JPH11237650A - Optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical switching device to provide a large signal ON/ OFF ratio with small variations in an nonlinear optical response of a material by signal light incident almost at the critical angle of total reflection. SOLUTION: An optical switch consists of a 1st medium 11 having a refractive index n1 and a 2nd medium 12 having a smaller refractive index n2 than the 1st medium 11 and joined with the 1st medium on a plane. At least one of the 1st medium 11 and the 2nd medium 12 varies in refractive index by light irradiation and the switch has a light input part which guides light at an angle ArcSin (n2/n1) of incidence from the 1st medium 11 to the 2nd medium 12, a light output part which takes out the reflected light of the 1st medium 11, and a light output part which takes out the transmitted light of the 2nd medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch for switching optical data at a high speed in an optical communication system, and more particularly to an optical switch utilizing a total reflection characteristic of light.

[0002]

2. Description of the Related Art In recent years, demands for increasing the capacity of data transfer with the expansion of optical communication systems have increased, and optical switches capable of high-speed processing have been required. Such an optical switch is required to have various characteristics such as efficiency, high integration, and high reliability in addition to high speed.

A conventional optical switch using total reflection of light control disclosed in US Pat. No. 4,828,362 has a configuration in which a region where a refractive index change occurs near an intersection of an intersection waveguide is provided. Is used to control the transmittance by irradiating light.

In an optical switch using total reflection disclosed in Japanese Patent Application Laid-Open No. Hei 7-152553, a voltage is applied using an electrochromic material as a means for changing a refractive index.

[0005]

A conventional optical switch using total reflection of optical control cannot increase the intensity of a signal in an ON state, and therefore requires a large change in refractive index. Therefore, there is a problem that it is necessary to use a large nonlinear material or to use a strong control light.

Further, the method of applying a voltage using an electrochromic material has a problem that control of an electric signal is slower than that of an optical signal.

The present invention is intended to solve the above-mentioned problems of the prior art. By making light incident near the critical angle of total reflection, the signal intensity in the ON state is increased, and even a small change in the refractive index is achieved. An object of the present invention is to provide an optical switch capable of performing a switch operation.

[0008]

According to a first aspect of the present invention, there is provided a total reflection type switch comprising a first medium having a refractive index of n1 and a refractive index which can be changed by light irradiation. And a first medium joined to the first medium in a plane and having a refractive index n2 of the first medium.
And the incident angle from the first medium to the second medium is defined as ArcSin (n2 / n).
It is characterized by having a means for guiding light in 1) and a means for extracting light output from the second medium.

In a total reflection type switch according to a second aspect of the present invention, the first medium is made of GaAs, InGaAs, or GaAs.
s / AlGaAs quantum well, InGaAs / InAlG
The second medium includes at least one of aAs quantum wells, and the second medium includes GaP and InP.

In a total reflection switch according to a third aspect of the present invention, the first medium is made of semiconductor-doped glass, and the second medium is made of non-semiconductor-doped glass.

A total reflection switch according to a fourth aspect of the present invention includes two optical switches, wherein one optical output unit and the other optical input unit are connected by a waveguide.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. FIG. 1 is an explanatory diagram showing an optical arrangement of a total reflection optical switch according to Embodiment 1 of the present invention;
FIG. 2 is an explanatory diagram showing the angle dependence of the reflectance according to the first embodiment, and FIG. 3 is an explanatory diagram showing the angle dependence of the transmittance change of the total reflection optical switch according to the first embodiment.

In FIG. 1, the switch according to the first embodiment is constructed by joining a first medium 11 having a refractive index n1 and a second medium 12 having a refractive index n2 smaller than the refractive index n1 in a planar state. Is done. From the first medium 11 to the second medium 12
When p-polarized light is incident at an incident angle of θ1 to the medium 2,
Is expressed by the following equation.

1- | (n2cosθ1-n1cosθ
2) / (n2cosθ1−n1cosθ2) | ² cosθ2 = (1−sin2θ2) 0.5 sinθ2 = n1 / n2 × sinθ1 As an example, the incident angle dependence of the transmittance when n1 = 1.5 and n2 = 1.0 The properties are shown in FIG. As is clear from FIG. 2, the critical angle Arcsin (1.0 / 1.5) = 41.8.
In the vicinity, the transmittance changes greatly.

