JP4006854B2 - Light switch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical switch for switching optical data at high speed in an optical communication system, and more particularly to an optical switch capable of operating switching of a switch unit having a semiconductor layer at high speed.
[0002]
[Prior art]
In recent years, the demand for increasing the capacity of data transfer accompanying the expansion of optical communication systems has increased, and an optical switch capable of high-speed processing is required.
An optical switch, for example, irradiates light to a switch unit having a semiconductor layer, and changes the optical response characteristics (for example, dielectric constant) of the semiconductor layer depending on the number of pairs of electrons and holes generated. It is configured to be associated with ON / OFF.
For example, in the optical switch, a state where the number of pairs of electrons and holes generated by irradiating light increases is an ON state, and a state where the number of electrons and holes is small is an OFF state.
[0003]
The optical switch as described above can shorten the time required to change from the OFF state to the ON state by adjusting the light intensity, but it is necessary to change from the ON state to the OFF state. The time depends on the physical properties of the materials that make up the semiconductor layer.
[0004]
In general, optical switches are required to have high speed. For example, in the conventional optical switch shown in Jpn. J. Appl. Phys. 28 (1989) L1098, both ends of a narrow quantum well are connected with a wide quantum well. In the sandwiched structure, the tunneling phenomenon from a narrow quantum well to a wide quantum well is used to increase the switching time.
[0005]
In the optical switch shown in Surface Science 267 (1992) 634, the switching time is increased by utilizing the relaxation of electrons from the Γ point of the AlGaAs quantum well layer to the X point of the AlAs barrier layer.
This is because an electron that has transitioned from a ground state to an energy level called a Γ point by irradiating light is lower than this energy level and higher than the energy level of the ground state, and Since the excited electrons can be brought into a stable state by rapidly transitioning electrons to the X point, which is a stable or metastable energy level, the change in optical response due to the presence of electrons at the Γ point Therefore, the time required for the change from the ON state to the OFF state can be shortened, and the switching operation can be speeded up.
[0006]
[Problems to be solved by the invention]
The conventional optical switch using the tunnel phenomenon or the movement of the electronic state from the Γ point to the X point operates normally until a small number of times, but when the number exceeds a predetermined number, the number of electrons increases. There is a problem that the optical switch gradually accumulates excessively and the optical switch does not operate normally.
In particular, in an optical switch that uses the movement of an electronic state from the Γ point to the X point, the number of electrons that can be transitioned to the X point is limited.
Therefore, if the number of electrons generated more than the number that can be transferred to the X point by irradiating light to the optical switch a plurality of times during a short time interval does not change from the ON state to the OFF state after a predetermined number of times Switching operation is not performed. That is, there is a problem that the switching operation becomes extremely poor if the ON / OFF operation is switched over a predetermined number of times during a short time interval.
[0007]
The present invention has been made to solve the above-described problems. By irradiating light to the optical switch a plurality of times, the optical performance does not deteriorate even if the ON / OFF operation is switched over a predetermined number of times. The purpose is to obtain a switch.
[0008]
[Means for Solving the Problems]
An optical switch according to the present invention includes a switch unit having a semiconductor layer whose optical response characteristics change by light irradiation , and a voltage application unit that applies a voltage to the switch unit, and the switch unit irradiates light. Each time the switching operation is performed a predetermined number of times, the voltage application unit operates so as to provide time for voltage application from the voltage application unit to the switch unit.
[0009]
The optical switch according to the present invention is characterized in that the switch portion is provided with an n-type doping layer at one end of the semiconductor layer and a p-type doping layer at the other end.
[0010]
The optical switch according to the present invention has a GaAs / AlGaAs multiple quantum well structure or an InGaAs / InAlGaAs multiple quantum well structure as a semiconductor layer.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a diagram for explaining the optical switch according to the first embodiment.
In the figure, reference numeral 10 denotes a switch unit, and the switch unit 10 includes a semiconductor layer.
For example, when the semiconductor layer of the switch unit 10 is irradiated with light, a change in optical response characteristics (for example, dielectric constant, refractive index, etc.) generated according to the number of pairs of free electrons and holes generated is changed to ON / OFF of the switch. It is configured to be associated with OFF.
