JP5691033B2 - Waveguide type optical gate switch - Google Patents

Description

  The present invention relates to a waveguide-type optical gate switch, for example, a phase change material for turning on / off a waveguide-type optical gate switch, and more particularly, to a configuration for performing amorphization quickly and easily. It is.

  In recent years, with the progress of optical communication systems, the capacity of optical communication networks has been increased, and optical devices having various functions have been developed accordingly. In particular, an optical switch that controls the transmission amount of an optical signal propagating through an optical waveguide is a key device.

  For example, in such an optical switch, a phase change optical switch that performs ON / OFF of an optical signal using a phase change material from the viewpoint of downsizing or increasing the switch speed has attracted attention (for example, Patent Document 1). reference).

  The present inventor has also proposed several optical switches using phase change materials (see, for example, Patent Document 2 or Patent Document 3). For example, in a directional coupler type optical switch using a phase change material, a phase change material portion is provided between a pair of core layers extending in parallel with each other in the directional coupling portion.

  In this configuration, a phase change between a crystalline state and an amorphous state is performed by applying a current pulse to the phase change material portion or irradiating control light. As a result, the complex refractive index (mainly the real part) at the operating wavelength of the phase change material changes, and the optical coupling amount changes with the change in the refractive index of the pair of waveguides, so that the output port is switched. Works as. If attention is paid to one of the input / output waveguides, it is an optical gate switch.

Referring now to FIG. 9, an example of a conventional waveguide-type optical gate switch. Figure 9 is a diagram illustrating the configuration of a conventional waveguide-type optical gate switch, FIG. 9 (a) is a schematic perspective plan view, FIG. 9 (b) 9 (a) in the B-B ' It is a schematic sectional drawing in alignment with the dashed-dotted line which connects.

As shown in the figure, a striped SiO ₂ core layer 63 is provided on a quartz substrate 61 via a lower cladding layer 62, and this SiO ₂ core layer 63 is covered with an upper cladding layer 64. A recess is provided in the upper cladding layer 64 immediately above the SiO ₂ core layer 63, and a phase change material film 65 such as a GST (Ge ₂ Sb ₂ Te ₅ ) film is disposed in the recess.

  In this waveguide type optical gate switch, an optical pulse is applied to the phase change material film 65 to change from a crystalline state to an amorphous state or from an amorphous state to a crystalline state. As a result, the complex refractive index (mainly the imaginary part) at the signal light wavelength of the phase change material film 65 changes and operates as an optical gate switch.

JP 2004-117448 A JP 2006-184345 A JP 2009-128718 A

However, in the configuration of the conventional waveguide type optical gate switch, it is difficult to rapidly reduce the temperature of the phase change material film, and there is a problem that the change from the crystalline state to the amorphous state hardly occurs. There is a problem that it becomes an obstacle to speeding up. In particular, SiO ₂ present in the vicinity of the phase change material has a low thermal conductivity, and thus prevents heat dissipation of the phase change material.

FIG. 10 is an explanatory diagram of the film thickness dependence of the cooling rate of the GST film, FIG. 10 (a) is a simulation model, and FIG. 10 (b) is a simulation result. As shown in FIG. 10 (a), in the simulation, with the length in the width 800nm covers the GST layer 71 of 2000nm in the SiO ₂ film 72 was changed the thickness of the GST layer 71. In the simulation, it is assumed that the thermal conductivity of GST is 1.5 W · m ⁻¹ · K ⁻¹ , the specific heat capacity is 250 J · kg ⁻¹ · K ⁻¹ , and the initial value is 900 K. ing.

As shown in FIG. 10 (b), the temperature of the central portion of the GST film is rapidly cooled as the film thickness is reduced. For example, in the case of a film thickness of 20 nm, the temperature is lowered to about 100 ° C. in 3 ns. On the other hand, although not shown, it was difficult to cool in the time of about 10 ns required for amorphization at the conventional phase change material film thickness of about 200 nm.

  Accordingly, it has been found that in order to facilitate the amorphization for realizing the ON state, it is desirable to reduce the thickness of the phase change material film, in particular, to 100 nm or less.