Therefore, the refractive index change due to light is 0.001.
As shown in FIG. 3, the dependency of the transmittance change on the incident angle in the case of (1) does not show the transmittance change in total reflection at a large incident angle, and takes a large value at the critical angle. This indicates that when the change in the refractive index of the medium is small due to light modulation, the efficiency of the switch can be greatly improved by total reflection near the critical angle. The same applies to the case where s-polarized light is used, and it can be used as an optical switch that does not depend on polarization.

Embodiment 2 FIG. As shown in FIG.
A GaAs layer 4 is formed on a substrate 41 by molecular beam epitaxy.
2 is bonded to the GaAs layer as a signal light input unit, and a Si right-angle prism 43 bonded to the waveguide is bonded to the GaAs layer 42 as an OFF signal light output unit. At the same time, the end surface of the InP substrate 41 is cut at an angle as an ON signal light output portion, and a quartz right-angle prism 45 coupled to a waveguide is bonded to the cut surface. The control light 46 is made of GaAs by a lens or a fiber.
The s layer 42 is irradiated vertically. O not irradiating control light 46
In the FF state, the signal light 46 is totally reflected at the interface between the GaAs layer 42 and the InP substrate 41 and is output to the OFF signal output unit 44.
Since the refractive index of the aAs layer 42 changes, the signal light 46 is Ga
The light is transmitted from the As layer 42 to the InP substrate 41 and output to the ON signal output unit 45. When the apex angle of the substrate surface of the right-angle prism 43 is set to 10 °, the GaAs layer 42 is removed from the InP substrate 41.
The incident angle of light to the substrate becomes 67.8 °, and GaAs and InP
Takes a value close to the critical angle of total reflection of 68.1 ° determined from the refractive indexes (3.5 and 3.2, respectively).

Here, the power dependence of the refractive index change when the GaAs exciton is optically excited is 2.6 × 10 ⁻⁵ (cm).
² / W), and the power dependence of the transmittance change when the light pulse is focused on a spot having a diameter of 100 μm is shown in FIG.
Is shown in At this time, the optical switch recovery time is GaAs
It is determined by the lifetime of excitons in the film 42, and is about 20 ns.

Embodiment 3 As shown in FIG. 6, CdSe-doped TiO ₂ is deposited on a quartz substrate 61 by sputtering.
A film 62 is formed, and a right-angle prism 63 made of a high refractive index glass with a waveguide is used as a signal light input portion on the TiO ₂ film 62.
A right-angle prism 64 made of high refractive index glass with a waveguide is bonded as an FF signal light output portion, and a right angle prism 65 made of high refractive index glass with a waveguide is bonded to the quartz substrate 61 as an ON signal light output portion. When the apex angle of the substrate surface of the rectangular prism 63 to 12 °, a quartz substrate 61 from the TiO ₂ layer 62
The incident angle of light to the light becomes 35 °, which is close to the critical angle of total reflection 34.6 ° determined by the refractive indexes (2.55, 1.55, respectively) of TiO ₂ and quartz.

Here, the power dependence of the refractive index change when the excitons of CdSe in TiO ₂ are photoexcited is 4.0 ×
FIG. 7 shows the power dependence of the transmittance change when the light pulse is irradiated to a spot having a diameter of 100 μm with a light pulse of 10 ⁻¹⁰ (cm ² / W). At this time, the optical switch recovery time is determined by the lifetime of the excitons of CdSe, and is about 30 ps.

Embodiment 4 FIG. As shown in FIG. 8, the ON signal light output part of the first optical switch 81 and the signal light input part of the second optical switch 82 are connected by a waveguide. In this case, the first optical switch 81 and the second optical switch 82 use the optical switch according to the second or third embodiment. When the signal light is input at a pulse interval shorter than the recovery time of the optical switch 81, an optical pulse after the time (arrow a) at which the control light is irradiated is output from the ON signal output unit until the recovery time. When the irradiation time of the control light by the second optical switch 82 is adjusted to the first pulse (arrow b) of the input pulse train, only one pulse (signal 3) can be cut out at the OFF signal output unit. It becomes possible.

