JP2737003B2 - Signal detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal detection method for detecting an optical signal by detecting a voltage generated based on current-voltage characteristics of a superconductor.

[Prior art] As a conventional signal detection method using a superconductor, particularly a method for detecting an optical signal, a method using a Josephson junction is known [Japanese Journal of Applied Physics].
ics vol.23 L333 (1984)] The optical signal detection method, as shown in FIG. 4, the oxide superconductor _{BaPb 0. 7 Bio 0. 3} O 3 (B
A microbridge-type Josephson junction is formed from a PBO) thin film, and this junction is irradiated with light to utilize the change in the critical current value of the Josephson junction. In a detector that provides such a detection method, BPBO
Which has a low critical temperature of about 13K. That is, to operate the detector, liquid helium or the like must be used. The characteristics of such a detector are determined by the characteristics of the Josephson junction.

[Problems to be Solved by the Invention] In the above conventional example, when a large number of detectors are used at the same time, for example, as in an image sensor, it is difficult to correct variations in characteristics between the detectors due to processing variations. There's a problem.

Further, since the wavelength range of light to be detected is also limited by the spectral characteristics of the superconductor, there is a problem that it is not suitable for signal detection in a wide wavelength band.

Further, there is a problem that the accuracy of alignment is required because the area of the light irradiation to the joint is very limited.

That is, an object of the present invention is to solve the above-described problems by detecting an optical signal by detecting a voltage generated based on current-voltage characteristics of a superconductor.

[Means for Solving the Problems] A feature of the present invention is that a current is generated by inputting an optical signal to a signal input portion, and the current is electrically connected to the signal input portion. Are located separately
An optical signal is injected into a signal detector using a superconductor, and a current exceeding a critical current value of the superconductor is applied to the superconductor to detect a voltage generated at both ends of the superconductor. There is a signal detection method to detect.

Here, as the superconductor as a signal detection unit used for achieving such a method, a material in which a material having a superconductor property of a single crystal or a polycrystal is formed into a thin wire is preferable. In order to operate the detector at a higher temperature, a material having a higher critical temperature is preferable. In this regard, Y-Ba-C
Materials having a critical temperature higher than 77K, such as uO, Bi-Sr-Ca-Cu-O, and Tl-Sr-Ca-Cu-O ceramic materials, are suitable.

On the other hand, the operating temperature of the detector may be lower than the critical temperature of the superconductor to be used, but a temperature close to the critical temperature is more preferable in order to increase the detection sensitivity of the input signal.

Further, as a material used for the signal input portion, a photoconductive material that can cope with an optical signal such as infrared, visible, or ultraviolet light is preferable.

In particular, InSb, Si, Ga
As, a-Si, CdS, CdSe and the like are preferable.

[Operation] When a signal input portion made of a photoconductive material is irradiated with light,
The electrons in the valence band are excited and transition to the conduction band. The electrons excited in this conduction band are moved by the applied magnetic field to generate a photocurrent.

On the other hand, when a current flows through the superconducting material, no voltage is generated to a certain value, but when the current exceeds a critical current value, the superconducting state is broken and a voltage is generated.

The present invention utilizes such a physical phenomenon. That is, a bias current slightly smaller than the critical current is applied to both ends of the superconductor. If the current obtained by the photoconductive effect is further added to this current, if the total current value becomes larger than the superconducting critical current, the superconductivity is broken, and a voltage is generated across the superconductor. . The current applied here is not limited to the one due to the photoconductive effect, but may be anything that can generate a current, such as the photovoltaic effect and the Denver effect.

That is, by detecting the generated voltage,
The input signal can be detected.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

Embodiment 1 FIG. 1 shows a conceptual diagram of an embodiment based on the present invention. In the figure, 1 is a superconductor, 2 is a current injection electrode, 3 is a voltage measurement electrode, 4 is a bias current application power source, 5 is a photoconductive cell driving power source, 6 is a photoconductive cell, and 7 is a signal detection. It is a voltmeter.

First, the oxide superconductor YBa ₂ Cu ₃ O _7-δ (0 ≦ δ <0.5)
To MgO substrate (not shown) by magnetron sputtering
A thin film formed on the upper surface and obtained by a photolithography technique or the like is processed. In this example, the oxide superconductor was a belt-shaped superconductor 1 having a thickness of 5000 mm, a width of 20 μm, and a length of 5 mm. Next, four electrodes of Cr and Au were put on this band and the thickness was 1000 mm.
The electrode was prepared to have a width of 50 μm, and was used as a current injection electrode 2 and a voltage measurement electrode 3.

