WO2005017611A1 - 平面光導波回路型光可変減衰器 - Google Patents
平面光導波回路型光可変減衰器 Download PDFInfo
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- WO2005017611A1 WO2005017611A1 PCT/JP2004/011700 JP2004011700W WO2005017611A1 WO 2005017611 A1 WO2005017611 A1 WO 2005017611A1 JP 2004011700 W JP2004011700 W JP 2004011700W WO 2005017611 A1 WO2005017611 A1 WO 2005017611A1
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- optical waveguide
- optical
- adjusting means
- variable
- phase
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
- G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
- G02B6/2935—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
- G02B6/29352—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means in a light guide
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29398—Temperature insensitivity
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/21—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour by interference
- G02F1/225—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour by interference in an optical waveguide structure
Definitions
- the present invention relates to a planar optical waveguide circuit type variable optical attenuator applied to the optical communication field and the like.
- planar optical waveguide circuit type optical variable attenuator As one example of an optical variable attenuator applied to optical communication and the like, there is a planar optical waveguide circuit type optical variable attenuator.
- This planar optical waveguide circuit type optical variable attenuator is formed by forming an optical waveguide layer on a substrate such as silicon, and the optical waveguide layer has a core and a clad (for example, see Non-Patent Document 1).
- FIG. 10 (a) is a plan view showing the configuration of a planar optical waveguide circuit type optical variable attenuator using a Mach-Zehnder optical interferometer circuit 30, and FIG. 10 (b) is a plan view of FIG. It is VIII-VIII sectional drawing of.
- an optical waveguide layer 3 is formed on a substrate 7 made of silicon or the like, and the optical waveguide layer 3 is formed by a core (optical waveguide) 1 and a clad 2 covering the core 1. ing.
- the core 1 forms a Matsuhatsu-Donda optical interferometer circuit 30.
- the Mach-Zehnder optical interferometer circuit 30 includes at least one (here, two) input optical waveguides la and lb, and an optical splitter that splits light input from the input optical waveguides la and lb. 21a, at least one (here, two) output optical waveguides lc, Id, an optical coupling portion 21b provided on the input side of the output optical waveguides lc, Id for coupling light, and an optical coupling portion 21b And two connecting optical waveguides le and If that connect the optical branching section 21a.
- the two connecting waveguides le and If are arranged side by side with an interval therebetween.
- the optical branching part 21a and the optical coupling part 21b are each formed by two cores 1 arranged side by side in close proximity to each other.
- 2 la and the optical coupling section 21b are formed by a 2 ⁇ 2 directional optical coupler.
- the optical circuit device shown in Fig. 10 (a) has two connection optical waveguides le and If of the Mach-Zehnder optical interferometer circuit 30, and the phase of the propagating light propagating through the connection optical waveguides le and If, respectively.
- Phase adjusting means 8a and 8a 'for adjustment are formed. These phase adjusting means 8a, 8a 'are formed, for example, by thin film heaters 9a, 9a', and are provided above the cladding 2.
- phase shifter is formed by the phase adjusting means 8a and 8a 'and the phase portion connecting optical waveguides Is and It formed below the formation region of the phase adjusting means 8a and 8a'.
- reference numeral 23 denotes an electrode for supplying power to the thin film heaters 9a and 9a '.
- the phase adjusting means 8a and 8a ' have the same configuration. For example, by operating only the phase adjusting means 8a, the following operation is performed.
- thermo-optic effect which is a phenomenon in which the refractive index of silica-based glass or the like changes with temperature, and the above-described effect changes the phase of light propagating through a core whose refractive index has changed.
- the propagating lights propagating through le and If have a phase difference from each other.
- the effective optical waveguide length of the heated phase portion connection optical waveguide Is changes due to the thermo-optic effect due to the heat generated by the thin film heater 9a as the phase adjusting means 8a.
- the optical circuit device shown in FIG. 10A is an optical waveguide interferometer with variable light transmittance and light branching ratio, and can obtain the function of a variable optical attenuator.
- the phase adjusting means 8a ' is provided as a spare when the phase adjusting means 8a breaks down, for example.
- the temperature coefficient dnZdT of the refractive index of the silica glass forming the core so 10- 5 (lZ ° C) degree, cotton, for example, the length of the 5mm If the temperature of the core 1 is increased by 20 ° C., the effective optical path length of the core 1 changes by about 1 m.
- the characteristic line a in FIG. 11 is the input power in the planar lightwave circuit type optical variable attenuator shown in FIG. 6 is a characteristic line showing a relationship between force and insertion loss. From this characteristic line a, it can be seen that an optical attenuation of about 10 dB is obtained for an input power of about 430 mW, and a maximum optical attenuation of 22.5 dB is obtained for an input power of 520 mW.
- the characteristic line b in Fig. 11 shows the difference (PDL: polarization) between the input power and the insertion loss (TE polarization and TM polarization) in the planar lightwave circuit type optical variable attenuator shown in Fig. 10. (Dependency loss). From the characteristic line a and the characteristic line b, it can be seen that the difference due to the polarization of the insertion loss when the optical attenuation is about 10 dB is about ⁇ 2 dB.
- Such an optical variable attenuator is used in an optical wavelength division multiplexing (WDM) system in, for example, a backbone network of an optical communication system.
- WDM optical wavelength division multiplexing
- a rare-earth-doped optical fiber amplifier that amplifies light of multiple wavelengths simultaneously is used.
- the optical amplification efficiency has wavelength characteristics, a difference in light intensity depending on the wavelength occurs.
- only light of a specific wavelength is separated or inserted in the middle of a transmission path, a difference in light intensity depending on the wavelength also occurs there.
- a variable optical attenuator is used to accurately and dynamically equalize the light intensity difference due to the wavelength. Since the light intensity difference due to such a wavelength is about 0 to 10 dB, the range of the optical attenuation normally required for the optical variable attenuator is about 0 to 10 dB.
- Non-Patent Document 1 “Development of Variable Optical Attenuator” Sumimoto et al., Showa Electric Cable Review, Vol. 52, No. 1 (2002)
- a large amount of light attenuation for example, 30 dB or more, may be required when the communication device is maintained or when only a specific channel is stopped.
- highly accurate control of the amount of light attenuation is not required. Therefore, there has been a demand for a planar lightwave circuit-type optical variable attenuator that can obtain an arbitrary amount of optical attenuation with high accuracy in an optical attenuation amount range of about 0 to 10 dB and a large optical attenuation of 30 dB or more. .
- the Mach-Zehnder optical interferometer circuit 30 obtains the optical attenuation using interference, it is said to be 30 dB or more.
- both the two planar lightwave circuit type optical variable attenuators must be set to the maximum optical attenuation.
