WO2022082965A1 - 一种波长锁定器和可调激光器组件 - Google Patents

一种波长锁定器和可调激光器组件 Download PDF

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Publication number
WO2022082965A1
WO2022082965A1 PCT/CN2020/135491 CN2020135491W WO2022082965A1 WO 2022082965 A1 WO2022082965 A1 WO 2022082965A1 CN 2020135491 W CN2020135491 W CN 2020135491W WO 2022082965 A1 WO2022082965 A1 WO 2022082965A1
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Prior art keywords
light
linearly polarized
prism
polarized light
emitting surface
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PCT/CN2020/135491
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English (en)
French (fr)
Inventor
汤学胜
余斯佳
张博
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武汉光迅科技股份有限公司
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Publication of WO2022082965A1 publication Critical patent/WO2022082965A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/065—Mode locking; Mode suppression; Mode selection ; Self pulsating
    • H01S5/0657—Mode locking, i.e. generation of pulses at a frequency corresponding to a roundtrip in the cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/06808—Stabilisation of laser output parameters by monitoring the electrical laser parameters, e.g. voltage or current

Definitions

  • the present application belongs to the technical field of optical communication, and more particularly, to a wavelength locker and a tunable laser assembly.
  • DWDM Dense Wavelength Division Multiplexing
  • the frequency interval of optical channels continues to narrow, and the center frequency deviation of multiplexed optical channels is required.
  • manufacturers of wavelength division multiplexing equipment generally require that the maximum deviation of the output light wavelength of the optical emission light source-semiconductor laser from the center frequency of the ITU-T standard does not exceed ⁇ 2.5 GHz. Affected by external environmental factors and the aging of the light source, the wavelength drift in the whole life cycle of the semiconductor laser can easily exceed this range. Therefore, it is necessary to adopt an effective wavelength locking technology to improve the wavelength stability of the communication light source-semiconductor laser.
  • the integrated tunable laser assembly (Integrable Tunable Laser Assembly, abbreviated as ITLA) for digital coherent optical communication directly integrates the wavelength locker functional unit.
  • ITLA Intelligent Tunable Laser Assembly
  • the integrated wavelength locking function in the communication light source has become the norm.
  • the optical path structure commonly used by the wavelength locker is shown in Figure 1. After obtaining part of the optical signal from the tunable laser, part of the laser is input to the beam splitter, which is divided into two parts after the beam splitter.
  • the photodetector PD1 part of it is received by the photodetector PD1 after being filtered by the Fabry-Perot etalon (F-P Etalon); the other part directly enters the photodetector PD2 as a reference signal, and the electrical signal of PD1 and the laser
  • the wavelength is related to the optical power, and the PD2 electrical signal is only related to the output power of the laser.
  • the frequency discrimination signal generated by the ratio of these two signals is used to drive the control of the laser, and then adjust the wavelength to stabilize the laser to the required ITU-T wavelength.
  • the generation of the frequency discrimination signal uses the periodic characteristics of the F-P Etalon transmission spectrum to generate the ITU-T frequency standard required for each output wavelength of ITLA, and uses the reference signal of PD2 to form a differential system to eliminate the influence of the power fluctuation of the tunable laser, so that The change of the frequency of the laser will cause the change of the transmitted light intensity of the F-P Etalon filter, and the ratio of the light intensity detected by the two photodetectors is maintained at a constant value to achieve a stable output of the frequency of the laser.
  • the wavelength at which the laser is locked can usually be at the peak or the bottom of the transmission spectrum curve of the F-P Etalon filter.
  • the reflectivity of the clear surface of the F-P Etalon filter determined by the free spectral range directly determines the sharpness of the transmission spectrum, which in turn determines the wavelength locking sensitivity (slope of the locking point), and the etalon clears
  • the structure of the traditional wavelength locker shown in Figure 1 is relatively scattered, which is not suitable for integration in a miniaturized package, and the locking range and the locking point slope need to be comprehensively considered, so it is often difficult to obtain high wavelength locking sensitivity.
  • the present application provides a wavelength locker and a tunable laser assembly, the purpose of which is that the wavelength locker of the present application integrates the spectroscopic function and the etalon, and has a simple structure and a layout. Compact and small in size.
  • a wavelength locker includes a beam splitting unit 1, a first photodetector 2 and a second photodetector 3, the beam splitting unit 1 including the light incident surface, the first light emitting surface and the second light emitting surface;
  • the light-incident surface and the first light-emitting surface are coated with a reflective medium film layer with the same reflectivity to form a reflective cavity mirror of the etalon;
  • the beam splitting unit 1 is used to decompose the received linearly polarized light into a first linearly polarized light and a second linearly polarized light. Received by the photodetector 2, the second linearly polarized light is received by the second photodetector 3 after being emitted from the second light emitting surface;
  • the ratio of the electrical signals generated by the first photodetector 2 and the second photodetector 3 forms a frequency discrimination signal.
  • the beam splitting unit 1 includes a first prism 11 and a second prism 12 , and one of the inclined surfaces of the first prism 11 is glued with one of the inclined surfaces of the second prism 12 to form the first prism. gluing surface, the first gluing surface is coated with a polarizing beam splitting dielectric film;
  • the polarization beam splitting dielectric film is used to decompose the linearly polarized light into the first linearly polarized light and the second linearly polarized light with orthogonal polarization states;
  • Two surfaces of the first prism 11 are configured as the light incident surface and the first light exit surface.
  • one surface of the second prism 12 is configured as the second light emitting surface, and the second light emitting surface is coated with an anti-reflection film.
  • the beam splitting unit 1 further includes a first compensation sheet 13, the first compensation sheet 13 is glued with the second prism 12 to form a second glue surface, and the second glue surface Anti-reflection coating;
  • the light-emitting surface of the first compensation sheet 13 is configured as the second light-emitting surface, and the second light-emitting surface is coated with the same reflective medium film layer as the light-incident surface, so as to form a reflective cavity mirror of the etalon. .
  • the first prism 11 is a quadrilateral prism, two surfaces of the quadrilateral prism are parallel to each other, and the two parallel surfaces are set as the light incident surface and the first pass-through surface.
  • smooth surface the second prism 12 is a triangular prism; or,
  • Both the first prism 11 and the second prism 12 are triangular prisms.
  • the beam splitting unit 1 includes a birefringent crystal 14, and the birefringent crystal 14 is configured to decompose the linearly polarized light into the first linearly polarized light and the second linearly polarized light with orthogonal polarization states. Two linearly polarized light;
  • One surface of the birefringent crystal 14 is configured as the light incident surface, and the other surface of the birefringent crystal 14 is divided into a first part and a second part, and the first part is configured as the first part light surface.
  • the second part is configured as the second light emitting surface, and the second light emitting surface is coated with an anti-reflection coating.
  • the beam splitting unit 1 further includes a second compensation sheet 15, the second compensation sheet 15 is glued with the second part to form a third glued surface, and the third glued surface is coated with With anti-reflection coating;
  • the light-emitting surface of the second compensation sheet 15 is configured as the second light-emitting surface, and the second light-emitting surface is coated with the same reflective medium film layer as the light-incident surface, so as to form a reflective cavity mirror of the etalon .
  • the wavelength locker further includes a half-wave plate 4, the half-wave plate 4 is disposed adjacent to the light incident surface, and the half-wave plate 4 can rotate around the axis of the optical path.
  • a tunable laser assembly is provided, and the tunable laser assembly includes the wavelength locker described in the present application.