  An object of the present invention is to increase the heat dissipation efficiency of the phase change material portion and to make the phase change material portion amorphous in a short time.

To solve the above problem,
(1) The present invention provides an optical waveguide comprising a single crystal core layer and a cladding layer surrounding the single crystal core layer, and light propagating through the optical waveguide by changing a complex refractive index provided in the optical waveguide. And a phase change material portion that changes a transmission amount of the phase change material portion, wherein the phase change material portion includes at least a phase change material film having a film thickness of 100 nm or less per layer, and the phase change material. The different material films having higher thermal conductivity than the film are alternately laminated in multiple layers, and are arranged in the divided portion of the single crystal core layer.

In this way, by forming the phase change material film constituting the phase change material part in multiple layers, the film thickness per layer can be reduced, and another material having a high thermal conductivity between the phase change material films. By providing the film, the heat dissipation efficiency can be increased. Thereby, the time required for amorphization by rapidly cooling the phase change material melted by the irradiation of the control light, that is, the switching time can be greatly shortened. In particular, by making the thickness 100 nm or less per layer, it becomes possible to make it amorphous in a few ns as shown in FIG.

( 2 ) Further, according to the present invention, in the above (1), the different material film is any one of Au, Pt, Al, Al ₂ O ₃ , diamond, BN, SiC, and AlN. The different material film may be a material having good thermal conductivity, and a metal such as Au, Pt, or Al, or a dielectric such as Al ₂ O ₃ , diamond, BN, SiC, or AlN may be used. In particular, Al ₂ O ₃ or diamond that is transparent to the control light is suitable.

(3) Further, the present invention is Oite above (1) or (2), between the phase change material layer and the different type material layer, interposing a low protective film hardness than SiO _2. In this way, by interposing a protective film having a hardness lower than that of SiO ₂ , the volume change associated with the phase change of the phase change material film is facilitated, and the film can be prevented from being peeled off, thereby extending the life. Become.

( 4 ) The present invention also provides an optical waveguide comprising a single crystal core layer and a cladding layer surrounding the single crystal core layer, and is propagated through the optical waveguide by changing a complex refractive index provided in the optical waveguide. A waveguide-type optical gate switch having a phase change material portion that changes a transmission amount of light to be transmitted, the phase change material portion being made of a phase change material film having a thickness of 100 nm or less, and the single crystal core A layer is laminated on the layer through a protective film having a hardness lower than that of SiO ₂ .

Thus, heat dissipation efficiency can be improved by forming a phase change material part from a phase change material film with a film thickness of 100 nm or less and laminating on a single crystal core layer with good thermal conductivity. Further, by stacking through a protective film having a hardness lower than that of SiO ₂ , volume fluctuation accompanying phase change can be facilitated.

( 5 ) Moreover, this invention embeds at least one part of the said phase change material part in the recessed part provided in a part of said single-crystal core layer in said ( 4 ). Thus, by making the phase change material portion into an embedded structure, the mismatch between the effective refractive index laminated waveguide portion and the Si waveguide portion in the gate transmission state is reduced, and an optical gate switch with low loss can be configured. it can.

( 6 ) Moreover, the present invention is the above ( 5 ), wherein the recesses are a plurality of recesses having a width of 1/2 or less of the wavelength of light propagating through the optical waveguide, and the interval between the adjacent recesses is set. The wavelength of light propagating through the optical waveguide is ½ or less. In this way, the structure of the phase change material portion becomes invisible from the propagating light by making the fine uneven structure less than 1/2 of the wavelength of the propagating light, so the effect of the structure of the phase change material portion on the light propagation Can be reduced.

( 7 ) Further, the present invention provides the above-mentioned ( 4 ), wherein the phase change material portion is a plurality of divided phase change material film elements having a width of 1/2 or less of the wavelength of light propagating through the optical waveguide, The interval between the adjacent divided phase change material film elements is set to ½ or less of the wavelength of light propagating through the optical waveguide.

