JPS6068321A - Optical switch - Google Patents

Abstract

PURPOSE:To obtain an optical switch which performs switching operation stably at an extremely high speed by forming a optical waveguide in a specific shape. CONSTITUTION:This optical switch consists of a single-mode optical waveguide 11 for input, single mode optical waveguide 12 for output, two arms 13 and 14 made of single-mode optical waveguide, two optical waveguides 17 and 18 for control, etc. The arms 13 and 14 have the same linear refractive index depending upon light intensity. One-side terminals of both arms 13 and 14 are connected to one terminal of the optical waveguide 11 in common through a Y- shaped branching part 15, and the other-side terminals are connected to one terminal of the optical waveguide 12 through a Y-shaped optical coupling part 16 so that light beams having the same power are incident to the arms 13 and 14. The two optical waveguides 17 and 18 are connected to halfway points of the arms 13 and 14 so that light propagates to the other terminal. An electrode 19 for applying an electric field is provided in the arm 13.

Description

[Detailed description of the invention] [Technical part! ′? 1. The present invention relates to an ultra-compact, ultra-high speed optical switch that can control large optical power using a minute optical control signal.

[Prior Art] Conventionally, an optical switch as shown in FIG. 1 has been proposed as a means for obtaining optical switching having this type of optical amplification characteristic. As shown in FIG. 1, a medium l whose refractive index changes depending on the light intensity is introduced into a Fabry-Fist-Perot resonator 2. When the signal light 3 as the controlled light is input into the Fabry-Perot resonator 2 so as to resonate therein, its optical input/output (iin - Iout) characteristics will have a certain intensity as shown in Figure 2. ■ Optical input. This shows the so-called °° differential gain characteristic in which the optical output suddenly increases at .

When the intensity of the incident light is set to such an intensity ro and another control light 4 is input into the Fabry-Perot resonator 2, as shown in FIG. A large change in light intensity of light 3 can be obtained. For this reason, it is expected that a #8 transistor, which is almost equivalent to a transistor in electrons, will be performed in the optical domain, and such a structure is called an optical triode.

However, in this lightning switch, the wavelength of the signal light must closely match the resonance characteristics of the Fabry-Perot resonator, and the input power of the controlled light must be extremely stable. Furthermore, since a resonator is used, the effective optical path length becomes long, and a high-speed response of 10 pS or less is impossible.

[Objective] Therefore, an object of the present invention is to provide an optical switch that eliminates the above-mentioned drawbacks and allows for ultra-high speed and stable Nuwitching.

[Structure of the Invention] In order to achieve the above object, the present invention includes an input optical waveguide, an output optical waveguide, two single mode optical waveguides having a nonlinear refractive index that depends on the optical intensity, One end of each of the two single mode optical waveguides is connected to one end of the input leading waveguide so that light of the same power is incident on each of the two mourning mode optical waveguides. The other ends of the two single mode optical waveguides are connected to one end of the output optical waveguide, and the control optical waveguide is connected to one of the two arms to control its refractive index. The structure is such that it is connected to the middle of one arm so that control light for the purpose of control is input.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of the optical switch according to the present invention, in which 11 is a single mode input optical waveguide, 12 is a single mode output optical waveguide, 13 and 14. is a two-tree arm consisting of a single mode leading waveguide. The two arms 13 and 14 have the same nonlinear refractive index depending on the light intensity.

One end of each of the two arms 13 and 14 is commonly connected to one end of the input optical waveguide 11 via a Y-shaped branch 15 so that light of the same power is incident on each of the two arms 13 and 14. The other ends of both arms 13 and 14 are connected to one end of the output optical waveguide 12 via a Y-shaped optical coupling section 16. Furthermore, two wooden arms 13 and 14
In the middle of each, two control optical waveguides 17 and 18 are provided so that the light propagates to the other ends of both arms 13 and 14.
Connect each of them. 19 is an electrode for applying an electric field to one arm 13;

All the optical waveguides described above are preferably in the form of single mode waveguides having a core and a cladding covering the core, and are constructed of a material whose refractive index changes depending on the intensity of the propagating light. Here, it goes without saying that at least one of the core and the cladding, which are the constituent parts of the optical waveguide, should have a nonlinear refractive index.

In the above configuration, a signal light having an optical intensity of Tin is input to the other end of the input optical waveguide, and one of the control leading waveguides 1
When the control light with the optical intensity 21c is input to the other end of 7, the optical power 1out of the output light emitted from the output single mode optical waveguide 12 is divided into 1/2 at the branching part 15, and 2 If the light from the tree arms 13 and 14 is perfectly combined at the joint 16, then c. Here, n2 is a change in refractive index corresponding to the intensity of light within the optical waveguide. Note that the light intensity in the optical waveguide is Ic, and the refractive index that does not depend on the incident light intensity is n,
), the refractive index n of the optical waveguide is expressed as n=n□+n21. In addition, the length from the control light incidence part 20 to the coupling part 16 in the arm 13, a = 2π/
εoCnλ0 is a constant and ε. is the permittivity of vacuum, and C is the speed of light in vacuum. is the wavelength of light in a vacuum. δ is the phase difference at the Y-shaped coupling portion 18 of the light propagating within the two arms 13 and 14 for a weak optical input that does not cause nonlinearity of the refractive index. This phase difference δ is
By appropriately selecting the lengths of arms 13 and 14 during production, or by changing the refractive index of arm 13 by applying a voltage or flowing current to electrode 19, an appropriate value, for example 180 degrees, is selected. be able to. In addition, electrode 1
8 is merely for adjusting the phase difference between the two arms 13 and 14, and 1 the optical switch of the present invention can be said to be of an all-optical type.