  • the present application provides a wavelength locker and a tunable laser assembly, wherein the wavelength locker includes a beam splitting unit, a first photodetector and a second photodetector, the beam splitting unit includes a light incident surface, a first light exit surface and a second light exit surface; the light entrance surface and the first light exit surface are coated with the same reflectivity
  • the reflective medium film layer of the etalon is used to form a reflective cavity mirror of the etalon;
  • the beam splitting unit is used to decompose the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, the first linearly polarized light from After the first light-emitting surface emerges, it is received by the first photodetector, and the second linearly polarized light is emitted from the second light-emitting surface and then received by the second photodetector; wherein, the The ratio
  • the spectroscopic function and the etalon are integrated together, which has a simple structure, compact layout and small size, which is very suitable for being integrated in the miniaturized package of nano ultra-compact tunable laser assembly (Nano ITLA).
  • the wavelength locking range is comparable to the conventional structure, and the locking sensitivity is higher.
  • Fig. 1 is the structural representation of the wavelength locker in the prior art
  • FIG. 2 is a schematic structural diagram of a first wavelength locker provided by an embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of a second wavelength locker provided by an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a third wavelength locker provided by an embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of a fourth wavelength locker provided by an embodiment of the present application.
  • FIG. 6 is a schematic structural diagram of a fifth wavelength locker provided by an embodiment of the present application.
  • FIG. 7 is a schematic structural diagram of a sixth wavelength locker provided by an embodiment of the present application.
  • FIG. 8 is a schematic structural diagram of a seventh wavelength locker provided by an embodiment of the present application.
  • FIG. 9 is a schematic diagram of the principle of wavelength locking provided by an embodiment of the present application.
  • FIG. 10 is a schematic schematic diagram of another wavelength locking principle provided by an embodiment of the present application.
  • a wavelength locker in this embodiment, includes a beam splitting unit, a first photodetector and a second photodetector, and the beam splitting unit includes a light incident surface and a first light exit surface and a second light-emitting surface; the light-incident surface and the first light-emitting surface are coated with a reflective medium film layer with the same reflectivity, so as to form a reflective cavity mirror of the etalon.
  • the beam splitting unit is used to decompose the received linearly polarized light into a first linearly polarized light and a second linearly polarized light.
  • the first linearly polarized light is emitted from the first light emitting surface, it is After being received by the first photodetector, the second linearly polarized light is received by the second photodetector after being emitted from the second light emitting surface.
  • the ratio of the electrical signals generated by the first photodetector and the second photodetector forms a frequency discrimination signal, wherein the first linearly polarized light passes through the light incident surface and the first light exit surface.
  • the reflector mirror of the etalon is then received by the first photodetector, and the electrical signal generated by the first photodetector is related to the wavelength and optical power of the laser; the electrical signal generated by the second photodetector is only Related to the output power of the laser, the frequency discrimination signal generated by the ratio of these two signals is used to control the laser, adjust the wavelength of the laser output, and then stabilize to the desired wavelength.
  • the wavelength locker further includes a half-wave plate, the half-wave plate is disposed adjacent to the light incident surface, and the half-wave plate can be rotated around the axis of the optical path to adjust the beam splitting ratio of the beam splitting unit.
  • the process of adjusting the splitting ratio is as follows: in the process of making the wavelength locker, the half-wave plate is rotated around the axis of the optical path. During the rotation of the half-wave plate, the polarization state of the output light wave of the semiconductor laser will be changed. The light intensity ratio of the first linearly polarized light and the second linearly polarized light formed by the polarization splitting of the beam unit will also change accordingly.
  • the spectroscopic function and the etalon are integrated together, the structure is simple, the layout is compact, and the size is small, which is very suitable for integration in the miniaturized package of the nano ultra-compact tunable laser assembly (Nano ITLA).
  • this embodiment provides a wavelength locker
  • the wavelength locker includes a beam splitting unit 1 , a first photodetector 2 and a second photodetector 3
  • the beam splitting unit 1 includes a light incident surface A , a first light-emitting surface B and a second light-emitting surface C; the light-incident surface A and the first light-emitting surface B are coated with a reflective medium film layer with the same reflectivity to form the etalon reflective cavity mirror.
  • the beam splitting unit 1 includes a first prism 11 and a second prism 12, one of the inclined surfaces of the first prism 11 and one of the inclined surfaces of the second prism 12 are glued to form a first glued surface D, the The first glued surface D is coated with a polarization beam splitting dielectric film, and the polarization beam splitting dielectric film is used to decompose the linearly polarized light into a first linearly polarized light and a second linearly polarized light with orthogonal polarization states.
  • Two surfaces of the first prism 11 are configured as the light incident surface A and the first light exit surface B, and one surface of the second prism 12 is configured as the second light exit surface C,
  • the second light-emitting surface C is coated with an anti-reflection film.
  • the wavelength locker further includes a half-wave plate 4, which is arranged adjacent to the light incident surface A, and the half-wave plate 4 can be rotated around the axis of the optical path to adjust the beam splitting unit 1 the splitting ratio.
  • the process of adjusting the splitting ratio is as follows: in the process of making the wavelength locker, the half-wave plate 4 is rotated around the axis of the optical path. During the rotation of the half-wave plate 4, the polarization state of the output light wave of the semiconductor laser will be changed. Therefore, the ratio of the light intensity of the first linearly polarized light and the second linearly polarized light formed by the polarization and splitting of the beam splitting unit 1 will also change accordingly.
  • the first prism 11 is a quadrilateral prism, and two surfaces of the quadrilateral prism are parallel to each other, and the two parallel surfaces are set as the light incident surface A and the first light passing surface, so
  • the second prism 12 is a triangular prism.
  • the quadrilateral prism can be a parallelogram prism or a trapezoidal prism, and the quadrilateral prism can be a parallelogram prism as an example for explanation.
  • the beam splitting unit 1 is formed by gluing the inclined surface of the parallelogram prism and the inclined surface of the triangular prism.
  • the two opposite non-glued surfaces of the parallelogram prism are parallel to each other, and are coated with a partially reflective dielectric film with the same reflectivity, forming a Fabry. - Reflector mirror for Perot etalon.
  • the two opposite non-glued surfaces of the parallelogram prism are respectively configured as the light incident surface A and the first light emitting surface B, the light incident surface A and the first light emitting surface B are parallel to each other, and All are coated with a partially reflective dielectric film with the same reflectivity to form the reflective cavity mirror of the Fabry-Perot etalon.
  • the beam splitting unit 1 of this embodiment integrates the functions of a beam splitter and an etalon at the same time, and has a compact structure. Compared with the F-P etalon filter provided separately in FIG. 1 , the The thickness of the equivalent etalon formed between the light incident surface A and the first light emitting surface B is obviously reduced.
  • the parallelogram prism and the triangular prism are glued together to form a first gluing surface D, and the first gluing surface D is coated with a polarization beam splitting dielectric film, which can decompose a beam of incident light of any polarization state into polarization
  • the first linearly polarized light (S-polarized light) and the second linearly polarized light (P-polarized light) are vertically distributed up and down.
  • the first linearly polarized light formed by the polarization beam splitting of the first glued surface D is repeatedly reflected between the two opposite light-transmitting surfaces of the parallelogram prism to form multi-beam interference.
  • One of the surfaces of the triangular prism is configured as the second light emitting surface C, and the second linearly polarized light formed by the polarization and splitting of the first gluing surface D is directly projected into the second photodetector 3 through the second light emitting surface C of the triangular prism.
