Optical device and wavelength-variable laser

Abstract

This optical device comprises, for example: a base; a plurality of optical components fixed to the base; an etalon filter serving as an optical component; and an electric heating member integrated with the etalon filter and having a transparent base material which is optically in series with the etalon filter and which transmits light, and a transparent electric heating body which is provided on the surface of the transparent base material, which is optically in series with the etalon filter and the transparent base material, and which transmits light. In the optical device, the transparent electric heating body may be positioned on the side opposite to the etalon filter side with respect to the transparent base material or may be positioned between the transparent base material and the etalon filter.

Description

Optical Devices and Tunable Lasers

[0001] The present invention relates to optical devices and tunable lasers.

[0002] This application is a patent application filed in FY2022 under the "Commissioned Research for Research and Development of Innovative Information and Communications Technology / Research and Development of Bandwidth-Extended Optical Node Technology to Realize Beyond 5G Ultra-High-Speed ​​and Large-Capacity Networks - Research and Development of Bandwidth-Extended Optical Node Technology for Expanding the Bit Rate-Distance Product of Optical Networks" by the National Institute of Information and Communications Technology, a National Research and Development Agency, and subject to Article 17, Paragraph 1 of the Industrial Technology Enhancement Act.

[0003] A chip-integrated wavelength tunable laser is known (see Patent Document 1). The wavelength tunable laser in Patent Document 1 integrates an amplifier unit that emits and amplifies light and an optical filter that has predetermined wavelength characteristics.

[0004] Patent No. 2687464

[0005] In the configuration of Patent Document 1, for example, when the amount of current to the amplifier is increased to increase the laser output, heat generated in the amplifier may be transferred to the optical filter, affecting the wavelength characteristics of the optical filter. Therefore, it is preferable that the temperature of the optical filter can be individually adjusted. In addition, it is preferable that the temperature of the optical filter can be adjusted with greater precision.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel and improved optical device and tunable laser that allows, for example, the temperature of optical filters to be adjusted individually and with greater precision.

[0007] The optical device of the present invention includes, for example, a base, a plurality of optical components fixed to the base, an etalon filter as the optical component, and an electric heating member that is integrated with the etalon filter, is optically in series with the etalon filter, and has a transparent electric heating body that transmits light.

[0008] In the optical device, the electric heating member may have a transparent substrate that is optically serial to the etalon filter and the transparent electric heating body, transmits light, and is provided on the surface of the transparent electric heating body.

[0009] In the optical device, the transparent electric heater may be located on the opposite side of the transparent substrate from the etalon filter.

[0010] In the optical device, the transparent electric heater may be located between the transparent substrate and the etalon filter.

[0011] The optical device may include a wiring portion for supplying power to the transparent electric heater, and the wiring portion may be provided at a position outside the light passing area of ​​the transparent electric heater.

[0012] In the optical device, the etalon filter may have a body and a dielectric film provided on an input end and an output end of the body, and the body may be made of glass or silicon.

[0013] In the optical device, the transparent electric heater may be made of indium tin oxide.

[0014] In the optical device, the transparent electric heater may be capable of changing the temperature of the area where the etalon filtered light passes within a range of room temperature or higher and 150° C. or lower by changing the power supplied thereto.

[0015] The optical device may include a temperature detector that detects the temperature of the etalon filter or the electric heating member.

[0016] In the optical device, the temperature detection section may be a temperature sensing resistance wiring layer whose resistance value changes in response to a change in temperature.

[0017] In the optical device, the electric heating element may be optically in series with the etalon filter and the transparent electric heating element, may transmit light, and may have a transparent substrate provided on the surface of the transparent electric heating element, and the temperature measuring resistance wiring layer may be located on the opposite side of the transparent substrate from the etalon filter.

[0018] In the optical device, the electric heating element may have a transparent substrate that is optically in series with the etalon filter and the transparent electric heating element, transmits light, and is provided on the surface of the transparent electric heating element, and the temperature measuring resistance wiring layer may be located between the transparent substrate and the etalon filter.

[0019] In the optical device, the temperature sensing resistance wiring layer may be made of a metal film laminated with Ti / Pt.

[0020] In the optical device, the electric heating member may be interposed between the etalon filter and a heating element other than the electric heating member.

[0021] In the optical device, a heat shielding member may be interposed between the etalon filter and a heating element other than the electric heating member.

[0022] In the optical device, the etalon filter may be fixed to the base or another member fixed to the base via a first bonding material.

[0023] In the optical device, the etalon filter and the electric heating member may be bonded together via a second bonding material having a higher thermal conductivity than the first bonding material.

[0024] The wavelength tunable laser of the present invention includes, for example, an optical amplification unit that generates and amplifies light and outputs the light from a first end and a second end opposite the first end, a first mirror that reflects the light output from the first end, a second mirror that reflects the light output from the second end, an etalon filter that is provided between the optical amplification unit and the first mirror or the second mirror, has predetermined wavelength characteristics, and passes the light output from the optical amplification unit, and an electric heating member that is integrated with the etalon filter, is optically in series with the etalon filter, and has a transparent electric heating body that transmits light.

[0025] The wavelength tunable laser may include a lens that is provided between the optical amplifier and the etalon filter and through which light traveling between the optical amplifier and the etalon filter passes.

[0026] The wavelength-tunable laser may include a temperature control mechanism that adjusts the temperature of the optical amplification unit, and a heat-shielding member that is interposed between the temperature control mechanism and the etalon filter and that suppresses heat conduction between the temperature control mechanism and the etalon filter.

