JP2003337355A - Very high speed optical memory method and apparatus using bistable semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a very high speed optical memory method and apparatus using a bistable semiconductor laser capable of controlling each bit and reading out information at the necessary timing. <P>SOLUTION: The very high speed optical memory apparatus using bistable semiconductor laser includes an array 5 having a plurality of bistable semiconductor lasers performing AND gate operation and 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, 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. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrafast optical memory method and device using a bistable semiconductor laser.

[0002]

2. Description of the Related Art At present, an optical fiber communication system has been developed as a communication transmission system for an 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, but all-optical systems that perform optical signal processing are expected for such ultra-high speed. Has been done. In particular, all-optical packet-based routing technology is needed.

FIG. 5 is a schematic diagram of a conventional fiber delay line buffer memory.

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

However, in the system using such a fiber delay line buffer memory, it is difficult to control each bit and read information at a necessary timing.

[0006]

[Non-Patent Document 1] Tamura, Yamayoshi, Kawaguchi "All-Optical Optical Signal Processing Using Ultrafast Polarized Bistable Surface-Emitting Semiconductor Lasers," LQE 2000-42 (August 2000)

[Non-Patent Document 2] Yamayoshi, Kawaguchi, "All-Optical Ultrafast DEMUX Using Polarization Bistability of Surface-Emitting Semiconductor Laser," PS98-15 (June 1998)

[Non-Patent Document 3] Kawaguchi, "Bist
available laser diode and thei
r application; State of t
heart, “IEEE J. Selected. To
p. Quantum Electron. , 3 (199
7) 1254.

[0007]

Therefore, the inventors of the present invention are provided with a plurality of bistable semiconductor lasers that perform AND gate operation and memory operation, and are of the all-optical type without converting an optical signal into an electric signal. It has been a challenge to develop an ultra-high-speed optical memory capable of recording a series of optical signals in each bistable semiconductor laser one bit at a time and reading the recorded signals as a time series signal at a necessary timing.

Further, as will be described in detail later, when the number of bits increases, the optical spatial parallel signal converter for receiving the optical time series signals for input and output and the optical time series signal converter for receiving the optical parallel signals are divided by the number of bits. However, there is a drawback that the device becomes large in size, and it has been a problem to solve it.

In view of the above situation, the present invention can control information for each bit and read information at a necessary timing,
Another object of the present invention is to provide an ultrafast optical memory method and device using a bistable semiconductor laser having a shift register function.

[0010]

In order to achieve the above-mentioned object, the present invention provides [1] a plurality of dual gates that perform AND gate operation and memory operation in an ultrafast optical memory method using a bistable semiconductor laser. Equipped with a stable semiconductor laser, it is an all-optical type without converting an optical signal into an electric signal, and records a time-series optical signal in each bistable semiconductor laser one bit at a time, and records it as a time-series signal at a necessary timing. It is characterized by reading out a signal.

[2] In an ultra-high-speed optical memory device using a bistable semiconductor laser, an array having a plurality of bistable semiconductor lasers performing AND gate operation and memory operation, and optical signal writing for writing an optical signal in this array Means and an optical signal readout means for reading out the optical signals written in the array, which are all-optical type without converting the optical signals into electric signals and time-sequential optical signals for each bistable semiconductor laser by 1 bit. It is characterized in that the recording signals are recorded one by one and the recording signal is read out as a time-series signal at a necessary timing.

[3] In the ultrahigh-speed optical memory device using the bistable semiconductor laser described in [2], the optical signal writing means is an optical branching unit to which a time-series optical signal is input.
It is characterized by comprising a delay line, a half mirror, and a set light irradiation means and a reset light irradiation means for the half mirror.

[4] In the ultrahigh-speed optical memory device using the bistable conductor laser described in [2], the optical signal reading means is a half mirror, an analyzer, an optical gate means, and a gate light pulse irradiation. It is characterized by comprising means and an optical delay / merging line of the read signal light.

[5] In the ultrafast optical memory device using the bistable semiconductor laser described in [4] above, the optical gate means is an optical gate element.