  • the second light-emitting surface C is coated with an anti-reflection coating, and the purpose of coating the anti-reflection coating is to reduce the intensity of the reflected light and avoid the formation of an etalon effect with the light incident surface A of the parallelogram prism.
  • the first photodetector 2 and the second photodetector 3 are arranged corresponding to the two linearly polarized beams of orthogonal polarization states polarized and split by the beam splitting unit 1, and receive the first linearly polarized light and the second linearly polarized light respectively.
  • Polarized light, the first photodetector 2 and the second photodetector 3 convert the received optical signal into a frequency discrimination signal required for wavelength locking.
  • FIG. 2 There is a variable implementation for the embodiment shown in FIG. 2 .
  • the difference from FIG. 2 is that the first light emitting surface B is arranged on a triangular prism, and the second light emitting surface C is arranged on a parallelogram prism.
  • two surfaces of the parallelogram prism are respectively configured as light incident surface A and second light exit surface C, and one surface of the triangular prism is configured as first light exit surface B, that is, a parallelogram
  • the light-incident surface A of the prism and the first light-emitting surface B of the triangular prism are parallel to each other, and are coated with a reflective dielectric film of the same reflectivity, which constitutes the reflective cavity mirror of the Fabry-Perot etalon.
  • the second light-emitting surface C of the parallelogram prism is coated with an anti-reflection coating.
  • the electrical signal generated by the second photodetector 3 that receives the second linearly polarized light is related to the wavelength and optical power of the laser; the first photoelectric signal that receives the first linearly polarized light (S-polarized light)
  • the electrical signal generated by the detector 2 is only related to the output power of the laser, and the frequency discrimination signal generated by the ratio of the two signals is used to drive the control of the laser, and then adjust and stabilize to the desired wavelength.
  • the beam splitting unit 1 further includes a first compensation sheet 13 , and the first compensation sheet 13 is glued with the second prism 12 to form a second glued surface E, the first compensation sheet 13 is Anti-reflection coating is plated on the second glued surface E.
  • the light-emitting surface of the first compensation sheet 13 is configured as the second light-emitting surface C, and the second light-emitting surface C is coated with the same reflective medium film layer as the light-incident surface A to form the etalon. reflector mirror.
  • the outgoing light-transmitting surface of the triangular prism and the incident light-transmitting surface of the first compensation sheet 13 are parallel to each other, and the two are glued to each other to form a second glued surface E, and the second glued surface E is coated with an anti-reflection film,
  • the purpose of the anti-reflection coating is to reduce the intensity of the reflected light and avoid the formation of additional etalon effects.
  • the second light-emitting surface C of the first compensation sheet 13 and the light-incident surface A of the parallelogram prism are parallel to each other, and are coated with a partially reflective dielectric film with the same reflectivity to form a Fabry-Perot etalon reflective cavity mirror.
  • the second linearly polarized light formed by the polarization splitting of the first glued surface D is repeatedly reflected between the light incident surface A of the parallelogram prism and the second light exit surface C of the first compensator 13 to form multi-beam interference.
  • the first compensation sheet 13 is preferably made of the same material as the triangular prism, and the thickness of the first compensation sheet 13 is set according to the following principles:
  • optical thickness ⁇ s of the equivalent F-P Etalon passed by the first linearly polarized light and the optical thickness ⁇ p of the equivalent F-P Etalon passed by the second polarized light differ by ⁇ /4, where ⁇ is the wavelength of the laser.
  • the equivalent F-P Etalon through which the first linearly polarized light passes and the equivalent F-P Etalon through which the second linearly polarized light passes have almost the same free spectral range (FSR).
  • the actual thickness of the first compensation sheet 13 has a certain tolerance, and the optical thickness difference between the first linearly polarized light and the second linearly polarized light passing through the corresponding F-P Etalon can be adjusted online by adjusting the angle of the incident light.
  • the wavelength locker of this embodiment can effectively improve the wavelength locking sensitivity without greatly increasing the product size.
  • the principle analysis below please refer to the principle analysis below.
  • the beam splitting unit 1 further includes a third prism (not marked in the figure), the third prism is a triangular prism, and the third prism is the same as the second prism.
  • the prism 12 is disposed opposite to the parallelogram prism, and the inclined surface of the triangular prism is glued with another inclined surface of the parallelogram prism.
  • the shape of the beam splitting unit 1 is relatively regular, which is convenient for clamping, so as to reduce the risk of the beam splitting unit 1 being damaged in the process of manufacturing the wavelength locker.
  • the first prism 11 and the second prism 12 are both triangular prisms, and the triangular prisms are isosceles right-angled triangular prisms, and the inclined surfaces of the two triangular prisms are glued to each other,
  • the first gluing surface D is formed, the two right-angle surfaces of the first prism 11 are respectively configured as the light incident surface A and the first light exit surface B, and one of the right angle surfaces of the second prism 12 is configured as the second light exit surface C.
  • the remaining coating methods and working principles are basically the same as those in Embodiment 2, and will not be repeated here.
  • the beam splitting unit 1 further includes a first compensation sheet 13 , and the first compensation sheet 13 is glued with the second prism 12 to form a second glue Surface E, the second glued surface E is coated with an anti-reflection film.
  • the light-emitting surface of the first compensation sheet 13 is configured as the second light-emitting surface C, and the second light-emitting surface C is coated with the same reflective medium film layer as the light-incident surface A to form the etalon. reflector mirror.
  • a wavelength locker includes a beam splitting unit 1 , a first photodetector 2 and a second photodetector 3 .
  • the beam splitting unit 1 includes an input A light surface A, a first light exit surface B and a second light exit surface C; the light incident surface A and the first light exit surface B are coated with a reflective medium film layer with the same reflectivity to form a reflective cavity mirror of the etalon .
  • the wavelength locker further includes a half-wave plate 4, which is arranged adjacent to the light incident surface A, and the half-wave plate 4 can be rotated around the axis of the optical path to adjust the beam splitting unit 1 the splitting ratio.
  • the process of adjusting the splitting ratio is as follows: in the process of making the wavelength locker, the half-wave plate 4 is rotated around the axis of the optical path. During the rotation of the half-wave plate 4, the polarization state of the output light wave of the semiconductor laser will be changed. Therefore, the ratio of the light intensity of the first linearly polarized light and the second linearly polarized light formed by the polarization and splitting of the beam splitting unit 1 will also change accordingly.
  • the beam splitting unit 1 includes a birefringent crystal 14, and the birefringent crystal 14 is used to decompose the linearly polarized light into the first linearly polarized light and the second linearly polarized light with orthogonal polarization states; the birefringent One of the faces of the crystal 14 is configured as the light incident face A, and the other face of the birefringent crystal 14 is divided into a first part (upper part in FIG. 7 ) and a second part (lower part in FIG. 7 ) ), the first part is configured as the first light emitting surface B.
  • the second part is configured as the second light emitting surface C, and the second light emitting surface C is coated with an anti-reflection film.
  • the optical axis of the birefringent crystal 14 is parallel to the main optical section, the main axis is at an acute angle with the light incident surface A, the light incident surface A and the first light exit surface B are parallel to each other, and are coated with a reflective medium film of the same reflectivity, forming Cavity mirror for the Fabry-Perot etalon.
  • the birefringent crystal 14 can decompose a beam of incident light of any polarization state into a first linearly polarized light (P-polarized light) and a second linearly polarized light (S-polarized light whose polarization states are orthogonally distributed up and down by utilizing the birefringence characteristic of the crystal. Light).