  In this way, the structure of the phase change material portion becomes invisible from the propagating light by forming an assembly of fine divided phase change material film elements having a wavelength of 1/2 or less of the wavelength of the propagating light. Can reduce the influence of light on the propagation of light. Moreover, since each divided phase change material film element is fine, the ratio of the surface area is increased, and heat is less likely to stay, so that rapid cooling is facilitated.

( 8 ) Further, according to the present invention, in the above ( 4 ), a part of the single crystal core layer constitutes a multimode interference type 1 × 1 coupler, and the phase change material portion is made to be the multimode interference type. Laminate on 1 × 1 coupler.

  The signal light input to the multi-mode interference type 1 × 1 coupler is condensed once in the multi-mode interference type 1 × 1 coupler and then condensed again at the position where it is coupled to the output waveguide. By providing the portion at the location where the light is condensed, the dimension of the phase change material portion can be reduced. Furthermore, since the width of the lower multimode interference type 1 × 1 coupler is larger than the width of the single crystal core layer, the heat capacity is increased, the heat dissipation characteristics are improved, and the cooling efficiency is increased.

  According to the disclosed waveguide type optical gate switch, the heat dissipation efficiency of the phase change material portion is increased, so that the phase change material film can be amorphized reliably and in a short time, whereby the optical signal can be transmitted. It becomes possible to improve the switching speed of ON-OFF.

It is a notional block diagram of the waveguide type optical gate switch of an embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram of a waveguide type optical gate switch according to a first embodiment of the present invention. It is a schematic sectional drawing of the phase change material part of the waveguide type optical gate switch of Example 1 of this invention. FIG. 5 is a configuration explanatory diagram of a waveguide type optical gate switch according to a second embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a waveguide type optical gate switch according to a third embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a waveguide type optical gate switch according to a fourth embodiment of the present invention. FIG. 10 is a configuration explanatory diagram of a waveguide type optical gate switch according to a fifth embodiment of the present invention. It is a structure explanatory drawing of the waveguide type optical gate switch of Example 6 of this invention. It is a configuration explanatory view of a conventional waveguide type optical gate switch. It is explanatory drawing of the film thickness dependence of the cooling rate of a GST film | membrane.

  Here, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a conceptual configuration diagram of a waveguide type optical gate switch according to an embodiment of the present invention, and FIG. 1A is a schematic cross-section when a phase change material portion is provided in a split portion of a single crystal core layer. FIG. FIG. 1B is a schematic cross-sectional view in the case where the phase change material portion is provided immediately above the single crystal core layer.

  As shown in FIG. 1 (a), a stripe-shaped single crystal core layer 3 is provided between a lower clad layer 2 and an upper clad layer 4 provided on a substrate 1 to constitute an optical waveguide, and a single crystal core layer The phase change material portion 5 is provided in the divided portion 3 to constitute an optical gate portion.

The phase change material portion 5 is formed by alternately laminating a plurality of phase change material films 6 and different material films 7 having higher thermal conductivity than the phase change material films 6. A protective film 8 having a hardness lower than that of SiO ₂ is interposed between the phase change material film 6 and the different material film 7. In the figure, the phase change material film 6 has two layers, but may have three or more layers.

    As the single crystal core layer 3 constituting the optical waveguide in this case, a semiconductor single crystal such as Si, SiGe, InP, GaAs, InGaAsP, InAlAs, InGaAs, GaN, and GaNAs is desirable. In selecting the material, it is necessary to select a material having a low absorption rate in the wavelength band of the optical signal. For example, Si or InGaAsP is desirable in the 1.3 μm to 1.55 μm band.

  As a substrate structure constituting the optical waveguide, an SOI (Sbiconductor on Insulator) substrate formed by a substrate bonding technique or a lateral seeding method to form the single crystal core layer 3, or sapphire having high thermal conductivity. It is desirable to use a SOS (Silicon on Sapphire) substrate using a substrate.

