JPS6161659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optically controlled optical switch that is used in the field of optical communications or optical waveguides and that modulates optical signals or controls the transmission direction of optical signals. The present invention provides a light control type optical switch that can control signal light.

The object of the invention is to improve the switching time, in particular the cut-off time of optically controlled optical switches.

The configuration of a conventional light-controlled optical switch is as shown in FIG. 1, and is composed of a total reflection type optical switch using LiNbO ₃ and a photovoltaic film formed by oblique evaporation of CdTe. That is, 1 is a dielectric substrate made of LiNbO ₃ and has an electro-optic effect, and 2 is a dielectric substrate having an electro-optic effect.
An optical waveguide is formed by diffusing Ti, 3 is a CdTe photovoltaic film, and 4 is a metal electrode.

In the optically controlled optical switch having the above configuration, when the signal light 5 is incident, the signal light travels straight and is emitted to the output path 6 in a normal state, that is, when no control light is incident. However, when the control light 7 is incident on the photovoltaic element 3, an electric field due to the photovoltaic force is applied to the vicinity of the intersection of the optical waveguide 2 through the metal electrode 4, causing a change in the refractive index within the waveguide 2, and the incident The light undergoes total reflection near the intersection, and the emitted light is emitted from the exit path 8.

In the conventional optically controlled optical switch having the configuration shown in FIG.
Figure a shows the temporal change in the light intensity of the modulated output light 8, and Figure 2 b shows the temporal change in the light intensity.

As is clear from FIG. 2b, although the rise time of the modulated output light is less than a second, it takes several minutes for the modulated output light to rise. This slow fall time is due to the high internal resistance of the photovoltaic film, and has been a major drawback of conventional light-controlled optical switches.

Let's consider why the fall time is longer than the rise time in the conventional art. Generally, the response time of a light-controlled optical switch is approximately determined by the product of the capacitance C between the electrodes and the internal resistance R of the photovoltaic element, that is, the CR product. Comparing the internal resistance R _ON of the photovoltaic force when the control light is incident and the internal resistance R _OFF of the photovoltaic force when it is blocked, it is generally found that due to the photoconduction phenomenon of the photovoltaic layer, R _ON <R
There is _{an OFF} relationship. Therefore, the rise time τ _ON
(=CR _ON ) and fall time τ _OFF (=CR _OFF )
In general, τ _ON < τ _OFF . Moreover, τ _OFF is several tens to tens of thousands of times larger than τ _ON , resulting in a longer fall time, which has been a major drawback of conventional optically controlled optical switches.

The present invention solves the conventional problems and provides a light-controlled optical switch that cuts off the output light in a short time.

FIG. 3 shows a light-controlled optical switch according to an embodiment of the present invention. The structure of the optical switch is similar to that shown in FIG. 1, but the structures of the photovoltaic film and electrodes are different. That is, in the same figure, 9 is a LiNbO ₃ substrate, and 10 is a LiNbO 3 substrate.
A Ti diffusion waveguide, 11 and 12 are photovoltaic elements formed by simultaneous oblique vapor deposition, 13 and 14 are electrodes, the first control light 15 is irradiated to 11, and the second control light 16 is irradiated to 12. is irradiated. Therefore, when the electrode 13 is used as a reference, photovoltaic forces of different polarities are generated at the electrode 14 for the first control light and the second control light. According to such a configuration, when the first control light is irradiated, the optical switch is operated and the output of the input light 16 is switched from the output path 17 to the output path 18, similar to the conventional optical switch shown in FIG. By irradiating the second control light, it is possible to perform an operation that can shorten the cut-off time by applying a voltage of opposite polarity.

FIGS. 4a, 4b, and 4c show the optical intensities of the first control optical signal, the second control optical signal, and the output signal light with respect to time, respectively, when operating the optically controlled optical switch. As is clear from these figures, by inputting the second control light signal immediately after cutting off the first control light signal, the fall time of the output signal light is significantly shortened compared to the conventional method.

In addition, in this example, a total internal reflection type optical switch and
Although a photovoltaic device made by oblique evaporation of CdTe has been cited as a composite device, it can also be applied to optical switches that apply the electro-optic effect and photovoltaic devices made of semiconductors other than CdTe.

As explained above using the embodiments, the light-controlled optical switch of the present invention can significantly shorten the cut-off time of the conventional light-controlled optical switch by modifying the electrodes and using another control light. It is.

The optically controlled optical switch of the present invention is particularly useful in the fields of optical communication, optical measurement, optical control, etc., exhibits its value, and can greatly contribute to the advancement of optical technology and the optical industry. .

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional optically controlled optical switch.
FIGS. 2a and 2b are diagrams showing the switching characteristics of the same switch, FIG. 3 is a perspective view of a light-controlled optical switch according to an embodiment of the present invention, and FIG. 4 is a diagram showing the switching characteristics of the same switch. 9...LiNbO ₃ substrate, 10...Ti diffusion waveguide,
11, 12...Photovoltaic element, 13, 14... Electrode, 15... First control light, 16... Second control light.

Claims (1)

[Scope of Claims] 1. An optical waveguide is formed on a dielectric substrate having an electro-optical effect, with the output light side branching into a plurality of branches from a branching part, and a first electrode having one terminal and the other terminal extending. and a second electrode with a predetermined terminal extending therefrom are formed in the vicinity of the optical waveguide so as to face each other.
forming a first photovoltaic element for applying a first electric field across the optical waveguide during light irradiation between one terminal of the electrode and a predetermined terminal of the second electrode;
forming a second photovoltaic element for applying a second electric field in a direction opposite to the first electric field during light irradiation between the other terminal of the electrode and a predetermined terminal of the second electrode; A light-controlled optical switch characterized in that immediately after cutting off light irradiation to the second electromotive force element, light irradiation is performed to the second electromotive force element. 2. The optically controlled optical switch according to claim 1, wherein the first and second photovoltaic elements are formed of obliquely deposited semiconductor films. 3. The optically controlled optical switch according to claim 1, wherein the first and second photovoltaic elements are formed of obliquely deposited CdTe films.