[6] In the ultrafast optical memory device using the bistable semiconductor laser described in [4], the optical gate means is a saturable absorber.

[7] A plurality of bistable semiconductor lasers that perform AND gate operation and memory operation, are all-optical type without converting optical signals into electric signals, and output time-series optical signals to each bistable semiconductor laser. An ultra-high-speed optical memory device capable of recording 1 bit at a time and reading the recording signal as a time-series signal at a required timing, and transferring the recording signal from one bistable semiconductor laser to another bistable semiconductor laser. And has a shift register function for recording.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

FIG. 1 is a schematic view of an ultrafast optical memory device using a bistable semiconductor laser showing a first embodiment of the present invention.

In the figure, 1 is an ultrahigh-speed optical signal (input signal), 1A is a header, 2 is an optical time series signal / optical space parallel signal converter, 3, 4, 13 are half mirrors, 5 is one-dimensional or Two-dimensional polarized bistable surface emitting semiconductor laser (VC
SEL) array, 6 is set light, 7 is reset light, 11
Is an analyzer (transmits 0 ° polarized light), 12 is an optical gate element, 14 is a gated optical pulse, 15 is an optical space parallel signal / optical time series signal converter, and 16 is an ultrahigh-speed optical signal (output signal)
Is.

In the following, the writing of a signal to an ultrafast optical memory using a bistable semiconductor laser and the reading of a signal from an ultrafast optical memory using a bistable semiconductor laser will be described in detail.

FIG. 2 shows a signal to an ultrahigh-speed optical memory using a bistable semiconductor laser, which shows a first embodiment of the present invention in which an optical branch / delay line is used for converting an optical space parallel signal into an optical time series signal. It is a schematic diagram explaining writing of.

In this figure, 21 is an ultrahigh-speed optical signal (input signal), 21A is a header, 22 is an optical branch / delay line,
22A is an input port, 22B is an output port, 23 is a half mirror, 24 is a one-dimensional or two-dimensional polarized bistable surface emitting semiconductor laser (VCSEL) array, 25 is set light,
Reference numeral 26 is a reset light.

Here, the operation principle of the VCSEL element will be described.

In a surface-emitting semiconductor laser whose optical waveguide has a square cross-sectional shape, there are two eigenmodes whose electric field directions are along the sides of the square. Here, 0 ° mode, 90
° mode. The optical gain of the surface emitting semiconductor laser is almost equal to the two lasing modes, 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 the incident pulse light, and the polarization after switching is retained even when the incident pulse disappears. Therefore, a polarization bistable optical memory can be realized. The polarization switching speed is extremely fast at 7 ps, which is the fastest switching speed of the optical bistable device in the world. It can be expected to be applied as an ultrahigh-speed optical functional element such as optical demultiplexing (optical DEMUX) in ultrahigh-speed optical communication and direct conversion of an optical RZ signal into an optical NRZ signal.

Next, a polarized bistable surface emitting semiconductor laser (V
Writing signals to the CSEL) array 24 will be described with reference to FIG.

First, an electric field is perpendicular to the paper surface (90
(Referred to as “light”), each polarization bistable surface emitting semiconductor laser (VCSEL) array 2
The oscillated polarized light of No. 4 is reset perpendicularly to the paper surface (90 ° light).

As shown in FIG. 2, a header 21A is added to the ultrahigh-speed time series optical signal. An optical signal polarized in the plane of the paper (referred to as 0 ° light) enters from the input port 22A of the optical branching / delay line 22, is branched, is delayed by bit intervals, and then exits from each output port 22B. Injected into the VCSEL array 24 via 23.

Next, when the optical signal most delayed by the optical branching / delay line 22 reaches the VCSEL array 24, the 0 ° polarized set light 25 is incident on the VCSEL array 24 by the signal from the header 21A. VCS
The polarization of the EL array 24 is not switched only by the signal light, but when the set light 25 and the signal light are simultaneously incident,
Switch from 0 ° light to 0 ° light.

Therefore, as shown in FIG.
When is incident, the “1” and “0” signals, which are injected into the VCSEL array 24, are recorded in the VCSEL array 24 as oscillation polarization.