Further, the phase change material film 6 is made of tetrahedral materials such as α-Si, α-Ge, α-GaSb, α-GaAs, α-Sb, Ge-Sb-Te chalcogenide materials, and Sb-Te chalcogenite materials. A material having a proven record in a phase change optical disk such as a chalcogenide material such as AsSe ₃ or AsS ₃ , a transition metal oxide material such as NiO, HfO ₂ , ZrO ₂ , or ZnO is desirable. In particular, the change in the optical absorption due to the phase change large _Ge 2 _-Sb 2 -Te ₅ or _{Ge 6 -Sb 2 -Te 9 Ge-} Sb-Te chalcogenide based materials and the like are desirable.

As the protective film, a phase change in volume in order to facilitate the accompanying changes, _SiO 2 -ZnS mixed film added with ZnS soft SiO ₂ than SiO ₂ is desirable. The SiO ₂ —ZnS mixed film also has an action of preventing the diffusion of the material constituting the phase change material film 6.

The different material film 7 may be a material having a good thermal conductivity, and a metal such as Au, Pt, or Al or a dielectric such as Al ₂ O ₃ , diamond, BN, SiC, or AlN may be used. good. In particular, Al ₂ O ₃ or diamond that is transparent to the control light is suitable. By making such another kind of material film 7 adjacent to the phase change material film 6, it becomes easy to quickly discharge the heat of the phase change material film 6 and make it amorphous in a short time.

  By irradiating the phase change means 6 with control light through the lens 9, the phase of the phase change material portion 5 is changed by changing the complex refractive index of the phase change material film 6. An amorphous state with a small light absorption coefficient is obtained by melting and rapid cooling due to a rapid rise in temperature, and a crystalline state with a large light absorption coefficient is obtained by relatively slow temperature rise and slow cooling to such an extent that it does not melt. At this time, the extinction ratio of the optical signal propagating through the single crystal core layer 3 due to the change in the light absorption coefficient mainly due to the change of the imaginary part of the complex refractive index, not the change of the refractive index mainly due to the change of the real part. Control at high speed.

The extinction ratio depends on the length of the phase change material portion 5 (see Japanese Patent Application No. 2009-182141 if necessary). In the case of using Ge ₂ -Sb ₂ -Te ₅ big change in light absorption due to the phase change material film 6 and to the phase change, by making the length of the phase change material portion 5 than 1.0 .mu.m, The extinction ratio can be set to -30 dB or less.

  Alternatively, as shown in FIG. 1B, a stripe-shaped single crystal core layer 3 is provided between the lower clad layer 2 and the upper clad layer 4 provided on the substrate 1 to form an optical waveguide, and the single crystal A phase change material portion 11 is provided in the vicinity immediately above the core layer 3 to constitute an optical gate portion.

The phase change material portion 11 is formed by covering a phase change material film 12 having a thickness of 100 nm or less with a protective film 13 having a hardness lower than that of SiO ₂ . In this case, the single crystal core layer 3, the phase change material film 12 and the protective film 13 are made of the same materials as those in the waveguide type optical gate switch shown in FIG. The lower limit thickness is desirably 10 nm.

  As described above, when the phase change material portion 11 is provided in the vicinity immediately above the single crystal core layer 3, a recess may be provided in a part of the single crystal core layer 3. By making the phase change material portion 11 into an embedded structure, the mismatch between the laminated waveguide portion and the Si waveguide portion having an effective refractive index in the gate transmission state is reduced, and an optical gate switch with low loss can be configured.

  Further, by forming the concave portion with a plurality of minute concave portions whose width is ½ or less of the wavelength of light propagating through the optical waveguide and whose mutual distance is ½ or less of the wavelength of light propagating through the optical waveguide, Since the structure of the change material part 11 becomes invisible from the propagating light, the influence of the structure of the phase change material part 11 on the light propagation can be reduced.

  Alternatively, the phase change material portion 11 is divided into a plurality of divided phase change material films whose width is ½ or less of the wavelength of light propagating through the optical waveguide and whose mutual interval is ½ or less of the wavelength of light propagating through the optical waveguide. It may consist of elements. Also in this case, since the structure of the phase change material portion 11 becomes invisible from the propagation light, the influence of the structure of the phase change material portion 11 on the light propagation can be reduced. Moreover, since each divided phase change material film element is fine, the ratio of the surface area is increased, and heat is less likely to stay, so that rapid cooling is facilitated.