The critical temperature of the superconductor in such a configuration was 88K. This detector is put in liquid nitrogen (77K), and the power supply 4 for bias current application is 10 mV, and the power supply 5 for driving the photoconductive cell is 5
10V was applied. Here, the photoconductive cell 6 is placed in a room temperature part, and when the light is not irradiated to this, the signal detection voltmeter 7
It was OV and superconductivity was not broken. Next, when the photoconductive cell 6 was irradiated with 5 mW of He-Ne laser, the voltmeter 7 for signal detection showed 3 mV. This means that a current higher than the critical current value has flowed into the superconductor 1 due to the light irradiation, which has broken the superconducting state.

Embodiment 2 FIG. 2 shows a second embodiment of the present invention. The configuration of the detector is a PN junction 8 using the photovoltaic effect, which is a signal receiving unit.
And a detection unit. When light is not irradiated to the PN junction 8 in liquid nitrogen, the voltage is OV.
When the same light was applied to Example 1, a voltage was generated. This is because the current flowing in the superconductor 1 increased due to the photovoltaic effect, and the superconducting state was broken.

In order to increase the light receiving sensitivity, the photoconductive cell 6 is used in the first embodiment.
In this example, a small heater can be attached to the PN junction as was used at room temperature.

Embodiment 3 FIG. 3 shows an embodiment of an element in which the photodetector shown in FIG. 2 is formed into an array. In the figure, 1 is a line width of 15 μm, a film thickness of 0.5 μm,
Superconducting thin wires of 50 μm length are arranged on a straight line. Reference numeral 9 in the figure denotes a voltage measurement circuit system for reading the voltage of each superconducting thin wire portion. Here, a series of light receiving units (PN junctions) 8 in the figure
It is separated from the superconductor part 1 so that different temperatures can be set in the part 1 and the part 8. When 10 mlux light was incident on the left half of this device, a voltage was generated on the left half. This means that the element can be used as a line sensor.

[Effects of the Invention] As described above, according to the signal detection method of the present invention, 1. Compared with the conventional method (for example, when irradiating a junction of a Josephson junction with light), the optical signal and the position of the detector It is easy to match, that is, it is possible to input a signal to an input unit (reception unit) of any required size.

2. By appropriately selecting the material of the optical signal input section (receiving section), it is possible to detect an optical signal in a wider wavelength band than in the past.

3. Compared with the conventional one (for example, in the case of a Josephson junction, the detection characteristics are determined by the junction characteristics, and the characteristics of the element are greatly varied when a multi-configuration is used), and a simple thin wire-shaped superconductor is used. Therefore, processing accuracy, reproducibility, reliability, and the like are improved, and variations in characteristics are reduced.
This facilitates integration of elements.

There are such effects.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a detector using a photoconductive cell for achieving the signal detection method of the present invention. FIG. 2 is a schematic diagram showing the configuration of another detector using the photovoltaic effect for achieving the signal detection method of the present invention. FIG. 3 is a schematic configuration diagram of an element in which the photodetector shown in FIG. 2 is arranged in an array. FIG. 4 is a schematic perspective view of a detector used in a conventional signal detection method. DESCRIPTION OF SYMBOLS 1 ... Superconductor, 2 ... Current injection electrode 3 ... Voltage measurement electrode 4, ... Bias current application power supply 5 ... Photoconductive cell drive power supply, 6 ... Photoconductive cell 7 ... Signal detection Voltmeter for 8 PN junction 9 Voltage measurement circuit system 10 Optical fiber 11 BPBO film

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takehiko Kawasaki 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Norio Kaneko 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-64-86575 (JP, A) JP-A-64-50486 (JP, A) JP-A-1-184423 (JP, A) JP-A-1-102973 (JP, A A)

Claims (1)

(57) [Claims] 1. An optical signal is input to a signal input section to generate a current, and the current is generated by a superconductor electrically connected to the signal input section but arranged separately from the signal input section. The optical signal is detected by injecting the signal into the used signal detection unit and detecting a voltage generated at both ends of the superconductor by flowing a current exceeding the critical current value of the superconductor to the superconductor. Characteristic signal detection method.