JPH04180036A - Optical logical element - Google Patents

Abstract

PURPOSE:To obtain the optical logic element of an ultra-high speed by using the bond quantum wells of small absorption and small effective carrier life. CONSTITUTION:An incident surface 23 is formed in such a manner that the active layers 22 formed by alternately laminating about 40 layers each of the bond quantum well layers 1 pinching 1st quantum well layers with 1st barrier layers and 2nd quantum well layers and 2nd barrier layers 221 attain about 16.8 deg. angle with the layer surface. The 1st quantum level Ee1 of the electrons and the 1st quantum level Eh1 of the holes of the 1st quantum well layers and the 1st quantum level Ee2 of electrons and the 1st quantum level Eh2 of holes of the 2nd quantum well layers in the bond quantum well layers are so determined as to satisfy Ee1>Ee2 and Ee1-Eh1<E2-Eh2. Signal light 24 is made incident perpendicularly on the incident surface 23 and control light 25 is made incident perpendicularly on the layer surface. The intensity of the signal light 24 transmitted through the boundary face is switched by the intensity of the control light 25.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical logic element used for optical information processing and the like.

[Conventional technology]

In recent years, digital information processing that utilizes the highly parallel information transmission and processing characteristics of light has attracted attention.

For this purpose, it is necessary to develop a so-called planar logic element that controls light two-dimensionally. One of these is an optical cable that turns on and off optical signals using light. Conventionally, the structure shown in Fig. 4 as a solid optical gate is called Applied Physics Let's
Jewell, J.L. et al. (1985), Vol. 46, p. 918 (1985).

This optical gate has a structure in which a quantum well layer 42 is sandwiched inside a Fabry-Perot resonator 41 having a pair of reflecting mirrors 34. Optical switching is performed using the resonance characteristics of the Fabry-Perot resonator 41. When the control light 25 is not incident, the signal light 24 is in a highly transparent state. When the control light 25 is incident, absorption by the quantum well layer 42 is saturated by the control light 25, and the refractive index of the quantum well layer 42 changes, resulting in a low transmission state for the signal light 24.

Furthermore, an optical gate as shown in FIG. 5 was proposed by Tomita in Japanese Patent Application Laid-Open No. 187221/1983. Light (p-polarized light) having an electric field vector perpendicular to the plane of the quantum well layer enters this optical cable as signal light 24. When the control light 25 is not present, the signal light passes through the interface with the quantum well layer 42 and is emitted from the back surface. However, when the control light is incident, exciton absorption in the quantum well layer is saturated, the spectral width is expanded, and the refractive index for the signal light is increased. At this time, since the traveling direction of the signal light is approximately at a critical angle with respect to the interface with the quantum well layer, switching is performed by utilizing the fact that it is totally reflected and no longer emerges from the interface with the quantum well layer.

[Problem to be solved by the invention]

The response speed of the optical gate described above is determined by the carrier lifetime in the quantum well layer, and is therefore slow, ranging from several hundred ps to several ±ns, which is impractical. Recently, as reported by Takeuchi et al. at the 37th Joint Applied Physics Conference 3l-a-F-6 (Spring 1990)1, a method using the tunneling phenomenon of a coupled quantum well with the structure shown in Figure 6 has been reported. proposed to reduce the effective carrier lifetime, and obtained an absorption recovery time of 3 ps.

However, in the structure shown in FIG. 6, there is a level whose optical transition energy is smaller than the level related to the change in absorption coefficient, so it is difficult to use this coupled quantum well in a device because of the large absorption.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-speed optical logic element using a coupled quantum well with low absorption and a short effective carrier lifetime.

[Means to solve the problem]

In order to solve the above-mentioned problems, the first optical logic element of the present invention has a first quantum level of electrons of E. 1. The first quantum level of the hole is Ehl, the first quantum level of the electron is Ee2, the first quantum level of the hole is Eh2, and E, 1> E −2 and Eel A second quantum well that satisfies Ehl<E-2Eh2 is quantum-mechanically coupled with light having an electric field vector perpendicular to the surface of the coupled quantum well layer as signal light at a critical angle with respect to the interface between the coupled quantum well layer and air. The control light is incident on the coupled quantum well layer at an angle smaller than the critical angle, and at the same time, the control light is made incident on the input point of the signal light at an angle of incidence smaller than the critical angle, and the intensity of the signal light exiting from the interface is adjusted. The configuration is characterized in that control is performed using the intensity of the control light.