[0027] The present invention provides novel and improved optical devices and tunable lasers that, for example, allow the temperature of optical filters to be individually and more precisely adjusted.

[0028] FIG. 1 is an exemplary and schematic plan view showing an optical device of a first embodiment with its top cover removed. FIG. 2 is an exemplary and schematic side view of a portion of the optical device of the first embodiment. FIG. 3 is an exemplary and schematic front view of an electric heating member included in the optical device of the first embodiment. FIG. 4 is an exemplary and schematic plan view showing an optical device of a second embodiment with its top cover removed. FIG. 5 is an exemplary and schematic side view of a portion of the optical device of the second embodiment. FIG. 6 is an exemplary and schematic plan view showing an optical device of a third embodiment with its top cover removed. FIG. 7 is an exemplary and schematic plan view showing an optical device of a fourth embodiment with its top cover removed. FIG. 8 is an exemplary and schematic plan view showing an optical device of a fifth embodiment with its top cover removed. FIG. 9 is an exemplary and schematic plan view showing an optical device of a sixth embodiment with its top cover removed. FIG. 10 is an exemplary and schematic plan view showing an optical device of a seventh embodiment with its top cover removed. FIG. 11 is an exemplary and schematic side view of a portion of an optical device according to an eighth embodiment. FIG. 12 is an exemplary and schematic side view of a portion of an optical device according to a ninth embodiment. FIG. 13 is an exemplary and schematic side view of a portion of an etalon filter and an electric heating element included in an optical device according to a tenth embodiment. FIG. 14 is an exemplary and schematic front view of an electric heating element and a temperature measuring resistance wiring layer included in an optical device according to an eleventh embodiment. FIG. 15 is a cross-sectional view taken along the line XV-XV of FIG. 14. FIG. 16 is an exemplary and schematic plan view of a portion of the internal configuration of an optical device according to an eleventh embodiment. FIG. 17 is a cross-sectional view of an etalon filter, an electric heating element, and a temperature measuring resistance wiring layer included in an optical device according to a twelfth embodiment, taken at the same position as in FIG. 15. FIG. 18 is an exemplary and schematic plan view of an etalon filter, an electric heating element, and a temperature measuring resistance wiring layer included in an optical device according to a thirteenth embodiment.

[0029] Exemplary embodiments of the present invention are disclosed below. The configurations of the embodiments described below, as well as the actions and results (effects) brought about by the configurations, are merely examples. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

[0030] The following embodiments have similar configurations. Therefore, according to the configurations of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, in the following, similar configurations are given similar reference numerals, and duplicated descriptions may be omitted.

[0031] In this specification, ordinal numbers may be assigned for convenience to distinguish between parts, members, parts, directions, lights, etc. Note that ordinal numbers do not indicate priority or order, nor do they specify a number.

[0032] In each drawing, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect with each other and are perpendicular to each other. Note that each drawing is a schematic diagram, and the shape and dimensions of each part may differ from the actual shape and dimensions.

[0033] 1 is a plan view showing an optical module 100A (100) according to a first embodiment with its top cover removed. The optical module 100A (100) is an example of an optical device having a tunable laser.

[0034] 1, the optical module 100A includes a housing 1. The housing 1 includes an output port 1a, four side walls 1b, a bottom wall 1c, and a top cover (not shown).

[0035] The bottom wall 1c is a plate-shaped member located at the end opposite the Z direction. The bottom wall 1c intersects the Z direction and is perpendicular to it, and extends in the X and Y directions with a substantially constant thickness in the Z direction. The bottom wall 1c is made of a material with high thermal conductivity, such as copper tungsten (CuW), copper molybdenum (CuMo), or aluminum oxide (Al2O3).

[0036] Each of the side walls 1b is a plate-shaped member, and extends in the Z direction, substantially perpendicular to the bottom wall 1c, and perpendicular to the X direction or the Y direction.

[0037] The output port 1a is provided on the side wall 1b located at the end in the X direction. The lens 2 is housed within the output port 1a. The output port 1a also supports an optical fiber 3 that outputs output light to the outside.

[0038] The top cover is a plate-shaped member located at the end in the Z direction. The top cover intersects and is perpendicular to the Z direction, extends in the X and Y directions with a substantially constant thickness in the Z direction, and is substantially parallel to the bottom wall 1c.

[0039] The output port 1a, side wall 1b, and top cover are made of a material with a low coefficient of thermal expansion, such as an Fe-Ni-Co alloy or aluminum oxide (Al2O3).

[0040] The storage chamber in the housing 1 is, for example, hermetically sealed. An inert gas such as nitrogen gas may be stored in the housing 1. In this case, nitrogen gas is an example of the gas.

[0041] The housing 1 contains components such as the chip-on submount 4, lenses 51 and 52, etalon filter 11, mirror 10a, optical isolator 6, beam splitter 23, photodiode 24, and carrier 60. These components are supported by the housing 1 directly or indirectly via other members or components. Among these components, the chip-on submount 4, lenses 51 and 52, mirror 10a, etalon filter 11, optical isolator 6, beam splitter 23, and photodiode 24 are examples of optical components. Optical components are components that output light, receive light, transmit light, or affect light. Note that the housing 1 may contain and support optical components other than the above-mentioned components, as well as electronic or electrical components other than optical components. The housing 1 is an example of a base.