- a lightwave circuit type optical variable attenuator twice the power required to obtain the maximum light attenuation is required. Therefore, the maximum power is required for an optical variable attenuator for an optical line where optical communication is not performed, such as during maintenance of a communication device, and there is a problem that much power is wasted, which is not practical.
- the circuit size is approximately doubled because two conventional planar lightwave circuit type optical variable attenuators are cascaded. There was also a title.
- the present invention has the following configurations as means for solving the problems.
- a first aspect of the present invention includes a substrate, and an optical waveguide layer having a core and a clad formed on the substrate, wherein the core includes at least one input optical waveguide, An optical branching unit that branches light input from the optical waveguide, at least one output optical waveguide, an optical coupling unit provided on an input side of the output optical waveguide, the optical coupling unit, and the optical branching unit And a Mach-Zehnder optical interferometer circuit having two connection optical waveguides arranged side by side with an interval therebetween, and provided in at least one of the two connection optical waveguides to adjust the phase of the propagating light.
- a phase adjusting means for variably adjusting the light input;
- a slit formed in the optical waveguide layer in a direction intersecting the optical waveguide at a longitudinally intermediate portion of the optical waveguide and at least one of the optical output waveguides;
- a liquid refractive index matching agent having a refractive index close to the refractive index; a position including a path of the transmitted light in the optical waveguide of at least one of the optical input waveguide and the optical output waveguide;
- a means for solving the problem is provided by a configuration having a matching agent moving means for moving the refractive index matching agent in the slit to one of the positions deviated from the passing force.
- the phase adjustment means provided in each of the two connection optical waveguides includes two connection optical waveguides. This is a means for solving the problem with a configuration that is a phase control means for controlling the phase by making the rates of change of the polarization difference of the phase of the propagating light to be different from each other.
- the phase adjusting means provided in each of the two connection optical waveguides includes two of the connection optical waveguides. This is a means for solving the problem by having a configuration as a birefringence index adjusting means for making the change rates of the birefringence of the connecting optical waveguide different from each other.
- a fourth aspect of the present invention in addition to the configuration of the third aspect described above, the distance between the forming portions of the phase adjusting means provided on at least one of the two connection optical waveguides is reduced.
- a means for solving the problem is provided by providing a stress adjusting unit for releasing or increasing the stress applied to the connection optical waveguide at the time of phase adjustment by the phase adjusting means.
- the stress adjustment unit includes:
- the two connection optical waveguides each include the phase adjusting means having a heating means. At least one of the phase adjusting means is formed at an interval.
- the above-mentioned area is provided as a means for solving the problem by a configuration in which a heat insulating means for suppressing diffusion of heat applied to the connection optical waveguide by the heating means is formed.
- connection optical waveguide force interval of the optical waveguide layers on both sides of the phase adjusting means forming portion is set.
- An optical waveguide removing portion formed by removing a part of the optical waveguide layer is formed as a free space along a longitudinal direction of the connection optical waveguide in a region where the optical waveguide layer has been removed.
- each of the two connection optical waveguides is provided with the phase adjusting means, and one of the connection optical waveguides is provided.
- the heat insulating means extends along a longitudinal direction of the connection optical waveguide in a region interposed with the connection optical waveguide.
- the present invention is a means for solving the problem with a configuration in which the optical waveguide layer is removed from the optical waveguide layer.
- a tenth aspect of the present invention is the same as the seventh aspect, except that one of the two connection optical waveguides juxtaposed to each other is a first connection optical waveguide and the other is a first connection optical waveguide.
- a second connecting optical waveguide wherein the first connecting optical waveguide is formed with first and fourth phase adjusting means, which are the phase adjusting means, sequentially in the longitudinal direction at an interval, and the second connecting optical waveguide;
- Third and second phase adjusting means which are the phase adjusting means, are sequentially formed in the optical waveguide at intervals in the longitudinal direction, and the first phase adjusting means has the same structure as the third phase adjusting means.
- the second phase adjustment means has the same configuration as the fourth phase adjustment means, and the first recess is provided with a first recess at a first distance beside the first phase adjustment means. It is formed as an optical waveguide layer removed portion, and is substantially equal to the first distance beside the third phase adjusting means. A third recess is formed at a third distance as the optical waveguide layer removed portion, and a third recess is formed on a side of the second phase adjusting means at a second distance different from the first distance.
- the second concave portion is formed as the optical waveguide layer removing portion, and the fourth phase adjusting means is formed.
- a fourth recess is formed at the side of the step at a fourth distance substantially equal to the second distance as the optical waveguide layer removed portion.
- an eleventh aspect of the present invention in addition to the configuration of any one of the seventh to tenth aspects, further comprises the optical waveguide layer removing section, wherein the optical waveguide layer removing portion is provided on a surface of the substrate. It is formed by removing it all the way to the surface!
- the substrate further comprises a substrate removing portion formed below the optical waveguide layer removing portion.
- the substrate removing portion has a concave cross-sectional shape having a portion wider than a lower portion of the optical waveguide layer removing portion.
- the matching agent moving means is provided around at least a part of the slit. This is a means for solving the problem with a configuration having a thin film heater.
- the phase adjusting means includes a thin-film heater provided on the connection optical waveguide.
- the optical waveguide layer has a configuration in which the optical waveguide layer is made of a silica-based glass.
- a seventeenth aspect of the present invention provides a means for solving the problem with a configuration in which the substrate is a silicon substrate, in addition to the configuration of any one of the first to sixteenth aspects.
- an eighteenth aspect of the present invention solves the problem with the configuration of any one of the first to seventeenth aspects, in which the slit is sealed with a glass plate. Means.
- a nineteenth aspect of the present invention provides the glass plate according to the eighteenth aspect, In addition, a configuration in which the adhesive is bonded to the optical waveguide layer around the slit with an adhesive is used as means for solving the problem.
- a twentieth aspect of the present invention has a problem in that, in addition to the configuration of the eighteenth aspect, the glass plate is joined to the optical waveguide layer around the slit by low-melting glass. As a means to solve the problem.
- a metal film is interposed between the glass plate and the optical waveguide layer, and the metal of the metal film is formed.
- the glass plate and the optical waveguide layer are joined together by diffusion to solve the problem.
- a twenty-second aspect of the present invention provides a means for solving the problem, in addition to the configuration of the twenty-first aspect, wherein the metal film has a configuration made of copper or a copper alloy.
- an inert gas is enclosed in the slit together with the refractive index matching agent.
- liquid refractive index matching is provided in a slit intersecting the output or input optical waveguide of the Mach-Zehnder optical interferometer circuit formed by the core of the optical waveguide layer, and intersecting the longitudinal middle of the optical waveguide. Add the agent.
- the refractive index matching agent has a refractive index that is equal to or close to the refractive index of the core of the optical waveguide layer.
