JPS59228635A - Optical switching element - Google Patents

Abstract

PURPOSE:To correct beam deformation originating from 1 deg. deflection, reduce the decrease in the coupling efficiency of a light beam coupling system, and obtain a device with small insertion loss by attaining 2 deg. deflection to a mutually opposite direction at the time of optical-path switching. CONSTITUTION:A flat plate 4 which has thickness (t) and decreases in refractive index with an electric field or heat is made of, for example, a rutile crystal base plate and has electrodes 5 and 6 on the opposite surfaces spaced by l from the opposite positions in surface directions. A light beam 7 is made incident to the flat plate 4 from near the electrode 5 almost in parallel to the surface of the flat plate 4, and a voltage is impressed between the electrodes 5 and 6 to induce variation in refractive index near right under the electrodes 5 and 6. The light beam 7 projected after being deflected twice is a nearly parallel beam. The distance l and the voltage impressed between the electrodes 5 and 6 are selected properly so that the beam crosses itself almost at the mid-point between the electrodes 5 and 6, thereby suppresses the variation in the diameter of the beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switching element that is inserted into an optical path and constitutes an optical switch that switches the optical path.

Conventional optical switching elements that utilize the optical deflection phenomenon mainly use Bragg diffraction, which propagates elastic waves within a specific crystal or on the surface of the crystal and utilizes periodic changes in the refractive index caused by the 9 elastic waves. It is something. In addition, recently, deflection elements using a refractive index gradient thought to be caused by an electric field or heat have been proposed (for example, IEICE Technical Report 0Q
E81-77).

However, with a Bragg diffractive deflection element.

Since the intensity of the diffracted light decreases significantly as the incident angle of the light beam changes, the accuracy required for adjusting the incident angle becomes stricter. Further, even if the light beam is incident at the optimum angle of incidence, zero-order light remains, so special consideration is required to reduce the amount of crosstalk. On the other hand, in the case of using a refractive index gradient thought to be caused by an electric field or heat, the deflection angle θ changes significantly depending on the distance from the electrode and the beam diameter is finite, as shown in Figure 7 (,). Therefore, the deflected beam is deformed, and the coupling efficiency of the parallel beam coupling system decreases significantly as the deflection angle θ increases. For example, refer to FIG. 1(b).

When a light beam 3 with a deme diameter of 200 μm is deflected onto a rutile crystal substrate 2 made of a deflection element having characteristics as shown in FIG. 0.4 to 0.0 from electrode 1.
The light beam 3 will pass through a range of 6 mrn,
The partial deflection angle of the light beam 3 varies from 0.4 degrees to 0.28 degrees. This results in the deflected beam becoming divergent.

An object of the present invention is to compensate for the above-mentioned beam deformation caused by a deflection element using a refractive index gradient caused by an electric field or heat with a simple structure, thereby reducing crosstalk and beam deformation, thereby improving the coupling efficiency of a parallel beam coupling system. It is an object of the present invention to provide an optical switching element that exhibits less deterioration in performance.

According to the present invention, an optical switching element can be obtained that is composed of a flat plate made of a material whose refractive index decreases when an electric field or heat is applied, and first and second electrodes formed on both sides of the flat plate, respectively. .

According to the second aspect of the present invention, a flat plate made of a material whose refractive index decreases when an electric field or heat is applied, first and second electrodes respectively formed on both sides of the flat plate, and the first and second electrodes formed on both sides of the flat plate, respectively. An optical switching element is obtained which is composed of first and second electrodes and third and fourth electrodes formed to face each other.

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

FIG. 2(a) is a front sectional view showing the structure of one embodiment of the optical switching element according to the present invention. The optical switching element of this embodiment has a flat plate 4 having a thickness L whose refractive index decreases due to an electric field or heat, and a flat plate 4 which is spaced from each other by a distance t in the plane direction from opposing positions on opposing surfaces of the flat plate 4. The electrode 5 formed at the
and 6.

The flat plate 4 is made of, for example, a rutile crystal substrate. The operation of the present invention will be explained below.

A light beam 7 is made to enter the flat plate 4 from near the electrode 5 so as to be almost parallel to the plane of the flat plate 40 on which the electrodes 5 and 6 are formed, and a voltage is applied to the electrodes 5 and 6 so that the light beam 7 is directly below the electrodes 5 and 6. Induces a refractive index change in the vicinity. This refractive index change induced in the vicinity directly under the electrode tends to increase toward the inside of the flat plate 4 because the refractive index directly under the electrode decreases. Therefore, the beam passing directly under the electrode is deflected toward the inside of the flat plate.