  • P-polarized light first linearly polarized light
  • S-polarized light second linearly polarized light
  • the first photodetector 2 and the second photodetector 3 are arranged corresponding to the first linearly polarized light and the second linearly polarized light, and receive the energy of the corresponding polarized light respectively.
  • the first photodetector 2 and the second photodetector 3 Convert the received optical signal into a frequency discrimination signal required for wavelength locking.
  • FIG. 7 There is a variant implementation for the embodiment shown in FIG. 7 , which differs from FIG. 7 in that the other face of the birefringent crystal 14 is divided into a first part (upper part in FIG. 7 ) and a second part part (the lower part in FIG. 7 ), the second part is configured as the first light emitting surface B.
  • the first part is configured as the second light emitting surface C, and the second light emitting surface C is coated with an anti-reflection film.
  • the electrical signal generated by the second photodetector 3 that receives the second linearly polarized light is related to the wavelength and optical power of the laser; the first photoelectric signal that receives the first linearly polarized light (P-polarized light)
  • the electrical signal generated by the detector 2 is only related to the output power of the laser, and the frequency discrimination signal generated by the ratio of the two signals is used to drive the control of the laser, and then adjust and stabilize to the desired wavelength.
  • the beam splitting unit 1 further includes a second compensation sheet 15 , and the second compensation sheet 15 is glued with the second part to form a third glued surface F, and the second compensation sheet 15 is formed.
  • Anti-reflection coating is plated on the three glued surface F;
  • the light-emitting surface of the second compensation sheet 15 is configured as the second light-emitting surface C, and the second light-emitting surface C is coated with the same reflective medium film layer as the light-incident surface A to form the etalon. reflector mirror.
  • the outgoing light-transmitting surface of the birefringent crystal 14 and the incident light-transmitting surface of the second compensator 15 are parallel to each other, and the two are glued together to form a third glued surface F, and the third glued surface F is plated with antireflection.
  • the purpose of antireflection coating is to reduce the intensity of reflected light and avoid the formation of additional etalon effects.
  • the second light-emitting surface C of the second compensation plate 15 and the light-incident surface A of the birefringent crystal 14 are parallel to each other, and are coated with a partially reflective dielectric film with the same reflectivity, forming the Fabry-Perot standard Equipped with mirrors.
  • the first linearly polarized light formed by the polarization beam splitting of the birefringent crystal 14 is repeatedly reflected between the light incident surface A and the first light exit surface B of the polarization beam splitting birefringent crystal 14 to form multi-beam interference, and from the light incident surface A->The optical length of the propagation path between the first light-emitting surface B, which is equivalent to the optical thickness of the F-P Etalon through which the first linearly polarized light passes.
  • the second linearly polarized light formed by the polarization and splitting of the birefringent crystal 14 is repeatedly reflected between the light incident surface A of the birefringent crystal 14 and the second light exit surface C of the second compensation plate 15 to form multi-beam interference.
  • the second compensation plate 15 is preferably made of the same material as the birefringent crystal, and the thickness of the second compensation plate 15 is set according to the following principles:
  • optical thickness ⁇ p of the equivalent F-P Etalon passed by the first linearly polarized light and the optical thickness ⁇ s of the equivalent F-P Etalon passed by the second polarized light differ by ⁇ /4, where ⁇ is the wavelength of the laser.
  • the equivalent F-P Etalon through which the first linearly polarized light passes and the equivalent F-P Etalon through which the second linearly polarized light passes have almost the same free spectral range (FSR).
  • the actual thickness of the second compensation sheet 15 has a certain tolerance, and the optical thickness difference between the first linearly polarized light and the second linearly polarized light passing through the corresponding F-P Etalon can be adjusted online by adjusting the angle of the incident light.
  • the wavelength locker of this embodiment can effectively improve the wavelength locking sensitivity without greatly increasing the product size.
  • the principle analysis below please refer to the principle analysis below.
  • a tunable laser assembly is also provided, and the tunable laser assembly includes the wavelength locker described in any of the foregoing embodiments.
  • Embodiment 2 receives the transmission spectrum of the F-P etalon, and the generated electrical signal (PIN1) changes periodically with the input optical frequency of the laser; the electrical signal (PIN2) generated by the second photodetector 3 ) receives the reference optical power output by the laser.
  • the ratio of these two signals PIN1/PIN2 is usually used to generate the frequency discrimination signal.
  • the relationship between the frequency discrimination signal (PIN1/PIN2) and the input optical frequency of the laser is shown in the figure The solid line is shown in trace1.
  • trace2 is the target value ( ⁇ ) of the frequency discrimination signal maintained in the lock wave.
  • the working principles of positive locking and negative locking are basically the same, and the positive locking is taken as an example and explained here.
  • the measured frequency discrimination signal is greater than the target value ⁇ (PIN1/PIN2> ⁇ ), it indicates that the optical frequency of the laser is too large, and the control parameters of the laser need to be adjusted to move the wavelength of the laser to a longer wavelength; if the measured signal frequency discrimination signal If it is less than the target value ⁇ (PIN1/PIN2 ⁇ ), it indicates that the laser light frequency is too small, and the control parameters of the laser need to be adjusted to move the wavelength of the laser to a shorter wavelength.
  • the frequency discrimination signal is used to determine the change of the laser wavelength, adjust the driving control of the laser in time, maintain the ratio of the two detection signals PIN1 and PIN2 to a constant value ⁇ , and realize the frequency stabilization of the laser.
  • Embodiment 3 receives the equivalent F-P etalon transmission spectrum of the first linearly polarized light
  • the second photodetector 3 receives the second linearly polarized light through another equivalent F-P etalon transmission spectrum
  • the optical thicknesses of the two equivalent F-P etalons differ by ⁇ /4, therefore, they have complementary transmission spectra to each other, as shown in Figure 10, the peak point optical frequency and valley value of the equivalent F-P etalon transmission spectrum curve trace3
  • the point light frequencies respectively correspond to the valley point light frequency and the peak point light frequency of another equivalent F-P etalon transmission spectrum curve trace4.
  • the light intensity ratio detected by the two photoelectric detectors is used as the frequency discrimination signal, and the frequency stable output of the laser is realized by maintaining the ratio signal as a constant value.
  • the ratio of the detection signals of the two photodetectors is used as the frequency discrimination signal, and the intensities of the two detection signals at the target frequency point cannot be too different, otherwise the detection accuracy of the frequency discrimination signal will be affected.
  • a half-wave plate 4 is set at the input end of the optical path, the polarization state of the semiconductor laser can be changed by rotating the half-wave plate 4, and the amplitude of the two detection signals can be dynamically adjusted, so that the intensities of the two detection signals at the target frequency point are as consistent as possible.