The second optical logic element of the present invention has a Fabry-Perot cavity consisting of two parallel reflecting mirrors, in which the first quantum level of electrons is Eel and the first quantum level of holes is Ehl. One quantum well, the first quantum level of electrons is Ea2, and the first quantum level of holes is Eゎ, so that E, + > E −2 and E −+ E h + < E. The second quantum well satisfying 2-Eh2 has a quantum-mechanically coupled coupled quantum well layer as an active layer, and utilizes changes in the refractive index and absorption coefficient of the coupled quantum well layer depending on the intensity of the incident control light. The structure is characterized by controlling the transmission or reflection characteristics of the Fabry-Perot resonator.

[Effect]

FIG. 1 is an energy diagram of a coupled quantum well J in the present invention. This will provide a detailed explanation of the invention. When control light is incident on the coupled quantum well layer 1, the optical carriers generated saturate the optical transition at the first level of the first quantum well layer 11, changing the refractive index and absorption coefficient. This causes the optical logic element to be switched. The carrier lifetime is determined by the speed of tunneling into the second quantum well layer 12 separated by the first barrier layer 13, so it is as fast as ps.

The energy of optical transition in the second quantum well layer 12 is E. 2-
Eh2, which is greater than the optical transition energy Ee, -Eh of the first quantum well layer 11;
Since the light having the optical transition energy is not absorbed by the second quantum well layer 12, the absorption coefficient is small as in the case of a single quantum well layer. Therefore, a high-speed optical gate can be realized.

[Embodiment] FIG. 2 is a configuration diagram showing a first embodiment of the present invention. I
I n O,52G a O,3 on the nP substrate 21
The first quantum well layer with a thickness of 10 m consisting of 9 Auo, o+AS is I no, s+ A no, is A
A first barrier layer with a thickness of 5 nm made of S and I n O,6
A coupled quantum well layer 1 sandwiched between 15 m thick second quantum well layers made of 9G a O, 3, A s o 6 ° Po, 33, and a 20 m thick second barrier layer made of InP. 22
A reactive ion beam (R
The incident surface 23 is formed by etching by IBE).

In this coupled quantum well layer, the first quantum level of electrons in the first quantum well layer is Ee+ = 50 meV, the first quantum level of holes is Eb + -826.7 meV, and the first quantum level of electrons in the second quantum well layer is Ee+ = 50 meV. Since the first quantum level of is Ee+ = 42 meV and the first quantum level of hole is Eh2 = 906.2 meV, E, l > E -2 and Eat Eb + < E-2Eh2 are satisfied. According to the second condition, the lowest energy exciton in the active layer 22 is in the first quantum well layer, and the absorption of light of this energy in the second quantum well layer is small.

The signal light 24 is made perpendicularly incident on the incident surface 23. Signal light 24
is p-polarized light with respect to the interface between the active layer 22 and air, and its energy is 865 meV, which is lomeV lower energy than the energy of excitons in the active layer 22.

Control light 25 having an energy of -880 meV is incident perpendicularly to the layer surface. When the intensity of the control light 25 is small, the refractive index at a light energy of 865 meV is 3.4, the critical angle for this refractive index is 72.9 degrees, and the polarization angle is 73.6 degrees, so the transmitted light intensity is large at the interface. is obtained. However, when the intensity of the control light 25 increases, the absorption by excitons becomes saturated and the width of the absorption spectrum widens. Therefore, the signal light 2 is on the lower energy side than the energy of excited city absorption.
4 has a refractive index of 38 for light with an energy of 865 meV.
It increases to 48. Since the critical angle for this refractive index is 732 degrees, the signal light 24 is totally reflected at the interface and no transmitted light appears, and the intensity of the signal light 240 passing through the interface is switched by the intensity of the control light 25. When the control light disappears, the carriers in the first quantum well layer become E
Since el>Eel, the light quickly tunnels into the second quantum well layer and the absorption in the first quantum well layer is restored. Therefore, the response time of the optical gate is on the order of lps, and an ultra-high-speed optical logic element can be realized.