  Alternatively, a multimode interference type 1 × 1 coupler may be provided in a part of the single crystal core layer 3 and laminated on the phase change material portion 11 multimode interference type 1 × 1 coupler. In this case, the dimensions of the phase change material portion 11 can be reduced, and the heat dissipation characteristics are improved, thereby increasing the cooling efficiency.

Alternatively, two single crystal core layers for propagation and a single crystal core layer for coupling that optically couples between the two single crystal core layers for propagation are provided, and a phase change is formed on the single crystal core layer for coupling. A waveguide type optical gate switch may be configured by laminating material films. In particular, it is desirable that the phase change material film has a thickness of 100 nm or less and 10 nm or more and is laminated via a protective film having a hardness lower than that of SiO ₂ .

  Based on the above, the waveguide type optical gate switch according to the first embodiment of the present invention will be described next with reference to FIGS. FIG. 2 is a configuration explanatory view of the waveguide type optical gate switch according to the first embodiment of the present invention, FIG. 2 (a) is a schematic perspective plan view, and FIG. 2 (b) is a diagram in FIG. 2 (a). It is a schematic sectional drawing along the dashed-dotted line which connects AA 'in FIG.

As shown in the figure, using an SOI substrate, an SiO ₂ film having a thickness of 150 nm to 200 nm formed on the silicon substrate 21 is used as the lower cladding layer 22, and the single crystal silicon layer formed thereon is etched in a stripe shape. Thus, for example, the single crystal silicon core layer 23 having a width of 450 nm and a height of 220 nm is formed. At this time, for example, a divided portion having a length of 2 μm is formed in the single crystal silicon core layer 23, and the phase change material portion 25 is embedded in the divided portion. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24.

FIG. 3 is a schematic cross-sectional view of the phase change material portion of the waveguide type optical gate switch according to the present invention, and the phase change is performed by using a mask sputtering method using a metal mask at the dividing portion formed in the single crystal silicon core layer 23. The material part 25 is formed. Thickness, for example, _Al 2 _{O 3} film 27 and the thickness of 20nm, for example, the 50nm of _Ge 2 _-Sb 2 -Te ₅ Composition of GST film 28 for example a thickness of 10nm of _SiO 2 -ZnS mixed film The protective films 26 are alternately stacked. Finally, the metal mask is replaced with a larger one to form a buried protective film 29 made of a SiO ₂ —ZnS mixed film.

In this case, the interval between the single crystal silicon core layer 23 and the GST film 28 is, for example, about 50 nm to 100 nm. In the drawing, the surface of the buried protective film 29 is shown flat, but since there is not much difference in refractive index between the SiO ₂ —ZnS mixed film and SiO ₂ , this buried protective film 29 is used as the upper cladding layer. It works and does not need to be flat.

  Next, the qualitative operation of the waveguide type optical gate switch according to the first embodiment of the present invention will be described. Assume that the GST film 28, which is a phase change material film, is initially in a crystalline state. Since the absorption coefficient is large in the crystalline state, most of the signal light having a wavelength of 1500 nm propagating through the optical waveguide is absorbed by the phase change material portion 25 and does not pass therethrough.

Here, when a control light pulse having a high pulse width of about 10 ns, for example, about 100 mW, is collected from the upper surface of the substrate with a lens and irradiated to the phase change material portion 25, the temperature of the GST film 28 rapidly increases. Although it melts beyond the melting point, it is rapidly cooled by the action of the Al ₂ O ₃ film 27 that is thin and has excellent thermal conductivity, and changes to an amorphous state. Since the GST film 28 in the amorphous state has a small absorption coefficient, the signal light propagating through the optical waveguide is hardly absorbed by the GST film 28 and is transmitted.