Now, the incident light beam 7 is first deflected near the electrode 5 and then heads into the flat plate 4, but as mentioned above, the deflection angle 01 is partially different, and as shown in FIG. It changes from a part close to 5 to 1011 degrees to +012 degrees (however, θII) θ12). The voltage applied to the electrode 5 at this time,
If the distance t is appropriately selected, the deflected beams intersect inside the flat plate 4, as shown by the broken line in FIG. 2(a), and are guided directly below the electrode 6. Since the beam guided directly below the electrode 6 intersects within it as described above, the portion closest to the electrode 5 passes through the portion closest to the electrode 6. Therefore, the deflection angle θ2 of the deflection received near the electrode 6 is the second
As shown in figure (b), it changes continuously from -021 degrees to -022 degrees, and the part that receives a deflection of +011 degrees is 1021 degrees, and the part that is deflected 1012 degrees is 〇22
degree (however, 1-02.1>1-02□1).

At this time, if the voltage applied to the electrode 6 is appropriately selected, it is possible to set θ1 degrees to 02 degrees = 0 degrees for each part within the beam. Therefore, the light beam 7 that is emitted after being deflected twice becomes a nearly parallel beam.

The remaining problem may be variations in the beam diameter, but if the distance t and the voltages applied to electrodes 5 and 6 are appropriately selected so that the intersection within the beam occurs approximately at the midpoint between electrodes 5 and 6, then Fluctuations in the beam diameter of the input and output beams can be suppressed.

FIG. 3 is a front sectional view showing another embodiment of the optical switching element according to the present invention, and the embodiment shown in FIG.
This is an optical switching element for a ×2 optical switch, whereas the optical switching element of this embodiment is an optical switching element for a 2×2 optical switch. The optical switching element of this embodiment includes a flat plate 14 with a thickness t whose refractive index is reduced by an electric field or heat, and a position on opposing surfaces of the flat plate 14 that is spaced apart from each other by a distance t in the plane direction from opposing positions. and electrodes 10 and 11 formed on opposite surfaces of a flat plate 14 to face the electrodes 8 and 9, respectively. Of the incident light beam,
One of the light beams 12 is directed from the vicinity of the electrode 8 to the electrodes 8 to 11.
The other light beam 13 is directed from near the electrode 10 so as to be almost parallel to the flat plate 140 surface on which the electrodes 8 to 11 are formed. Flat plate】4. The following operation is.

Since this is the same as the example shown in FIG. 2, the explanation will be omitted.

FIG. 4 is a front sectional view showing an example of application of the optical switching element for a 1×2 optical switch shown in FIG. 2. When no voltage is applied to the electrodes 22 and 23 that constitute the optical switching element, the light beam that enters the rutile crystal substrate 15 that constitutes the optical switching element from the vicinity of the electrode 22 from the optical fiber 19 via the rod lens 16 is as follows. The light beam passes straight through the rutile crystal substrate 15 and is emitted from the end face of the rutile crystal substrate 15, and this emitted light beam is coupled to the optical fiber 20 via the rod lens 17 and transmitted through the optical fiber 20. go. On the other hand, when a voltage is applied to the electrodes 22 and 23, the light beam that enters the rutile crystal substrate 15 from the vicinity of the electrode 22 from the optical fiber 19 via the rod lens 16 is deflected for the first time in the vicinity of the electrode 22. Rutile crystal substrate 15
The light beam passes through the inside of the rutile crystal substrate 15, is deflected a second time near the electrode 23, and is emitted from the end face of the rutile crystal substrate 15 near the electrode 23. and is transmitted through the optical fiber 21.

The present inventor actually used the size II as a substrate material.
A thin film heater (width i mrn
The long-term loss was 4 dB, and it was confirmed that the beam coupling loss was improved by 91.5 dB due to the beam deformation compensation effect of the optical switching element.

As is clear from the above description, the optical switching element according to the present invention can be expected to have the effect of compensating for the beam deformation caused by one degree of deflection by deflecting the beam twice in opposite directions when switching the optical path. Therefore, the decrease in coupling efficiency of the optical beam coupling system due to deflection is alleviated, and a device with low insertion loss can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the deflection state of a conventional deflection element using a refractive index gradient, and FIG. 2 is a front sectional view and a deflection state explanatory diagram showing the configuration of an embodiment of the optical switching element according to the present invention. FIG. 3 is a front sectional view showing the structure of another embodiment of the optical switching element according to the present invention, and FIG. 4 is a front sectional view showing an example of application of the optical switching element shown in FIG. 2. 1... Electrode, 2... Rutile crystal substrate, 3... Light beam. 4... Flat plate, 5, 6... Electrode, 7... Light beam,
8-11... Electrode, 12.13... Light beam, 14
...Flat plate, 15...Rutile crystal substrate, 16...1
8...Rod lens. 19-21... Optical fiber, 22.23... Electrode. →D (mm) (Q) Fig. 1

Claims (1)

[Scope of Claims] 1. An optical switching element comprising a flat plate made of a material whose refractive index decreases upon application of an electric field or heat, and first and second electrodes formed on both sides of the flat plate, respectively. 2. A flat plate made of a material whose refractive index decreases when an electric field or heat is applied, first and second electrodes formed on both sides of the flat plate, and first and second electrodes formed on both sides of the flat plate, respectively. The third and fourth electrodes are formed opposite to the second electrode.
An optical switching element consisting of an electrode.