JPH04146402A - Optical switch and its production - Google Patents

Abstract

PURPOSE:To offer a waveguide type optical switch which can perform switching with low power consumption by filling a slit provided in a core layer with liquid whose refractive index is nearly equal to that of the core and installing a means for locally heating the liquid. CONSTITUTION:On the way of a waveguide 5, one slit 8 interposing the liquid, whose refractive index is nearly equal to that of the core 3 of the waveguide, is provided so that it forms the angle of about 45 deg. with an optical path, and the intersecting part of the waveguide is cut by the slit 8. A thin film heater 9 consisting of a resistance heating element is formed on a surface near the slit 8. When the liquid in the slit 8 is gasified by energizing the thin film heater 9, light is reflected on the inner surface of the slit 8 and bent to a waveguide branch path 3c side(exit side 13) orthogonally crossed. Meanwhile, by stopping energizing and heating, the periphery of the slit 8 is cooled by heat transmission and the gasified liquid is condensed and restored to the liquid, so that the light advances straight to an optical waveguide branch path 3b(exit side 12) again.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical switch used for switching or blocking the optical path of propagating light, and a method for manufacturing the same.

[Prior Art] As optical communication systems become more sophisticated, there is an increasing need for space-division optical switches with low insertion loss and low tallostoke characteristics.

Conventionally, as shown in FIG. 10, in the above-mentioned optical switch, an air gap G is provided at the intersection of optical fibers (or optical waveguides) a, b, and c, and by injection/removal of liquid in this gear G, A method has been proposed to perform optical switching by controlling the total reflection conditions at the optical fiber and gap interface (Kanayama, Ando; Study on total reflection optical switching by liquid injection, 1986 Institute of Electronics, Information and Communication Engineers Spring National Conference Convention, C-419, pl-196).

[Problem II to be Solved by the Invention] The optical switch shown in FIG. 10 is capable of switching with low insertion loss and almost no polarization dissimilarity in both the reflection state and the transmission state when the intersection angle θ is close to 90°. It is. In order to increase the switching speed with this method, liquid must be injected into and removed from the gap at high speed.

However, in the optical switch described in the above paper, the injection and removal of liquid is performed manually, making high-speed switching difficult.

An object of the present invention is to eliminate the drawbacks of the prior art described above, to perform liquid injection and removal at high speed, and to integrate optical switches of multi-channel optical waveguides on one substrate.

Another object of the present invention is to provide a waveguide optical switch that can perform switching with low power consumption and a method for manufacturing the same.

[Means for Solving the Problems] The optical switch of the present invention has a substantially rectangular core through which light propagates (
An optical waveguide covered with a cladding having a refractive index nw) lower than the cladding with a refractive index <nc), a slit provided in the middle of the core to sandwich a liquid whose refractive index is approximately equal to that of the core, and a slit that sandwiches the liquid locally with a refractive index substantially equal to that of the core. The heating device is configured to include heating means. This involves a step of evaporating the liquid in the slit by heating, and a step of stopping the heating to condense the vaporized liquid and return it to liquid.

The optical waveguide is preferably provided on a flat substrate, with at least a branch path serving as a light input portion and two branch paths serving as a light output portion arranged orthogonally to each other. Therefore, the core of the optical waveguide is configured in a matrix of m rows and n columns (m, n≧2) as necessary.

The slit portion for sandwiching the liquid is approximately 45 mm wide at this orthogonal portion with respect to the optical path propagating within the core of each branch path.
They are arranged so as to form an angle of °.

Specifically, the means for locally heating the liquid is provided as a thin film heater with a power supply line on the upper surface of the cladding provided with the slit portion. In this case, from the viewpoint of power consumption, it is preferable that the thin film heater with the power supply line be covered with an insulator so that it is not in contact with the liquid. It may be provided on the lower surface of the substrate.

The waveguide optical switch in which the thin film heater with a power supply line is covered with an insulator can be manufactured by the following steps (a) to (e).