  Note that the wavelength of the control light may be any wavelength that can be absorbed by the phase change material regardless of the state of the phase change material. Here, the wavelength of the control light is 650 nm, which is an easily available laser emission wavelength. If the cooling rate after melting is low, the phase cannot be changed to an amorphous state. The lens (similar to the lens 9 shown in FIG. 1) increases the absorption efficiency by matching the shape of the focused beam spot with the shape of the phase change material portion 25.

  In the first embodiment of the present invention, since the thickness of the GST film 28 is set to 50 nm which is 100 nm or less, the light absorption region can be rapidly cooled in nanosecond order. In addition, in order to perform gate operation at a high extinction ratio, it is necessary to increase the volume of the phase change material, and therefore, here, the GST film 28 of two layers is used for multilayering.

  On the other hand, when the amorphous GST film 28 is irradiated with a control light pulse with a low pulse width of about 100 ns, for example, about 30 mW, the temperature of the GST film 28 rises and becomes higher than the crystallization temperature, but the melting point is Do not exceed. When the GST film 28 is cooled relatively slowly with a long pulse, the GST film 28 changes to a crystalline state again.

  Next, a waveguide type optical gate switch according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration explanatory view of a waveguide type optical gate switch according to a second embodiment of the present invention, FIG. 4 (a) is a schematic perspective plan view, and FIG. 4 (b) is in FIG. 4 (a). It is a schematic sectional drawing along the dashed-dotted line which connects AA '. The basic optical waveguide of the second embodiment is the same as that of the first embodiment.

In the waveguide type optical gate switch according to the second embodiment, the length is, for example, directly above the single crystal silicon core layer 23 via the protective film 31 made of, for example, a 20 nm thick SiO ₂ —ZnS mixed film. A GST film 32 having a Ge ₂ —Sb ₂ —Te ₅ composition of ₂ μm and a thickness of 100 nm or less, for example, 50 nm is deposited by mask sputtering, and the surface is covered with a protective film 33 made of a SiO ₂ —ZnS mixed film. Thus, the phase change material portion 30 is formed. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24. Here, both ends of the GST film 32 are tapered so that the refractive index change continuously changes.

In the second embodiment, since the phase change material portion 30 is merely provided immediately above the single crystal silicon core layer 23, the manufacture is facilitated. In addition, since Si forming the single crystal silicon core layer 23 has high thermal conductivity, it is not necessary to provide another material film made of Al ₂ O ₃ or the like as in the first embodiment, so that the configuration is simplified. The operation of the switch is the same as in the first embodiment.

  Next, a waveguide type optical gate switch according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory diagram of a configuration of a waveguide type optical gate switch according to a third embodiment of the present invention, FIG. 5 (a) is a schematic perspective plan view, and FIG. 5 (b) is a diagram in FIG. It is a schematic sectional drawing along the dashed-dotted line which connects AA '. The basic optical waveguide of the third embodiment is the same as that of the first embodiment.

In the waveguide type optical gate switch of the third embodiment, for example, a recess having a length of 2 μm and a depth of 50 nm is formed on the surface of the single crystal silicon core layer 23. Using a mask sputtering method in the recess, the thickness is, for example, 20 nm _SiO 2 -ZnS protective film 35 via the thickness of a mixed layer is 100nm below, for example, 50 nm of _Ge 2 _-Sb 2 -Te ₅ A GST film 36 having a composition is deposited and the surface thereof is covered with a protective film 37 made of a SiO ₂ —ZnS mixed film to form a phase change material portion 34. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24.

  In the third embodiment, since the phase change material portion 34 is embedded in the recess provided in the single crystal silicon core layer 23, the mismatch between the laminated waveguide portion and the Si waveguide portion having an effective refractive index in the gate transmission state is small. An optical gate switch with low loss can be configured.

  Next, a waveguide type optical gate switch according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a configuration explanatory view of a waveguide type optical gate switch according to a fourth embodiment of the present invention, FIG. 6 (a) is a schematic perspective plan view, and FIG. 6 (b) is a diagram in FIG. 6 (a). It is a schematic sectional drawing along the dashed-dotted line which connects AA '. The basic optical waveguide of the fourth embodiment is the same as that of the first embodiment.