The switch unit 10 is irradiated with control light 13 and signal light 14. The control light 13 controls the ratio of light transmitted or reflected by the semiconductor layer whose optical response characteristics change due to the light of the switch unit 10.
The switch unit 10 generates a pair of free electrons and holes that have transitioned to the Γ point inside the semiconductor layer in accordance with the intensity of the control light 13 to be irradiated.
Reference numeral 20 denotes a voltage application unit that applies a voltage to the switch unit. The voltage application unit 20 includes, for example, a DC power source.
[0012]
FIG. 2 is a diagram for explaining the optical switch according to the first embodiment. Specifically, FIG. 2 is a diagram for explaining a specific example of the switch unit 10 according to the first embodiment.
The semiconductor layer of the switch unit 10 includes, for example, a semiconductor layer 101 whose dielectric constant is changed by light, an n-type doping layer electrode 102, and a p-type doping layer 103.
[0013]
The voltage application unit 20 is a direction in which electrons and holes are more likely to be injected into the n-type doping layer 102 of the switching unit 10 (here, the direction from the n-type doping layer 102 toward the p-type doping layer 103). A voltage is applied to.
FIG. 3 is a diagram for explaining the optical switch according to the first embodiment. Specifically, FIG. 3 is a diagram for explaining an example of the operation of the optical switch. In the figure, the horizontal axis is time.
In the figure, t ₁ is the time required for performing the switching operation a plurality of times, and t ₂ is the time for which the voltage application unit 20 operates.
For example, the voltage application unit 20 is configured to apply a voltage to the switching unit 10 every time the switching unit 10 performs a switching operation (that is, light irradiation) a plurality of times.
[0014]
Since the optical switch according to the first embodiment has the above-described configuration, electrons (particularly energy levels) excited inside the switch unit 10 (particularly the semiconductor layer 101) by irradiating the switch unit 10 with light. Can be moved from the semiconductor layer 101 to the n-type doping layer 102 and holes can be moved from the semiconductor layer 101 to the p-type doping layer 103. The number of holes can be reduced efficiently.
Therefore, the optical switch can be operated efficiently if the voltage application unit 20 is operated after the light irradiation (that is, switching operation) exceeding the predetermined number of times.
[0015]
In addition, by investigating in advance how many times the switch unit 10 having a semiconductor layer emits light (when ON / OFF operation is performed) the switching performance deteriorates, and the number of times If the voltage application unit 20 is configured to operate every time, the optical switch can be operated stably and most efficiently.
[0016]
Embodiment 2. FIG.
The optical switch of the second embodiment is characterized in that the semiconductor layer 101 has, for example, a type II GaAs / AlGaAs multiple quantum well structure having a GaAs layer and an AlGaAs layer.
In the Type II GaAs / AlGaAs multiple quantum well structure, electrons relax at high speed from the Γ point of the GaAs layer to the X point of the AlGaAs layer in about picoseconds.
[0017]
Using this relaxation process, it is possible to perform picosecond switch calculations. However, since the recombination emission lifetime of electrons and hole carriers is on the order of microseconds, carriers are gradually accumulated by switching operations at picosecond intervals. Operation will be reduced.
In the optical switch according to the first embodiment, the n-type doping layer 102 is bonded to the semiconductor layer 101 and the p-type doping layer 103 is bonded to the semiconductor layer 101, whereby excessive electrons are generated in the semiconductor layer 101. , Holes are injected into the n-type doping layer 102 and the p-type doping layer 103.
[0018]
FIG. 4 is a diagram for explaining the optical switch according to the first embodiment. Specifically, FIG. 4 is a diagram for explaining the energy level of the optical switch when a voltage is applied by the voltage application unit.
In the figure, 1011a and 1011b are energy level diagrams of the GaAs layer, and 1012a and 1012b are energy level diagrams of the AlGaAs layer.
11 is a Γ point of the GaAs layer, and 11a and 11b are subband levels in the GaAs layer.
12 is the X point of the AlGaAs layer, and 12a is the subband level in the AlGaAs layer.
As shown in the figure, an n-type doping layer 102 is joined to one of the multiple quantum well layers, and a p-type doping layer 103 is joined to the other, and the n-type doping layer 102 is changed to a p-type while the voltage application unit 20 is operating. A voltage is applied in the direction of the doping layer 103.