(a) Step of sequentially laminating a low refractive index layer, a core layer, and a cladding layer as a glass film for a guiding waveguide on a substrate; (b) Forming a metal film and a photoresist film on the cladding layer; (c) Forming slits in the metal film, cladding layer, and core layer using a dry etching process; (d) After peeling off the photoresist film, apply the photoresist film again on the metal film. After patterning, a step of patterning a thin film heater and a power supply line on the metal film by a dry etching process; (e) After that, an insulating film is formed on the pattern of the thin film heater and power supply line; The process of filling the insulating film with liquid.

[Function] When the liquid in the slit is evaporated and vaporized by the heating means, the light that has entered the optical waveguide is totally reflected due to the difference in refractive index at the slit interface, and the light is reflected at the leading waveguide branch orthogonal to the optical waveguide branch. guided by the path. On the other hand, if the heating is stopped and the vaporized liquid is condensed and returned to liquid form, the slit will be filled with a liquid whose refractive index is approximately the same as the material of the core of the leading waveguide, and the light will appear as though there is no slit. Go straight. The light is thus switched.

This liquid injection and removal operation is performed by evaporation and condensation of the liquid by heating and cooling, thereby realizing a high-speed optical switching operation.

Furthermore, by forming the element structure on a substrate, a multi-channel matrix type optical switch can be integrated on one substrate.

When a thin film heater with a power supply line is configured to be covered with an insulator, since the thin film heater is not in contact with the liquid, it is possible to efficiently evaporate and condense the liquid by heating and cooling. Optical switching can be performed with low power consumption. Furthermore, stable optical switching operation can be achieved over a long period of time.

As the optical waveguide material, silicon substrate or glass (
For example, a material whose main component is silicon oxide is used, which is formed into a film on a quartz (quartz) substrate. On the other hand, the liquid material used for the switch portion is suitably one having approximately the same refractive index as the core portion of the optical waveguide, such as methylcyclo.

Core refractive index (n, = 1.460
Examples of liquids with a refractive index close to 1.468) include the following.

CCJ, tetrachloromethane (n = 1.4598. b p ; 76.5 °C)
CJs CNO2 trichloronitromethane (n = 1
．． 46075) CHs Cs H1゜OH methylcyclohexanor (n
= 1.461, bp; 155 °C) (c2H
8) GeCHt CH2C0H (n = 1.461
2. b p; t36℃) C4Ht tc J
Cyclohexyl chloride (n = 1.46216
, b p ; 143.3°C) Cx4H4,7-cyclohexylodadecane (n = 1.4634. b
p; 179℃) HCF CJ CSo C
2H% (n=1.4636.bp; 71°C) c,
Hs F fluorobenzene (n = 1.46412, b p ; 84',
85°C) CsH++OH cyclohexanol (n = 1.4656. b p ; 161.1°C)
CsH1* Turpentine oil (n = 1.4663. b p ; 155°C) where n is the refractive index of the liquid + bP is the boiling point of the liquid.

However, since the essence of the present invention is to combine the refractive indices of the solid part and the liquid part, the above-mentioned combination of the optical waveguide and the liquid material can be selected within the conditions. By mixing two types of soluble liquids (or two or more types), A and B, a liquid with a refractive index close to nw may be realized.

[Examples] The present invention will be described in detail below using illustrated examples.

FIG. 1 is a top view of the optical switch board of the present invention, and FIG.
The figure is an enlarged view of the AA cross section.

The optical waveguide 5 is formed of a structure in which layers of silicon oxide having different refractive indexes are stacked on a flat substrate 1 made of single crystal silicon, and has a substantially rectangular core (refractive index n) through which light propagates.
1) 3 and upper and lower claddings 4.6 having a low refractive index n6 that cover the core.

The optical waveguide core on the substrate has at least three branches 3a and 3b configured to be orthogonal to each other.