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

In this figure, 27 is a half mirror, 2
Reference numeral 8 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 ultrahigh-speed optical signal (output signal).

Reading of the optical signal (recording) written as shown in FIG. 2 is performed as follows.

"1" and "0" from the VCSEL array 24
Laser oscillation light of 0 ° polarization and 90 ° polarization is continuously (CW) emitted according to the signal. 0 ° by analyzer 28
Only the polarized light passes and enters the saturable absorber 29. Next, the gate light pulse 30 is incident on the saturable absorber 29,
The CW light from the VCSEL array 24 is cut out as pulsed light. Next, the optical pulse is arranged in time series by the optical delay / merge line 31, and is read out as an ultrahigh-speed optical signal (output signal) 33.

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

According to the above-mentioned embodiment, it is shown by the detailed computer simulation using the rate equation that the ultra high speed optical memory operation is possible.

It has been mentioned above that this analysis method is suitable for analysis of this kind of optical memory operation, and the result agrees well with the experimental result.

It is known from [Non-Patent Documents 1 to 3].

FIG. 4 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. FIG. 4A shows an ultrafast optical signal (0
4) time waveform, FIG. 4B shows the set light (0 °), FIG.
4C shows the reset light (90 °), FIG. 4D shows the 0 ° polarization component of the memory output, FIG. 4E shows the gate light pulse, and FIG. 4F shows the read output. The vertical axis represents optical power (μW) and the horizontal axis represents time (ps).

In the time waveform of the ultrafast optical signal shown in FIG. 4A, the pulse width of the optical signal is 1 ps and the pulse interval is 5 p.
and the signal transmission rate is 200 Gbit / s.
The optical signal power of each channel is 5 μW. The case of 6 channels was analyzed according to the schematic diagrams shown in FIGS. The header 21A having a pulse width of 10 ps is read, a 1 ps set light (10 μW) is generated with an appropriate time delay, and the VCSE is simultaneously generated with the signal light of the sixth channel.
It is set so as to enter the L array 24.

As a result, as shown in FIG. 4D, the 0 ° polarization component of the memory output becomes "0" or "1" and is stored depending on whether the optical signal is "0" or "1". At this time, the optical output of the memory is about 500 μW, which is 10
It has the advantage of being 0 times (20 dB) larger.

Next, as shown in FIG. 4 (e), 1 ps,
Saturable absorber 2 with a gate light pulse 30 of about 100 μW
The absorption of 9 is saturated, and the signal light is read as shown in FIG.

At the time when the reading of the signal light is completed, FIG.
As shown in (c), reset light 2 of 1 ps and 20 μW
At 6, the optical memory is reset to a 90 ° signal.

By this series of operations, the memory can be stored in the unit of optical packet, and can be read out in the unit of optical packet when necessary.

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

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

In this figure, 201 is a half mirror,
Reference numeral 202 denotes a two-dimensional polarized bistable surface emitting semiconductor laser (VCS).
EL) array, 203 is an optical gate element, and 204 is a reflector.

The apparatus of this embodiment is obtained by replacing the polarization bistable surface emitting semiconductor laser array 24 shown in the first embodiment with a two-dimensional array 202, and uses an optical time-series signal / optical spatial parallel signal converter (shown in the figure). None), reset light generator (not shown), set light generator (not shown), gate light generator (not shown), analyzer 11, optical gate element 12, and optical space parallel signal / optical time series signal converter. It has a device (not shown), and a reflector 204, an optical gate element 203, and a gate light generator are added to this device.

First, as shown in the first embodiment, writing of a signal to the two-dimensional polarization bistable surface emitting semiconductor laser array 202 will be described. First, by inputting reset light having an electric field in the direction perpendicular to the paper surface (called 90 ° light), the oscillation polarization of each polarization bistable surface emitting semiconductor laser is reset perpendicular to the paper surface (called 90 ° light). It

A header is added to the ultra-high-speed time series signal. An optical time-series signal polarized within the plane of the paper (referred to as 0 ° light) is converted by an optical time-series signal / optical spatial parallel signal converter and injected into different polarization bistable surface emitting semiconductor lasers for each bit. Next, the optical signal is transmitted to the VCSEL array 20.
When reaching the first stage of _No. 2 (A _{1 to} A _{4 in} FIG. 6), the set light of 0 ° polarization enters the VCSEL array 202 by the signal from the header. The polarization of the VCSEL 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, the "1" and "0" signals injected into the VCSEL array 202 are V
It is recorded as the oscillating polarization of the CSEL.

