JPS5858524A - Optical switch - Google Patents

Abstract

PURPOSE:To obtain an optical switch which is easy to manufacture and operates on low electric power without receiving limitations in electric power sources for driving by disposing a heating electrode on a main waveguide and a branch waveguide consisting of optical transmission media which are formed on the surface of a substrate and of which the refractive indices change with temps. by interposing an insulating layer. CONSTITUTION:Ti or the like is diffused on the surface of a substrate 1 consisting of LiNbO3 to form a main waveguide 2 and a branch waveguide 3. The angles that these waveguides assume is 2-3 deg.. An insulating layer 5 consisting of SiO2 or the like is formed in a suitable area centering at the branching point of both waveguides 2, 3 and a heating electrode 4 consisting of an Ni-Cr alloy is provided thereon over both waveguides 2, 3. While no electric conduction is performed at the electrode 4, <=1/10 of the light propagating in the waveguide 2 emits from the waveguide 3, but when a voltage V is applied to the electrode 4, its refractive index is increased by the heating and the light emits mainly from the waveguide 3. Thus the optical switch which is easy to manufacture and operates on low electric power without receiving limitations for electric power sources for driving is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switch that utilizes the property of a crystal material that its refractive index changes depending on the temperature.

In the field of optical information processing such as optical fiber communications, optical memory devices, and optical printers, devices that control the direction of light and turn on and off the passage of light are essential. Conventional optical switches used as devices of this type include those that utilize the acousto-optic effect of crystalline materials or those that utilize the electro-optic effect. Figure 3 is a schematic perspective view of an optical switch that controls the direction of light using the electro-optic effect;
The figure is a sectional view taken along the line IV--IV in FIG. 3. LiN
b0. T on the surface of the substrate 60 made of dielectric crystal material of fI
A Y-shaped waveguide 7 whose refractive index is higher than that of the substrate 6 is formed by i-diffusion method or the like. The waveguide 7 has a waveguide 7a on the light input side and waveguides 7b and 7c on the output side branched from the waveguide 7a to the left and right in plan view with respect to the light traveling direction. and,
An insulating layer 9 such as Sl is formed on the surface of the substrate 6 near the branch point of the waveguide 70, and on this insulating layer 9, a control electrode 8m,
8b, 8e and 8d are formed in layers. Control electrode 8
b is a region directly above the waveguides 7a and 7b KTo, which is formed into a shape that matches this.

Further, the control electrode 8C is located directly above the waveguides 71 and 7cO, and is shaped to match the waveguides 71 and 7cO. On the other hand, the control electrode 8a has the same shape as the control electrode 8b and is arranged in parallel at a position outside the area immediately above the waveguide 7, and the control electrode 8d, which has the same shape as the control electrode 8C, is also arranged in parallel. ing.

Thus, when a full DC voltage is applied between the control electrodes 8b, 8d and the control electrode 818C, the waveguide 7&and the waveguide 7b
and 7cK, an electric field (indicated by an arrow in FIG. 4) is formed in the C-axis direction of the dielectric crystal.

A difference occurs in the refractive index of the waveguides 7b and 7C, and the light wave incident from the waveguide 7a side propagates unevenly in one of the waveguides 7b or #ise, and is mainly emitted from the waveguide with a higher refractive index. become. Therefore.

By controlling the direction of voltage application to each control electrode, the emission direction of the light wave can be controlled.

However, in the optical switch as described above.

Since the shape of the control electrode needs to match the no-ζ turn of the waveguide, advanced technology is required to form it. In addition, if the waveguide is made into a single mode, a waveguide with a width of about 5 SW+ is required.

It is not easy to form the control electrodes, and furthermore, although a DC voltage of several 1O2 is applied to the control electrodes, the distance between the control electrodes becomes extremely small, which poses problems in terms of withstand voltage. Furthermore, since a DC power source is required as a power source for driving the optical switch, there are restrictions on the device configuration.

On the other hand, in an optical switch using the acousto-optic effect, Fi
, PbMoO4, Tea, etc. are used.

Furthermore, it is extremely expensive because it uses a transducer that converts electrical signals into ultrasonic waves. Furthermore, since a large amount of high-frequency power is required to drive the optical switch, there is a problem in that the manner in which it can be used is restricted.