3c, and these three branches are placed in a positional relationship where their axes intersect, as shown in FIG. Of these, branch road 3a
serves as a light input section to the optical waveguide core, and the remaining two branches 3b and 3c function as light output sections. here,
For the optical waveguide core (branch 3a) of the light entrance 1lI111, the branch 3b of one exit 1!112 is the entrance (1!11
The other branch 3C on the outlet side 13 is formed on the extension line of the first branch 3a, and is perpendicular to the branch 3a on the inlet side.

In the middle of the optical waveguide 5, a slit 8 for sandwiching a liquid having a refractive index substantially equal to that of the core 3 is provided so as to form an angle of approximately 45° with respect to the optical path propagating within each core channel. The intersecting portions of the optical waveguides are cut by the slits 8.

When the groove of the slit 8 is filled with a liquid having a refractive index almost equal to the material of the core 3 of the optical waveguide, the light travels straight as if the slit 8 were not present. On the other hand, when the liquid in this slit 8 is vaporized, the entrance side 1 of the optical waveguide 5 is
The light entering from the slit interface is totally reflected due to the difference in refractive index at the slit interface, and is guided to the optical waveguide branch 3C on the exit side 13, which is perpendicular to the optical waveguide branch 3a.

The upper surface 14 on the optical switch substrate and the inner surface of the slit 8 are filled with a liquid 6 having the same refractive index as the core 3 of the optical waveguide, as shown in FIG.

In the case of glass whose main component is silicon oxide and whose refractive index n1 is 1.461 for the core 3, if methylcyclohexanol is selected as the liquid, the refractive indexes will almost match. This liquid is supplied to the slit 8 from a liquid storage tank provided on the upper surface of the cladding 4, and this liquid storage tank is made by sealing methylcyclohexanol in a metal paragauge 20, for example, as shown in FIG. configured.

A thin film heater 9 made of a resistance heating element is formed on the surface near the slit 8 as a means for locally heating this portion, that is, the liquid. By energizing the thin film heater 9, only the vicinity of the slit 8 is heated, and the liquid within the slit 8 can be vaporized. At this time, the light is reflected on the inner surface of the slit 8 and bent toward the orthogonal optical waveguide branch 3C side (exit 11!113).

On the other hand, if the electrical heating is stopped, the area around the slit 8 will be immediately cooled by heat transfer, and the vaporized liquid will immediately condense and return to liquid.
) Go straight towards. Note that the surface of the thin film heater 9 is coated with an insulating film to provide insulation from the liquid 6 on the upper surface (however, it is not shown in the figure).

In short, the groove of the slit 8 is filled with a liquid 6 having a refractive index almost equal to the refractive index of the core 3 of the optical waveguide 5, and the thin film heater 9 is formed on the upper surface of the cladding 4 around the slit 8. By energizing this thin film heater 9, only the vicinity of the slit 8 is heated, and the liquid within the slit 8 is vaporized. As a result, the light that was propagating inside the core 3 from the entrance side 11 to the exit @ 12 direction is reflected by the inner surface of the slit 8 because the liquid inside the slit 8 is vaporized, and the light is guided orthogonally. It is bent into the wave core branch 3C and propagated to the exit side 13.

On the other hand, if the electrical heating of the thin film heater 9 is stopped, the area around the slit is immediately cooled by heat transfer, and the vaporized liquid immediately condenses and returns to liquid, so that the light travels straight toward the exit side 12 again. In this manner, by performing the liquid injection and removal operations into the slot 8 by evaporating and condensing the liquid through heating and cooling, high-speed switching operations are realized.

Below, a method for manufacturing the above optical switch will be described.

First, a substantially rectangular orthogonal core optical waveguide 5 is formed on a substrate 1 made of single crystal silicon. This consists of a cladding (hereinafter referred to as a low refractive layer) 2 below the core, a core 3. The portion of the cladding 4 above the core is a laminated buried optical waveguide branch.