In the waveguide type optical gate switch of the fourth embodiment, for example, grooves 38 having a length of 70 nm and a depth of 50 nm are formed on the surface of the single crystal silicon core layer 23 at intervals of, for example, 30 nm. Using a mask sputtering method in this groove 38, the thickness is, for example, 100 nm or less, for example, 50 nm of Ge ₂ —Sb ₂ — through a protective film 40 made of a SiO ₂ —ZnS mixed film of 10 nm. A GST film 41 having a Te ₅ composition is deposited, and the surface thereof is covered with a protective film 42 made of a SiO ₂ —ZnS mixed film to form a phase change material portion 39. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24.

  In the fourth embodiment, since the GST film 41 is buried in the periodic groove 38 provided in the single crystal silicon core layer 23 to form the phase change material portion 39, the volume of the GST film 41 is larger than that of the third embodiment. Becomes smaller and cooling becomes easier.

Further, the structure as the GST film 41 in this case is a structure in which fine structures with a width of 50 nm are periodically arranged at intervals of 50 nm, and the width and interval are not more than ½ of the wavelength of light propagating through the optical waveguide. Therefore, the structure of the phase change material portion 39 is not visible from the propagation light, and the influence of the structure of the phase change material portion 39 on the light propagation can be reduced.

  Next, a waveguide type optical gate switch according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a configuration explanatory view of a waveguide type optical gate switch according to a fifth embodiment of the present invention, FIG. 7A is a schematic perspective plan view, and FIG. 7B is a diagram in FIG. It is a schematic sectional drawing along the dashed-dotted line which connects AA '. The basic optical waveguide of the fifth embodiment is the same as that of the first embodiment.

In the waveguide type optical gate switch of the fifth embodiment, the waveguide propagation direction is directly above the single crystal silicon core layer 23 via the protective film 44 made of, for example, a 20 nm thick SiO ₂ —ZnS mixed film. the length, for example, 50nm, length of the waveguide propagation vertically, for example, 1000 nm, is 100nm or less in thickness, for example, 50nm of _Ge 2 _-Sb 2 of -Te ₅ composition GST layer 45, for example, 50nm of The phase change material portion 43 is formed by depositing the mask sputtering method at intervals and covering the surface with a protective film 46 made of a SiO ₂ —ZnS mixed film. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24. Note that the length of the entire phase change material portion 43 in the waveguide propagation direction is, for example, 2 μm.

  In the fifth embodiment, since only the GST film 45 having a fine structure is deposited, the manufacturing is facilitated and the volume is reduced, so that the cooling is facilitated. Also in this case, since the width and interval of the GST film 45 are ½ or less of the wavelength of light propagating through the optical waveguide, the structure of the phase change material portion 43 becomes invisible from the propagating light, and the phase change material portion 43 The influence of the structure on the propagation of light can be reduced.

  Next, a waveguide type optical gate switch according to a sixth embodiment of the present invention will be described with reference to FIG. 8A and 8B are configuration explanatory views of a waveguide type optical gate switch according to Embodiment 6 of the present invention, FIG. 8A is a schematic perspective plan view, and FIG. 8B is a diagram in FIG. It is a schematic sectional drawing along the dashed-dotted line which connects AA '. In the sixth embodiment, a multimode interference type 1 × 1 coupler is provided in a part of the single crystal silicon core layer, and other basic configurations are the same as those of the second embodiment.

In the waveguide type optical gate switch according to the sixth embodiment, the thickness provided in a part of the single crystal silicon core layer 23 is, for example, just above the multimode interference type 1 × 1 coupler 47 having a width of 4.0 μm. but, for example, 20 nm of _SiO 2 length through the protective film 49 made of -ZnS mixed film is, for example, a thickness in the 2μm of 100nm or less, for example, a _Ge 2 _-Sb 2 -Te ₅ GST film 50 having the composition of 30nm The phase change material portion 48 is formed by depositing by a mask sputtering method and covering the surface with a protective film 51 made of a SiO ₂ —ZnS mixed film. Next, a SiO ₂ film having a thickness of 150 nm to ₂₀₀ nm is deposited to form the upper cladding layer 24.

