JPS5849918A - Optical switch - Google Patents

Abstract

PURPOSE:To obtain a stable optical switch, by coupling two optical waveguides, which have parts parallel to each other and have different propagation constants, with a prescribed acoustic wave. CONSTITUTION:An optical switch consists of two optical waveguides 2 and 3 which are formed by diffusing titanium on a substrate consisting of a lithium niobate and have parallel parts, an ultrasonic transducer 4, and a sound absorber 5. For optical waves of wavelength lambda=0.8mum of optical waveguides 2 and 3, beta1=17.4437 and beta2=17.4751 are true, and¦beta1-beta2¦=0.0314 is true. Ultrasonic waves having a wave vector component (k) (wavelength lambdaa=200.1mum for m=1) which satisfies k=+ or -¦beta1-beta2¦/m (m is a positive constant) are applied by the transducer 4. The light of lambda=0.8mum which is incident from an end A of the optical waveguide 2 and is outputted to an end B when ultrasonic waves are not applied is transferred to the optical waveguide by application of ultrasonic waves when lengths of parallel parts of optical waveguides 2 and 3 satisfy the phase matching condition, and this light is outputted from an end C. Consequently, a stable optical switch is obtained.

Description

[Detailed description of the invention] The present invention relates to an optical switch used for optical communications and the like.

One of the conventional configuration methods for optical switches is a mechanical switch that switches the optical path by moving an optical fiber, grism, or mirror, but this elliptical switch has a limit in high speed because it contains mechanical moving parts. However, the reliability is not as high as that of optical fibers, and it is sometimes not suitable for integrating optical circuits.

In order to overcome these drawbacks, a number of proposals have been made for configurations of the original switch that do not include mechanical operating parts. One method is to use rotation of the plane of polarization. In this method, after the light is made into vibration components in a specific direction by a polarizer, the plane of polarization is rotated or passed through a polarization plane conversion element, and then the polarization element is used to convert the light according to the direction of the plane of polarization. The direction in which the light travels is selected◎
When using an electric polarization plane conversion element, a voltage is applied between the electrodes provided on it, and when a soft magnetic optical crystal is used as the conversion element, a magnetic field is generated parallel to the traveling direction of the light. When a magnetic field is applied, the plane of polarization rotates in proportion to the traveling distance in the magneto-optical crystal, and when the direction of the magnetic field *'i: is reversed, the effect that the direction of rotation of the plane of polarization is also reversed is applied.

Another method of configuring an optical switch is to apply coupling between optical waveguides. In other words, when two optical waveguides are located close to each other, a transition of optical power occurs between the two optical waveguides.◎This ft. , the amount of power transferred is
It depends on the difference between the leakage electromagnetic fields of the two waveguide modes, that is, the strength of the coupling and the propagation constant. In optical waveguides using electro-optic crystals, the coupling strength and phase difference between guided modes are
Switching is performed by a configuration controlled by a voltage applied to a control electrode provided on an optical waveguide.0 In the method of configuring an optical switch as described above, an electro-optic crystal is used and a voltage is applied to the control electrode. As rainbow charges move in the electric field of It is difficult to do so. Furthermore, even in the method of using magneto-optic crystals, it is currently difficult to obtain a material that satisfies the characteristics required for use in the original switch.

An object of the present invention is to provide a new configuration method for an optical switch that is different from the above-described configuration method, and to compensate for the above-mentioned drawbacks.

The optical switch of the present invention includes two or more optical waveguides having mutually parallel portions and having different propagation constants, and among the optical waveguides, a first optical waveguide has a propagation constant β1, and a first optical waveguide has a propagation constant β1. An elastic wave with a wave number vector component k = ±1β, -β, l/m (where m is a positive integer) in a direction parallel to the second optical waveguide and the -0th optical waveguide and the When adding to the second optical waveguide and the vicinity including the gap pipe between the two binary waveguides, the light wave propagating in the second optical waveguide moves into the second optical waveguide and does not apply the elastic wave. The 4I characteristic is that the light wave does not sometimes migrate.〇The present invention will be explained in detail below using an embodiment with reference to the drawings.〇The figure is a plan view showing the main part of an embodiment of the present invention. It is a diagram,
1 is a substrate, 2 is a FJ first optical waveguide, 3 is a 20th optical waveguide, 4 is an ultrasonic transducer, and 5 is a sound absorbing material. The substrate 1 is made of niobium-based lithium (LiNboI), and the optical waveguides 2 and 3 are formed by diffusing titanium (TiJ) into the substrate 1.The refractive index of the substrate 1 is n and w2.2.
2, and the effective refractive index of the tenth optical waveguide 2 is n,=2.
221, effective refractive index in of the 20th optical waveguide 3, = 2.2
At of T1 is changed so that it becomes 25.

For a light wave of wavelength J −0.8 μm in vacuum, the propagation constant βI of the first optical waveguide 2 is 17.4437, the propagation constant β of the second optical waveguide 3 is 17.4751, and J/
.

=βll-0,0314.

In this embodiment, the ultrasonic wave applied to the substrate 1 by the ultrasonic transducer 4 travels parallel to the mutually parallel portions of the optical waveguides 2 and 3. Therefore, the wave number vector of the ultrasonic wave in this direction is strong in the magnitude of the wave number vector (kfl), and in creation, as mzl = 0
．． 0314 super taO wavelength az200.5pm'k
Nru0 A light wave of λ=0.8 μm is introduced from the A end of the 10 optical waveguide 2 of the optical switch of this embodiment as described above, and when no ultrasonic wave is applied by the ultrasonic transducer 4, the light wave is Output to the B end of the 0-party waveguide 2.

When ultrasonic waves are applied, the light wave moves from the first optical waveguide 2 to the second optical waveguide M3, and the length of the parallel portion of both optical waveguides is a perfect coupling length that satisfies the phase matching condition, When , the signal is completely shifted and outputted only to the C end of the second optical waveguide.

In the original switch using the electro-optic crystal described above and applying multiplication waveguide coupling, strict manufacturing precision is generally required for K in order to satisfy the phase matching condition.
It is difficult to realize perfect optical switching, and attempts such as adding auxiliary electrodes have been made. In the optical switch of the present invention, correction of the phase matching condition is as follows:
This can be done by adjusting the intensity or amplitude of the ultrasonic waves. In the embodiment described above, the substrate 1 is LiNb0. However, in the present invention, a medium of elastic waves is used. This is an application of JQ$lp changes associated with storm changes, but is not an application of the electrophotonic effect. It is rare that the medium used has a large photoelastic constant, and 8i0. , glass, etc. can also be used, and it is also possible to select the propagation mode of elastic waves depending on the structure and material of the optical switch. Optical branch circuits, etc. can also be formed by the method of the present invention.As explained above, optical branching circuits, etc. It provides a new optical switch that performs a switching action and compensates for the shortcomings of the conventional technology.

[Brief explanation of the drawing]

The drawing is a plan view showing an embodiment of the present invention.

Claims (1)

[Claims] A first optical waveguide having a propagation constant β, which includes two or more optical waveguides having mutually parallel portions and having different propagation constants; is β, and the wave vector component k in the direction parallel to the 20-light wave path is k=±1β1-1.17m (where mu positive C is an integer)
The elastic wave that is
When the 4tIL paths are added to the vicinity including the mutually parallel portion and the gap between the two optical waveguides, the light wave propagating in the second optical waveguide transfers into the second optical waveguide, and An optical switch 0 characterized in that the light wave does not shift when no elasticity tBL is applied.