[0042] In this embodiment, the chip-on submount 4, lenses 51 and 52, etalon filter 11, mirror 10a, optical isolator 6, beam splitter 23, and photodiode 24 are supported on a carrier 60 directly or indirectly via other members. The carrier 60 is, for example, a Peltier module with a temperature adjustment function. In this case, the carrier 60 is an example of a temperature adjustment mechanism capable of adjusting the temperature of the laser element 4a. The Peltier module will be described in detail later. Note that a temperature adjustment mechanism other than a Peltier module, such as a heater as a resistance heating module, may be provided corresponding to the chip-on submount 4.

[0043] The chip-on submount 4 has a laser element 4a, a submount 4b, and a thermistor 4c. The laser element 4a is a semiconductor laser element. The laser element 4a has an optical amplifier 4a1. The chip-on submount 4 may also be called a light-emitting unit.

[0044] The optical amplifier 4a1 has a laser medium such as a semiconductor active layer, and generates and amplifies light in response to a supplied current. The optical amplifier 4a1 outputs light from one end 4a11 and another end 4a12 opposite the end 4a11. The end 4a11 is an example of a first end, and the end 4a12 is an example of a second end.

[0045] A mirror 10b is provided at the end 4a12. The mirror 10b reflects at least a portion of the incoming light. In this embodiment, the mirror 10b reflects a portion of the light output from the optical amplifier 4a1 and inputs it to the optical amplifier 4a1, while also transmitting a portion of the light output from the optical amplifier 4a1. The mirror 10b is, for example, a dielectric multilayer film mirror. The mirror 10b is an example of a second mirror.

[0046] The submount 4b supports the laser element 4a. The submount 4b is made of an insulating material with high thermal conductivity. The thermistor 4c may also be referred to as a temperature sensor. The thermistor 4c is mounted on, for example, the submount 4b.

[0047] The light output from the end 4a11 of the optical amplifier 4a1 passes through the lens 51. The lens 51 is, for example, a collimator lens.

[0048] The light passing through the lens 51 passes through the etalon filter 11 and reaches the mirror 10a.

[0049] The etalon filter 11 has predetermined wavelength characteristics and transmits light of a wavelength corresponding to the wavelength characteristics. The etalon filter 11 has a body with end faces formed as parallel flat surfaces, and a dielectric film formed on each end face that reflects or transmits light with a predetermined reflectance. The body is made of, for example, glass or silicon. The etalon filter 11 has a generally plate-like shape and extends in the X direction at a generally constant height, intersecting the X direction.

[0050] A heater 12 is provided on an end face of the etalon filter 11. In this embodiment, the etalon filter 11 and the heater 12 form a subassembly. The heater 12 changes the optical path length of the etalon filter 11, thereby changing the wavelength characteristics of the etalon filter 11. The heater 12 generates heat by the supplied power and heats the etalon filter 11. The heater 12 is an example of an electric heating member. The heater 12 will be described in detail later.

[0051] The mirror 10a reflects at least a portion of the light that reaches it. In this embodiment, the mirror 10a reflects all of the light that reaches the mirror 10a so that the light returns to the etalon filter 11. The mirror 10a is, for example, a dielectric multilayer mirror. The mirror 10a is an example of a first mirror.

[0052] The light output from the end 4a12 of the optical amplifier 4a1 and transmitted through the mirror 10b reaches the optical isolator 6 via the lens 52. The lens 52 is, for example, a collimating lens.

[0053] The optical isolator 6 transmits the incoming light, in this case the light coming from the lens 52 , towards the beam splitter 23 and blocks the light from returning from the beam splitter 23 .

[0054] The beam splitter 23 outputs most of the light to the lens 2 and outputs a portion of the light to the photodiode 24. The lens 2 collects the light from the beam splitter 23 and couples it into the optical fiber 3.

[0055] The photodiode 24 receives the light from the beam splitter 23 and outputs a detection signal corresponding to the intensity of the received light. The detection signal is input to a controller (not shown) via wiring (not shown). The controller controls the operation of the laser element 4 a based on the detection signal from the photodiode 24.

[0056] In this configuration, the optical amplifier 4a1 and the etalon filter 11 are interposed between the mirrors 10a and 10b, and a resonant mechanism is formed in which light resonates by reciprocating between the mirrors 10a and 10b at a predetermined wavelength. In this resonant mechanism, the resonant wavelength can be changed by changing the temperature of the etalon filter 11 to change the optical path length.

[0057] Furthermore, in this configuration, by providing a lens 51 between the laser element 4a and the etalon filter 11, the distance between the optical amplifier 4a1 of the laser element 4a and the etalon filter 11 can be increased. The optical amplifier 4a1 generates heat during operation. Therefore, if the distance between the optical amplifier 4a1 and the etalon filter 11 were short, the heat generated by the optical amplifier 4a1 could make it difficult to accurately adjust the temperature of the etalon filter 11 using the heater 12. In this regard, in this embodiment, by providing the lens 51, the distance between the optical amplifier 4a1 and the etalon filter 11 can be increased. Therefore, the thermal effect of the optical amplifier 4a1 on the etalon filter 11 can be suppressed, thereby enabling more accurate temperature adjustment of the etalon filter 11 using the heater 12, and therefore wavelength control. The optical amplifier 4a1 is an example of a heating element.