- the refractive index matching agent in the slit is evacuated from the path of the propagating light in the output or input optical waveguide.
- the amount of optical attenuation in the output or input optical waveguide can be made extremely high, for example, 35 dB or more.
- the matching agent can be moved in the slit with low power, and the slit can be reduced in size as compared with a planar optical waveguide type variable optical attenuator. A large amount of light attenuation can be obtained.
- FIG. 1 (a) is a main part configuration diagram showing a first embodiment of a planar optical waveguide circuit type optical variable attenuator according to the present invention
- FIG. 1 (b) is a diagram of FIG. 1 (a).
- FIG. 1 (c) is a sectional view taken along line II II of FIG. 1 (a).
- FIG. 2 (a) -FIG. 2 (e) show a manufacturing process of the planar optical waveguide type optical variable attenuator according to the first embodiment of the present invention, taken along the line II in FIG. FIG.
- FIG. 3 (a) —FIG. 3 (f) show a manufacturing process of the planar optical waveguide circuit type variable optical attenuator according to the first embodiment of the present invention along line II-II in FIG. 1 (a). It is explanatory drawing shown in a cross section.
- FIG. 4 (a) is a plan view showing an operation state of the planar optical waveguide circuit type optical variable attenuator according to the first embodiment of the present invention which is different from the state shown in FIG. 1, and FIG. 4 (b) Is a cross-sectional view taken along line II-II in FIG. 4 (a).
- FIG. 5 is a view showing insertion loss and PDL in the state shown in FIG. 1 and power input to the first phase shifter in the planar optical waveguide circuit type optical variable attenuator according to the first embodiment of the present invention. It is a graph which shows the relationship of quantity.
- FIG. 6 is a schematic plan view of a principal part of a second embodiment of a planar optical waveguide circuit type variable optical attenuator according to the present invention.
- FIG. 7 (a) is a sectional view taken along line III-III of FIG. 6,
- FIG. 7 (b) is a sectional view taken along line IV-IV of FIG. 6,
- FIG. 7 (c) is a sectional view taken along line V-V of FIG. It is.
- FIG. 8 is a cross-sectional view showing another state of the refractive index matching agent in the optical shutter of the third embodiment of the planar optical waveguide circuit type variable optical attenuator according to the present invention.
- FIGS. 9 (a) to 9 (h) are cross-sectional views showing a manufacturing process of an optical shutter section in a planar optical waveguide circuit type variable optical attenuator according to a third embodiment of the present invention. .
- FIG. 10 (a) is an explanatory view of a main part showing a conventional planar optical waveguide circuit type optical variable attenuator, and FIG.
- FIG. 10 (b) is a sectional view taken along line VI-VI of FIG. 10 (a).
- FIG. 11 is a graph showing the relationship between the amount of power input to a phase shifter, the insertion loss, and the PDL in the conventional planar optical waveguide type optical variable attenuator shown in FIG.
- the planar lightwave circuit type optical variable attenuator of the first embodiment includes a Mach-Zehnder optical interferometer circuit 30 formed by a core 1 and phase adjusting means 8a, 8a.
- the circuit configuration of the Matsuhazunda optical interferometer circuit 30 is substantially the same as that of the conventional Mach-Zehnder optical interferometer circuit 30 shown in Fig. 10 (a).
- the output optical waveguide Id of the Mach-Zehnder optical interferometer circuit 30 is formed, for example, 2 mm longer than the output optical waveguide lc.
- a slit 12 is formed in the middle of the longitudinal direction of the output optical waveguide Id in a direction crossing the output optical waveguide Id, and the slit 12, the refractive index matching agent 13 provided in the slit 12 and the slit 12 are formed.
- the optical shutter unit 50 having the matching agent moving means 1 la and 1 lb for moving the refractive index matching agent 13 to a position including the path of the propagating light of the output optical waveguide 1 d and a position retracted from the path of the propagating light is provided. Established.
- the refractive index matching agent 13 is provided in a part of the slit 12, and also has a liquid silicon-based oil force having a refractive index close to (here, substantially equal to) the refractive index of the core 1.
- the slit 12 is filled with a refractive index matching agent 13 and a gas 14 such as nitrogen gas which is an inert gas.
- the matching agent moving means 11a and lib are formed by thin film heaters 16a and 16b.
- the thin film heaters 16a and 16b are formed in a substantially U-shape so as to surround the slit 12.
- reference numerals 26 and 27 denote optical input units
- reference numerals 28 and 29 denote optical output units, respectively.
- the optical branching part 21a and the optical coupling part 21a of the Mach-Zehnder optical interferometer circuit 30 are formed to have the same length, and the coupling efficiency r? Of the optical branching part 21a and the optical coupling part 21b is: In each case, it is set to be 50% for light of wavelength 1.55 m.
- the connecting optical waveguides le and If are formed to have the same length, and the connecting optical waveguides 1 e and If each have a straight portion having a length of 5 mm in the longitudinal direction. They are arranged in parallel at 250 m intervals. Phase adjustment means 8a, 8a 'formed by thin-film heaters 9a, 9a' are formed on the straight portions of the connection optical waveguides le, If, respectively, as in the conventional example shown in Fig. 10 (a). I have.
- FIG. 1 (b) shows a cross-sectional view taken along the line II of FIG. 1 (a), and as shown in FIGS. 1 (a) and 1 (b), the formation of the phase adjusting means 8a, 8a ′ In the optical waveguide layer 3 on both sides of the portion, the area from the surface of the optical waveguide layer 3 to the surface of the substrate 7 along the longitudinal direction of the connection optical waveguide le, If The optical waveguide layer removed portion 5 is formed by being removed in the thickness direction. The optical waveguide layer removing portion 5 is formed by removing the optical waveguide layer 3 until it reaches the surface of the substrate 7, and is spaced from the phase portion connecting optical waveguide Is, It. It is formed in parallel with the phase connection optical waveguide Is, It.
- the optical waveguide removing unit 5 is configured to release the stress applied to the connection optical waveguides le and If when the phase adjustment is performed by the phase adjustment means 8a and 8a ′.
- the wave paths le and 1 f are arranged so as to be in contact with the free space for stress release at an interval.
- the stress due to the thermal expansion of the optical waveguide layer is sufficiently released in the direction perpendicular to the substrate, and the thermal expansion of the optical waveguide layer is horizontal in the direction parallel to the substrate. Is not sufficiently released, a new anisotropic internal stress is generated, and the birefringence of the optical waveguide layer is further increased by the anisotropic stress.
- the amount of phase change in the phase shifter part differs between the TE polarized light and the TM polarized light, which are the two polarized lights existing in the optical waveguide circuit, and the light propagating through the connection optical waveguides le and If is different.
