JPS63260083A - Optical functional element - Google Patents

Abstract

PURPOSE:To two-dimensionally photodetect an infrared light and to process an image at an ultrahigh speed by forming a two-dimensional arraylike optical bistable device of a high temperature superconducting material. CONSTITUTION:A stripelike high temperature superconducting material is formed on a substrate 6 as an electrode A1. The material is superposed through an oxide film 5 becoming a tunnel barrier in a direction different from previous one as an electrode B2. Another part is wholly covered with a light shielding material 7 except an opening 3. When an element is driven by a constant-current operation, a superconducting state is broken when a current flowing through a Josephson junction Jij exceeds a critical current I0, and it becomes a normal conducting state, thereby generating a voltage V0. When a bias current Is1<I0 flows to a junction Jio and a light in which a light absorption sufficiently occurs at the band gap 2DELTA of the superconducting material is made to irradiate the junction Jij, Cooper pairs of electrons are broken by the absorption, the superconducting state is damaged, and it is transferred to a normal conducting state. Accordingly, an optical bistable device generating bivalent voltages by the bias current Is1 and an optical pulse is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical functional device, and particularly to an optical functional device suitable for use as a high-speed surface processing type functional device used in optical information processing.

[Conventional technology]

It is known that when a Josephson junction in a superconducting state is irradiated with Xi waves corresponding to an energy gap of 2Δ, quasiparticles are formed and the system transitions from a superconducting state to a normal conducting state. . For example, tunneling in solids by Burstein.

Plenum Press, pp. 353-370 (1969) B, Hurstein & S, Lundqv.
istTunneling Phenomena i
n 5olid, PlenumPress, New
York (] 969) pl) 353-370, etc.

[Problem that the invention seeks to solve]

Since the above conventional technology uses Pb or Sn as a superconducting material, the energy gap is on the order of millielectron volts (meV). Therefore, the electromagnetic waves corresponding to this are in the microwave region. Also, Nio,
Due to its small Lugie gap, it becomes superconducting only at the temperature of liquid He, making it extremely difficult to use as an electromagnetic wave receiver.

The present invention provides an optical functional element that uses a high-temperature superconducting material to perform two-dimensional infrared light reception and image processing at ultra-high speed by exploding a two-dimensional array of optical bistable devices. The purpose is to

As a result, compared to surface-treated optical bistable devices that use saturation of exciton absorption in a superlattice or optical bistable devices that use bulk ionic crystals, they are significantly faster and require less optical input. It is possible to obtain excellent performance.

[Means for solving problems]

The vane objective is achieved by constructing an array matrix of Josephson junctions of high temperature superconducting material, as shown, for example, in FIG.

This structure will be explained using FIGS. 1 and 2.

FIG. 1 is a top view of the array, and FIG. 2 is a cross-sectional view of one of its junctions. A striped high-temperature superconducting material is formed on the substrate 6 to form an electrode A. (1) Tunnel
Electrode B is formed by stacking stripes of high/temperature superconducting material in a direction different from 1 with an oxide film 5 serving as a barrier interposed therebetween.

(2) Leave the opening 3 and cover the entire surface with a light-shielding material 7.

In Figure @1, only a portion is shown for ease of explanation.

[Effect]

Now let's assume that electrodes A are A, A2, A1 from the left.

Insert electrode B from above into B1. Let B,...,,H,. Ji.

The position of the Sefson junction and the window provided thereon is defined as J. In Figure 1.

It is assumed that light is incident on Jll and J3□, and that other Josephson junctions and superconducting electrodes are not irradiated with light.

In order to understand the operation of this device, it will be explained using FIGS. 3 and 4. FIG. 3 shows the current/voltage characteristics of the Josephson junction JIJ placed below the critical temperature Tc. When the element is driven by constant current operation, Jl.

The current flowing through is the critical current value. In the following case, it flows as a DC Josephson current, and no potential difference occurs between electrodes B, , A, at both ends of the element.

Engineering. When it heats up, the superconducting state is broken and it becomes a normal conducting state, producing a voltage v0. When the current is subtracted from this state, it becomes 1
It returns to the origin 0 via point b in the figure and point 0.

Now, I,,<I. A current is passed through junction J10,
The junction Jlj is irradiated with light whose energy has the following relationship with respect to the band gear P2Δ made of high temperature superconducting material.

2Δ drama hν<20Δ Here, the numerical value is selected to mean that sufficient light absorption occurs, and it is possible to absorb light over a wide range.