For the core 3 part, photolithography is used to
A pattern of orthogonal optical waveguide branches is formed. Low refractive layer 2. The cladding 4 part is 3i0z or 5ift
By doping impurities such as P2O2°B201 into the core 3 and doping impurities such as T i 02 and Ge 02 into the core 3, the refractive index of the core portion is made higher than that of the cladding portion, thereby forming an optical waveguide. be done. The cladding and core films are formed by chemical vapor deposition (cVD),
plasma CVD, etc.) sputtering method.

In this embodiment, the thickness of the low refractive layer 2 and the cladding 4 are 10 μm and 20 μm, respectively, and the core 3 has a thickness of 1 μm.
Both widths are approximately 10 μm.

Next, a slit 8 is formed at the intersection of the optical waveguide branches. It is necessary to dig the trench vertically until the core layer is completely removed, and in this example, it is necessary to dig the trench to a depth of 30 μm or more. On the other hand, the width of the slit 8 is as small as possible, 10 μm.
The following is desirable. In this example, a reactive ion etching (RIB) method is effective for such processing. In this example, a groove with a depth of 35 μm and @8 μm was processed over a length of 60 μm.

Finally, the resistance heating element 8 and the power supply lines 10 and 10 are formed around the slit 8 by vapor deposition of a metal material. For example, chromium is suitable as a material for the resistance heating element constituting the thin film heater 9, and gold or the like is suitable as a material for the power supply, Ill0.10.

The optical switch has cores arranged in a matrix of m rows and n columns (<m, n>2) on a silicon substrate, and a large number of optical switches can be integrated therein.

An example of an integrated optical switch is shown in FIG. here 4
×4 optical switches are formed on one substrate. Arrow 1
Four independent incoming lines indicated by 11-114 are switched and distributed into two outgoing lines indicated by arrows 121-124 and 131-134. Note that switching power supply lines are not shown in this figure to avoid complexity.

The optical switch substrate manufactured as described above is immersed in methylcyclohexanol and sealed. At this time, it is important not to mix impurity gas etc. to prevent the liquid from evaporating.
This is important to keep the condensation temperature constant and ensure reliable operation.

FIG. 4 is an overall configuration diagram of the optical switch.

The substrate is sealed in a metal package 20, and when encapsulating methylcyclohexanol, deaeration is performed so that the inside is filled with pure methylcyclohexanol vapor phase 21 and liquid phase 22. A power supply line 24 for switching is led out from the package 2o with a hermetic seal. The package 20 is surrounded by a heater 25 and a heat insulating material 26 to keep the package temperature higher than the outside air temperature and lower than the boiling point of methylcyclohexanol.

The feature of the above optical switch is that the smaller the size of the slit 8 formed in the optical waveguide 5, the smaller the heat capacity around the slit, so the power supplied to the thin film heater 9 is smaller.
However, the point is that high-speed switching operation is possible.

Furthermore, if the manufacturing method described in the above embodiment is used, it is possible to fabricate a small switch element on a silicon substrate or a glass substrate such as quartz, and a high-speed switching operation of several tens of milliseconds is possible. has the advantage of

FIG. 5 shows a modified embodiment of the thin film heater 9 shown in FIG. That is, the thin layer heater 9 provided on the upper surface of the cladding is formed in a "U" shape, and electricity is supplied from both ends of the thin layer heater 9 through power supply lines 10 and 10. In this way, the thin film heater 9 can be formed into various shapes.

FIG. 6 is a modified embodiment of the liquid storage tank shown in FIG. That is, the liquid 6 is stored in a liquid storage tank 15 provided on the lower surface of the substrate 1, and the liquid 6 is supplied from there to the slit 8.

By the way, in the embodiments shown in FIGS. 1 to 4 above, the thin film heater 9 is in contact with the liquid 6, so the power supply lines 10 and 10 must be covered with an insulator so that they do not come into contact with the liquid 6 and conduct electricity. Also, since the thin film heater 9 is in direct contact with the liquid 6, if the thin film heater 9 is not energized, the slit 8
In addition to the liquid 6 inside, the liquid near the top surface of the thin film heater 9 is also heated.

