ° light. Therefore, as shown in Fig. 3, when the set light 25 enters, the VC SEL array

The “1” and “0” signals injected into 24 are recorded as oscillation polarization in the VCSEL array 24.

FIG. 4 is a schematic diagram illustrating reading of a signal from an ultra-high-speed optical memory using a bistable semiconductor laser according to a first embodiment of the present invention.

In this figure, 27 is a half mirror, 28 is an analyzer, 29 is a saturable absorber,

30 is a gate light pulse, 31 is an optical delay / merging line, 32 is a mirror, and 33 is an ultra-high-speed optical signal (output signal).

The reading of the optical signal (record) written as shown in FIG. 3 is performed as follows.

From the VC SEL array 24, 0 ° and 90 ° polarized laser oscillation light is continuously (CW) emitted according to the “1” and “0” signals. Only the 0 ° polarized light passes through the analyzer 28 and enters the saturable absorber 29. Next, the gate light pulse 30 is incident on the saturable absorber 29, and the CW light from the VCSEL array 24 is cut out as pulse light. Next, the optical pulses are arranged in chronological order by the optical delay / merging line 31 and read as an ultra-high-speed optical signal (output signal) 33.

As described above, the memory can be stored in the unit of an optical bucket and can be read out in the unit of an optical bucket when necessary.

The above-mentioned embodiment shows that one operation of the ultra-high-speed optical memory is possible by a detailed computer simulation using a rate equation.

It is known from the above-mentioned Non-Patent Documents 1 to 3 that this analysis method is suitable for analysis of one operation of this kind of optical memory, and that the result agrees well with the experimental result.

FIG. 5 is a diagram showing a simulation result of an ultrafast optical memory using a bistable semiconductor laser according to the first embodiment of the present invention, and FIG. 5 (a) shows an ultrafast optical signal (0). Figure 5 (b) is the set light (0 °), Figure 5 (c) is the reset light

(90 °), FIG. 5 ((1) shows the 0 ° polarization component of the memory output, FIG. 5 (e) shows the gate light pulse, and FIG. 5 (f) shows the read output. , The vertical axis is optical power

(W), and the horizontal axis indicates time (ps).

In the time waveform of the ultrafast optical signal shown in Fig. 5 (a), the pulse width of the optical signal is 1 Ps, pulse interval is 5 ps, and signal transmission speed is 200 Gbit / s. The optical signal power of each channel is 5. According to the schematic diagrams shown in Figs. 3 and 4, the case of 6 channels was analyzed. A header with a pulse width of 10 ps is read, and a set light (10 uW) of 1 ps is generated with an appropriate time delay and incident on the VCSEL array 4 simultaneously with the signal light of the sixth channel. Set as follows. As a result, as shown in Fig. 5 (d), the 0 ° polarization component of the memory output becomes “0” power and “1” depending on whether the optical signal is “0” power or “1” and is stored. . At this time, the optical output of the memory is about 500 / W, which is an advantage that it is 100 times (20 dB) larger than the optical signal.

Next, as shown in FIG. 5 (e), the absorption of the saturable absorber 29 is saturated with the gate light pulse 30 of lps, about 100 W, and the signal light is converted to the signal light of FIG. 5 (f). Read as shown in.

When the reading of the signal light is completed, the optical memory is reset to a 90 ° signal by the reset light 26 of 1 ps, 20 W as shown in FIG. 5 (c).

With this series of operations, memory can be stored in the unit of an optical bucket and read out in the unit of an optical bucket when necessary.

Next, a second embodiment of the present invention will be described.

FIG. 6 is a schematic diagram of an ultrafast optical memory device using a bistable semiconductor laser according to a second embodiment of the present invention.

In this figure, 101 is a half mirror, 202 is a two-dimensional polarization bistable surface emitting semiconductor laser (VCSEL) array, 203 is an optical gate element, and 204 is a reflector.