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Abstract

一种波长锁定器和可调激光器组件，波长锁定器包括分束单元（10）、第一光电探测器（2）和第二光电探测器（3），分束单元（10）包括入光面、第一出光面和第二出光面；入光面与第一出光面上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜；分束单元（10）用于将接收到的线偏振光分解为第一线偏振光和第二线偏振光，第一线偏振光从第一出光面出射后，被第一光电探测器（2）所接收，第二线偏振光从第二出光面出射后，被第二光电探测器（3）接收；其中，第一光电探测器（2）和第二光电探测器（3）产生的电信号的比值形成鉴频信号。将分光功能和标准具集成在一起，结构简单，布局紧凑，尺寸较小，非常适合集成于纳米超紧凑型可调激光器组件的小型化封装中。

Description

一种波长锁定器和可调激光器组件
相关申请的交叉引用
本申请基于申请号为202011144159.2、申请日为2020年10月23日的中国专利申请提出，并要求中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请属于光通信技术领域，更具体地，涉及一种波长锁定器和可调激光器组件。
背景技术
随着光通信速率和容量的提高，密集光波分复用(DWDM，Dense Wavelength Division Multiplexing)光传输系统中光载波信道数不断增加，光信道频率间隔不断变窄，复用光信道中心频率偏差要求也愈发严格。对于当前大规模铺设的50GHz信道频率间距的DWDM高速光通信系统，波分复用设备的生产厂家普遍要求光发射光源--半导体激光器输出光波长与ITU-T标准中心频率最大偏差不超过±2.5GHz。受外界环境因素和光源老化的影响，半导体激光器全生命周期内的产生波长漂移很容易超出该范围，因此，有必要采用有效的波长锁定技术，提高通信光源--半导体激光器的波长稳定性。
光通信市场上，一些公司相继推出波长锁定器产品，专门用于提高激光器的波长稳定性。例如，用于数字相干光通信的集成可调谐激光器组件(Integrable Tunable Laser Assembly，简写为ITLA)内部则直接集成了波长锁定器功能单元。通信光源内部集成波长锁定功能已经成为常态，波长锁定器普遍采用的光路结构如图1所示，从可调谐激光器获取部分光信号后，部分激光输入至分光片，经分光片后被分成2部分，一部分经法布里-珀罗(Fabry-Perot)标准具(F-P Etalon)滤波器后，被光电探测器PD1所接收；另一部分直接进入光电探测器 PD2作为参考信号，PD1电信号与激光器的波长和光功率相关，PD2电信号则只与激光器的出光功率相关，用这两个信号比值产生的鉴频信号来驱动激光器的控制，进而对波长进行调整，将激光稳定到所需的ITU-T波长。
鉴频信号的产生利用F-P Etalon透射光谱的周期性特征产生ITLA各个输出波长所需的ITU-T频率标准，另外利用PD2的参考信号构成差分系统消除可调谐激光器的功率起伏带来的影响，这样激光器频率变化会引起F-P Etalon滤波器透射光强的变化，维持两路光电探测器探测的光强比值为定值，实现激光器的频率稳定输出。在光通信应用领域，激光器被锁定的波长通常可以在F-P Etalon滤波器透射光谱曲线的峰顶，也可以在谷底，一般标定在滤波器透射光谱曲线腰的位置上，更有利于辨别激光器波长漂移的方向。自由光谱范围(透射光谱相邻峰间的波长间隔)确定的F-P Etalon滤波器的通光面的反射率直接决定透射光谱锐度，进而决定了波长锁定灵敏度(锁定点斜率)，标准具通光面反射率越高，波长锁定灵敏度越高，波长锁定范围越小；反之，通光面反射率越低，波长锁定灵敏度越低，波长锁定范围越大。图1所示的传统波长锁定器的结构较分散，不适用于集成在小型化的封装中，而且需要综合考虑锁定范围和锁定点斜率，因此往往难以获得较高的波长锁定灵敏度。
鉴于此，克服该现有技术产品所存在的不足是本技术领域亟待解决的问题。
发明内容
针对现有技术的以上缺陷或改进需求，本申请提供了一种波长锁定器和可调激光器组件，其目的在于，本申请的波长锁定器将分光功能和标准具集成在一起，结构简单，布局紧凑，尺寸较小。
为实现上述目的，按照本申请的一个方面，提供了一种波长锁定器，所述波长锁定器包括分束单元1、第一光电探测器2和第二光电探测器3，所述分束单元1包括入光面、第一出光面和第二出光面；
所述入光面与所述第一出光面上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜；
所述分束单元1用于将接收到的线偏振光分解为第一线偏振光和第二线偏振光，所述第一线偏振光从所述第一出光面出射后，被所述第一光电探测器2所接收，所述第二线偏振光从所述第二出光面出射后，被所述第二光电探测器3接收；
其中，所述第一光电探测器2和所述第二光电探测器3产生的电信号的比值形成鉴频信号。
在一些可选实施例中，所述分束单元1包括第一棱镜11和第二棱镜12，所述第一棱镜11的其中一个斜面与所述第二棱镜12的其中一个斜面胶合形成第一胶合面，所述第一胶合面上镀有偏振分束介质膜；
所述偏振分束介质膜用于将线偏振光分解为偏振态正交的所述第一线偏振光和第二线偏振光；
所述第一棱镜11的其中两个面被配置为所述入光面和所述第一出光面。
在一些可选实施例中，所述第二棱镜12的其中一个面被配置为所述第二出光面，所述第二出光面上镀有增透膜。
在一些可选实施例中，所述分束单元1还包括第一补偿片13，所述第一补偿片13与所述第二棱镜12胶合形成第二胶合面，所述第二胶合面上镀有增透膜；
所述第一补偿片13的出光面被配置为所述第二出光面，所述第二出光面上镀有与所述入光面相同的反射介质膜层，以构成标准具的反射腔镜。
在一些可选实施例中，所述第一棱镜11为四边形棱镜，所述四边形棱镜的其中两个面相互平行，相互平行的两个面被设置为所述入光面和所述第一通光面，所述第二棱镜12为三角棱镜；或，
所述第一棱镜11和所述第二棱镜12均为三角棱镜。
在一些可选实施例中，所述分束单元1包括双折射晶体14，所述双折射晶体14用于将线偏振光分解为偏振态正交的所述第一线偏振光和所述第二线偏振光；
所述双折射晶体14的其中一个面被配置为所述入光面，所述双折射晶体 14的另一个面被划分为第一部分和第二部分，所述第一部分被配置为所述第一出光面。
在一些可选实施例中，所述第二部分被配置为所述第二出光面，所述第二出光面上镀有增透膜。
在一些可选实施例中，所述分束单元1还包括第二补偿片15，所述第二补偿片15与所述第二部分胶合形成第三胶合面，所述第三胶合面上镀有增透膜；
所述第二补偿片15的出光面被配置为所述第二出光面，所述第二出光面上镀有与所述入光面相同的反射介质膜层，以构成标准具的反射腔镜。
在一些可选实施例中，所述波长锁定器还包括半波片4，所述半波片4邻近所述入光面设置，所述半波片4可以绕着光路的轴线旋转。
为实现上述目的，按照本申请的另一个方面，提供了一种可调激光器组件，所述可调激光器组件包括如本申请所述的波长锁定器。