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

FIG. 7 shows an optical signal surface emitting semiconductor laser A ₁ ,
B _1, C _1, is a schematic view showing an arrangement in more detail a row of D _1.

In the above-mentioned conventional optical packet memory,
Generally, when the number of bits increases, the number of input / output ports of the optical time-series signal / optical space parallel signal converter is required, which is a serious problem in terms of configuration. The present invention solves this problem by providing an optical shift register function for collectively transferring and recording the signals recorded in some bistable semiconductor lasers to another bistable semiconductor laser.

FIG. 6 is 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. The A ₁ to A ₄ by the operation principle shown in FIG. 1, "1" and "0" signal is recorded as respective 0 ° and 90 ° oscillation polarization. A ₁ ~ A
The output of the surface emitting semiconductor laser of _{No. 4} is emitted with a diffraction spread of several degrees, and B ₁ to
It is focused on the surface emitting semiconductor laser of B ₄ . Reflector 204
When a gate light pulse is incident from the outside near
Optical gate element 20 through which the output of the surface emitting semiconductor laser is transmitted
3 are arranged. Surface emitting semiconductor laser and reflector 20
Lasing polarization of the (the c speed of light) 2l / c When l the distance short between the gate is opened than B ₁ .about.B ₄ between 4, A ₁ ~ by injection of the output of A ₁ to A ₄ The oscillation polarization is the same as that of A _4, and signals are written and recorded. For example, when 1 is 5 cm, the gate opening time is 30 ps or less. Next, A _{1 to} A ₄ are reset by reset light having 90 ° polarization, and a new signal is written. Then you open the gate in the gate light, the signal of B ₁ .about.B ₄ is a C ₁ -C _4, signals of A ₁ to A ₄ is recorded is written into B ₁ ~B _4. The signal is read out by the CW of the surface emitting semiconductor laser at the final stage (D _{1 to} D ₄ in the figure).
This can be realized by reading the output as described later.

FIG. 8 shows surface emitting semiconductor lasers A ₁ to A _{1 for} optical signals.
FIG. 9 is a timing chart showing the recording of A _N , and FIG. 9 is a timing chart showing this shift register function, that is, A ₁ to B ₁ , B ₁ to C ₁ , and C ₁ to D _1.
5 is a timing chart showing how signals are transferred to and recorded from the recording medium.

In the ultrahigh-speed optical memory device with 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. 6 is obtained by the AND gate operation of the set light and the signal light. Recording is performed on the surface emitting semiconductor lasers A _{1 to} A _N. The input of the gate light, the signal after being transferred is recorded in the B ₁ .about.B _N, the oscillation polarization of A ₁ to A _N reset light is reset to 90 °, recording the next signal.

The reading of the record is performed as follows. VC
Laser oscillation lights of 0 ° polarization and 90 ° polarization are continuously (CW) emitted from the final stage of the SEL array 202 (D _{1 to} D _{4 in} FIG. 6) according to the “1” and “0” signals. Only the 0 ° polarized light is transmitted by the analyzer 11, and the optical gate element 1
Incident on 2. Next, the gate light pulse is applied to the optical gate device 1.
2 and C from the final stage of the VCSEL array 202
W light is passed and cut out as pulsed light. Next, the optical pulses are arranged in time series by the optical space parallel signal / optical time series signal converter. From the above, memory is stored in optical packet units,
It becomes possible to read out in optical packet units when necessary.

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

The present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0058]

As described in detail above, according to the present invention, the following effects can be achieved.

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

(2) A recording signal can be transferred from one bistable semiconductor laser to another bistable semiconductor laser for recording.