- the difference in optical attenuation determined by the phase difference, PDL occurs.
- the birefringence of the optical waveguide layer 3 in the region where the connecting optical waveguides le and If are formed and the vicinity thereof is increased. Restrained.
- the heat applied to the connection optical waveguides le and If by the thin film heaters 9a and 9a ′ as the heating means is transmitted to the outside of the region near the phase adjusting means 8a and 8a ′. It also functions as a heat insulating means for suppressing this.
- the heat of the thin-film heaters 9a and 9a 'forming the phase adjusting means 8a and 8a' is configured to be efficiently transmitted to the phase portion connecting optical waveguides Is and It.
- the thin-film heaters 9a and 9a ' are connected to, for example, a power supply wiring (not shown) similar to the power supply wiring 23 shown in FIG.
- the long side of the slit 12 forms an intersection angle ⁇ of 45 degrees with the optical axis of the output optical waveguide Id, and has a width of 30 m and a length of 250 m. Is formed.
- a region formed on the side where propagation light is input to the slit 12 is denoted by ly, and a region formed on the side where propagation light is output from the slit 12 is denoted by ly. Indicated by lz.
- FIG. 1 (c) is a cross-sectional view taken along the line II-II of FIG. 1 (a), and the slit 12 extends from the surface of the optical waveguide layer 3 to the surface of the substrate 7.
- the slit 12 is sealed with a lid 15 having a borosilicate glass plate strength. It is adhered on the upper cladding layer 2 by an adhesive (not shown).
- the thin film heaters 16a, 16b forming the matching agent moving means 11a, lib are formed on the upper cladding layer 2 near the slit 12, and near both ends in the longitudinal direction of the slit 12. In addition, it is formed in a U-shape so as to surround the slit 12.
- the slit 12 and the output optical waveguide Id intersect at an intersection 24 near the thin film heater 16a.
- V power supply wiring (not shown) is connected to the thin-film heaters 16a and 16b.
- variable optical attenuator Next, a method for manufacturing the variable optical attenuator according to the present embodiment will be described with reference to the drawings.
- FIG. 2 and 3 are explanatory diagrams for explaining a method of manufacturing the planar optical waveguide type variable optical attenuator of the present embodiment.
- Fig. 2 shows the state of each step of the manufacturing process of the planar optical waveguide circuit type optical variable attenuator by a cross-sectional view taken along the line II in Fig. 1 (a).
- the state of each manufacturing process of the circuit-type variable optical attenuator is shown by a cross-sectional view taken along line II-II in FIG. 1 (a).
- a lower cladding layer 2a having a thickness of 20 m and a film were formed on a silicon substrate 7 by using a flame hydrolysis deposition method (FHD method).
- the layer of the core 1 having a thickness of 6 m is formed.
- GeO is added to the layer of the core 1 so that the refractive index of the layer of the core 1 is 0.8% higher than that of the lower cladding layer 2a.
- an optical waveguide circuit of a core 1 having a width of 6.5 / zm is formed by photolithography and dry etching.
- the optical waveguide circuit of the core 1 is formed as shown in FIG.
- FIG. 2 (b) is shown by a cross section taken along the line II in FIG. 1 (a)
- the core 1 is connected to the phase portion connecting optical waveguide Is, of the linear portion of the connecting optical waveguide le, If.
- the cross section of It is shown
- FIG. 3 (b) is a cross section taken along the line II-II of FIG. 1 (a), so that the core 1 is a cross section of the output optical waveguide Id at a portion corresponding to the intersection 24. It is shown.
- an upper cladding layer 2b having a thickness of 20 m is formed using the FHD method, and the optical waveguide circuit of the core 1 is formed inside the cladding 2.
- an optical waveguide layer 3 is formed using the FHD method, and the optical waveguide circuit of the core 1 is formed inside the cladding 2.
- FIG. 2 (d), FIG. 3 (d) and FIG. 1 (a) a sputtering method and a lift-off method were used.
- the upper surface of the optical waveguide layer 3 corresponding to each linear portion of the connecting optical waveguides le and If (the phase connecting optical waveguide Is, It) and the longitudinally opposite ends of the slit 12 correspond to a shape surrounding a U-shape.
- the thin film heaters 9a, 9a ', 16a, and 16b made of Ta are provided in the portions to be formed.
- the thin film heaters 9a and 9a ' are formed to have a length of 5 mm, a width of 10 m, and a film thickness of 1.0 m.
- the length in the side direction is 110 ⁇ m, ⁇ 20 ⁇ m, and the film thickness is 1. O / zm.
- a power supply wiring (not shown) composed of three layers of Ti / Ni / Au is formed by a method similar to the method of manufacturing the thin film heaters 9a, 9a ', 16a, and 16b.
- an insulating film (not shown) made of SiO2 for protecting and insulating the thin film heater and the power supply wiring is formed by sputtering.
- both sides of the thin film heaters 9a and 9a ′ forming the phase adjusting means 8a and 8a ′ are sandwiched.
- An optical waveguide layer removing section 5 is formed in the optical waveguide layer 3.
- the optical waveguide layer removing section 5 removes the region which is parallel and spaced along the longitudinal direction of the linear portion of the connection optical waveguide le, If by dry etching until reaching the surface of the optical waveguide layer 3, the surface force substrate 7 and the surface.
- the dimensions of the optical waveguide layer removing portion 5 are, for example, 5 mm in length and ⁇ in width.
- the optical waveguide layer in the region corresponding to the slit 12 is similarly removed to form the slit 12.
- the slit 12 has a width of 30 ⁇ m and a length of 250 ⁇ m.
- An intersection 24 is formed so as to intersect with the output optical waveguide Id at a position 50 m from the slit end near the film heater 16a.
- a refractive index matching agent 13 is injected into the slit 12.
- the refractive index matching agent 13 is injected, for example, in such an amount that the third thin film heater 16a side of the slit 12 is about half-filled, so that the intersection 24 is filled with the refractive index matching agent 13.
- the lid 15 is adhered on the slit 12 with an adhesive in an atmosphere of nitrogen gas which is a gas 14 and sealed to form an optical shutter section 50.
- the signal light is input from the optical input section 26 of the input optical waveguide la, and is branched at the optical branching section 21a, then propagates through the connecting optical waveguides le and If, is coupled at the optical coupling section 21b, and propagates to the output optical waveguide Id. Then, the propagating light propagates toward the light output end 29 through the slit 12 provided in the middle of the output optical waveguide Id.
- the intersection 24 Since the refractive index of the core 1 is substantially equal to that of the core 1 and is filled with the refractive index matching agent 13, the loss of signal light when passing through the intersection 24 is very small, for example, about 0.2 dB.
- the signal light that has entered the intersection 24 of the slit 12 from the region ly of the slit 12 propagates to the region lz where almost no reflection occurs on the slit wall surface.