[0019]
Electrons are injected into the n-type doping layer 102 and holes are injected into the p-type doping layer 103 so that electrons and holes in the multiple quantum well layer can be eliminated.
Further, the energy ev1 (e: the amount of charge of electrons, v1: the voltage applied between the adjacent quantum wells) given to the adjacent quantum well layers and the subband levels 11a, 11b, 12a in the quantum well are made to coincide. If the applied voltage v applied by the voltage application unit 20 and the distance between the quantum wells of the GaAs / AlGaAs multiple quantum well layer having a GaAs / AlGaAs multiple quantum well structure are adjusted, a part of electrons at the X point by the tunnel effect Moves to the subband levels 11a and 11b while some of the holes move to the subband level 12a, so that electrons move to the n-type doping layer 102 and holes move to the p-type doping layer 103 side at a higher speed. Since it can be moved, electrons and holes can be annihilated at a higher speed, and the switching operation can be performed at a higher speed. That.
Further, when the wavelength of the irradiated light is set to 700 (nm) to 800 (nm), it is possible to perform the switching operation efficiently.
[0020]
Since the optical switch according to the second embodiment has the above-described configuration, electrons and holes generated in the semiconductor layer by irradiating the switch unit 10 with light are converted into the n-type doping layer 102 and the p-type doping. Since it can be moved to the layer 103, the number of electrons that have transitioned to the X point can be reduced. Therefore, even if a switching operation exceeding a predetermined number of times is performed, the operation does not deteriorate.
[0021]
Here, the semiconductor layer 101 having a type II GaAs / AlGaAs multiple quantum well structure having a GaAs layer and an AlGaAs layer has been described as an example. However, the present invention is not limited to this. Even those using a quantum well structure have the same effects as described above.
At this time, when the wavelength of light to be irradiated is 1300 (nm) to 1600 (nm), the switching operation can be efficiently performed.
[0022]
【The invention's effect】
The optical switch according to the present invention can be operated without deteriorating the switching operation.
[0023]
According to the optical switch of the present invention, since the switch unit is provided with the n-type doping layer at one end of the semiconductor layer and the p-type doping layer at the other end, the electrons generated inside the semiconductor layer are generated. The holes generated inside the semiconductor are injected into the n-type doping layer into the p-type doping layer and disappear by recombination. Therefore, excessive electrons and holes generated inside the semiconductor layer can be efficiently reduced, and switching is performed. The operation can be performed without deteriorating the operation.
[0024]
According to the optical switch of the present invention, since the semiconductor layer has a GaAs / AlGaAs multiple quantum well structure or an InGaAs / InAlGaAs multiple quantum well structure, electrons generated inside the semiconductor layer are transferred to the n-type doping layer. The holes generated in step 1 are injected into the p-type doping layer and disappear by recombination, so that excessively generated electrons and holes in the semiconductor layer can be efficiently reduced, and the switching operation is not deteriorated. be able to.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an optical switch according to a first embodiment.
FIG. 2 is a diagram for explaining the optical switch according to the first embodiment.
FIG. 3 is a diagram for explaining the optical switch according to the first embodiment;
FIG. 4 is a diagram for explaining an optical switch according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Switch part 20 Voltage application part 13 Control light 14 Signal light 101 Semiconductor layer 102 N-type doping layer 103 p-type doping layer 1011a, 1011b Energy level of GaAs layer 1012a, 1012b Energy level of AlGaAs layer

Claims (3)

A switch unit having a semiconductor layer whose optical response characteristics change by light irradiation;
A voltage application unit that applies a voltage to the switch unit;
An optical switch that operates so as to provide time for voltage application from the voltage application unit to the switch unit every time a switching operation of irradiating light in the switch unit is performed a predetermined number of times .   2. The optical switch according to claim 1, wherein the optical switch part is provided with an n-type doping layer at one end of the semiconductor layer and a p-type doping layer at the other end.   2. The optical switch according to claim 1, wherein the semiconductor layer has a GaAs / AlGaAs multiple quantum well structure or an InGaAs / InAlGaAs multiple quantum well structure.

Images