[0058] FIG. 2 is a side view of a portion of the optical module 100A. As described above, in this embodiment, the carrier 60 is configured as a Peltier module 60P. As shown in FIG. 2, the Peltier module 60P includes a first substrate 60a, a second substrate 60b, and multiple thermoelectric elements 60c. The thermoelectric elements 60c are columnar semiconductor elements disposed between the first substrate 60a and the second substrate 60b. The thermoelectric elements 60c are made of a P-type or N-type semiconductor, such as a bismuth telluride-based semiconductor. The multiple thermoelectric elements 60c are connected in series to form a PN junction via wiring patterns (not shown) provided on the first substrate 60a and the second substrate 60b. Electric power is supplied from wiring (not shown) to a circuit including the multiple thermoelectric elements 60c connected in series via the wiring patterns. As a result, the Peltier module 60P absorbs or generates heat depending on the direction of the power current. The Peltier module 60P is capable of adjusting the temperature of the laser element 4a in accordance with a value detected by, for example, the thermistor 4c, and is an example of a temperature adjustment mechanism and also an example of a heating element.

[0059] In this embodiment, the etalon filter 11 / heater 12 subassembly and the mirror 10a are supported by the Peltier module 60P via a heat shield 70, which has a lower thermal conductivity than the housing 1, the Peltier module 60P, or metal materials. In other words, the heat shield 70 is interposed between the etalon filter 11 / heater 12 subassembly and the mirror 10a and the optical amplifier 4a1 or the Peltier module 60P, suppressing heat conduction therebetween. The heat shield 70 is made of, for example, glass. This configuration can suppress a decrease in the accuracy of the etalon filter 11 temperature adjustment function performed by the heater 12, which may be caused by heat from the Peltier module 60P during temperature adjustment or heat transferred from the optical amplifier 4a1 via the Peltier module 60P. The heat shield 70 has a block shape, but is not limited thereto. For example, the heat shield 70 may have a hollow portion.

[0060] In this configuration, the etalon filter 11 and the heater 12 are integrated via a bonding material 91. The heat-shielding member 70 is fixed to the carrier 60 via the bonding material 90, and the subassembly of the etalon filter 11 and the heater 12 and the mirror 10a are fixed to the heat-shielding member 70 via the bonding material 90. In this case, the heat-shielding property of the bonding material 90 is higher than that of the bonding material 91. In other words, the thermal conductivity of the bonding material 91 is higher than that of the bonding material 90. This configuration further suppresses heat conduction from the Peltier module 60P and the optical amplifier 4a1 to the etalon filter 11, the heater 12, and the mirror 10a. Furthermore, the heater 12 can heat the etalon filter 11 more efficiently and quickly, and the temperature of the etalon filter 11, and therefore the wavelength of the light, can be controlled more accurately. Furthermore, the responsiveness of wavelength control can be improved. The bonding material 90 is an example of a first bonding material, and the bonding material 91 is an example of a second bonding material.

[0061] Furthermore, the etalon filter 11, heater 12, and mirror 10a are supported on a Peltier module 60P together with the chip-on submount 4 and lenses 51 and 52. With this configuration, the temperature adjustment function of the Peltier module 60P can suppress, for example, a decrease in coupling efficiency between the optical components caused by a change in the relative positional relationship between these optical components.

[0062] 2, the heater 12 is integrated with the etalon filter 11 and is in contact with and overlaps the etalon filter 11 in the thickness direction (X direction). Note that the arrangement of the etalon filter 11 and the heater 12 in the X direction may be reversed.

[0063] 3 is a front view of the heater 12. The heater 12 has a transparent substrate 12a, a transparent heating element 12b, and two wiring portions 12c. The wiring portion 12c is electrically connected to the transparent heating element 12b and supplies power to the transparent heating element 12b.

[0064] 2, the transparent base material 12a has a generally plate-like shape and extends in the X direction at a generally constant height, intersecting the X direction. The transparent base material 12a is made of, for example, glass or silicon.

[0065] As shown in FIG. 3 , the transparent heater 12b is formed on the end face (surface) of the transparent substrate 12a in the thickness direction (opposite to the X direction). In this embodiment, the transparent heater 12b is located on the opposite side of the transparent substrate 12a from the etalon filter 11. The transparent heater 12b has a film-like shape and extends in the X direction with a substantially constant thickness, intersecting the X direction. The transparent substrate 12a, the transparent heater 12b, and the etalon filter 11 are optically arranged in series. The transparent heater 12b also has a transmittance of, for example, 85% or more. Specifically, the transparent heater 12b is made of ITO (indium tin oxide).

[0066] The two wiring portions 12c, 12c extend in the Z direction at a predetermined width in the Y direction at the end of the transparent base material 12a in the Y direction and the end opposite the Y direction. The wiring portion 12c is made of, for example, a metal film laminated with Cr / Ni, and is laminated on the transparent heating element 12b. The wiring portion 12c is opaque. The transparent heating element 12b and the wiring portion 12c are made by, for example, vapor deposition or sputtering.

[0067] Furthermore, it is preferable that a dielectric film be provided on the end surface of the heater 12 in the optical axis direction. The dielectric film is preferably provided on the end surface of at least one of the transparent substrate 12a and the transparent electric heater 12b in the optical axis direction. In this configuration, adjusting the film thickness of the dielectric film makes it possible to adjust the reflectance in accordance with changes in the refractive index, thereby achieving an anti-reflection effect. The dielectric film can also be used as a reflective film. Furthermore, adjusting the film thicknesses of the transparent electric heater 12b, the dielectric film, and the etalon filter 11 adjusts the reflectance of the two opposing reflective surfaces, thereby increasing the transmittance of the etalon filter 11. Furthermore, in this configuration, if a wiring portion 12c is provided on the transparent electric heater 12b, it is preferable that a dielectric film be provided in the area of ​​the transparent electric heater 12b where the wiring portion 12c is not provided.