- the refractive index of the refractive index matching agent 13 is higher than, for example, the refractive index of the upper cladding layer 2.
- the optical shutter section 50 has a light attenuation amount of about 0 to 10 dB due to the phase adjustment by the phase adjusting means 8 a and 8 a ′ formed in the Mach-Zehnder optical interferometer circuit 30 having almost no light attenuation. Any light attenuation can be obtained in the range.
- the thin film heater 9a when the thin film heater 9a is energized and heated, the effective optical waveguide length of the phase part connection optical waveguide Is is changed by the thermo-optic effect due to heat generation, and the phase of light propagating through the phase part connection optical waveguide Is is changed.
- the light transmittance of the Matsuhazu-Sunder optical interferometer circuit 30 it is possible to obtain an arbitrary amount of optical attenuation in a range of about 0-10 dB, as in the conventional variable optical attenuator. .
- the thin film heaters 16a and 16b of the optical shutter unit 50 are both non-power-supplying. It is held at 24. This is because when the gas and the liquid are sealed in the narrow slit 12, the liquid has a property of being held at one end of the slit 12 due to surface tension.
- the surface tension of the refractive index matching agent 13 on the thin-film heater 16a side of the slit 12 decreases, so that the slit 12 extends along the longitudinal direction of the slit 12.
- a gradient is generated in the surface tension of the refractive index matching agent 13 of FIG. Since the liquid in the narrow slit 12 moves in the direction of high surface tension and the gas 14 moves in the direction of low surface tension, if such a gradient of surface tension occurs, the liquid refractive index matching agent 13 Is heated
- the thin film heater 16b moves to a position where the passing force of the propagating light of the output optical waveguide Id is also saved.
- the intersection 24 is then filled with gas 14.
- FIG. 4 (a) is a cross-sectional view taken along the line II-II of the optical shutter unit 50 in FIG. 4A.
- the optical variable attenuator of the first embodiment does not drive the phase adjusting means 8a, 8a 'of the Matsuhatsu-Zonda optical interferometer circuit 30 and also controls the thin film heaters 16a, 16b of the optical shutter unit 50. Therefore, a large optical attenuation of about 35 dB or more can be obtained in a completely unpowered state without supplying power.
- the phase adjusting means 8a, 8a ′ of the Mach-Zehnder optical interferometer circuit 30 for example, if the optical attenuation in the Mach-Zehnder optical interferometer circuit 30 is set to 20 dB, the optical variable attenuator Very large light attenuation of about 55 dB or more can be obtained.
- the insertion loss in the unpowered state was measured.
- the insertion loss for dB and TM polarization was 1.22 dB. This is about 0.2 dB higher than the insertion loss of the conventional variable optical attenuator, and it can be understood that the loss is increased by the slit 12.
- the insertion loss increases with an increase in the amount of supplied power, and the maximum insertion loss of 25. OdB is obtained at about 72 mW.
- the optical attenuation which is the difference from the insertion loss in the initial state where the power input is OmW, is a maximum of about 23.8 dB.
- the insertion loss of about 11.2 dB was obtained up to about 58 mW. As a result, good PDL characteristics of about 0.5 dB or less have been obtained.
- the supply of electric power to the phase adjusting means 8a is stopped, and the thin-film heater 16a is supplied with electric power and heated, and as shown in FIGS. 4 (a) and 4 (b), the refractive index matching agent 13 is supplied to the thin-film heater 16a.
- the power supply to the thin film heater 16a was stopped.
- the refractive index matching agent 13 was held at the slit end on the fourth thin-film heater 16b side by the capillary force.
- the insertion loss at this time was measured, it was 41.5 dB.
- the optical attenuation which is the difference from the insertion loss in the initial state, is as high as 40 dB or more.
- the power of about 72 mW was supplied only to the phase adjusting means 8a, and the insertion loss was measured. As a result, 65.3 dB was obtained. At this time, it can be seen that the optical attenuation, which is the difference from the insertion loss in the initial state, is a very high value of about 60 dB or more.
- the Mach-Zehnder optical interferometer circuit 30 in which the optical waveguide layer removing section 5 is formed in the vicinity of the connection optical waveguides le and If, and the connection optical waveguides le and If
- the phase adjusting means 8a, 8a 'and the optical shutter unit 50 an arbitrary amount of light attenuation can be obtained by inserting the TE-polarized light and the TM-polarized light within an optical attenuation range of about 0 to 10 dB.
- An optical variable attenuator that can be obtained with high precision in a state where the loss difference is small and that can obtain a large optical attenuation of 60 dB or more in a power supply state and 40 dB or more in a non-power supply state can be realized.
- FIG. 7 (a) shows a cross-sectional view taken along the line III-III of FIG. 6,
- FIG. 7 (b) shows a cross-sectional view taken along the line IV-IV of FIG. 6,
- FIG. Fig. 6 shows a sectional view taken along line V-V.
- the optical branching unit 21a and the optical coupling unit 21b are formed by Y-branches having a branching ratio of 1: 1. It should be noted that the Y branching device having a branching ratio of 1 to 1 has a characteristic that the wavelength dependence of the branching ratio is smaller than that of the 2 ⁇ 2 directional coupler.
- connection optical waveguides le and If juxtaposed with each other forms the first connection optical waveguide le, and the other forms the second connection optical waveguide If.
- Each of the first and second connecting optical waveguides le and If is provided with two phase adjusting means 8a, 8b ', 8a' and 8b at intervals in the longitudinal direction.
- a first phase adjustment means 8a is formed near the input side of the first connection optical waveguide le, and a fourth phase adjustment means 8b 'is formed near the output side, and the input of the second connection optical waveguide If
- a third phase adjusting means 8a 'is formed near the side, and a second phase adjusting means 8b is formed near the output side.
- the first phase adjusting means 8a, the third phase adjusting means 8a ', the second phase adjusting means 8b, and the fourth phase adjusting means 8b' all have the same configuration, and these phase adjusting means 8a , 8a ', 8b, 8b' are configured similarly to the phase adjusting means 8a, 8a 'provided in the first embodiment, and have thin-film heaters 9a, 9b', 9a ', 9b.
- the distance between the first phase adjusting unit 8a and the optical waveguide layer removing unit 5 (5a) adjacent in the width direction to the first phase adjusting unit 8a, the third phase adjusting unit 8a 'and the third phase adjusting unit 8a' The distance between the third phase adjusting means 8a 'and the optical waveguide layer removing portion 5 (5a) adjacent in the width direction is the same as the first set distance D1. That is, the widths of the optical waveguide layers 3a and 3b shown in FIG. Is formed.