Due to its absorption, the Cooper pair of electrons is destroyed, the superconducting state is broken, and the state changes to the normal conducting state.

In the figure, it is indicated by a-b. At this time, a voltage V, □ is generated between the poles A and B1. If the current is kept at 1 ml, the IPf pressure vkl will continue to occur even if the light irradiation is stopped. If you reduce the ml.

The IV characteristic returns from b to the origin via C.

The voltage becomes zero.

Therefore, a binary voltage is generated by the bias current of 1 ml and the optical pulse. The optical bistable device was obtained by modifying the 0 bias current with El. By setting an appropriate value between 1 and 2, an IV% characteristic as shown in FIG. 4 can be obtained. The transition to d-e and generation of voltage vb2 by light irradiation is the same as in the example shown in Fig. 3, but in the case of Fig. 4,
Because In2 is large.

The difference is that when light irradiation is stopped, both the voltage and current decrease and the superconducting state is returned to, even without changing the bias current. Therefore, in order to continue to generate (1) and (2), it is necessary to continue the light irradiation.

In this way, the 2a1 type optical bistable mode can be selected by the set value of the bias current.

This can be determined by the presence or absence of voltage between 89 and 89.

Now, attention is paid to electrode B1. Light enters J1□ and J1□
, Jl, . . . Jl4 is assumed not to be irradiated with light. All junctions operate at constant current, so
A voltage, ■, 1 is generated only between Ax and B1, and A2-B
1. The voltage between A3-Hl and A4-B1 is zero.

In other words, it can be seen that information on one position can be obtained without being influenced by the supernormal conduction state of each junction J, 1.

Incidentally, the diffusion of quasiparticles caused by light is thought to be a cause of interference between junctions.

In high-temperature superconductivity, the lifetime of quasiparticles is about 2 to 3 orders of magnitude shorter than in the case of A/ or Pb, so the diffusion length is small, and if the distance between elements is 0.5 μm or more, interference can be ignored. However, unnecessary light irradiating superconducting electrodes that do not form a junction will cause deterioration of the superconducting state, so it is necessary to cover the parts other than the necessary junctions with a material that does not transmit light (
7) in Figure 2.

〔Example〕

This will be explained below using examples.

Example 1 on a single crystal substrate 6 of barium titanate.

A crystal of YxBl-xCu04 was prepared using a sputtering method.

Form into a shape with a thickness of 2000 people. A first electrode is obtained by processing into a stripe shape with a width of 5 μm using an Ar ion beam. Next, a quantum barrier layer 5 of A/203 was applied to the pole 1 by sputtering to a thickness of 20λ, and YxHl-
Place xCOO4 on top.

The stripe pattern was made perpendicular to the second electrode. The thickness and width are the same as 1.

After 7 anneals in an oxygen atmosphere, a resin containing a dissolved pigment that is opaque to signal light is applied and a window is patterned to form 7. The number of electrodes.

1000XI O00 0 electrode spacing is %5μm
□ Garb-InAs Sb laser pulse light (3,57 μm) is expanded into a parallel beam of 822 cmφ, and C
Through the pattern printed on the aF2 board, ]X]cm
is projected onto an element having an effective area of , and the position information is transmitted to electrodes A1 to . . . . , B1~1°. The voltage information at 0 is read out and input to an external Josephson computer.

Then another pattern on CaF2 is projected onto the device,
The number of locations where the superconducting state is broken has been increased.

Since the bias current of 1 ml remains constant, a voltage is generated at both the junction where the previous irradiation was performed and the junction where the current irradiation was applied, resulting in a so-called °AND operation.

搏Here, if we cut the bias current to 1, all the biases are:
It becomes a superconducting state, and the voltage becomes zero between all electrodes, resulting in a reset state.

The response speed of this element is the speed at which a pair of Coopers in a superconducting state becomes a quasi-particle due to light and becomes a normal conducting state, and
It depends on the time it takes for the generated quasiparticle to disappear.

Regarding this point, conventional superconducting materials such as Sn and Pb
It takes a time of several hundred ps to several n3, and is on the order of μS for AI, making it unsuitable for high speed issues. Therefore, in the past, a technical idea such as the present invention did not exist at all.

The high-speed response of the high-temperature superconducting material used in the present invention was 500f.
The investigation was carried out using Raman light generated by a dye laser of S. As a result, a response time of ]Ops was obtained for one junction. This indicates that the lifetime of quasiparticles in the high-temperature superconducting material YBaCuO is extremely short compared to conventional superconducting materials.