[0068] In the heater 12 having this configuration, the light passage area A is set to be located within the transparent substrate 12a and the transparent heating element 12b. That is, the laser light passes through the transparent substrate 12a and the transparent heating element 12b. On the other hand, the two wiring portions 12c are opaque and do not overlap with the passage area A, and are therefore arranged outside the passage area A. With this configuration, the passage area A can be provided in the transparent heating element 12b, which is heated by passing current, and the transparent heating element 12b can be made wider, so that the light passage area in the etalon filter 11 can be heated more efficiently and quickly by the transparent heating element 12b. Furthermore, the transparent heating element 12b can reduce unevenness in the amount of heat generated by the etalon filter 11 depending on the location, so that the heater 12 can more accurately adjust the temperature of the etalon filter 11, and ultimately control the wavelength. The specifications of the transparent substrate 12a, the transparent heating element 12b, and the wiring portion 12c, such as the positions and shapes thereof, are not limited to those shown in FIG. 3, but can be modified in various ways.

[0069] The specifications of the heater 12, particularly the transparent heating element 12b, such as material, length, width, thickness, etc., are determined according to the control range of the light wavelength so as to obtain the required heating performance for the etalon filter 11. As an example, when the optical module 100A is used as a wavelength tunable laser, the specifications of the heater 12 are set so that the heater 12 can heat at least the pass region A of the etalon filter 11 to 150°C and so that at least the light pass region of the etalon filter 11 can be changed within a range of, for example, from room temperature to 150°C by changing the supplied power.

[0070] Table 1 shows the transmittance, surface resistivity, and power consumption according to the film thickness of the transparent heating element 12b. Through diligent research by the inventors, it was confirmed that when the film thickness of the transparent heater 12b (ITO) is 100 Å or more and 400 Å or less, the transmittance is 85% or more and 96% or less, the surface resistivity is 32.5 Ω / sq or more and 130.0 Ω / sq or less, and the power consumption is 0.025 W or more and 0.1 W or less, as shown in Table 1. In this case, it was confirmed that the temperature can be raised from room temperature to 150°C at a voltage of 3 V or less and a current of 0.05 A or less. The wiring portion 12c is a metal film laminated with Cr / Ni and has a film thickness of 2000 Å.

[0071] The FSR (Free Spectral Range) of the etalon filter 11 can be expressed by the following equation (1): FSR=λ ２ / (2nL cos θ + λ) (1) where λ is the wavelength, n is the refractive index of the etalon filter 11 (body), L is the thickness of the etalon filter 11 (body), and θ is the tilt angle of the etalon filter 11 in the thickness direction with respect to the optical axis of the incident light. The refractive index n is 1.5 when the material of the body of the etalon filter 11 is glass, and 3.5 when the material is silicon. When the FSR is set to 700 [GHz], from equation (1), the thickness L when the body is made of glass is 0.14 [mm], and the thickness L when the body is made of silicon is 0.06 [mm]. When the FSR is set to 300 [GHz], from equation (1), the thickness L when the body is made of glass is 0.34 [mm], and the thickness L when the body is made of silicon is 0.14 [mm]. Integrating the etalon filter 11 with the transparent substrate 12a of the heater 12 increases the rigidity and strength of the etalon filter 11 and the heater 12. The thickness of the transparent substrate 12a is preferably 0.01 mm or more and 0.2 mm or less, and more preferably 0.05 mm or more and 0.1 mm or less.

[0072] A temperature detector may be provided around the etalon filter 11 to detect the temperature of the etalon filter 11 or the heater 12. The temperature detector may be, for example, a thermistor, and may be provided on the surface of the etalon filter 11, the heater 12, or the heat-shielding member 70. In this case, in temperature adjustment control of the etalon filter 11 using the heater 12, feedback control may be performed based on the detection value of the temperature detector.

[0073] As described above, in this embodiment, the heater 12 (electric heating member) that heats the etalon filter 11 is integrated with the etalon filter 11. Therefore, the heater 12 can individually and more accurately adjust the temperature of the etalon filter 11. Furthermore, in this embodiment, the heater 12 has a transparent substrate 12a and a transparent electric heater 12b, and the etalon filter 11, the transparent substrate 12a, and the transparent electric heater 12b are optically arranged in series. Therefore, the light passage area of ​​the etalon filter 11 can be heated more efficiently and quickly by the transparent electric heater 12b. Furthermore, because uneven heating of the etalon filter 11 by the transparent electric heater 12b can be reduced, the heater 12 can more accurately adjust the temperature of the etalon filter 11, and ultimately control the wavelength.

[0074] In this embodiment, the heater 12 has a transparent substrate 12 a, and the transparent heating element 12 b is provided on the transparent substrate 12 a. This configuration has the advantage that the transparent heating element 12 b can be more reliably supported by the transparent substrate 12 a. Furthermore, since the transparent heating element 12 b can be formed without affecting the end faces of the etalon filter 11, it has the advantage that the reflectance and transmittance at the end faces of the etalon filter 11 can be more accurately set.