As shown in FIG. 9, the OFF signal light output section of the first optical switch 91 and the signal light input section of the second optical switch 92 are connected by a waveguide. In this case, the first optical switch 91 and the second optical switch 92 use the optical switch according to the second or third embodiment.
When the signal light is input at a pulse interval shorter than the recovery time of the optical switch, the light pulse after the time (arrow c) at which the control light is irradiated is not output from the OFF signal output unit until the recovery time. When the irradiation time of the control light at 92 is adjusted to the last pulse (arrow d) in the input pulse train, only one pulse (signal 2) can be cut out at the ON signal output unit.

[0023]

As described above, according to the present invention, it is possible to increase the signal intensity in the ON state by using a configuration in which light is incident at the critical angle of total reflection, and to reduce the change in the refractive index even if the change in the refractive index is small. The operation of the optical switch becomes possible.

GaAs, InGaAs, GaAs / Al
At least one of a GaAs quantum well and an InGaAs / InAlGaAs quantum well is provided in the refractive index changing layer,
By using aP and InP as a substrate, it is possible to obtain an optical switch that operates with relatively weak control light.

By using semiconductor-doped glass for the refractive index changing layer and using glass without semiconductor doping as the substrate, it is possible to obtain an optical switch having a high recovery speed.

By connecting one optical output portion and the other optical input portion of the two optical switches by a waveguide, it becomes possible to cut out a short pulse from the optical switch having a slow recovery speed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an optical arrangement of a total reflection optical switch according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the angle dependence of the reflectance according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an angle dependency of a transmittance change of the total reflection optical switch according to the first embodiment of the present invention;

FIG. 4 is an explanatory diagram showing a total reflection optical switch according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing power dependence of control light of a total reflection optical switch according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a total reflection type optical switch according to Embodiment 3 of the present invention.

FIG. 7 is an explanatory diagram showing the power dependence of control light of a total reflection optical switch according to Embodiment 3 of the present invention.

FIG. 8 is an explanatory diagram showing a total reflection type optical switch according to Embodiment 4 of the present invention.

FIG. 9 is an explanatory diagram showing a total reflection optical switch according to Embodiment 4 of the present invention.

[Explanation of symbols]

11 first medium, 12 second medium, 41 InP substrate, 42 GaAs film, 43 right angle prism made of Si for signal light input section, 44 right angle prism made of Si for OFF signal light output section, 45 ON signal light output Section right angle prism made of Si, 46 control light, 61 quartz substrate, 62 CdSe
Doped TiO ₂ film, 63 high-refractive-index glass right-angle prism for signal light input section, 64 high-refractive-index glass right-angle prism for OFF signal light output section, 65 high-refractive-index glass glass for 65 ON signal light output section Right angle prism, 81 first total reflection type optical switch, 82 second total reflection type optical switch,
91 a first total reflection optical switch, 92 a second total reflection optical switch.

Claims (4)

[Claims] 1. A first medium having a refractive index of n1 and a first medium having a refractive index of n1.
And a second medium having a refractive index n2 smaller than that of the first medium, and the first medium is irradiated with light.
An optical switch in which the refractive index of at least one of the medium and the second medium changes, wherein the incident angle from the first medium to the second medium is Ar.
an optical input unit for guiding light with cSin (n2 / n1), a first optical output unit for extracting reflected light from the first medium, and an optical input unit for extracting transmitted light from the second medium An optical switch, comprising: a second optical output unit. 2. The method according to claim 1, wherein the first medium is GaAs, InGa.
As, GaAs / AlGaAs quantum well, InGaAs
2. The optical switch according to claim 1, comprising at least one of / InAlGaAs quantum well, and wherein said second medium contains GaP or InP. 3. The optical switch according to claim 1, wherein the first medium is a semiconductor-doped glass, and the second medium is a non-semiconductor-doped glass. 4. An optical switch comprising the two optical switches according to claim 1, wherein an optical output section of one optical switch and an optical input section of the other optical switch are connected by a waveguide.