- the distance between the second phase adjusting unit 8b and the optical waveguide layer removing unit 5 (5b) adjacent to the second phase adjusting unit 8b in the width direction, the fourth phase adjusting unit 8b 'and the fourth phase adjusting unit 8b' The distance between the optical waveguide layer removing portion 5 (5b) adjacent to the fourth phase adjusting means 8b 'in the width direction is formed at a second set distance D2 which is equal to the second set distance D2. 1.
- the set distance D1 is formed to be different from each other. That is, the widths of the optical waveguide layers 3a 'and 3b' shown in FIG. 7B are equal to each other, and these widths are different from the widths of the optical waveguide layers 3a and 3b shown in FIG. 7A. I have.
- the phase is adjusted according to 8b, the amount of release of the stress applied to the connection optical waveguides le and If is made different.
- the birefringence of the connecting optical waveguides le and If generated by the stress is different, and the polarization difference of the phase of the propagating light determined by the birefringence (the phase of the TE polarized light and the Difference rate of change)
- the surface portion of the substrate 7 opposed to the lower portion of the optical waveguide layer removing portion 5 has one upper layer of the substrate 7.
- a substrate removing portion 4 is formed by removing the portion, and the substrate removing portion 4 is formed by cutting a lower portion of the optical waveguide layer removing portion 5 in a direction in which the lower portion of the optical waveguide layer removing portion 5 is wider than an interval between the opposing surfaces of the optical waveguide layer removing portion 5. It has a rectangular recess.
- This concave portion has a width of 70 m, which is 20 m wider than the lower portion 50 m of the optical waveguide layer removing portion 5, a depth of 10 ⁇ m, and a length of 5 mm.
- the substrate removing section 4 is formed, for example, by immersing the optical waveguide type optical variable attenuator chip in a KOH aqueous solution after forming the optical waveguide layer removing section 5, utilizing anisotropic etching of the KOH to the silicon substrate. This is performed by etching the silicon substrate 7.
- the substrate removing section 4 is also formed on the slit 12 side as shown in FIG. 7 (c).
- the slit 12 is filled with a refractive index matching agent 13 in a part thereof, and is further filled with an inert gas of argon gas 14. (Bonding) is performed by a glass seal using a low-melting glass.
- argon gas By applying argon gas and applying a glass seal to the lid 15 using low-melting glass, the thin-film heater 16 The heating by a and 16b makes it possible to move the refractive index matching agent 13 more reliably, so that the reliability of the shirt part 50 can be further improved.
- the other configuration of the second embodiment is the same as that of the first embodiment, and the manufacturing method is also the same as that of the first embodiment.
- the stress due to the thermal expansion of the optical waveguide layer is sufficiently released in the direction perpendicular to the substrate, and the thermal expansion of the optical waveguide layer in the direction horizontal to the substrate. Since the stress due to expansion is not sufficiently released, an anisotropic internal stress is newly generated, and the birefringence is further increased by the anisotropic stress, and the first connected optical waveguide le is propagated.
- a difference in optical attenuation, PDL which is determined by the difference between the phase difference in TM-polarized light and the phase difference in TE-polarized light between the light and the light propagated through the second connecting optical waveguide If .
- the distance between the first phase adjusting means 8a and the optical waveguide layer removing section 5 (5a) adjacent to the first phase adjusting means 8a is formed as the first set distance D1.
- the distance between the second phase adjusting means 8b and the optical waveguide layer removing section 5 (5b) adjacent to the second phase adjusting means 8b is set to a second set distance D2 different from the first set distance.
- connection optical waveguide le in the portion where the first phase adjustment means 8a is formed and the connection optical waveguide If in the portion where the second phase adjustment means 8b is formed Since the anisotropy of the stress during heating can be made different from each other, the rate of change of the birefringence with respect to the amount of phase adjustment is determined by the first connection The wave path le and the portion of the second connection optical waveguide If where the second phase adjusting means 8b is formed are different from each other.
- the first phase adjusting means 8a (first phase shifter) and the second phase adjusting means 8b (second phase shifter) are simultaneously driven, and the first phase adjusting means 8b (second phase shifter) is driven simultaneously.
- the light propagating through the first connecting optical waveguide le and the second connecting optical waveguide If can be made equal between the TE polarized light and the TM polarized light. That is, PDL can be reduced to zero in principle.
- the insertion loss in the unpowered state was measured when the intersection 24 was filled with the refractive index matching agent 13.
- the insertion loss for the TE polarization was 1.3 dB
- the insertion loss for the TM polarization was 1.32 dB.
- the light attenuation amount of the second embodiment is set to 5, 10, 15, and 20 dB.
- Power to the first phase shifter and the second phase shifter power to the first and second phase adjusting means 8a and 8b as described above, The relationship between insertion loss and PDL was determined. Table 1 shows the results.
- the power supply to the first and second phase adjusting means 8a and 8b is stopped, and the thin-film heater 16a is supplied with electric power and heated, and the refractive index matching agent 13 is moved to the thin-film heater 16b side and crossed.
- the power supply to the thin film heater 16a was stopped. Note that, similarly to the first embodiment, even after the power supply to the thin film heater 16a is completely stopped due to the suspension of the power supply to the thin film heater 16a, the refractive index matching agent 13 remains at the end of the slit 12 on the thin film heater 16b side due to the capillary force. Was held.
- the insertion loss measured at this time was 37.7 dB. That is, at this time, it can be seen that the optical attenuation, which is the difference from the insertion loss in the initial state, is a high value of 36 dB or more.
- the intersection 24 is filled with the gas 14, 79.30mW and 44.10mW of electric power are supplied to the first and second phase adjustment means 8 (8a, 8b), respectively.
- the insertion loss was measured, it was 57.7 dB. That is, at this time, the optical attenuation, which is the difference from the insertion loss in the initial state, was a very high value of about 56 dB or more.
- the PDL at this time was as low as 0.5 dB.
- an arbitrary optical attenuation can be obtained with high accuracy and low PDL within an optical attenuation range of about 0 to 20 dB, and the power attenuation is 56 dBb.
- an optical variable attenuator capable of obtaining a large optical attenuation of 36 dB or more in a non-powered state.
- FIG. 8 shows a cross-sectional configuration of the optical shutter unit 50 in the third embodiment.
- FIG. 8 corresponds to a cross section taken along line VV of FIG.
- a first point of the third embodiment different from the second embodiment is that the lid 15 of the optical shutter unit 50 is bonded by diffusion bonding of a copper thin film.
- a second point of the third embodiment different from the second embodiment is that the third embodiment has a liquid injection groove 43 connected to the slit 12 and the refractive index matching agent 13 through the liquid injection groove 43 after the lid 15 is joined. This is the point of injection.
