JPH04221937A - Chaos generator - Google Patents

Abstract

PURPOSE:To easily generate a light chaos with high controllability by using a semiconductor laser. CONSTITUTION:A laser beam 4 oscillated from the semiconductor laser 1 is received by a reverse biased photodiode 2 and the signal outputted from the anode of this photodiode 2 is amplified by a nonlinear amplifier 3 and is then fed back to the anode of the semiconductor laser 1, by which the laser beam 4 is put into the chaos state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chaos generator, and is particularly suitable for use in generating optical chaos.

0002

[Prior Art] Chaos is a phenomenon in which the change is unstable despite deterministic changes over time, or to put it another way, chaos is a phenomenon in which the changes occur in a deterministic manner over time. It is about fluctuation.

In recent years, optical chaos has attracted attention as a key to realizing basic elements for future nonlinear information processing. Conventionally,
As a method for generating this optical chaos, there is a known method in which optical chaos is generated by adjusting the tilt angle of a mirror of an optical resonator such as a Fabry-Perot resonator.

0004

However, the above-described conventional method for generating optical chaos requires delicate optical adjustment to generate optical chaos, and has a drawback in controllability.

[0005] Accordingly, an object of the present invention is to provide a chaos generating device that can easily generate optical chaos with high controllability using a semiconductor laser.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a first invention provides a chaos generating device that includes a semiconductor laser (1) and a laser beam (4) oscillated from the semiconductor laser (1). It consists of a photodiode (2) that receives light, at least a linear amplifier (6) and a rectifier (7), and the input side is connected to the anode of the photodiode (2),
It includes a nonlinear amplifier (3) whose output side is connected to the anode of the semiconductor laser (1).

[0007] The second invention is a chaos generator, which includes:
A semiconductor laser (1) and a photodiode (2) that receives the laser beam (4) oscillated from the semiconductor laser (1).
and a nonlinear amplifier (3) consisting of at least a triode, whose input side is connected to the anode of the photodiode (2) and whose output side is connected to the anode of the semiconductor laser (1).
).

[0008] Here, the nonlinear amplifier refers to an amplifier in which harmonic components of an input signal of a constant frequency are mixed into an amplified output signal.

[0009]

[Operation] Laser light (
4) is received by a reverse biased photodiode (2), and the signal output from the anode of this photodiode (2) is amplified by a nonlinear amplifier (3) and then fed back to the anode of the semiconductor laser (1). Accordingly, the laser beam (4) can be brought into a chaotic state. In other words, optical chaos can be generated. In this case, the generation of this optical chaos can be easily controlled by controlling the voltage applied to the photodiode (2) or the gain of the nonlinear amplifier (3), and does not require any delicate optical adjustment. do not.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a chaos generator according to an embodiment of the present invention.

As shown in FIG. 1, the chaos generator according to this embodiment mainly includes a semiconductor laser (laser diode) 1 and, for example, an avalanche photodiode 2.
and a nonlinear amplifier 3.

A predetermined current (for example, about 70 mA) is passed through the semiconductor laser 1 in the forward direction by a constant current source, thereby causing the laser beam 4 to oscillate. This laser light 4 is received by an avalanche type photodiode 2. A voltage VAPD is applied to the cathode of this avalanche photodiode 2, and the anode is grounded via a resistor R1 of, for example, 50Ω. As a result, the avalanche photodiode 2 is reverse biased.

The anode of this avalanche photodiode 2 is connected to the input terminal of a nonlinear amplifier 3 via a capacitor C. The output terminal of this nonlinear amplifier 3 is connected to the anode of the semiconductor laser 1 via a delay device 5. As this delay device 5, for example, various known delay elements can be used, and for example, a BNC cable can also be used.

In this embodiment, the nonlinear amplifier 3 includes an FET 6 as a fast-response linear amplifier and a rectifying diode 7. A power supply voltage VD is applied to the drain of this FET6 via a resistor R2. Further, the source of this FET 6 is connected to the anode of a rectifying diode 7, and the cathode of this rectifying diode 7 is grounded.

Next, the operation of the chaos generator according to this embodiment constructed as described above will be explained.

As shown in FIG. 1, laser light 4 oscillated from a semiconductor laser 1 is received by an avalanche photodiode 2. As shown in FIG. The received laser beam 4 is photoelectrically converted by the avalanche photodiode 2, and a signal is output from the anode of the avalanche photodiode 2. This signal is supplied via capacitor C to the gate of FET6. An example of a signal supplied to the gate of this FET 6 is shown in FIG. 2A. The signal supplied to the gate of this FET6 is amplified by this FET6. An example of this amplified output signal is shown in FIG. 2B. The output signal of this FET 6 is rectified by a rectifying diode 7, and is shown in FIG. 2C.
You will get the output shown in . Here, harmonic components are automatically mixed into the output signal of this rectifying diode 7 during rectification by this rectifying diode 7.

