JP2566923B2 - Light switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention provides an inversion Δβ type directional coupler type waveguide optical switch by utilizing a thermo-optical effect in a refractive index changing operation for switching the operating state of the switch. , Which is an inexpensive switch.

[Industrial applications]

The present invention relates to an optical switch, and more particularly to an inverting Δβ type directional coupler type waveguide optical switch.

The waveguide optical switch can be miniaturized and integrated, has a low operating voltage, has a possibility of high-speed operation, and is suitable for mass production. Therefore, its practical application is expected. The waveguide optical switch includes a directional coupler type, a crossed waveguide type, a total reflection type, and the like. Among them, the directional coupler type switch has a feature that the operating voltage is relatively low. However, this switch has a problem that high precision is required for production, and in order to solve this problem, there is an inverting Δβ type switch in which electrodes are divided so that an operating point can be electrically adjusted.

However, the conventional inversion Δβ type directional coupler type waveguide optical switch is expensive, and its cost reduction is strongly demanded.

[Conventional technology]

FIG. 2 shows a conventional example of an inverting Δβ type directional coupler type optical switch. In the figure, reference numeral 1 indicates a substrate made of a crystal having an electro-optical effect (eg, LiNbO ₃ ), and the substrate 1 is made of Ti.
Are diffused to form two optical waveguides 2 and 3 having the same characteristics. Electrodes 4 are divided into two in the light traveling direction in the optical coupling regions of these optical waveguides that are close to each other, and the operating voltage V of the electrodes 4 is reversed in polarity between regions A and B. Applied in the region A, a propagation constant difference + Δβ is generated in the region A, and −Δβ is generated in the region B between the optical waveguides 2 and 3,
Then, by changing the operating voltage V, the propagation constant difference Δ
By changing β, the operating state of the switch is switched from the non-coupling state (optical path straight traveling state) to the coupling state (optical path crossing state) or vice versa.

[Problems to be solved by the invention]

The conventional optical switch, in particular, the inverting Δβ type directional coupler type waveguide optical switch as described above uses the electro-optic effect to generate the propagation constant difference Δβ, and therefore the substrate forming the optical waveguide is electrically connected. Must be an optical crystal.
However, the electro-optic crystal is expensive, so that there is a problem that an inexpensive switch cannot be obtained.

[Means for solving problems]

In order to solve the above problems, the present invention is an inverting Δβ type directional coupler type waveguide optical switch, in which two optical waveguides are provided on a substrate having a thermo-optical effect in which the refractive index of light changes according to temperature. In the first half of the optical coupling region of the optical waveguide which is close to each other, the first waveguide is formed on one of the waveguides.
Is provided, and in the latter half of the optical coupling area,
A second heat generating portion is provided on one of the other waveguides, and the first half portion and the second half portion are configured so as to generate predetermined propagation constant differences having different polarities and equal absolute values. And

In the present specification, “on the waveguide” where the first and second heat generating portions are provided means above the substrate (whether contacting or not contacting), and the waveguide has a predetermined thermal property. It is used to indicate a position where an action can be exerted.

[Work]

In the above optical switch, when a required operating voltage is applied to the heating element, the optical waveguide is heated to cause a required propagation constant difference, whereby the operating state of the switch is switched.

The above-mentioned thermo-optical effect is possessed by many kinds of substances, and the degree of freedom in selection is high. Therefore, the cost of the switch can be reduced by using an inexpensive substrate material for the switch.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 11 denotes a substrate made of a material having a thermo-optical effect (for example, glass), the substrate is subjected to ion exchange to form optical waveguides 12 and 13, and a heating element 20 is formed in the optical coupling region. There is. The optical coupling region is divided into a first half portion indicated by reference symbol A and a second half portion indicated by reference symbol B. The heat generating element 20 includes a heat generating portion 21 formed in the optical waveguide 12 in the second half B of the optical coupling area, a heat generating portion 22 formed in the optical waveguide 13 in the first half A of the optical coupling area, and these heat generating portions 21, 22. It is composed of conductive portions 23, 23, 25 for energizing the. The heat generating portions 21 and 22 can be formed as a high resistance film, and the conductive portions 23 and 2 can be formed.
3,25 can be formed as a low resistance film. The high resistance film and the low resistance film may be made of different materials, or may be made of the same material and have different film thicknesses.

When the voltage V is applied to the heating element 20, the heating parts 21, 2
Due to the heat generated at 2, the region B of the optical waveguide 12 and the optical waveguide 1
The area A of 3 is heated, and the optical waveguide 12,
Between 13, the propagation constant difference + Δβ occurs in the region A, and the propagation constant difference −Δβ occurs in the region B. Therefore, by changing the applied voltage V (that is, changing the heating temperature) to change the propagation constant difference Δβ, the operating state of the switch is switched from the non-coupled state to the optically coupled state and vice versa.

〔The invention's effect〕

As described above, the optical switch according to the present invention utilizes the thermo-optical effect for the refractive index changing operation necessary for optical path conversion, and therefore, an inexpensive material having the thermo-optical effect can be used as the substrate, which is inexpensive. A switch is feasible.

Note that, as an effect peculiar to the illustrated embodiment, since the heating element is composed of the heating portion formed of the high resistance film and the conductive portion formed of the low resistance film, efficient switching operation is possible. .

[Brief description of drawings]

 FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional example. [Explanation of symbols] 11 …… Substrate 12,13 …… Optical waveguide 20 …… Heating element 21,22 …… Heating part 23,24,25 …… Conductive part

Claims (3)

(57) [Claims] 1. An inversion Δβ type directional coupler type waveguide optical switch, wherein two optical waveguides are formed on a substrate having a thermo-optical effect in which the refractive index of light changes according to temperature. A first heat generating portion is provided on any one of the waveguides in the front half of the optical coupling regions that are close to each other, and a second heating portion is provided on the other waveguide in the latter half of the optical coupling region. The optical switch is characterized in that the heat generating portion is provided, and the first half portion and the second half portion can generate predetermined propagation constant differences having different polarities and equal absolute values. 2. The optical switch according to claim 1, further comprising a conductive portion connecting the first and second heat generating portions. 3. The optical switch according to claim 2, wherein the first and second heat generating portions are formed of a high resistance film, and the conductive portion is formed of a low resistance film.