总体而言，通过本申请所构思的以上技术方案与现有技术相比，具有如下有益效果：本申请提供了一种波长锁定器和可调激光器组件，所述波长锁定器包括分束单元、第一光电探测器和第二光电探测器，所述分束单元包括入光面、第一出光面和第二出光面；所述入光面与所述第一出光面上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜；所述分束单元用于将接收到的线偏振光分解为第一线偏振光和第二线偏振光，所述第一线偏振光从所述第一出光面出射后，被所述第一光电探测器所接收，所述第二线偏振光从所述第二出光面出射后，被所述第二光电探测器接收；其中，所述第一光电探测器和所述第二光电探测器产生的电信号的比值形成鉴频信号。
在本申请中，将分光功能和标准具集成在一起，结构简单，布局紧凑，尺寸较小，非常适合集成于纳米超紧凑型可调激光器组件(Nano ITLA)的小型化封装中。
另一方面，波长锁定范围与传统结构相当，锁定灵敏度更高。
附图说明
图1是现有技术中波长锁定器的结构示意图；
图2是本申请实施例提供的第一种波长锁定器的结构示意图；
图3是本申请实施例提供的第二种波长锁定器的结构示意图；
图4是本申请实施例提供的第三种波长锁定器的结构示意图；
图5是本申请实施例提供的第四种波长锁定器的结构示意图；
图6是本申请实施例提供的第五种波长锁定器的结构示意图；
图7是本申请实施例提供的第六种波长锁定器的结构示意图；
图8是本申请实施例提供的第七种波长锁定器的结构示意图；
图9为本申请实施例提供的一种波长锁定的原理示意图；
图10为本申请实施例提供的另一种波长锁定的原理示意图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
在本申请的描述中，术语“内”、“外”、“纵向”、“横向”、“上”、“下”、“顶”、“底”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请而不是要求本申请必须以特定的方位构造和操作，因此不应当理解为对本申请的限制。
此外，下面所描述的本申请各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
实施例1：
在本实施例中，提供了一种波长锁定器，所述波长锁定器包括分束单元、第一光电探测器和第二光电探测器，所述分束单元包括入光面、第一出光面和第二出光面；所述入光面与所述第一出光面上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜。
在实际使用中，所述分束单元用于将接收到的线偏振光分解为第一线偏振光和第二线偏振光，所述第一线偏振光从所述第一出光面出射后，被所述第一光电探测器所接收，所述第二线偏振光从所述第二出光面出射后，被所述第二光电探测器接收。
所述第一光电探测器和所述第二光电探测器产生的电信号的比值形成鉴频信号，其中，第一线偏振光经过了所述入光面与所述第一出光面所构成的标准具的反射腔镜后被所述第一光电探测器所接收，所述第一光电探测器产生的电信号与激光器的波长和光功率相关；所述第二光电探测器产生的电信号则只与激光器的出光功率相关，用这两个信号比值产生的鉴频信号来控制激光器，对激光器输出的波长进行调整，进而稳定到所需的波长。
进一步地，所述波长锁定器还包括半波片，所述半波片邻近所述入光面设置，所述半波片可以绕着光路的轴线旋转，以调节分束单元的分光比。调节分光比的过程为：在波长锁定器制作过程中，绕着光路的轴线旋转所述半波片，在半波片的转动的过程时，会引起半导体激光器输出光波偏振态的改变，经分束单元起偏分束形成的第一线偏振光和第二线偏振光的光强之比也会随之发生变化。
在本实施例中，将分光功能和标准具集成在一起，结构简单，布局紧凑，尺寸较小，非常适合集成于纳米超紧凑型可调激光器组件(Nano ITLA)的小型化封装中。
关于波长锁定器的具体结构请详见下述实施例2～实施例8。
实施例2：
参阅图2，本实施例提供一种波长锁定器，所述波长锁定器包括分束单元1、第一光电探测器2和第二光电探测器3，所述分束单元1包括入光面A、第一出光面B和第二出光面C；所述入光面A与所述第一出光面B上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜。
其中，所述分束单元1包括第一棱镜11和第二棱镜12，所述第一棱镜11的其中一个斜面与所述第二棱镜12的其中一个斜面胶合形成第一胶合面D，所 述第一胶合面D上镀有偏振分束介质膜，所述偏振分束介质膜用于将线偏振光分解为偏振态正交的第一线偏振光和第二线偏振光。
所述第一棱镜11的其中两个面被配置为所述入光面A和所述第一出光面B，所述第二棱镜12的其中一个面被配置为所述第二出光面C，所述第二出光面C上镀有增透膜。
进一步地，所述波长锁定器还包括半波片4，所述半波片4邻近所述入光面A设置，所述半波片4可以绕着光路的轴线旋转，以调节分束单元1的分光比。调节分光比的过程为：在波长锁定器制作过程中，绕着光路的轴线旋转所述半波片4，在半波片4的转动的过程时，会引起半导体激光器输出光波偏振态的改变，因此经分束单元1起偏分束形成的第一线偏振光和第二线偏振光的光强之比也会随之发生变化。
具体地，所述第一棱镜11为四边形棱镜，所述四边形棱镜的其中两个面相互平行，相互平行的两个面被设置为所述入光面A和所述第一通光面，所述第二棱镜12为三角棱镜。例如，四边形棱镜可以为平行四边形棱镜或梯形棱镜，在此以四边形棱镜可以为平行四边形棱镜为例解释说明。
分束单元1是由平行四边形棱镜的斜面与三角棱镜的斜面胶合而成，平行四边形棱镜的两个相对的非胶合面相互平行，镀有相同反射率的部分反射介质膜，构成了法布里-珀罗标准具的反射腔镜。
即，平行四边形棱镜的两个相对的非胶合面分别被配置为所述入光面A和所述第一出光面B，所述入光面A和所述第一出光面B相互平行，且均镀有相同反射率的部分反射介质膜，以构成法布里-珀罗标准具的反射腔镜。与图1所示的波长锁定器光路结构，本实施例的分束单元1同时集成分光片和标准具的功能，结构紧凑，相对于图1单独设置的F-P标准具滤波器，本实施例的入光面A和第一出光面B之间形成的等效标准具，厚度明显有所减小。
平行四边形棱镜与三角棱镜胶合形成了第一胶合面D，所述第一胶合面D上镀有偏振分束介质膜，该偏振分束介质膜可将一束任意偏振态的入射光分解为偏振态正交的上下分布的第一线偏振光(S偏振光)和第二线偏振光(P偏 振光)。
其中，第一胶合面D起偏分束形成的第一线偏振光在所述的平行四边形棱镜两个相对的通光面之间反复反射，形成多光束干涉，从入光面A->第一胶合面D->与第一胶合面D相对的通光面->第一出光面B的传播路径的光学长度，等效为F-P Etalon的光学厚度。
其中，三角棱镜的其中一个面被配置为第二出光面C，第一胶合面D起偏分束形成的第二线偏振光通过三角棱镜的第二出光面C直接投射进第二光电探测器3。在优选的方案中，第二出光面C上镀有增透膜，镀有增透膜的目的是为了减少反射光的强度，避免与平行四边形棱镜的入光面A之间形成标准具效应。
在本实施例中，第一光电探测器2和第二光电探测器3与分束单元1偏振分束的两束正交偏振态的线偏光对应设置，分别接收第一线偏振光和第二线偏振光，第一光电探测器2和第二光电探测器3将接收的光信号转换成波长锁定所需的鉴频信号。
针对图2所示的实施例存在一个可变的实施方式，与图2不同之处在于，第一出光面B被配置在三角棱镜上，第二出光面C被配置在平行四边形棱镜上。