- a copper metal thin film 41a is formed on the surface of the insulating film 42 formed on the optical waveguide layer 3 and the thin film heaters 16a and 16b, which is in contact with the lid 15, and this metal
- the lid 15 is joined by diffusion bonding between the thin film 41a and the copper metal thin film 41b formed on the joint surface of the lid 15.
- bonding is performed by diffusion of metal atoms, so stronger bonding can be performed.
- Sece bonding is performed by a solid-phase reaction, there is no problem such as displacement during bonding.
- the lid 15 can be sealed with higher accuracy.
- FIG. 9 is a cross-sectional view showing a manufacturing process of the planar optical waveguide circuit type variable optical attenuator of the third embodiment, and this cross section corresponds to a cross section taken along line VV of FIG. Also in the third embodiment, as shown in FIGS. 9A to 9D, the first and second steps are performed until the formation of the thin film heaters 16a and 16b and the formation of the power supply wiring (not shown). This is performed in the same manner as in the second embodiment.
- an insulating film 42 made of SiO is formed by sputtering.
- a metal thin film 41a made of copper is formed by sputtering and a lift-off method on the bonding surface of the insulating film 42 with the lid 15.
- the thickness of the metal thin film 41a is 3 / zm.
- a 0.1 ⁇ m-thick chromium film (not shown) is formed between the metal thin film 41a and the insulating film 42. ing.
- the optical waveguide layer 3 in a region corresponding to the slit 12 is removed to form a slit 12.
- a metal thin film 41b similar to the metal thin film 4la formed on the insulating film 42 is formed, and a liquid injection groove 43 is formed in the lid 15. Cover the slit 12 with the lid 15, hold the lid 15 at a pressure of about lOkgfZmm, and hold it for about 2 hours at 500 ° C in an inert gas atmosphere or vacuum to obtain the metal thin films 41a and 41b. Is diffusion bonded.
- the optical characteristics of the planar optical waveguide circuit type variable attenuator of the third embodiment were measured. As in the second embodiment, the optical attenuation of about 0 to 20 dB was 0.2 dB. Low PD below
- an optical attenuation of about 0 to 20 dB can be obtained with high accuracy, a low PDL of 0.2 dB or less can be obtained, and the power supply state can be reduced. 55dB or more, no power supply
- An optical variable attenuator that can obtain a large optical attenuation of 35 dB or more in a state can be obtained with high reliability.
- the present invention is not limited to the above embodiments, but can take various embodiments.
- the quartz optical waveguide circuit is used, but the planar optical waveguide circuit type variable optical attenuator of the present invention is formed by an optical waveguide using various materials such as polymers and semiconductors.
- the material for forming the optical waveguide circuit is appropriately selected in consideration of the required light loss value, reliability, cost, and the like, and the dimensions of the optical waveguide circuit are appropriately set.
- a silicon substrate is used as the substrate 7 in the present invention.
- the substrate 7 may be made of a glass material such as quartz glass, crystallized glass, silicon carbide, silicon nitride, Various substrate materials such as ceramics such as alumina can be used, and may be appropriately selected from the viewpoints of heat dissipation, stress applied to the optical waveguide layer 3, and the like.
- the material for forming the thin film heaters 9a, 9a ′, 16a, 16b in which the thin film heaters 9a, 9a ′, 16a, 16b are formed of a Ta film is not particularly limited.
- Various thin-film heater materials such as Ni, Cr, TaN (X is 0-1.0), Au, Pt, W, and alloys thereof can be used. That is, the material for forming the thin film heater may be appropriately selected in consideration of the required resistance value, reliability, and the like.
- the power refractive index matching agent 13 using a silicon-based oil as the refractive index matching agent 13 is a liquid refractive index matching agent having a refractive index close to the refractive index of the core 1. Then, the material is appropriately set.
- the glass lid 15 was used to seal the slit 12, but the lid 15 may be made of a glass material such as quartz glass or crystallized glass, silicon carbide, silicon nitride, or the like. Various materials such as ceramics such as alumina, single crystal materials such as silicon, resin materials, and metal materials can be applied.
- the material for forming the lid 15 is the bonding strength with the waveguide film. Coefficient of thermal expansion with the substrate and substrate 7, required reliability, etc.
- the lid 15 is connected with an adhesive or a low-melting glass seal.
- various bonding methods such as anodic bonding, diffusion bonding, thermocompression bonding, and soldering can be applied. It may be appropriately selected in consideration of strength, required reliability, and the like.
- the nitrogen gas or the argon gas is used as the gas 14, but the gas 14 is not limited to these gases, and is a gas having a stable characteristic such as an inert gas.
- gas materials can be used as long as they are materials, and they should be appropriately selected in view of required reliability, cost, and the like.
- the optical waveguide removing section 5 and the substrate removing section 4 are formed near the phase adjusting means 8a, 8a ′, 8b, 8b ′, and the phase of the connection optical waveguides le, If is formed.
- a stress applying means for further increasing (applying) the stress applied to the optical waveguide at the formation portion of the phase adjustment means is provided. Good
- copper was used as the metal thin film.
- a material should be appropriately selected in consideration of a bondable temperature, a heat-resistant temperature of the optical waveguide layer and the heater, a use temperature, and the like. Can be.
- the means for releasing the stress applied to the optical waveguide at the portion where the phase adjusting means is formed or increasing the calorie can be omitted.
- the amount of light attenuation can be varied with high accuracy within the range of, for example, 110 dB by the phase adjusting means formed in the Mach-Zehnder optical interferometer circuit 30, and by the operation of the optical shutter unit 50 side, it can be reduced to 35 dB or more. A large light attenuation can be obtained.
- first to fourth phase adjusting means 8a, 8b, 8a ′, 8b ′ are not limited to the formation positions in the second embodiment, and the first and fourth phase adjustment means are not limited to the formation positions in the second embodiment.
- the adjusting means 8a and 8b ' are formed in the first connection optical waveguide le, and the second and third phase adjusting means 8b and 8a' are formed in the second connection optical waveguide If! .
- phase adjusting means is provided for each of the two connection optical waveguides le and If, but the phase adjusting means may be provided for only one connection optical waveguide. Also, the number of phase adjusting means is not always one or two, but may be set appropriately. It is what is done.
- the force slit 12 in which the slit 12 is formed so as to intersect with the optical output waveguide can be formed so as to intersect with the optical input waveguide.
- a high-precision optical attenuation within a range of, for example, 0 to 10 dB is obtained by performing phase adjustment of the Mach-Zehnder optical interferometer circuit formed by the core of the optical waveguide layer.
- a liquid refractive index matching agent having a refractive index close to the refractive index of the core in a part of the slit crossing the middle part in the longitudinal direction of one output optical waveguide of the Mach-Zehnder optical interferometer circuit.