That is, as a heating method for the liquid in the slit 8, it is inefficient and increases power consumption.Furthermore, since the thin film heater 9 is always in contact with the liquid 6, it lacks long-term reliability due to rust, corrosion, etc. .

FIG. 7 shows an embodiment of a waveguide type optical switch that takes this point into consideration. FIG. 7(a) is a top view, and FIG. 7(b) is a sectional view thereof.

The optical waveguide 5 has a T-shaped optical waveguide structure, as in FIG. 1, and slits 8 are provided at orthogonal intersections. This slit 8 is provided so as to form an angle of approximately 45° with respect to the light propagating from the entrance side 11. By injecting and removing the liquid 6 into the slit 8 by evaporating and condensing the liquid through heating and cooling, the light propagating from the entrance fP111 direction is directed toward the exit side 12 direction or the exit side 13 direction. Switch.

First, the configuration will be explained.

A low refractive index layer 2 (refractive index nb) is formed on a substrate 1, and a substantially rectangular core 3 (refractive index nw) is formed thereon.

nw>n,) is provided. The core 3 is constructed of a so-called buried optical waveguide whose entire surface is covered with a cladding 4 having a refractive index na (ne < nw ). On this cladding 4, a thin film heater 9 (for example, a thin film layer made of Cr or Ti) and a power supply line 10, 10 are patterned. The thin film heater 9 and the power supply line 1
0.10, the entire surface is covered with the insulating layer 16. The refractive index of this insulating layer 16 is preferably approximately equal to the refractive index n of the core 3. Therefore, the material of this insulating layer 16 is approximately the same as the material of the core 3, for example, 5i02, G
A material containing additives for controlling the refractive index such as e, P, Aj, and Zn is used.

A liquid storage tank 7 is provided on this insulating layer 16, and this tank 7 is filled with liquid 6.

The liquid 6 is connected to a thin film heater 9. It is not in contact with the power supply line 10.10 and is insulated by the insulating layer 16. An insulating layer 16 is also formed on the inner wall surface of the slit 8 . This insulating layer 16 can suppress the temperature rise of the liquid 6 in the liquid storage tank 7. In other words, the liquid in the slit 8 can be naturalized with a lower voltage source 17, and high-speed switching becomes possible.

A specific example of the embodiment shown in FIG. 7 will be described.

The substrate 1 is made of S1 or glass (for example, S i O2
(containing at least one kind of additive such as Ge, Ti, P, B, Aj, F, Zn, etc.) is used. The low refractive index layer 2 includes SiO2 or SiO2 containing B, P, and F.
, Ge, etc. is used, and the cladding 4 is also made of the same material. Core 3 contains SiO2 with Ge, Ti, P, AJ, and Z.
n, Er.

A material containing at least one kind of additive such as Nd, Sm, Ce, Tm, F, Na, or B is used.

Cladding 4 (refractive index n.

) or the relative refractive index difference Δ of the low refractive index layer 2 (refractive index nb), nw −nC Δ=() selected to be a mode optical waveguide. The insulating layer 16 is also made of the same material as the core 3.

Note that the low refractive index layer 2. The thickness of the cladding 4 is 10 μm to several 1
The thickness and width of the core 3 are set in the range of 0 μm, and the thickness and width of the core 3 are several μm.
It is selected from the range of −10-odd μm.

The thickness of the insulating layer 16 is selected from a range of several thousand to several μm. The width of the slit 8 is several μm, and the length is several tens of micrometers.
It is selected from the range of μm to 100 μm.

It is desirable that the liquid 6 has a refractive index substantially equal to the refractive index nw of the core 3 and a boiling point as low as possible. For example, fluorobenzene C, H5F < temperature 2
Refractive index at 0℃ 1.46412℃ Boiling point 84.9℃
) can be used.

If, for example, a Ti thin film (thickness: 0.2 μm, width: 20 μm, length: 1 mm) is used for the thin film heater 9, the above-mentioned heater resistance will be approximately 0.5Ω, and the applied power of the voltage source 17 will be approximately 0.
．． By applying 4W, the surface temperature of the thin film heater 9 becomes approximately 120° C., and the liquid in the slit 8 can be vaporized.