具体来讲，所述平行四边形棱镜的其中两个面分别被配置为入光面A和第二出光面C，所述三角棱镜的其中一个面被配置为第一出光面B，即，平行四边形棱镜的入光面A和三角棱镜的第一出光面B相互平行，镀有相同反射率的反射介质膜，构成了法布里-珀罗标准具的反射腔镜。平行四边形棱镜的第二出光面C镀有增透膜。
在本实施方式中，接收第二线偏振光(P偏振光)的第二光电探测器3产生的电信号与激光器的波长和光功率相关；接收第一线偏振光(S偏振光)的第一光电探测器2产生的电信号则只与激光器的出光功率相关，用这两个信号比值产生的鉴频信号来驱动激光器的控制，进而调整和稳定到所需的波长。
实施例3：
区别于前述实施例2，参阅图3，所述分束单元1还包括第一补偿片13， 所述第一补偿片13与所述第二棱镜12胶合形成第二胶合面E，所述第二胶合面E上镀有增透膜。
所述第一补偿片13的出光面被配置为所述第二出光面C，所述第二出光面C上镀有与所述入光面A相同的反射介质膜层，以构成标准具的反射腔镜。
具体地，三角棱镜的出射通光面和第一补偿片13的入射通光面，相互平行，二者相互胶合形成第二胶合面E，所述第二胶合面E上镀有增透膜，镀有增透膜的目的是为了减少反射光的强度，避免形成附加的标准具效应。
在本实施例中，第一补偿片13的第二出光面C与平行四边形棱镜的入光面A相互平行，镀有相同反射率的部分反射介质膜，构成了法布里-珀罗标准具的反射腔镜。第一胶合面D起偏分束形成的第二线偏振光在平行四边形棱镜的入光面A和第一补偿片13的第二出光面C之间反复反射，形成多光束干涉，从入光面A->第一胶合面D->第二胶合面E->第二出光面C的传播路径的光学长度，等效为第二线偏振光通过的F-P Etalon的光学厚度。
在实际使用中，第一补偿片13优先采用与三角棱镜相同的材料制作，第一补偿片13的厚度按照如下原则进行设置：
第一线偏振光通过的等效的F-P Etalon的光学厚度δs和第二偏振光通过的等效的F-P Etalon的光学厚度δp相差λ/4，其中，λ为激光器的波长。
第一线偏振光通过的等效的F-P Etalon和第二线偏振光通过的等效的F-P Etalon具有几乎相同自由光谱范围(FSR)。
在实际应用场景下，第一补偿片13的实际厚度存在一定公差，可以通过调整入射光线的角度，在线调整第一线偏振光和第二线偏振光通过对应的F-P Etalon的光学厚度差。
区别于前述实施例2，本实施例的波长锁定器在不大幅度增加产品尺寸的情况下，可以有效提高波长锁定灵敏度，具体锁定区别详见下文中的原理分析。
实施例4：
区别于实施例2和实施例3，参阅图4，在本实施例中，分束单元1还包括第三棱镜(图中未标示)，第三棱镜为三角棱镜，所述第三棱镜与所述第二棱镜 12相对于所述平行四边形棱镜相对设置，三角棱镜的斜面与平行四边形棱镜的另一个斜面胶合。
在本实施例中，分束单元1的形状较规则，便于夹持，以减小在制作波长锁定器的过程中，分束单元1被损坏的风险。
实施例5：
区别于前述实施例2，参阅图5，在本实施例中，第一棱镜11和第二棱镜12均为三角棱镜，且三角棱镜为等腰直角三角棱镜，两个三角棱镜的斜面相互胶合，形成第一胶合面D，第一棱镜11的两个直角面分别被配置为入光面A和第一出光面B，第二棱镜12的其中一个直角面被配置为第二出光面C。其余镀膜方式以及工作原理与实施例2基本相同，在此，不再赘述。
实施例6：
区别于实施例5，参阅图6，在本实施例中，所述分束单元1还包括第一补偿片13，所述第一补偿片13与所述第二棱镜12胶合，形成第二胶合面E，所述第二胶合面E上镀有增透膜。所述第一补偿片13的出光面被配置为所述第二出光面C，所述第二出光面C上镀有与所述入光面A相同的反射介质膜层，以构成标准具的反射腔镜。
实施例7：
参阅图7，在本实施例中，提供一种波长锁定器，所述波长锁定器包括分束单元1、第一光电探测器2和第二光电探测器3，所述分束单元1包括入光面A、第一出光面B和第二出光面C；所述入光面A与所述第一出光面B上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜。
进一步地，所述波长锁定器还包括半波片4，所述半波片4邻近所述入光面A设置，所述半波片4可以绕着光路的轴线旋转，以调节分束单元1的分光比。调节分光比的过程为：在波长锁定器制作过程中，绕着光路的轴线旋转所述半波片4，在半波片4的转动的过程时，会引起半导体激光器输出光波偏振态的改变，因此经分束单元1起偏分束形成的第一线偏振光和第二线偏振光的光强之比也会随之发生变化。
所述分束单元1包括双折射晶体14，所述双折射晶体14用于将线偏振光分解为偏振态正交的所述第一线偏振光和所述第二线偏振光；所述双折射晶体14的其中一个面被配置为所述入光面A，所述双折射晶体14的另一个面被划分为第一部分(图7中的上部分)和第二部分(图7中的下部分)，所述第一部分被配置为所述第一出光面B。所述第二部分被配置为所述第二出光面C，所述第二出光面C上镀有增透膜。
具体地，双折射晶体14的光轴与光学主截面平行，主轴与入光面A呈锐角，入光面A与第一出光面B相互平行，且镀有相同反射率的反射介质膜，构成了法布里-珀罗标准具的反射腔镜。
所述双折射晶体14利用晶体的双折射特性可将一束任意偏振态的入射光分解为偏振态正交的上下分布的第一线偏振光(P偏振光)和第二线偏振光(S偏振光)。
其中，第一光电探测器2和第二光电探测器3与第一线偏振光和第二线偏振光对应设置，分别接收相应偏振态光的能量，第一光电探测器2和第二光电探测器3将接收的光信号转换成波长锁定所需的鉴频信号。
针对图7所示的实施例存在一个可变的实施方式，与图7不同之处在于，所述双折射晶体14的另一个面被划分为第一部分(图7中的上部分)和第二部分(图7中的下部分)，所述第二部分被配置为所述第一出光面B。所述第一部分被配置为所述第二出光面C，所述第二出光面C上镀有增透膜。
在本实施方式中，接收第二线偏振光(S偏振光)的第二光电探测器3产生的电信号与激光器的波长和光功率相关；接收第一线偏振光(P偏振光)的第一光电探测器2产生的电信号则只与激光器的出光功率相关，用这两个信号比值产生的鉴频信号来驱动激光器的控制，进而调整和稳定到所需的波长。
实施例8：
区别于前述实施例7，参阅图8，所述分束单元1还包括第二补偿片15，所述第二补偿片15与所述第二部分胶合，形成第三胶合面F，所述第三胶合面F上镀有增透膜；
所述第二补偿片15的出光面被配置为所述第二出光面C，所述第二出光面C上镀有与所述入光面A相同的反射介质膜层，以构成标准具的反射腔镜。
具体地，双折射晶体14的出射通光面和第二补偿片15的入射通光面，相互平行，二者相互胶合形成第三胶合面F，所述第三胶合面F上镀有增透膜，镀有增透膜的目的是为了减少反射光的强度，避免形成附加的标准具效应。
在本实施例中，第二补偿片15的第二出光面C与双折射晶体14的入光面A相互平行，镀有相同反射率的部分反射介质膜，构成了法布里-珀罗标准具的反射腔镜。其中，双折射晶体14起偏分束形成的第一线偏振光在偏振分束双折射晶体14的入光面A和第一出光面B之间反复反射，形成多光束干涉，从入光面A->第一出光面B之间传播路径的光学长度，等效为第一线偏振光通过的F-P Etalon的光学厚度。双折射晶体14起偏分束形成的第二线偏振光在双折射晶体14的入光面A和第二补偿片15的第二出光面C之间反复反射，形成多光束干涉，从入光面A->第三胶合面F->第二出光面C的传播路径的光学长度，等效为第二线偏振光通过的F-P Etalon的光学厚度。