[0075] Second Embodiment FIG. 4 is a plan view showing an optical module 100B (100) according to a second embodiment with the top cover removed. As shown in FIG. 4, in the optical module 100B, the laser element 4a includes an optical amplifier 4a1 and an optical filter 4a2. The optical filter 4a2 may be, for example, a distributed bragg reflector (DBR), a ring filter, a phase adjustment filter, or a Mach-Zehnder filter. Thus, even when the laser element 4a includes one or more optical functional units other than the optical amplifier 4a1, the same effects as those of the first embodiment can be achieved. Furthermore, compared to when each optical functional unit is provided separately, the optical module 100 can be configured more compactly.

[0076] 5 is a side view of a portion of the optical module 100B. As shown in FIG. 5, in the optical module 100E, the etalon filter 11 and the heater 12 are attached to the heat shield 70, but the mirror 10a is not. Also, as shown in FIG. 5, the heat shield 70 may have a beam structure. By using a beam structure, the cross-sectional area of ​​the heat conduction path in the heat shield 70 can be reduced, thereby further improving the heat shielding properties. This embodiment not only provides the same effects as the first embodiment, but also has the advantage of allowing the heat shield 70 to be configured smaller.

[0077] [Third Embodiment] Fig. 6 is a plan view showing an optical module 100C (100) according to a third embodiment with the top cover removed. As shown in Fig. 6, in the optical module 100C, the laser element 4a includes an optical amplifier 4a1, optical filters 4a2 and 4a3, and an SOA 4a4 (SOA: semiconductor optical amplifier). In this embodiment, the laser element 4a also includes one or more optical function units other than the optical amplifier 4a1, which provides the advantage of enabling the optical module 100 to be configured more compactly than when each optical function unit is provided separately.

[0078] 6 , in the optical module 100C, the subassembly of the etalon filter 11 and the heater 12 is integrated with the mirror 10a. The mirror 10a is, for example, a dielectric multilayer mirror. In this configuration, the heater 12 is provided on the opposite side of the etalon filter 11 from the mirror 10a. However, this is not limiting, and the heater 12 may be provided between the mirror 10a and the etalon filter 11. According to this embodiment, since the etalon filter 11, the heater 12, and the mirror 10a are integrated, the optical module 100 can be configured more compactly, which has the advantage of making it easier to secure space for arranging other components such as the photodiode 24.

[0079] [Fourth Embodiment] Figure 7 is a plan view showing an optical module 100D (100) according to a fourth embodiment with the top cover removed. As shown in Figure 7, the optical module 100D includes an etalon filter 11 between the lens 51 and the optical isolator 6. A mirror 10b is provided at the end 4a12 of the optical amplifier 4a1, and a mirror 10a is provided on the end face 11a of the etalon filter 11 opposite the lens 51. This configuration also achieves the same effects as the first embodiment. While the heater 12 is located closer to the lens 51 than the etalon filter 11, this is not limiting and the heater 12 may be located on the farther side from the lens 51, i.e., on the end face 11a where the mirror 10a is provided.

[0080] Fifth Embodiment Fig. 8 is a plan view showing an optical module 100E (100) according to a fifth embodiment with the top cover removed. As shown in Fig. 8, in the optical module 100E, the laser element 4a includes an optical amplifier 4a1, as well as optical filters 4a2 and 4a3 and an SOA 4a4. In this embodiment, the laser element 4a also includes one or more optical function units other than the optical amplifier 4a1, which provides the advantage of enabling the optical module 100 to be configured more compactly than when each optical function unit is provided separately.

[0081] Sixth Embodiment FIG. 9 is a plan view showing an optical module 100F (100) according to a sixth embodiment with the top cover removed. As shown in FIG. 9, the optical module 100F includes two etalon filters 11 arranged in series between the lens 51 and the optical isolator 6. A mirror 10b is provided at the end 4a12 of the optical amplifier 4a1, and a mirror 10a is provided on the end face 11a of the etalon filter 11 farthest from the lens 51, opposite the lens 51. A heater 12 is provided on the end face of each etalon filter 11 closer to the lens 51. This configuration also achieves the same effects as the first embodiment. Furthermore, this configuration offers the advantage of being able to control a wider wavelength band due to the increased number of etalon filters 11. The heater 12 may also be provided on the end face 11a of each etalon filter 11 opposite the lens 51.

[0082] Seventh Embodiment FIG. 10 is a plan view showing an optical module 100G (100) according to the seventh embodiment with the top cover removed. In addition to the same components as those of the first embodiment, the optical module 100G includes multiple lenses 50, a beam splitter 23G, an SOA 4a4, and the like. The lens 50 and the beam splitter 23G are interposed between a mirror 10a provided on the end face 11a of the etalon filter 11 and a mirror 10b provided on the end 4a12 of the optical amplifier 4a1. The heater 12 is provided on the end face of the etalon filter 11 opposite the end face 11a on which the mirror 10a is provided. This configuration also achieves the same effects as those of the first embodiment. The heater 12 may also be provided on the end face 11a of the etalon filter 11 on which the mirror 10a is provided.

[0083] Eighth Embodiment FIG. 11 is a side view of a portion of an optical module 100H (100) according to an eighth embodiment. In this embodiment, the etalon filter 11 is not directly supported by the heat shield 70, but is supported by the heat shield 70 via a heater 12. That is, in this embodiment, the heater 12 is interposed between the etalon filter 11 and the optical amplifier 4a1 or the Peltier module 60P. This configuration also achieves the same effects as the first embodiment. Furthermore, this configuration further reduces the thermal influence of the optical amplifier 4a1 or the Peltier module 60P on the etalon filter 11, enabling the heater 12 to more accurately adjust the temperature of the etalon filter 11 and, ultimately, control the wavelength.