Furthermore, considering that the response speed of this optical switch depends on the speed of temperature change on the surface of the thin film heater, the rise and fall times can be expected to be 1 ms.

The embodiment shown in FIG. 7 is a case of a so-called 1×2 type optical switch with one manual operation and two outputs, but the present invention is not limited to the above embodiment.For example, as shown in FIG. , 4
Like the output optical switch, the nxm type optical switch (n,
It can also be applied to m:≧2).

In FIG. 8, arrows 111 and 112 indicate optical fibers 18
1,182 indicates the direction of the optical signal input to the waveguide type optical switch 30, and arrows 121 and 122 indicate the direction of the optical signal input from the optical fiber 18.
3. Direction of the optical signal output from 184 is indicated by arrow 131
, 132 indicate the direction of the optical signals output from the optical fibers 185, 186, and slits 81 to 84 are provided at the intersections of the core branches of the optical waveguide 5, respectively. Although the power supply lines for supplying power to the thin film heaters 91 to 94 are omitted in this figure, they are naturally provided in the actual configuration.

FIG. 9 shows a method of manufacturing the waveguide type optical switch shown in FIGS. 7 and 8.

First, in fa), a core 3 film is formed on a quartz substrate 1, and a cladding 4 film is formed thereon.

Since the low refractive index layer 2 in FIG. 7 uses quartz glass for the substrate 1, this quartz glass also serves as the low refractive index layer 2. The core 3 and cladding 4 are formed by a physical vapor deposition method such as an electron beam evaporation method or a sputtering method, a flame deposition method, or a CVD method.
(including plasma CVD method).

Next, as shown in (b), a metal film 31, such as a Cr or Ti film, is formed on the cladding 4.

This metal 831 is formed by the above-mentioned electron beam evaporation method, sputtering method, or the like. Then, as shown in (c), a photoresist film 32 is applied on this metal film 31, and patterning is performed on the photoresist film 32 by exposure, development, and baking through a photomask.

Next, as shown in (d), this photoresist film 32
Using the pattern as a mask, metal l! is formed through a dry etching process. [Perform step 31 buttering, and further,
Said 7 photoresist film 32. Using the pattern of the metal film 31 as a mask, the cladding 4 and the core 3 are dry etched to form the slits 8.

Next, as shown in (e), first the photoresist film 32 is
After removing the metal film 31, a photoresist film is applied again on the metal film 31. Then, the photoresist film is patterned through the thin film heater 9 and a photomask for forming the power supply lines 10 and 10. Next, dry etching is performed using the pattern of this photoresist film as a mask to remove the metal film 3.
1 is patterned into a thin film heater 9 and a power supply line 10.10. After that, the photoresist film is removed.

Finally, as shown in FIG.
The insulating film 16, which is formed on the slit 8 and covers the entire surface thereof, is formed by a low pressure CVD method, for example, a plasma CVD method so that the inner wall surface of the slit 8 can also be covered.

In the waveguide optical switch manufactured as described above, the thin film heater that evaporates the liquid is not in contact with the liquid through an insulator, and therefore only the liquid near the slit can be locally heated. It is a heating method with low tt power and high efficiency of 14A. Further, since the power supply lines 10 and 10 are also covered with an insulator and are not in contact with liquid, there is no risk of short circuit. Furthermore, since the thin film heater and the power supply line are covered with an insulator, they are stable over a long period of time, and there are no problems such as deterioration due to rust, corrosion, or changes in resistance value.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained.

(1) Locally heating and
Switching operations can be performed by cooling, evaporating, and condensing, thus realizing high-speed optical switching operations.

(2) Since there are no moving parts in the optical switch, reliability against system failure is high.

(3) The manufacturing method is based on phosphorography and etching, which enables miniaturization of elements and integration of switches in multi-channel optical waveguides.