The device of this embodiment is a device in which the polarization bistable surface emitting semiconductor laser array 24 shown in the first embodiment is replaced by a two-dimensional array 202, and an optical time series signal / optical spatial parallel signal converter (shown in FIG. None), reset light generator (not shown), set light generator (not shown), gate light generator (not shown), analyzer 11, optical gate element 12, and optical spatial parallel signal / light It has a device composed of a time-series signal converter (not shown), and has a configuration in which a reflector 204, an optical gate element 103, and a gate light generator are added to this device. First, as described in the first embodiment, writing of a signal to the two-dimensional polarization bistable surface emitting semiconductor laser array 202 will be described. First, an electric field is applied in the direction perpendicular to the plane of the paper (referred to as 90 ° light). By inputting the reset light, the oscillation polarization of each polarization bistable surface emitting semiconductor laser becomes perpendicular to the plane of the paper (referred to as 90 ° light). Reset. A header is added to the ultra-high-speed time-series signal. The optical time-series signal polarized in the paper (called 0 ° light) is converted by the optical time-series signal / optical spatial parallel signal converter,

Each bit is injected into a different polarization bistable surface emitting semiconductor laser. Then, the optical signal VC SEL array 2 0 2 of the first stage (of FIG. 6 A, to A ₄₎ is 0 ° polarization set light when it reaches the, incident on the VCSEL array 10 2 by a signal from the header one I do. The polarization of the VC SEL array 202 is not switched only by the signal light, but is switched from 90 ° light to 0 ° light when the set light and the signal light are simultaneously incident. Therefore, when the set light is incident, “1” injected into the VCSEL array 202,

A “0” signal is recorded as the VCSEL oscillation polarization.

Next, the shift register function will be described with reference to FIGS. 6 and 7. FIG.

FIG. 7 is a schematic diagram showing the arrangement of the surface emitting semiconductor lasers A,, B,. C,.

In the conventional optical bucket memory described above, when the number of bits increases, the number of input / output ports of the optical time series signal / optical spatial parallel signal conversion device is generally required by the number of bits, which is a major configuration problem. . The present invention solves this problem by having an optical shift register function of collectively transferring signals recorded in some bistable semiconductor lasers to another bistable semiconductor laser and recording the signals.

FIG. 6 shows a conceptual diagram of a shift register using a two-dimensional polarization bistable surface emitting semiconductor laser array composed of a 4 × 4 surface emitting semiconductor laser. A by the operation principle shown in FIG. 2, the to A _4, "1" and "0" signals, respectively 0. And 90. Recorded as oscillation polarization. A, the output of the surface emitting semiconductor laser to A ₄ is emitted with a diffraction expansion rising a few degrees, it is condensed by the reflector 204 disposed on an upper surface B, and the surface emitting semiconductors lasers .about.B _4. An optical gate element 203 through which the output of the surface emitting semiconductor laser is transmitted when a gate light pulse is incident from the outside is disposed near the reflector 204. Have been. When the surface emitting semiconductor laser and 1 the distance between the reflector 204 2 1 / c When (c is the speed of light) briefly gate is opened than B, the laser oscillation polarization of .about.B ₄ is, A, to A ₄ a, the injection of the output of each is the same oscillation polarization and to a _4, signal pixel Re respectively written and recorded. For example, if 1 is 5 cm, the gate opening time will be less than 30 ps. Next, A, to A ₄ were reset by the reset light having a 90 ° polarization, and writes the new signal. Then you open the gate in the gate light, B, signals .about.B 4 is C, and -C _4, A, signal to A ₄ is B, is written are recorded respectively .about.B _4. Reading of signals (in the figure the column D, to D ₄₎ final stage can be realized by reading the CW output of the surface emitting semiconductor laser as described below.

Figure 8 is a timing Chiya Ichiboku showing the surface emitting semiconductor laser A of the optical signal, the recording of to A _N, Figure 9 is illustrates this shift Bok register function in the timing chart, ie from,, B, 5 is a timing chart showing the transfer and recording of signals from to d and from C and to.