[0084] Ninth Embodiment FIG. 12 is a side view of a portion of an optical module 100I (100) according to a ninth embodiment. In this embodiment, a subassembly of an etalon filter 11 and a heater 12 is housed in a recess 70a1 provided in the top surface 70a of a heat shield 70 and secured by a bonding material 90. This configuration also achieves the same effects as the first embodiment. Furthermore, this configuration not only enables the etalon filter 11 and the heater 12 to be reliably secured by the heat shield 70, but also allows for, for example, a portion of the side surface of the subassembly to abut against the side surface of the recess 70a1, thereby further improving the accuracy of the position and posture (angle) of the subassembly. Note that only one of the etalon filter 11 and the heater 12 may be housed in the recess 70a1.

[0085] 13 is a side view of a portion of an optical module 100J (100) according to a tenth embodiment. In this embodiment, the transparent heater 12b is provided between the etalon filter 11 and the transparent substrate 12a. This configuration also provides the same effects as the first embodiment. Furthermore, this configuration allows the etalon filter 11 to be heated more efficiently by the transparent heater 12b, thereby reducing the power consumption associated with heating the etalon filter 11.

[0086] Eleventh Embodiment FIG. 14 is a front view of the heater 12 included in the optical module 100K (100) of the eleventh embodiment. FIG. 15 is a cross-sectional view taken along the line XV-XV of FIG. 14. As shown in FIGS. 14 and 15, in this embodiment, the temperature-sensing resistance wiring layer 13 is disposed on the surface of the transparent electric heater 12b, on the opposite side of the transparent substrate 12a from the etalon filter 11. The temperature-sensing resistance wiring layer 13 has two end portions 13t and an extension portion 13a. The extension portion 13a extends between the two end portions 13t and 13t, bending with a predetermined width and thickness (height) on the surface of the transparent electric heater 12b. In this embodiment, the extension portion 13a extends in an inverted U-shape, opening in the opposite direction of the Z direction, outside the passing area A, i.e., at a position outside the passing area A. The temperature-sensing resistance wiring layer 13 is made of, for example, a metal film laminated with Ti / Pt. According to this embodiment, the same effects as those of the first embodiment can be obtained, and in addition, the wavelength control accuracy can be further improved since the temperature of the etalon filter 11 can be estimated based on the resistance value of the temperature measuring resistance wiring layer 13. The temperature measuring resistance wiring layer 13 is an example of a temperature detection unit. Note that the specifications of the temperature measuring resistance wiring layer 13, such as the position and shape, are not limited to those shown in FIG. 14 .

[0087] FIG. 16 is a plan view of a portion of the optical module 100K. As shown in FIG. 16 , two wiring patterns 70b1 extending substantially parallel to each other in the X direction (optical axis direction) with a predetermined width in the Y direction are provided on the top surface 70a (surface) of the heat shield 70. Two wiring patterns 70b1 extending substantially parallel to each other in the X direction with a predetermined width in the Y direction are provided on the top surface 70a (surface) of the heat shield 70. The wiring patterns 70b1 as conductors are electrically connected to the end 12t of the wiring portion 12c via respective bonding materials 90a (90). The wiring patterns 70b2 as conductors are electrically connected to the end 13t of the temperature measuring resistance wiring layer 13 via respective bonding materials 90b (90). The bonding materials 90a and 90b are conductive bonding materials, such as solder or a conductive adhesive. Furthermore, the end of the etalon filter 11 on the opposite side in the Z direction is bonded to the top surface 70a and the wiring patterns 70b1 and 70b2 via a bonding material 90c (90). The bonding material 90c is an insulating bonding material having insulating properties, such as a synthetic resin adhesive. With this configuration, the end of the assembly of the etalon filter 11 and the heater 12 on the opposite side in the Z direction can be more firmly fixed to the heat shield 70 via the bonding material 90 at both ends in the X direction. Furthermore, the bonding material 90a electrically connects the wiring portion 12c and the wiring pattern 70b1, and the bonding material 90b electrically connects the temperature measuring resistance wiring layer 13 and the wiring pattern 70b2. According to this configuration, the bonding materials 90a and 90b can be used to fix the subassembly and electrically connect the conductors, which has advantages such as reducing the amount of bonding material and reducing the labor and cost required for the bonding work compared to when a bonding material is used for both fixing the subassembly and electrically connecting the conductors. The bonding materials 90a and 90b are called conductive bonding materials, and the bonding material 90c is called an insulating bonding material.

[0088] [Twelfth and Thirteenth Embodiments] Fig. 17 is a cross-sectional view of the etalon filter 11, heater 12, and temperature measuring resistance wiring layer 13 included in an optical module 100L (100) of a twelfth embodiment, taken at the same position as in Fig. 15 . Fig. 18 is a plan view of the etalon filter 11, heater 12, and temperature measuring resistance wiring layer 13 included in an optical module 100M (100) of a thirteenth embodiment. In the twelfth embodiment, as shown in Fig. 17 , the temperature measuring resistance wiring layer 13 is provided between the etalon filter 11 and the transparent substrate 12a. In the thirteenth embodiment, as shown in Fig. 18 , the temperature measuring resistance wiring layer 13 is provided on the opposite side of the etalon filter 11 from the heater 12. These configurations also provide the same effects as the first embodiment.