(4) When the thin film heater with a power supply line is covered with an insulator, the thin film heater is not in contact with the liquid, so the liquid can be efficiently evaporated and condensed by heating and cooling. Optical switching operation can be performed stably over a long period of time with low power consumption.

[Brief explanation of the drawing]

FIG. 1 is a top view of an optical switch board showing an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the A-A section in FIGS. 1 and 5, and FIG. 3 is a diagram of a multi-channel optical waveguide. A top view of an optical switch board according to an embodiment of the present invention integrated into a switch,
FIG. 4 is a sectional view showing the overall structure of the optical switch of the present invention, FIG. 5 is a top view of the optical switch substrate showing a modified example of the thin film heater, and FIG. 6 is a second cross-sectional view showing a modified example of the liquid storage tank. An enlarged cross-sectional view similar to the one shown in the figure, and FIG. 7 show an embodiment of the waveguide type optical switch of the present invention in which a thin film heater is covered with an insulator, (a) is a top view, and fb) is a cross-sectional view. , FIG. 8 is a diagram showing an embodiment in which the waveguide type optical switch shown in FIG. 7 is integrated, FIG. 9 is a diagram showing a method for manufacturing the waveguide type optical switch shown in FIG. 7, and FIG. FIG. 2 is a schematic diagram of an optical switch. In the figure, 1 is the substrate, 2 is the lower cladding (low refractive index layer), and 3
is the core, 3a, 3b, 3c are the branches, 4 is the upper cladding,
5 is an optical waveguide, 6 is a liquid, 7 is a liquid storage tank, 8 is a slit, 9 is a thin film heater, 10 is a power supply line, 11 is a light inlet side, 12.13 is a light outlet side, 14 is an optical switch board 15 is a liquid storage tank, 16 is an insulating layer (insulator), 17 is a voltage source, and 20 is a parameter.

Claims (1)

[Claims] 1. An optical waveguide in which a substantially rectangular core through which light propagates is covered with a cladding having a lower refractive index than the cladding, and a liquid provided in the middle of the core with a refractive index substantially equal to that of the core. An optical switch comprising: a slit for sandwiching the liquid; and means for locally heating the liquid. 2. The optical switch according to claim 1, comprising a step of evaporating the liquid in the slit portion by heating, and a step of stopping the heating to condense the vaporized liquid and return it to liquid. 3. The optical switch according to claim 1, wherein the optical waveguide is constructed on a flat substrate. 4. The core on the substrate is composed of at least a branch path serving as a light incident portion and two branch paths serving as a light output portion, these branch paths being arranged orthogonally to each other, and the slit portion sandwiching the liquid, 4. The optical switch according to claim 3, wherein the orthogonal portion is provided so as to form an angle of approximately 45° with respect to the optical path propagating within the core of each branch path. 5. Claim 3, wherein the core of the optical waveguide is configured in a matrix of m rows and n columns (m, n>2).
Light switch as described. 6. The optical switch according to claim 1, wherein the means for locally heating the liquid is a thin film heater with a power supply line provided on the upper surface of the cladding provided with the slit. 7. The optical switch according to claim 6, wherein the thin film heater with a power supply line is covered with an insulator and is not in contact with liquid. 8. The optical switch according to claim 1 or 7, wherein the liquid is supplied to the slit portion from a liquid storage tank provided on the upper surface of the cladding. 9. The optical switch according to claim 1 or 7, wherein the liquid is supplied to the slit portion from a liquid storage tank provided on the lower surface of the substrate. 10. A method for manufacturing an optical switch comprising the following steps (a) to (e). (a) Step of sequentially laminating a low refractive index layer, a core layer, and a cladding layer as a glass film for an optical waveguide on a substrate; (b) Forming a metal film and a photoresist film on the cladding layer; Step of patterning by lithography; (c) Step of forming slits in the metal film, cladding layer, and core layer by dry etching process; (d) After peeling off the photoresist film, apply the photoresist film again on the metal film. (e) After that, an insulating film is formed on the pattern of the thin film heater and the power supply line, and this insulating film is The process of filling the top with liquid.