The present invention has been made in view of the above points, and an object of the present invention is to provide an optical switch that is easy to manufacture and can be operated with low power without being restricted by the driving power source. Apart from the conventional optical switch concept of utilizing the electro-optic effect or the acousto-optic effect of crystalline materials, the present invention provides an Ω refraction-1 refraction 1!1 degree-dependent force of the crystal material. This was created based on the novel idea of using Therefore, the optical switch of the present invention does not require that the plane of polarization of the light wave be polarized in a specific direction unlike conventional switches that utilize the electro-optic effect, and therefore can operate even with white light. The optical switch according to the present invention includes a main waveguide formed on the surface of a substrate and made of an optical transmission medium whose refractive index changes depending on temperature, a branch waveguide branched from the main waveguide at a branch point, and a branch waveguide in the main waveguide. A heating electrode formed over the appropriate length portion extending from the branch point in the direction opposite to the light traveling direction and the appropriate length portion extending from the branch point in the light traveling direction in the branch waveguide. It is a sign. In this case, on the substrate on which the main waveguide and the branch waveguide are formed,
Alternatively, an insulating layer made of ALρ1 or the like is formed.

By forming the heating electrode on this insulating layer, loss of light waves propagating through the waveguide into the metal (heating electrode) can be reduced.

LINbOma LtTaO, T@amm Crystal materials such as quartz.

Its refractive index has temperature dependence, and it has the property that the refractive index of culm waste at high temperatures is high. When light passes through the boundaries of materials with different refractive indexes.

A refraction phenomenon occurs so that the angle of refraction (the angle between the direction perpendicular to the boundary and the light beam) becomes smaller in a material with a high refractive index.

Therefore, when a waveguide is branched into two paths in the direction of propagation of a light wave, and one waveguide has a higher temperature than the other waveguide, the light wave passes through a waveguide with a higher temperature, that is, a higher refractive index. It is deflected to the side, propagates mainly through the high-temperature side waveguide, and is emitted. The present invention has been made based on this knowledge. That is, in the main waveguide and the branch waveguide branched from the main waveguide, an electrode is formed with a resistive heating element at an appropriate length part of the main waveguide and the branch waveguide on the light incident side near the branch point, and current is applied to the electrode. When the waveguide directly below is heated.

The light wave propagating through the main waveguide is deflected from this branch point toward the high-temperature branch waveguide, and the light wave is mainly emitted from the branch waveguide. If the electrodes are not energized and the temperature of the waveguide is uniform, the light wave will not be deflected to the branch waveguide and will be emitted from the main waveguide, so the traveling direction of the light wave will change depending on whether the electrode is energized or not. A converted optical switch is constructed.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. 19 is a schematic perspective view showing one embodiment of the present invention, and FIG. 2 is a plan view thereof. The substrate 1 is made of an 0LIN'bOs crystal material cut out so that the 1-2 axis direction is the thickness direction, and the surface KTl of this substrate 10 is diffused to form the main waveguide 2 and the branch waveguides w.
This forms I3. The main waveguide 2 is formed in a straight line, and a branch waveguide 3 that branches in a straight line from a branch point at the approximate center is adjacent to a portion on the output side from the approximate center of the waveguide.

Therefore, for main waveguide 2.

The light wave incident in the X-axis direction continues straight to the main waveguide 2.
K is configured such that the light is emitted from the branch point or propagated through the branch waveguide 3 from the branch point.

The width W of the main waveguide 20 is from several microns to several lθμ, and the angle formed by the main waveguide 2 on the output side and the branch waveguide 3 depends on the distance between the two output points of the optical switch and the length of the branch waveguide 3. Although the angle is determined, it may be set to, for example, about 2 to 3 degrees. This Ti
The diffused main waveguide 2 and branch waveguide 3 are
1 The refractive index is higher than that of the part that is not diffused, and especially for extraordinary light where the electric field direction is biaxial, the refractive index is about o.
, only ots are higher. When the temperature of the main waveguide 2 and branch waveguide 3 increases by 100° C., the refractive index increases by o, oos to 0.006. In addition, the diffusion depth of Ti is approximately 2.4 μm, which is sufficient to propagate two modes of light waves, TMi and TMi, in the thickness direction. It goes without saying that the intended purpose of the present invention can also be achieved even if the wave path 3 is formed to be able to propagate a single mode light wave.