Assuming δ=180 degrees, the value and timing of the intensity Tc of the control light necessary to change the phase difference of the two lights propagating within the two tree arms 13 and 14 in the Y-shaped coupling portion 1B by 180 degrees. The ratio of the signal light intensity Iin is 0.5 +
FIG. 5 shows the Ic-Iout characteristics when the ratio is 10. However, Iin is assumed to be constant. Therefore, the input power (Iin) of the signal light to the optical switch of the present invention and the power (2rc) of the control light are 2Ic :Iin = 1
:10.

Next, we will discuss the case where the control light is pulsed. first,
The above operating conditions (21c: Iin = l: 10
) and the corresponding signal light output (
The response characteristics of Iout) are shown in FIG. The intensity Ic of the control light is selected to be the magnitude shown by arrow A in FIG. 4, that is, 0.5. Therefore, as shown in Fig. 6, a signal light output (Iout) with an optical amplification degree of 10 times the control light power (2Ic) is obtained, and a leakage light of Ic/2 is obtained. (indicated by B in FIG. 6) occurs in the output light.

Any material having an optically nonlinear refractive index n2 can be used as the material constituting the switch of the present invention based on the operating principle described above. - As an example, Table 1 shows the values of non-resonant deviation 2 and no for absorption lines for typical semiconductor materials with non-linear refractive index.

Table 1 Note that it is known that the response time for the n2 fin, which is non-resonant with the absorption line, is on the order of ps or less.

When we prototyped an optical switch using GaAs as a constituent material and having an optical waveguide width of 0.08 pm to sufficiently confine light, we found that the length from the control light input part to the coupling part in one arm 13 was 3001 Lm. case, 77
This optical switch could be switched with an input optical power of 0 mW.

Note that this optical switch has an element length L (see Figure 4) of 4.
00 p-m, and the effective switching speed was 4.2 ps. Of course even greater light input, for example? ,? If W is used, the switching speed of the optical switch described above will be 0.42 pS, making sub-picosecond switching possible.

Semiconductors, ferroelectric materials, etc. other than the semiconductors shown in Table 1 can also be used as constituent materials of the optical waveguide. Furthermore, the literature by Bloss et al. (Applied
Physics Letters Paper 41 volumes 100
0 (1982)), GaAs
Superlattice GaAs superlattice has an even larger n2 than GaAg, and can be used as a material capable of high-speed switching with lower control optical power.

[Effects] As explained above, according to the present invention, it operates stably at room temperature, has a large optical amplification degree, and has a very high operating speed of about pS, which makes it suitable for optical signal processing and logical operations. It is possible to provide an optical switch that can be widely used as a basic element such as.

Furthermore, the optical switch of the present invention has the following advantages.

Changes in the refractive index of the optical waveguide caused by the (+) signal light cancel each other out in the two arms, so fluctuations in the intensity of the signal light do not affect the switch operation.

(2) It is not sensitive to the wavelength of the signal light, so a multi-axis mode laser or the like can also be used as a light source.

(3) Since multiple reflections are not used, high-speed response can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional optical switch, Figure 2 is a diagram showing the optical input/output characteristics of the switch, Figure 3 is a diagram showing the relationship between control light and signal light 1 in the switch, Fig. 4 is a configuration diagram showing an embodiment of the optical switch according to the present invention, Fig. 5 is a diagram showing an example of the relationship between control light and output light in the switch, and Fig. 6 is a diagram showing an example of the relationship between control light and output light in the switch. FIG. 3 is a diagram showing an example of response characteristics of output light. l...Medium with nonlinear refractive index. 2... Fabry-Perot resonator, 3... Signal light, 4... Control light, 11... Single mode optical waveguide for input, 12... Single mode optical waveguide for output, DESCRIPTION OF SYMBOLS 13, 14... Arm, 15... Branch part, 16... Coupling part, 17.18... Control optical waveguide, 19... Electrode, 20... Control light incidence part. 2 - - to Ofu

Claims (1)

[Scope of Claims] The input optical waveguide, the output optical waveguide, the two-tree width mode guide waveguide having a nonlinear refractive index dependent on light intensity, and the control optical waveguide are omitted; One end of each of the two single-mode leading waveguides is connected to one end of the input optical waveguide so that light of the same power is incident on each of the two single-mode optical waveguides;
Connecting each other end of the wooden single mode optical waveguide to one end of the output optical waveguide, and attaching the control optical waveguide to one of the two arms to control its refractive index. An optical switch, characterized in that the optical switch is connected in the middle of the one arm so as to input the control light.