  In the sixth embodiment, the characteristic that guided light is periodically condensed in the multimode interference type 1 × 1 coupler 47 is used. That is, the signal light input to the multi-mode interference type 1 × 1 coupler 47 is condensed once in the multi-mode interference type 1 × 1 coupler 47 and then condensed again at a position where it is coupled to the output waveguide. Since the phase change material part 47 is provided in the location which condenses, the dimension can be made small.

  Furthermore, since the multimode interference type 1 × 1 coupler 47 is thicker than the width of the single crystal silicon core layer 23, the heat capacity is increased, the heat dissipation characteristics are improved, and the cooling efficiency is increased. The operation of the switch is the same as in the first embodiment.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower clad layer 3 Single crystal core layer 4 Upper clad layer 5 Phase change material part 6 Phase change material film 7 Different material film 8 Protective film 9 Lens 10 Control light 11 Phase change material part 12 Phase change material film 13 Protective film 21 Silicon substrate 22 Lower clad layer 23 Single crystal silicon core layer 24 Upper clad layer 25, 30, 34, 39, 43, 48 Phase change material portions 26, 31, 33, 35, 37, 40, 42, 44, 46, 49, 51 Protective film 27 Al ₂ O ₃ film 28, 32, 36, 41, 45 , 50 GST film 29 Embedded protective film 47 Multimode interference type 1 × 1 coupler
61 Quartz substrate 62 Lower cladding layer 63 SiO ₂ core layer 64 Upper cladding layer 65 Phase change material film 71 GST film 72 SiO ₂ film

Claims (8)

An optical waveguide comprising a single crystal core layer and a clad layer surrounding the single crystal core layer;
A waveguide-type optical gate switch provided in the optical waveguide and having a phase change material portion that changes a transmission amount of light propagating through the optical waveguide by changing a complex refractive index;
The phase change material portion includes at least a phase change material film having a film thickness of 100 nm or less per layer;
A waveguide type optical gate switch that is configured by alternately laminating multiple different material films having higher thermal conductivity than the phase change material film, and disposed at a dividing portion of the single crystal core layer. _{2. The} waveguide type optical gate switch according to claim 1, wherein the different material film is made of any one of Au, Pt, Al, Al ₂ O ₃ , diamond, BN, SiC, and AlN. 3. The waveguide type optical gate switch according to claim 1, wherein a protective film having a hardness lower than that of SiO ₂ is interposed between the phase change material film and the different material film. An optical waveguide comprising a single crystal core layer and a clad layer surrounding the single crystal core layer;
A waveguide-type optical gate switch provided in the optical waveguide and having a phase change material portion that changes a transmission amount of light propagating through the optical waveguide by changing a complex refractive index;
The waveguide type optical gate switch, wherein the phase change material portion is made of a phase change material film having a thickness of 100 nm or less and is laminated on the single crystal core layer through a protective film having a hardness lower than that of SiO ₂ . 5. The waveguide type optical gate switch according to claim 4 , wherein at least a part of the phase change material part is embedded in a recess provided in a part of the single crystal core layer. The recess comprises a plurality of recesses having a width of 1/2 or less of the wavelength of light propagating through the optical waveguide, and the interval between the adjacent recesses is 1/2 or less of the wavelength of light propagating through the optical waveguide. The waveguide type optical gate switch according to claim 5 . The phase change material portion is composed of a plurality of divided phase change material film elements having a width of ½ or less of the wavelength of light propagating through the optical waveguide, and an interval between adjacent divided phase change material film elements is 5. The waveguide type optical gate switch according to claim 4 , wherein the waveguide type optical gate switch has a wavelength equal to or less than ½ of the wavelength of light propagating through the optical waveguide. Wherein together with a part of the monocrystalline core layer constitutes a multimode interference-type 1 × 1 coupler, the phase change material portion, in claim 4 which is laminated on the multimode interference-type 1 × on 1 coupler The waveguide type optical gate switch described.