CN112271551A - Wavelength locker and adjustable laser component - Google Patents
Wavelength locker and adjustable laser component Download PDFInfo
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- CN112271551A CN112271551A CN202011144159.2A CN202011144159A CN112271551A CN 112271551 A CN112271551 A CN 112271551A CN 202011144159 A CN202011144159 A CN 202011144159A CN 112271551 A CN112271551 A CN 112271551A
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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
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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
- H01S5/068—Stabilisation of laser output parameters
- H01S5/06808—Stabilisation of laser output parameters by monitoring the electrical laser parameters, e.g. voltage or current
Abstract
The invention discloses a wavelength locker and a tunable laser component, wherein the wavelength locker comprises a beam splitting unit, a first photoelectric detector and a second photoelectric detector, wherein the beam splitting unit comprises a light incident surface, a first light emergent surface and a second light emergent surface; the light incident surface and the first light emergent surface are plated with a reflecting medium film layer with the same reflectivity so as to form a reflecting cavity mirror of the etalon; the beam splitting unit is used for splitting the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, the first linearly polarized light is received by the first photoelectric detector after being emitted from the first light emitting surface, and the second linearly polarized light is received by the second photoelectric detector after being emitted from the second light emitting surface; wherein, the ratio of the electric signals generated by the first photodetector and the second photodetector forms a frequency discrimination signal. In the invention, the light splitting function and the etalon are integrated, the structure is simple, the layout is compact, the size is small, and the device is very suitable for being integrated in the miniaturized package of the nanometer ultra-compact type tunable laser component.
Description
Technical Field
The invention belongs to the technical field of optical communication, and particularly relates to a wavelength locker and a tunable laser component.
Background
With the improvement of optical communication rate and capacity, the number of optical carrier channels in a Dense Wavelength Division Multiplexing (DWDM) optical transmission system is increasing, the frequency interval of the optical channel is narrowing, and the requirement for the central frequency deviation of the multiplexed optical channel is becoming stricter. For DWDM high-speed optical communication systems with 50GHz channel frequency spacing laid on a large scale at present, manufacturers of wavelength division multiplexing equipment generally require that the maximum deviation between the output light wavelength of a light emitting light source, i.e. a semiconductor laser, and the ITU-T standard center frequency is not more than ± 2.5 GHz. The wavelength drift generated in the whole life cycle of the semiconductor laser is easily beyond the range under the influence of external environmental factors and light source aging, so that an effective wavelength locking technology is needed to be adopted to improve the wavelength stability of a communication light source, namely the semiconductor laser.
In the optical communication market, several companies have successively introduced wavelength locker products specifically for improving the wavelength stability of lasers. For example, an Integrated Tunable Laser Assembly (ITLA) for digital coherent optical communication directly integrates a wavelength locker function therein. The function of integrating wavelength locking in a communication light source is already a normal state, a light path structure commonly adopted by a wavelength locker is shown in fig. 1, partial laser is input to a light splitting sheet after partial optical signals are obtained from a tunable laser, the partial laser is divided into 2 parts after the partial laser passes through the light splitting sheet, and one part of the partial laser is received by a photoelectric detector PD1 after passing through a Fabry-Perot Etalon (F-P Etalon) filter; the other part directly enters the photoelectric detector PD2 as a reference signal, the PD1 electric signal is related to the wavelength and the optical power of the laser, the PD2 electric signal is only related to the light-emitting power of the laser, and a frequency discrimination signal generated by the ratio of the two signals is used for driving the control of the laser, so that the wavelength is adjusted, and the laser is stabilized to the required ITU-T wavelength.
The frequency discrimination signal is generated by using the periodic characteristics of an F-P Etalon transmission spectrum to generate an ITU-T frequency standard required by each output wavelength of ITLA, and in addition, a difference system is formed by using a reference signal of PD2 to eliminate the influence caused by power fluctuation of a tunable laser, so that the change of the laser frequency can cause the change of the transmission light intensity of the F-P Etalon filter, the light intensity ratio detected by two paths of photodetectors is maintained to be a fixed value, and the frequency stable output of the laser is realized. In the field of optical communication application, the wavelength locked by the laser can be generally positioned at the peak top and the valley bottom of a transmission spectrum curve of the F-P Etalon filter and generally calibrated at the position of the waist of the transmission spectrum curve of the filter, so that the wavelength drift direction of the laser can be distinguished more conveniently. The transmission spectrum sharpness is directly determined by the reflectivity of the light-passing surface of the F-P Etalon filter determined by the free spectrum range (wavelength interval between adjacent peaks of the transmission spectrum), and further the wavelength locking sensitivity (locking point slope) is determined, wherein the higher the reflectivity of the light-passing surface of the Etalon, the higher the wavelength locking sensitivity is, and the smaller the wavelength locking range is; conversely, the lower the light-transmitting surface reflectance, the lower the wavelength locking sensitivity, and the larger the wavelength locking range. The conventional wavelength locker shown in fig. 1 has a relatively dispersed structure, is not suitable for integration in a miniaturized package, and requires a combination of a locking range and a locking point slope, and thus it is often difficult to obtain a high wavelength locking sensitivity.