[Brief description of drawings]

FIG. 1 is a schematic view of an ultrafast optical memory device using a bistable semiconductor laser according to a first embodiment of the present invention (a conceptual diagram of a shift register using a two-dimensional polarized bistable surface emitting semiconductor laser array). .

FIG. 2 is a schematic diagram illustrating writing of a signal to an ultrafast optical memory using a bistable semiconductor laser according to the first embodiment of the present invention.

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

FIG. 4 is a diagram showing a simulation result of an ultrafast optical memory using the bistable semiconductor laser according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram of a conventional fiber delay line buffer memory.

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 is a schematic diagram showing in more detail the arrangement of one row of surface emitting semiconductor lasers A ₁ , B ₁ , C ₁ , D ₁ for optical signals according to a second embodiment of the present invention.

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

FIG. 9 is a timing chart showing the state of signal transfer and recording from the surface emitting semiconductor lasers A ₁ to B ₁ , B ₁ to C ₁ and C ₁ to D ₁ for optical signals according to the second embodiment of the present invention. Is.

[Explanation of symbols]

1,21 Ultra high-speed optical signal (input signal) 1A, 21A Header 2 Optical time series signal / optical space parallel signal converter 3,4,13,23,27,201,205 Half mirror 5,24,202 One-dimensional or Two-dimensional polarized bistable surface emitting semiconductor laser (VCSEL) array 6,25 Set light 7,26 Reset light 11,28 Analyzer (transmits 0 ° polarized light) 12,203 Optical gate element 14,30 Gate light pulse 15 Optical space parallel signal / optical time series signal converter 16,33 Ultra high speed optical signal (output signal) 22 Optical branch / delay line 22A Optical branch / delay line input port 22B Optical branch / delay line output port 29 Saturable absorption Body 31 Optical delay / merging line 32 Mirror 204 Reflector

Claims (7)

[Claims] 1. A plurality of bistable semiconductor lasers that perform an AND gate operation and a memory operation, are all-optical type without converting an optical signal into an electrical signal, and output a time-series optical signal to each bistable semiconductor laser. An ultra-high-speed optical memory method using a bistable semiconductor laser, which records one bit at a time and reads the recorded signal as a time-series signal at a required timing. 2. An array having (a) a plurality of bistable semiconductor lasers that perform an AND gate operation and a memory operation, (b) an optical signal writing means for writing an optical signal to the array, and (c) an array. And (d) an all-optical type optical signal reading means for reading the written optical signal without converting the optical signal into an electric signal, and recording the time-series optical signal in each bistable semiconductor laser one bit at a time. An ultra-high-speed optical memory device using a bistable semiconductor laser, which is characterized by reading a recording signal as a time-series signal at a required timing. 3. An ultra-high-speed optical memory device using the bistable semiconductor laser according to claim 2, wherein the optical signal writing means includes an optical branching / delay line to which a time-series optical signal is input, and a half mirror. An ultra-high-speed optical memory device using a bistable semiconductor laser, comprising: a set light irradiation unit and a reset light irradiation unit for the half mirror. 4. An ultra-high-speed optical memory device using the bistable semiconductor laser according to claim 2, wherein the optical signal reading means is a half mirror, an analyzer, an optical gate means, and a gate light pulse irradiation means. An ultra-high-speed optical memory device using a bistable semiconductor laser, comprising: an optical delay / merging line of the read signal light. 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. Memory device. 6. An ultrafast optical memory device using a bistable semiconductor laser according to claim 4, wherein the optical gate means is a saturable absorber. Optical memory device. 7. A plurality of bistable semiconductor lasers that perform an AND gate operation and a memory operation, are all-optical type without converting an optical signal into an electric signal, and output a time-series optical signal to each bistable semiconductor laser. An ultra-high-speed optical memory device capable of recording one bit at a time and reading a recording signal as a time-series signal at a required timing. The recording signal is transferred from one bistable semiconductor laser to another bistable semiconductor laser. An ultra high-speed optical memory device using a bistable semiconductor laser, which has a shift register function for recording.