In the ultrahigh-speed optical memory device with the shift register function according to the present invention, the number of bits corresponding to the number of surface emitting semiconductor lasers in the y direction shown in FIG. is recorded a, the surface emitting semiconductor laser to a _N by. The input of the gate one Bok light, the signal of B, after being recorded is transferred to ~ BN, A reset light, the oscillation polarization to A _N is reset to 90 °, recording the next signal. Reading of a record is performed as follows. The final stage (of FIG. 6 D, ~ D ₄₎ of the VC SEL array 202 "1" from, 0 ° polarized light and 90 ° polarization Les monodentate oscillation light in accordance with the "0" signal is emitted continuously (CW) Have been. The analyzer 11 passes only 0 ° polarized light and enters the optical gate element 12. Next, the gate light pulse is made incident on the optical gate element 12, passes through the CW light from the last stage of the VCSEL array 202, and is cut out as pulse light. Next, optical pulses are arranged in time series by an optical spatial parallel signal / optical time series signal converter. As described above, the memory can be stored in the unit of the light bucket, and can be read out in the unit of the light bucket when necessary.

According to the second embodiment of the present invention, a plurality of bistable surface-emitting semiconductor lasers performing an AND gate operation and a memory operation are provided, and all-optical type is used without converting an optical signal into an electric signal. Optical signal is recorded on each bistable semiconductor laser one bit at a time. An ultra-high-speed optical memory capable of reading a recording signal as a time-series signal at a necessary timing has a function of transferring a recording signal from one bistable semiconductor laser to another bistable semiconductor laser and recording.

It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. As described above, according to the present invention, the following effects can be obtained.

(1) All-optical routing can be performed on an optical bucket basis without converting optical signals into electrical signals, and high-speed optical communication can be achieved.

(2) The recording signal can be transferred from one bistable semiconductor laser to another and recorded. Industrial applicability

INDUSTRIAL APPLICABILITY An ultra-high-speed optical memory method using a bistable semiconductor laser and a device therefor according to the present invention contribute to increase the speed of optical communication, and can control information for each bit and read information at necessary timing. Further, it is suitable as an ultra-high-speed optical memory using a bistable semiconductor laser having a shift register function.

Claims

The scope of the claims

1. Equipped with a plurality of bistable semiconductor lasers that perform AND gate operation and memory operation, all-optical type without converting optical signals to electrical signals. An ultra-high-speed optical memory method using a bistable semiconductor laser, characterized in that data is recorded one by one and a recorded signal is read out as a time-series signal at a required timing.

2.

(a) an array having a plurality of bistable semiconductor lasers performing an AND gate operation and a memory operation,

(b) optical signal writing means for writing an optical signal to the array;

(c) optical signal reading means for reading an optical signal written in the array, (d) an all-optical type without converting the optical signal into an electric signal, and a time-series optical signal for each bistable semiconductor. An ultra-high-speed optical memory device using a bistable semiconductor laser characterized by recording one bit at a time on a laser and reading out a recorded signal as a time-series signal at a required timing.

3. An ultra-high-speed optical memory device using a bistable semiconductor laser according to claim 2, wherein the optical signal writing means comprises: an optical branch and delay line to which a time-series optical signal is input; An ultra-high-speed optical memory device using a bistable semiconductor laser, comprising: means for irradiating a half mirror with set light and reset light.

4. An ultra-high-speed optical memory device using a bistable semiconductor laser according to claim 2, wherein the optical signal readout means comprises a half mirror, an analyzer, an optical gate means, a gate light pulse irradiation means, An ultra-high-speed optical memory device using a bistable semiconductor laser, comprising: an optical delay of the emitted signal light and a merging line.

5. An ultrafast optical memory device using a bistable semiconductor laser according to claim 4, wherein the optical gate means is an optical gate element. One device.

6. An ultrafast optical memory device using the bistable semiconductor laser according to claim 4. An ultra-high-speed optical memory device using a bistable semiconductor laser, wherein the optical gate means is a saturable absorber.

7. Equipped with a plurality of bistable semiconductor lasers that perform AND gate operation and memory operation, all-optical type without converting optical signals into electrical signals, and time-series optical signals are transmitted to each bistable semiconductor laser by one bit. An ultra-high-speed optical memory device that can record data one by one and read out the recorded signal as a time-series signal at the required timing, transferring the recorded signal from one bistable semiconductor laser to another. An ultrahigh-speed optical memory device using a bistable semiconductor laser having a shift register function for recording.