Thus, 810.810. The insulating layer 5 made of the following is formed to have a layer thickness of approximately 0.2 μm. A heating electrode 4 made of a Ni--Cr alloy is formed on the insulating layer 5. The heating electrode 4 is formed at a suitable length portion behind the branch point in the main waveguide 2 in the light traveling direction (indicated by an arrow in the figure) and in an area directly above the suitable length portion in front of the branch point in the light traveling direction in the branching waveguide 3. It is. The width of the heating electrode 40 may be set to be the same as the width W of the main waveguide 2, etc., or may be set to be narrow so as to be unevenly distributed on the branch waveguide 3 side as shown in the figure. Both ends of the heating electrode 4 are led out to a position away from the area immediately above the main waveguide 2 and the branch waveguide 3, and are connected to a power source V. ■This power supply is.

Either a DC power source or a commercial frequency AC power source may be used, and by energizing the heating electrode 4 using the power source (2), the main waveguide 2 and the branch waveguide 3 located directly below the heating electrode 4 are heated. The length LFi of the heating electrode 4 is set to, for example, about 3 mm, and the end of the heating electrode 4 on the branch waveguide side is connected to the branch waveguide 3.
It is sufficient to extend it to the branch waveguide side until it is separated by about 10 μm from the main waveguide 2 which is adjacent to it. As will be described later, the heating of the branch waveguide 3 by the heating electrode 4 allows the light wave to be heated within the full-branch waveguide 3 to a position where the light wave branched into the single-branch waveguide 3 does not leak out into the adjacent main waveguide 2KK. This is to guide the wave.

In the optical switch configured as described above.

When the heating/heating electrode 4 is not energized, most of the light waves propagating through the main waveguide 2'i go straight through the branch point, when a light wave (for example, TM light) is incident in the X-axis direction from the main waveguide 2. The light is emitted from the main waveguide 2.

The light wave emitted from the branch waveguide 3 has an angle of less than 171° of the incident light. When a voltage is applied to the heating electrode 4 to energize it, the heating electrode 4 generates resistance and the main waveguide 2 in the region directly below it.
And the branch waveguide 3 is heated. Then, as the temperature of this portion rises, the refractive index increases, and for example, 1001C (D When the temperature rises, the refractive index increases by 0.005 to 0°006.

As a result, the light wave that has propagated from the main waveguide 2t to the vicinity of the branch point is deflected toward the branch waveguide 3 side having a high refractive index, propagates mainly through the branch waveguide 3, and is emitted. That is, when the heating electrode 4 is energized, the intensity of the emitted light is concentrated on the branch waveguide 31g, and when the heating electrode 4 is not energized, the light wave travels straight, so the intensity of the emitted light is concentrated on the main waveguide 2 side. The traveling direction of the light wave is controlled by turning on and off the current.

As is clear from the above, in the optical switch of the present invention, the heating electrode 4 is provided to heat the main waveguide 2 and the branch waveguide 3 near the branch point, and therefore is limited by its width. Moreover, it is easy to form because it has a simple shape, and there is no need to arrange multiple electrodes in the width direction of the waveguide in parallel, as in conventional optical switches that utilize the electro-optic effect, so it has a high withstand voltage. The top is not a problem either. This is particularly advantageous when it is possible to operate with single mode light waves, which is advantageous for optical switch FK multiplex communication.

That is, if the waveguide is made into a single mode in both the thickness direction and the width direction, the waveguide width will be less than 5μ, but since the electrode shape is simple, it is easy to form.

No restriction 1 on electrode formation is applied to the narrowing of the waveguide. Historically, since the power source is for heating the heating electrode 4t through resistance, it is only necessary to adjust its effective value as appropriate, and an appropriate power source such as a DC power source or an AC power source at a commercial frequency can be used.

As explained in detail above, the optical switch according to the present invention is easy to manufacture, is not limited by power supply, and the light wave to be operated is not limited by its polarization state, wavelength, etc., and is not operable in the past. White light can also be used. Note that the present invention is not limited to the specific embodiments described above.

Various modifications are possible within the technical scope of the present invention. For example, the material of the substrate 1 may be <LiNb> as described above.
0. In addition to quartz, various types of electric crystals having a refractive index temperature dependence can be used.

Furthermore, it goes without saying that the waveguide formed on the surface of the substrate 10 is not limited to one formed by Ti diffusion. Furthermore, the heating electrode 4
The material is not limited to Ni-0r alloy.