FIG. 3 is a block diagram showing a second embodiment of the present invention. I
An InP cladding layer 32 with a thickness of 2 μm is formed on the nP substrate 21.
, o+A The first quantum well layer with a thickness of 10 m is Ino, s+Aρ. ,, a first barrier layer with a thickness of 5 nm made of As and I n 0.69 Ga 0.31
ASO, 6? 15 layers m thick consisting of P O,33
Coupled quantum well layer 1 and InP sandwiched between second quantum well layers of
A second barrier layer 221 with a thickness of 20 m consisting of 4
An active layer 22 and a cladding layer 33 of InP having a thickness of 2 μm are sequentially laminated. The thickness of the substrate 21 is 100μ
After mirror polishing 5102, a reflecting mirror 34 of a dielectric multilayer film made of amorphous S1 is formed. The reflectance of the reflecting mirror 34 is 98%. In this coupled quantum well layer,
The first quantum level of electrons in the first quantum well layer is Ee1-1-
5O■, the first quantum level of the hole is Eh, = -826,7
1neV, the first quantum level of electrons in the second quantum well layer is EI2=42meV, and the first quantum level of holes is Ee2=
Since it is -906.2 meV, it satisfies Ee, >'Ee2 and Eel -Eh; <Es2-Eh=. From the second condition, the lowest energy exciton in the active layer 22 is in the first quantum well layer,
The absorption of light of this energy by the second quantum well layer is small.

The signal light 24 is perpendicularly incident on the reflecting mirror 34. Signal light 24
The energy is 865 meV, which is 10 meV lower than the energy of excitons in the active layer 22. Further, the signal light 24 is selected so as to oscillate in a Fabry-Perot resonator. Control light 25 having an energy of 880 meV is similarly incident. When the intensity of the control light 25 increases, absorption by excitons becomes saturated and the width of the absorption spectrum widens. For this reason, the refractive index for the light energy of 865 meV of the signal light 24, which is on the lower energy side than the energy of exciton absorption, increases, and the signal light 24 shifts from the resonance of the Fabry-Perot resonator, and the intensity of the transmitted light decreases. Switched. When the control light disappears, the carriers in the first quantum well layer quickly tunnel into the second quantum well layer because Ee>Eel, and absorption in the first quantum well layer is restored. Therefore, the response time of the optical gate is on the order of lps, and an ultra-high-speed optical logic element can be realized.

〔Effect of the invention〕

As detailed above, to summarize the effects of the present invention, a high-speed optical logic element can be obtained by using a coupled quantum well with low absorption and a small effective carrier life.

[Brief explanation of drawings]

FIG. 1 is an energy diagram of a coupled quantum well according to an embodiment of the present invention, FIG. 2 is a structural diagram showing an embodiment of the present invention, FIG. 3 is a structural diagram showing a second embodiment, and FIG. Figure 5 is a structural diagram showing the first conventional example, Figure 5 is a structural diagram showing the second conventional example, and Figure 6 is a structural diagram showing the conventional coupled quantum well. Well layer, 11...
...First quantum well layer, 12...Second quantum well layer, 13...First barrier layer, 21...
Substrate, 22...Active layer, 221...Second barrier layer, 23...Incidence surface, 24...Signal light, 25...Control light , 32... cladding layer, 33... cladding layer, 34... reflecting mirror, 41
...Fabry-Perot resonator, 42...Quantum well layer. Agent: Patent Attorney Susumu Uchihara, Electronics Engineer, Figure J, Figure 3

Claims (1)

[Claims] 1. A first quantum well in which the first quantum level of electrons is E_e_1 and the first quantum level of holes is E_h_1; A second quantum well with one quantum level of E_h_2 and satisfying E_e_1>E_e_2 and E_e_1-E_h_1<E_e_2-E_h_2 is quantum-mechanically coupled. Light having an electric field vector perpendicular to the coupled quantum well layer plane is used as signal light for the coupling. The control light is incident on the coupled quantum well layer at an angle smaller than and close to the critical angle with respect to the interface between the quantum well layer and the air, and at the same time, the control light is directed to the incident point of the signal light at an angle of incidence smaller than the critical angle. An optical logic element characterized by an incident light. 2. Inside a Fabry-Perot cavity consisting of two parallel reflecting mirrors, there is a first quantum well where the first quantum level of electrons is E_e_1 and the first quantum level of holes is E_h_1; The first quantum level is E_e_2, and the first quantum level of holes is E_h.
An optical logic element characterized in that an active layer is a coupled quantum well layer in which second quantum wells satisfying E_e_1>E_e_2 and E_e_1-E_h_1<E_e_2-E_h_2 are quantum mechanically coupled at _2.