- the two connecting optical waveguides are provided with phase adjusting means, respectively, and when the phase is adjusted by these phase adjusting means, the propagation propagating through the connecting optical waveguides is performed.
- the two phases are adjusted so that the polarization differences of the phases of the propagating lights propagating through the respective connection optical waveguides become equal to each other.
- each of the two connecting optical waveguides is provided with a phase adjusting means, and when the phase is adjusted by these phase adjusting means, the change in the birefringence of the connecting optical waveguide is changed.
- the two phase adjusting means are controlled so that the birefringence is such that the polarization differences of the phases of the propagating light propagating through the respective connecting optical waveguides are equal to each other.
- a structure for releasing or increasing the stress applied to the connection optical waveguide when the phase adjustment is performed by the phase adjustment means near at least one of the connection optical waveguides where the phase adjustment means is formed According to the configuration in which the rate of change of the birefringence of the connecting optical waveguide is different from each other when the phase is adjusted by the phase adjusting means, the connection can be easily performed by the configuration in which the stress is released or increased.
- the change rate of the birefringence of the optical waveguide can be set.
- connection optical waveguide forming portions of the phase adjusting means is provided with a free space and a space where stress applied to the connecting optical waveguide when the phase adjustment is performed by the phase adjusting means is released.
- the rate of change of the birefringence with respect to the amount of phase adjustment when the phase adjustment is performed by the two phase adjusting means can be made different from each other by releasing the stress. it can.
- each of the two connection optical waveguides is provided with a phase adjusting means formed by a heating means, and at least one of the phase adjusting means is provided with a heating means in the vicinity of a portion thereof.
- the phase adjusting means forming area of the connecting optical waveguide is efficiently heated. Power consumption can be reduced.
- the optical waveguide layers on both sides of the portion where the phase adjusting means is formed may have a region having an interval from the connection optical waveguide along the longitudinal direction of the connection optical waveguide. According to the configuration in which the optical waveguide layer is removed toward the surface and the optical waveguide layer removing section serves as a means for releasing the stress in the free space, the optical waveguide layer removing section can easily and accurately form the free space. A means for stress release can be formed.
- each of the two connection optical waveguides is provided with a phase adjusting means, and the distance between one of the phase adjusting means and the optical waveguide layer removing portion adjacent to the phase adjusting means is determined by: According to the configuration in which the distance between the other phase adjusting unit and the optical waveguide layer removing unit adjacent to the phase adjusting unit is formed to be different from each other, the phase adjustment is performed by the one phase adjusting unit and the other phase adjusting unit. The difference in the birefringence change rate of the connecting optical waveguide at the time of the operation can be accurately formed.
- the optical waveguide layers on both sides of the portion where the phase adjusting means is formed are arranged such that a region having an interval from the connection optical waveguide extends from the surface of the optical waveguide layer along the longitudinal direction of the connection optical waveguide to the substrate.
- the heat insulating means can be easily and accurately formed by the optical waveguide removing section, and the phase adjusting means can be formed. The formation region can be efficiently heated.
- connection optical waveguides juxtaposed to each other is formed as a first connection optical waveguide, and the other is formed.
- the first and second connecting optical waveguides are formed with two phase adjusting means at intervals in the longitudinal direction, respectively, and these two phase adjusting means and the optical waveguide are formed. According to the configuration in which the distance to the removing unit is set to the first and second set distances, the polarization dependence of the optical attenuation of the propagation light can be substantially reduced by appropriately setting the first and second set distances. The power consumption can be reduced.
- the phase adjustment of the connection optical waveguide is performed. Stress release and heat insulation of the means forming region can be effectively performed.
- the phase adjusting means of the connection optical waveguide is provided. Stress release and heat insulation of the formation region can be performed more effectively.
- the substrate removing portion is a concave portion having a rectangular cross section obtained by cutting a lower portion of the optical waveguide layer removing portion in a direction in which the lower portion of the optical waveguide layer removing portion is wider than an interval between opposed surfaces of the optical waveguide layer removing portion.
- stress release and heat insulation in the phase adjusting means forming region of the connection optical waveguide can be performed more effectively.
- the matching agent moving unit is a thin film heater provided near the slit
- the matching agent moving unit can be easily formed, and the refractive index matching agent can be moved accurately. be able to.
- the phase adjusting means is a thin film heater provided on the connecting optical waveguide
- the phase adjusting means can be easily formed, and the connecting optical waveguide can be easily formed by the thermo-optic effect.
- the phase of the propagating light can be changed.
- the optical waveguide layer is formed of silica-based glass, a highly reliable planar optical waveguide circuit type variable optical attenuator with low insertion loss can be realized.
- the substrate is a silicon substrate
- stress can be easily released from the phase adjusting means forming region of the connection optical waveguide, which has good heat dissipation, and high reliability and high planar light conduction can be achieved.
- a wave circuit type optical variable attenuator can be realized.
- the slit is bent.
- the state of movement of the index matching agent can be easily checked, and a highly reliable optical attenuator with a planar optical waveguide can be realized.
- the slit can be easily sealed.
- the slit can be easily sealed, and the reliability is further improved. It can be even higher.
- the glass plate is bonded to the optical waveguide layer by diffusion bonding between the glass plate and the metal film formed on the surface of the optical waveguide layer. Sex can be obtained.
- the metal film is made of copper or a copper alloy, so that the sealing is performed with high reliability without adversely affecting the optical waveguide characteristics. Can be stopped.
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Abstract
Description
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JP2005513187A JP3977399B2 (ja) | 2003-08-13 | 2004-08-13 | 平面光導波回路型光可変減衰器 |
US11/352,373 US7233714B2 (en) | 2003-08-13 | 2006-02-13 | Planar optical waveguide circuit type variable attenuator |
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JP2009222742A (ja) * | 2008-03-13 | 2009-10-01 | Nippon Telegr & Teleph Corp <Ntt> | 熱光学位相シフタおよびその製造方法 |
CN109814204A (zh) * | 2019-03-09 | 2019-05-28 | 北京爱杰光电科技有限公司 | 一种基于马赫曾德尔干涉仪的片上可调光衰减器 |
US20210387290A1 (en) * | 2018-12-17 | 2021-12-16 | Heraeus Precious Metals North America Conshohocken Llc | Process for forming an electric heater |
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JP2007065562A (ja) | 2005-09-02 | 2007-03-15 | Furukawa Electric Co Ltd:The | アレイ導波路回折格子 |
JP5100175B2 (ja) * | 2007-03-28 | 2012-12-19 | 古河電気工業株式会社 | アレイ導波路格子型の合分波装置 |
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JPWO2005017611A1 (ja) | 2007-11-01 |
JP3977399B2 (ja) | 2007-09-19 |
US20060204201A1 (en) | 2006-09-14 |
US7233714B2 (en) | 2007-06-19 |
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