JPS6325631A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To lead light made incident upon a cross part to a prescribed waveguide while suppressing its leakage and to reduce crosstalk by crossing waveguide respectively consisting of high and low refractive index parts and properly determining the field distribution of light beams made incident upon the crossing part to control a diffraction angle. CONSTITUTION:Two waveguides 8 forming respective high and low refractive index parts 9, 10 asymmetrically are crossed each other at a crossing point 11 so that respective high refractive index parts are opposed to each other on the input side and an electrode is formed on its crossing part 12 as a high refractive index parts to suppress the generation of a dispersion source. Light made incident upon a waveguide 8-2a is made incident upon a waveguide 8-2b through the crossing point 11, but because the field distribution of the light is deviated to the high refractive index part 9, light does not almost exist in a waveguide 8-1b and its leakage to the waveguide 8-2b can be reduced. Thereby, the light is led into a prescribed waveguide and crosstalk can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide optical switch that controls the traveling direction of light propagating in an optical waveguide.

[Conventional technology]

Conventionally, as a waveguide type optical switch, an electrode is provided in an X-crossing waveguide, and a region with a low refractive index is electrically created to block the optical path of the guided light along the center line of the intersection. There are some devices that change the backlight path by total reflection. This type of optical switch has a simple structure and can be made very compact.

The above-mentioned conventional technology will be explained below with reference to the drawings.

FIG. 6 is a plan view. In the figure, 1 and 2 are straight waveguides, which are formed on the substrate 3 so as to intersect at an intersection 4, and electrodes 6 are provided along the length direction at the intersection 5. be.

According to the optical switch having such a configuration, when no voltage is applied to the electrode 6, the entrance 1 of the straight waveguide 1 (or 2)
Light input from a (or 2a) exits exit 1b (or 2b)
The crossing angle φ of the waveguide section is selected so that the output state (hereinafter referred to as a cross state) is achieved.

When a voltage is applied to the electrode 4, the refractive index of the electrode portion is completely lowered to cause total reflection of the light, and the light input from the entrance 1a (or 2a) is outputted to the exit 2b (or Ib).
This will be referred to as the bar state below. ).

[Problems to be solved by the present invention]

However, it is difficult to obtain good crosstalk in the above-mentioned cross state, and it is necessary to set the crossing angle to about 8° or more. However, in this case, there is a drawback that the operating voltage becomes high because the angle of incidence on the electrode portion with a low refractive index becomes large.

The reason why this crosstalk occurs when the crossing angle φ is relatively large (4° or more) is that light confinement suddenly deteriorates at the place where the waveguide enters the crossing part 5, as shown in FIG. This is because diffraction occurs. That is, the guided light 7 is diffracted when it enters the intersection 5, and most of it travels as guided light 7a, but a small amount of unnecessary light 7b and 7c is generated, and among these, the diffracted light in the direction of the unnecessary light 7b passes through the waveguide. As a result, crosstalk will occur.

[Means for solving problems]

The present invention provides a waveguide type optical switch that completely controls the traveling direction of light propagating in the waveguides by crossing two waveguides. The diffraction angle is controlled by appropriately determining the field distribution of the incident light incident on the intersection.

[Effect]

According to the above configuration, by increasing the refractive index to prevent scattering sources from occurring at the intersection, the diffraction angle at the intersection becomes small, and the light incident on the intersection proceeds to the designated waveguide with little leakage. , crosstalk will be reduced.

〔Example〕

Embodiments of the present invention will be explained below with reference to the drawings. 0. FIG. 1 is a plan view of a waveguide showing the first embodiment, and FIG. 2 is a plan view of two waveguides intersecting each other. , In the figure,
A waveguide 8 has a structure in which a high refractive index section 9 and a low refractive index section 10 are provided asymmetrically.

Two waveguides 8 having such a structure are manually connected to the high refractive index section 9.
They are made to face each other and intersect at an intersection 11, and the intersection 12 is made into a high refractive index section 9 so as not to generate a scattering source, and an electrode (not shown) is provided therein.

The operation of this embodiment with the above configuration will be explained below. The principle of this operation is shown in the explanatory diagram of FIG.

The light input to the waveguide 8-2a passes through the intersection 11 9,
The light is incident on the waveguide 8-2b, but at this time, because the field distribution 13-2 of the light is biased toward the high refractive index portion 9, almost no light exists in the waveguide 8-1b. , waveguide 8
-Leakage into 2b is small. This will reduce crosstalk.

FIG. 4 is a plan view of the waveguide shown in the second embodiment, and FIG. 5 is a plan view of two waveguides intersecting each other. In the figure, 14 is a waveguide. It has a structure in which a high refractive index section 15 is provided and a low refractive index section 16 is provided around it.

Two waveguides 14 having such a configuration are made to intersect at an intersection 17, and the width of the high refractive index portion 15 becomes narrower as it approaches the intersection 17, and the intersection 18 is designed to prevent scattering sources from occurring. The high refractive index portion 15 is assumed to be similar to -. In this embodiment as well, although not shown, electrodes are provided at the intersections.

According to the above configuration, the width of the light field distribution is ω. Therefore, the root diffraction angle where ω is large becomes small, and by narrowing the high refractive index portion 15, ω can be totally increased.
This will reduce crosstalk.

〔Effect of the invention〕

According to the present invention described above, the following conditions were all analyzed using the 82M analysis method. Substrate refractive index 2.14, light wave number 1
．． When the 3 μm waveguide width is 8 μm and the refractive index of the waveguide part is 3 × 10 and the refractive index is 2.14 + (-5, the angle φ6 × 10 = 4.6°, the conventional -12 dB to -15 d
It can be improved to B.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a waveguide used in the first embodiment of the present invention,
Fig. 2 is a plan view of the waveguides with all of them intersecting, Fig. 3 is an explanatory diagram showing the state of field distribution, Fig. 4 is a plan view of the waveguide used in the second embodiment, and Fig. 5 is the waveguide. 6 is a plan view of a conventional row, and FIG. 7 is a plan view showing a state of light leakage. 8... Waveguide 9... High refractive index section 10... Low refractive index section 11... Intersection 12... Intersection Patent applicant Oki Electric Industry Co., Ltd. Representative patent attorney Takashi Kanakura Second 1 Plan view of the waveguide of the second embodiment 1 Plan view of crossed waveguides Explanatory diagram showing field distribution 2 ■ 3 Plan view of the waveguide of the second embodiment 41 2b Ib Conventional example View of the plan view of 6112 14-2b 14-4b Plan view of intersecting waveguides 5 l Plan view showing light leakage 7 Figure

Claims (1)

[Claims] A waveguide optical switch that controls the traveling direction of light propagating in the waveguides by intersecting one or two waveguides, comprising a high refractive index section and a low refractive index section. Cross the waveguides,
A waveguide optical switch is characterized in that the field distribution of incident light incident on the intersection is appropriately determined to control the diffraction angle. 2. A waveguide type according to claim 1, characterized in that the refractive index of the waveguide is asymmetrical with respect to the central axis of the waveguide, and the overlap of mutual light field distributions after the intersection is reduced. light switch. 3. A waveguide according to claim 1, characterized in that the film thickness, refractive index, or width of the waveguide is reduced near the intersection to widen the field distribution of the guided light and to reduce the diffraction angle. type optical switch. 4. A waveguide optical switch according to claim 1, characterized in that the refractive index of the intersection portion is increased.