[0089] While the above describes exemplary embodiments and modifications of the present invention, these are merely examples and are not intended to limit the scope of the invention. The above embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of each configuration, shape, and the like (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be appropriately modified and implemented.

[0090] For example, the transparent electric heater may be provided on the etalon filter instead of on the transparent substrate.

[0091] The present invention can be used in optical devices and tunable lasers.

[0092] DESCRIPTION OF SYMBOLS 1...Housing 1a...Output port 1b...Side wall 1c...Bottom wall 2...Lens 3...Optical fiber 4...Chip-on submount 4a...Laser element 4a1...Optical amplifier 4a11...End (first end) 4a12...End (second end) 4a2, 4a3...Optical filter 4a4...SOA 4b...Submount 4c...Thermistor 6...Optical isolator 10a...Mirror (first mirror) 10b...Mirror (second mirror) 11...Etalon filter 11a...End face (surface) 12...Heater (electric heating member) 12a...Transparent base material 12b...Transparent electric heating element 12c...Wiring portion 12t...End 13...Temperature measuring resistance wiring layer (temperature detection portion) 13a...Extension portion 13t...End 23, 23G...Beam splitter 24...Photodiode 50, 51, 52...Lens 60...Carrier 60a...First substrate 60b...Second substrate 60c...Thermoelectric element 60P...Peltier module 70...Heat shielding member 70a...Top surface (surface) 70a1...Concave portion 70b1, 70b2...Wiring pattern 90...Bonding material (first bonding material) 90a...Bonding material 90b...Bonding material 90c...Bonding material 91...Bonding material (second bonding material) 100, 100A to 100M...Optical module (tunable laser, optical device) A...Passing area X...Direction Y...Direction Z...Direction

Claims

1. An optical device comprising: a base; a plurality of optical components fixed to the base; an etalon filter as the optical components; and an electric heating member integrated with the etalon filter, optically in series with the etalon filter, and having a transparent electric heating body that transmits light.

2. The optical device according to claim 1, wherein the electric heating element is optically connected in series with the etalon filter and the transparent electric heating element, transmits light, and has a transparent substrate provided on the surface of the transparent electric heating element.

3. The optical device according to claim 2, wherein the transparent electric heater is located on the opposite side of the transparent substrate from the etalon filter.

4. The optical device according to claim 2, wherein the transparent electric heater is positioned between the transparent substrate and the etalon filter.

5. An optical device according to claim 1 or 2, further comprising a wiring section for supplying power to said transparent electric heating element, said wiring section being provided at a position outside the light passing area of said transparent electric heating element.

6. The optical device according to claim 1 or 2, wherein the etalon filter has a body and a dielectric film provided on the entrance end and exit end of the body, and the body is made of glass or silicon.

7. An optical device according to claim 1 or 2, wherein the transparent electric heater is made of indium tin oxide.

8. An optical device as described in claim 1 or 2, wherein the transparent electric heater is capable of changing the temperature of the light passing area of the etalon filter within a range of from room temperature to 150°C by changing the power supplied thereto.

9. The optical device according to claim 1 or 2, further comprising a temperature detection unit for detecting the temperature of said etalon filter or said electric heating member.

10. The optical device according to claim 9, wherein the temperature detection section is a temperature-sensing resistance wiring layer whose resistance value changes in response to temperature changes.

11. An optical device as described in claim 10, wherein the electric heating element is optically connected in series with the etalon filter and the transparent electric heating element, has a transparent substrate that transmits light and is provided on the surface of the transparent electric heating element, and the temperature measuring resistance wiring layer is located on the opposite side of the transparent substrate from the etalon filter.

12. An optical device as described in claim 10, wherein the electric heating element is optically connected in series with the etalon filter and the transparent electric heating element, transmits light, and has a transparent substrate provided on the surface of the transparent electric heating element, and the temperature measuring resistance wiring layer is positioned between the transparent substrate and the etalon filter.

13. The optical device according to claim 10, wherein the temperature sensing resistance wiring layer is made of a metal film laminated with Ti / Pt.

14. The optical device according to claim 1 or 2, wherein the electric heating member is interposed between the etalon filter and a heating element other than the electric heating member.

15. The optical device according to claim 1 or 2, wherein a heat insulating member is interposed between said etalon filter and a heating element other than said electric heating member.

16. The optical device according to claim 1 or 2, wherein the etalon filter is fixed to the base or another member fixed to the base via a first bonding material.

17. The optical device according to claim 16, wherein the etalon filter and the electric heating member are bonded together via a second bonding material having a thermal conductivity higher than that of the first bonding material.

18. A wavelength tunable laser comprising: an optical amplifier unit that generates and amplifies light and outputs the light from a first end and a second end opposite the first end; a first mirror that reflects the light output from the first end; a second mirror that reflects the light output from the second end; an etalon filter that is provided between the optical amplifier unit and the first mirror or the second mirror, has predetermined wavelength characteristics, and passes the light output from the optical amplifier unit; and an electric heating element that is integrated with the etalon filter, is optically in series with the etalon filter, and has a transparent electric heating element that transmits light.

19. The tunable laser according to claim 18, further comprising a lens provided between said optical amplifier section and said etalon filter, through which light traveling between said optical amplifier section and said etalon filter passes.

20. A tunable laser according to claim 18 or 19, comprising: a temperature control mechanism for adjusting the temperature of the optical amplification section; and a heat insulating member interposed between the temperature control mechanism and the etalon filter to suppress heat conduction between the temperature control mechanism and the etalon filter.

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