Example 2 The device of Example 1 was coated with 1nGaAsP/
The above experiment was conducted using InP laser light.

The light intensity pattern was obtained as positional information on the presence or absence of one pressure.

Example 3 (Lm, -, 5rx)2Cub4@Cu side] was prepared in the same manner as in Example 3 to produce a similar element. The device was cooled to 77K, and a 10 μm band optical fiber was passed through it for 500 m.
．． A -dimensional optical sensor was fabricated in the same manner as in Example 4, in which a 6 μm CO laser beam was received and a 1% pressure signal was obtained (FIG. 5). P b S s ++ ! Sex semiconductor laser light (6 μm) was irradiated, and the beam pattern of the semiconductor laser could be read.

Example 5 A laminated Josephson junction was produced using the same substrate and materials as in Example 1 (FIG. 6). In the figure, 8 is an insulating material having the same thickness as the electrode 1, and 10 is an inter-element insulating film that is transparent to signal light.

According to this embodiment, elements can be mounted with high density.

Examples of the light irradiation means used in the present invention include CO2 laser, hydrogen halide chemical laser (HP, D
F, He/, DC/, HBr, DBr) and semiconductor L/-f (Pb, -, Sn, Te, Garb.

Pb S *−xSe , , Ga In t +
-1As Ps -y -G a 1-, A I!
As ) -And He -Ne L/-The arrival is K
An r-ion laser can be used.

In addition to the YBaCu oxide mentioned in the explanation of the examples, superconducting materials such as 5cLa and Ce
, Pr, Nd, Pn, 8m, Eu.

Gd, Tb, Dy, Ho, Er, Tm, Yb.

Those using Lu, etc., and those using Ca instead of Ba.

It is also possible to use a material using Sr or the like, or a mixed crystal thereof.

〔Effect of the invention〕

According to the present invention, memory of two-dimensional optical image signals, two-dimensional parallel image processing, and conversion into electrical signals can be executed at ultra-high speed. This means that a speed increase of more than 104 was achieved compared to a similar bare-handed method using a superlattice of conductors in an intermediary.
The required optical signal is only a weak amount of light that shifts the superconducting state of the Girosefson element to the normal conducting state.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the Josephson optical bistable device array of the present invention, and FIG. 2 is a cross-sectional view thereof. 3 and 4 are diagrams showing current/voltage characteristics showing the operating principle of the optical bistable element, and FIGS. 5 and 6 are diagrams showing still other embodiments of the present invention. Explanation of symbols 1.2...High temperature superconducting electrode, 3...Window opened on diplexus Sefson junction, 4...Signal light,
6... Board. 7...Translucent resist. Kankou 4th prisoner / [5

Claims (1)

[Claims] 1. At least one first electrode made of a first superconducting material on a substrate, and at least one first electrode made of a superconducting material having Tc equal to or larger than the first superconducting material. at least one Josephson junction formed of a second electrode and an insulating film having a thickness that causes a tunnel effect between the first electrode and the second electrode; has a department;
This optical functional element is characterized in that this junction generates a potential difference depending on the irradiated light. 2. In the optical functional device according to claim 1,
An optical functional element characterized in that the first superconducting material has a Tc of 70 K or more, and the wavelength of the irradiated light is shorter than 60 μm. 3. In the optical functional device according to claim 2,
The wavelength of the irradiated light is approximately 0.6 μm or more and 11 μm
An optical functional element characterized by the following. 4. The optical functional device according to claim 1, 2, or 3, wherein the junction portions are connected in parallel. 5. The optical functional device according to claim 1, 2, 3, or 4, wherein the joint portions are arranged in a one-dimensional array. 6. An optical functional device according to claim 1, 2, 3, or 4, wherein the joints are arranged in a two-dimensional array. 7. Claims 1, 2, 3, 4,
6. The optical functional device according to item 5 or 6, wherein a portion other than the joint portion is covered with a light-shielding material. 8.Claims 1, 2, 3, and 4,
In the optical functional device according to item 5, item 6, or item 7, the first superconducting material and/or the second superconducting material are made of ternary and/or quaternary copper oxide. An optical functional element characterized by: 9.Claims 1, 2, 3, 4,
8. The optical functional device according to item 5, 6, 7, or 8, wherein the bonding portion is laminated in a direction perpendicular to the substrate surface.