在实际使用中，第二补偿片15优先采用与双折射晶体相同的材料制作，第二补偿片15的厚度按照如下原则进行设置：
第一线偏振光通过的等效的F-P Etalon的光学厚度δp和第二偏振光通过的等效的F-P Etalon的光学厚度δs相差λ/4，其中，λ为激光器的波长。
第一线偏振光通过的等效的F-P Etalon和第二线偏振光通过的等效的F-P Etalon具有几乎相同自由光谱范围(FSR)。
在实际应用场景下，第二补偿片15的实际厚度存在一定公差，可以通过调整入射光线的角度，在线调整第一线偏振光和第二线偏振光通过对应的F-P Etalon的光学厚度差。
区别于前述实施例7，本实施例的波长锁定器在不大幅度增加产品尺寸的情况下，可以有效提高波长锁定灵敏度，具体锁定区别详见下文中的原理分析。
在实际应用场景下，还提供一种可调激光器组件，所述可调激光器组件包括前述任一实施例所述的波长锁定器。
下面参照图9进一步解释实施例2、实施例4、实施例5和实施例7的波锁原理。如前所述，第一光电探测器2接收的是F-P标准具透射光谱，产生的电信号(PIN1)随着激光器的输入光频率周期性变化；第二光电探测器3产生的电信号(PIN2)接收的是激光器输出的参考光功率。为了消除可调谐激光器的功率起伏带来的影响，通常采用这两个信号比值(PIN1/PIN2)来产生鉴频信号，鉴频信号(PIN1/PIN2)与激光器输入光频率之间的关系如图中实线trace1所示。trace2为锁波中所维持的鉴频信号目标值(ξ)。trace1和trace2的交点(PIN1/PIN2＝ξ)即为激光器锁定的目标光频率点。根据锁定频率点处的trace1的斜率符号的不同可分为：正锁定与负锁定，正锁定与负锁定的工作原理基本相同，这里以正锁定为例加已说明。当测得鉴频信号大于目标值ξ(PIN1/PIN2>ξ)，则表明激光器的光频率偏大，需调整激光器的控制参数，使激光器的波长往长波长移动；若测得信号鉴频信号小于目标值ξ(PIN1/PIN2<ξ)，则表明激光光频率偏小，需调整激光器的控制参数，使激光器的波长往短波长移动。利用鉴频信号来判别激光器波长的变化，及时调整激光器的驱动控制，维持两路探测信号PIN1和PIN2比值为定值ξ，实现激光器的稳频。
下面参照图10进一步解释实施例3、实施例6和实施例8的波锁原理。。如前所述，第一光电探测器2接收的是第一线偏振光等效F-P标准具透射光谱，第二光电探测器3接收的是第二线偏振光经另一个等效F-P标准具透射光谱；两个等效的等效F-P标准具光学厚度相差λ/4，因此，具有彼此互补的透射光谱，如图10所示，等效F-P标准具透射光谱曲线trace3的峰值点光频率和谷值点光频率分别对应另外一个等效F-P标准具透射光谱曲线trace4的谷值点光频率和峰值点光频率。将两路光电探测器探测的光强比值作为鉴频信号，通过维持比值信号为定值，实现激光器的频率稳定输出。同时，为了获得更好的灵敏度，推荐将目标频率锁定点设置trace3/trace4的曲线的上升沿或下降沿，当鉴频信号偏离锁定值，即激光器的波长偏离目标频率时，两路光电探测器探测信号将会向不同的方向变化(一路信号变大另一路变小，或者一路信号变小另一路变大)，因此相对于未增加补偿片的方案，相同的频率变化，鉴频信号有更 大的变化幅度，具有更高的锁定精度。
在此，需要说明的是，采用两路光电探测器探测信号的比值作为鉴频信号，在目标频率点处两路探测信号的强度不能相差太大，否则会影响鉴频信号探测精度。在光路输入端设置了半波片4，可以通过旋转半波片4改变半导体激光器的偏振态，动态调节两路探测信号的幅度，使目标频率点下两路探测信号的强度尽可能一致。
本领域的技术人员容易理解，以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种波长锁定器，所述波长锁定器包括分束单元(1)、第一光电探测器(2)和第二光电探测器(3)，所述分束单元(1)包括入光面、第一出光面和第二出光面；
    所述入光面与所述第一出光面上镀有相同反射率的反射介质膜层，以构成标准具的反射腔镜；
    所述分束单元(1)用于将接收到的线偏振光分解为第一线偏振光和第二线偏振光，所述第一线偏振光从所述第一出光面出射后，被所述第一光电探测器(2)所接收，所述第二线偏振光从所述第二出光面出射后，被所述第二光电探测器(3)接收；
    其中，所述第一光电探测器(2)和所述第二光电探测器(3)产生的电信号的比值形成鉴频信号。
  2. 根据权利要求1所述的波长锁定器，其中，所述分束单元(1)包括第一棱镜(11)和第二棱镜(12)，所述第一棱镜(11)的其中一个斜面与所述第二棱镜(12)的其中一个斜面胶合形成第一胶合面，所述第一胶合面上镀有偏振分束介质膜；
    所述偏振分束介质膜用于将线偏振光分解为偏振态正交的所述第一线偏振光和第二线偏振光；
    所述第一棱镜(11)的其中两个面被配置为所述入光面和所述第一出光面。
  3. 根据权利要求2所述的波长锁定器，其中，所述第二棱镜(12)的其中一个面被配置为所述第二出光面，所述第二出光面上镀有增透膜。
  4. 根据权利要求2所述的波长锁定器，其中，所述分束单元(1)还包括第一补偿片(13)，所述第一补偿片(13)与所述第二棱镜(12)胶合形成第二胶合面，所述第二胶合面上镀有增透膜；
    所述第一补偿片(13)的出光面被配置为所述第二出光面，所述第二 出光面上镀有与所述入光面相同的反射介质膜层，以构成标准具的反射腔镜。
  5. 根据权利要求2～4任一项所述的波长锁定器，其中，所述第一棱镜(11)为四边形棱镜，所述四边形棱镜的其中两个面相互平行，相互平行的两个面被设置为所述入光面和所述第一通光面，所述第二棱镜(12)为三角棱镜；或，
    所述第一棱镜(11)和所述第二棱镜(12)均为三角棱镜。
  6. 根据权利要求1所述的波长锁定器，其中，所述分束单元(1)包括双折射晶体(14)，所述双折射晶体(14)用于将线偏振光分解为偏振态正交的所述第一线偏振光和所述第二线偏振光；
    所述双折射晶体(14)的其中一个面被配置为所述入光面，所述双折射晶体(14)的另一个面被划分为第一部分和第二部分，所述第一部分被配置为所述第一出光面。
  7. 根据权利要求6所述的波长锁定器，其中，所述第二部分被配置为所述第二出光面，所述第二出光面上镀有增透膜。
  8. 根据权利要求6所述的波长锁定器，其中，所述分束单元(1)还包括第二补偿片(15)，所述第二补偿片(15)与所述第二部分胶合形成第三胶合面，所述第三胶合面上镀有增透膜；
    所述第二补偿片(15)的出光面被配置为所述第二出光面，所述第二出光面上镀有与所述入光面相同的反射介质膜层，以构成标准具的反射腔镜。
  9. 根据权利要求1所述的波长锁定器，其中，所述波长锁定器还包括半波片(4)，所述半波片(4)邻近所述入光面设置，所述半波片(4)可以绕着光路的轴线旋转。
  10. 一种可调激光器组件，其中，所述可调激光器组件包括如权利要求1～9任一项所述的波长锁定器。
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