Various metals can be used. Yet again. Thickness direction is Y
If a LiNb 0° crystal cut in the axial direction is used as the substrate, and TE light is used as the light wave.

Even if heating electrodes are formed directly on each waveguide without forming the insulating layer 5, the propagation loss of light waves will not be a problem. Yet again. The lead-out portion of the heating electrode 4 other than the portion on the waveguide may be formed of a metal that generates a small amount of heat, such as Au or At.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view showing one embodiment of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a schematic perspective view of a conventional optical switch, and Fig. 4 is a line taken along the line 01V-IV in Fig. 3. FIG. (Explanation of symbols) 1...Substrate 2...Main waveguide 3...Branch waveguide 4...Heating electrode 5...Insulating layer Patent applicant Ricoh Co., Ltd. - Agent Masaaki Kobi No. 3 Figure 4 Procedural amendment February 19, 1980 Commissioner of the Japan Patent Office Shima 1) Haruki-dono 1 ・11 indications 1982 Patent application No. 156116 2 Title of the invention Optical switch 3 Person making the amendment 1f1・Relationship with Patent applicant name (7618) Patent attorney Xiao Shiqiao Masaaki 5, ? +l
i + Date of E command Self-initiated (] Increased from Supplement + Iヱ
Number of inventions in 1 None 7 Specification to be amended 8 Sleeves + E' contents Contents of amendment 1. In the description, the ``detailed description of the invention'' is replaced with the amendor as follows. Wow. (1) 3rd row from the 1st bottom, “crystal” stop @1r,
A mind that corrects 41 things in ``optics.'' (2) 5th line from the top of No. 5i4, “Crystal J and center Q not t1 “Optics” has been corrected. (3) a4gangbv-etc. lines 5 to 7, “ft1C*
Since an INK power source is required as a power source for driving the optical switch, there are restrictions on the device configuration. ” was deleted. 4jM 1st line from the bottom, “crystal” stopper gong, “optics”
Correct. In the 5th line from the top, correct the word ``white light'' to ``natural light.'' (6) In the second line from 15 Sada F, stop with “中・＼の”.
``Nikoi J [Hr Sei Ding Shin. (7) Page 5, 1st line from the bottom, l-LiNb01.Ll
'l'MO,. Crystal materials such as Te021 quartz" rlr LiN
bO3, PLZT-1 Mitsu, 6A, JJ 9, etc. O optical materials”. (8) 47 Lines 8 to 1 () from above, 1 substrate l is a LiNb0a crystal of dielectric crystal material cut out so that the kZ axis direction is the thickness direction, and Φσtkx r
The substrate 1 is made of LiNb0j, etc. (9) , m711: 111th line r'l'l't
- J and 64', Il" plate etc. kJ correction. (lO) From the 11th Sada, lines 13 to 155 "If this...
In particular, there is an advantage in using the OJ function for single-seven-band light waves, which are advantageous for optical switch multiplex communication. This switch is useful for multi-mode fiber communication systems where refraction changes due to heating are a problem, but optical switches can be used in fast mode, which is advantageous for multiplex communication. Applications to fiber optic systems also have advantages. Insert the statement ``. (II) Line 8 from the top of No. 12, 7 where it says “white light”
1 “°Natural light (LgD light, mercury lamp monochromatic light, etc.)” V
Please correct this. (12) Lines 12 to 133 from the 12th Sada E [Jiya et al.
``Refraction single temperature dependence 會舊 □ Modest disturbance crystals'', ``Quartz, ceramics, glass, - molecular materials, etc., refraction 4-temperature Naoyorikoshakura ku・cho Φ Φ below corrected to "Materials". From now on

Claims (1)

[Scope of Claims] 1. A main waveguide formed on the surface of a substrate and made of an optical transmission medium whose refractive index changes depending on temperature, and a branch waveguide branched from the main waveguide at a branch point. a heating electrode formed over an appropriate length portion of the main waveguide extending from the branch point in a direction opposite to the direction of light propagation; and a heating electrode formed over an appropriate length portion of the branch waveguide extending from the branch point in the direction of light propagation. A light switch comprising: 2. In the above item 1, the heating electrode has a temperature of t! An optical switch characterized in that it is formed with an insulating layer interposed between the i main waveguide and the branch waveguide.