The output signal of the rectifying diode 7 mixed with this harmonic component is supplied to the anode of the semiconductor laser 1 after being delayed by a predetermined time in the delay device 5 . That is, the signal output from the nonlinear amplifier 3 is fed back to the anode of the semiconductor laser 1 after being delayed for a predetermined time by the delay device 5.

At this time, when the laser beam 4 oscillated from the semiconductor laser 1 is observed with a spectrum analyzer, the occurrence of chaos is observed. In this case, the occurrence of this chaos can be controlled by changing the gain of the nonlinear amplifier 3 consisting of the FET 6 and the rectifying diode 7, or by changing the voltage VAPD applied to the avalanche photodiode 2. .

As an example, FIG. 3 shows a case where the occurrence of chaos is controlled by changing the voltage VAPD applied to the avalanche photodiode 2. In other words, as shown in Figure 3, as VAPD is increased,
The waveform observed with a spectrum analyzer is A → B → C
→D→E→F, and becomes chaotic at D and E. Conversely, if VAPD is decreased from state F,
F→E'→D'→C'→B'→ without going through the chaotic state
It changes to A'.

In this case, the upper limit frequency of the chaotic spectrum can be controlled by the cutoff frequency of the nonlinear amplifier 3. In addition, the reference mode of the chaotic spectrum (corresponds to the peak on the lowest frequency side of each waveform shown in Figure 3)
The frequency of can be controlled by the delay time of the feedback of the signal from the nonlinear amplifier 3, and therefore by the delay time in the delay device 5.

[0021] Chaos control can be achieved by suppressing the reference mode using the feedback gain or CR delay described above,
It is also possible to perform this by controlling passage/non-passage of the reference mode using a bandpass filter.

As described above, according to this embodiment, optical chaos can be generated using the semiconductor laser 1. Moreover, this optical chaos can be easily controlled with high controllability by changing the voltage VAPD applied to the avalanche photodiode 2, and there is no need for delicate optical adjustments as in the conventional method. I don't.

Furthermore, since the chaos generator according to this embodiment is composed of a semiconductor laser 1, an avalanche type photodiode 2, an FET 6, a rectifying diode 7, etc., it can be made monolithic using a compound semiconductor substrate. .

According to the chaos generator according to this embodiment, it is possible to realize a semiconductor laser having high resistance to return light, for example. Semiconductor lasers with high resistance to such return light are used, for example, in optoelectronic integrated circuits (OEI).
It is suitable for use as a light source for C).

Furthermore, for example, by using the chaos generating device according to this embodiment as an optical chaos source and adding an external circuit to the chaos generating device as the optical chaos source, various devices using optical chaos can be constructed. becomes possible.

Next, another embodiment of the present invention will be described. In this other embodiment, the nonlinear amplifier 3 in the above embodiment is constituted by a triode. FIG. 4 shows an example of the characteristics of the triode used as the nonlinear amplifier 3. As shown in FIG. 4, by properly biasing this triode, an output signal mixed with harmonic components similar to that shown in FIG. 2C can be obtained with respect to the input signal. In FIG. 4, Vp is the anode voltage, Ip is the anode current, and Vg is the grid voltage.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, it is possible to use other linear amplifiers in place of FET 6 in the embodiments described above. Further, instead of the avalanche type photodiode 2 in the above-described embodiment, it is possible to use various other photodiodes.

[0029]

As described above, according to the present invention, optical chaos can be easily generated with high controllability using a semiconductor laser.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a chaos generator according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of signal waveforms of each part of the chaos generator shown in FIG. 1;

FIG. 3 is a graph showing an example of a waveform observed when a laser beam oscillated from a semiconductor laser of the chaos generator shown in FIG. 1 is observed with a spectrum analyzer.

FIG. 4 is a graph showing an example of the characteristics of a triode used as a nonlinear amplifier in a chaos generator according to another embodiment of the present invention.

[Explanation of symbols]

1 Semiconductor laser 2 Avalanche photodiode 3 Nonlinear amplifier 4 Laser light 6 FET 7 Rectifier diode

Claims (2)

[Claims] 1. A semiconductor laser; a photodiode that receives laser light emitted from the semiconductor laser;
A chaos generating device comprising a nonlinear amplifier comprising at least a linear amplifier and a rectifier, whose input side is connected to the anode of the photodiode, and whose output side is connected to the anode of the semiconductor laser. 2. A semiconductor laser; a photodiode that receives laser light emitted from the semiconductor laser;
A chaos generator comprising: a nonlinear amplifier comprising at least a triode, an input side connected to the anode of the photodiode, and an output side connected to the anode of the semiconductor laser.