In view of this, overcoming the deficiencies of the prior art products is an urgent problem to be solved in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks and needs of the prior art, the present invention provides a wavelength locker and tunable laser module, which is capable of integrating the splitting function and the etalon, and has the advantages of simple structure, compact layout, and small size.
To achieve the above object, according to one aspect of the present invention, there is provided a wavelength locker, the wavelength locker comprising a beam splitting unit 1, a first photodetector 2, and a second photodetector 3, the beam splitting unit 1 comprising a light incident surface, a first light emitting surface, and a second light emitting surface;
the light incident surface and the first light emergent surface are plated with a reflecting medium film layer with the same reflectivity so as to form a reflecting cavity mirror of the etalon;
the beam splitting unit 1 is configured to split the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, where the first linearly polarized light is received by the first photodetector 2 after being emitted from the first light emitting surface, and the second linearly polarized light is received by the second photodetector 3 after being emitted from the second light emitting surface;
wherein the ratio of the electrical signals generated by the first photodetector 2 and the second photodetector 3 forms a frequency discrimination signal.
Preferably, the beam splitting unit 1 includes a first prism 11 and a second prism 12, one of the inclined planes of the first prism 11 and one of the inclined planes of the second prism 12 are glued to form a first glued surface, and the first glued surface is plated with a polarization beam splitting dielectric film;
the polarization beam splitting dielectric film is used for decomposing linearly polarized light into first linearly polarized light and second linearly polarized light with orthogonal polarization states;
two faces of the first prism 11 are configured as the light incident face and the first light emitting face.
Preferably, one of the surfaces of the second prism 12 is configured as the second light emitting surface, and the second light emitting surface is plated with an antireflection film.
Preferably, the beam splitting unit 1 further includes a first compensation plate 13, the first compensation plate 13 is glued with the second prism 12 to form a second glued surface, and an antireflection film is plated on the second glued surface;
the light emitting surface of the first compensation plate 13 is configured as the second light emitting surface, and the second light emitting surface is plated with a reflection medium film layer which is the same as the light incident surface so as to form a reflection cavity mirror of the etalon.
Preferably, the first prism 11 is a quadrangular prism, two surfaces of the quadrangular prism are parallel to each other, the two surfaces parallel to each other are set as the light incident surface and the first light passing surface, and the second prism 12 is a triangular prism; or the like, or, alternatively,
the first prism 11 and the second prism 12 are both triangular prisms.
Preferably, the beam splitting unit 1 comprises a birefringent crystal 14, and the birefringent crystal 14 is used for splitting linearly polarized light into the first linearly polarized light and the second linearly polarized light with orthogonal polarization states;
one of the faces of the birefringent crystal 14 is configured as the light incident face, and the other face of the birefringent crystal 14 is divided into a first portion configured as the first light emitting face and a second portion.
Preferably, the second portion is configured as the second light emitting surface, and an antireflection film is plated on the second light emitting surface.
Preferably, the beam splitting unit 1 further includes a second compensation plate 15, the second compensation plate 15 and the second portion are glued to form a third gluing surface, and the third gluing surface is plated with an antireflection film;
the light emitting surface of the second compensation plate 15 is configured as the second light emitting surface, and the second light emitting surface is plated with a reflection medium film layer which is the same as the light incident surface so as to form a reflection cavity mirror of the etalon.
Preferably, the wavelength locker further comprises a half-wave plate 4, the half-wave plate 4 being disposed adjacent to the light incident surface, the half-wave plate 4 being rotatable about the axis of the light path.
To achieve the above object, according to another aspect of the present invention, there is provided a tunable laser module including a wavelength locker according to the present invention.
Generally, compared with the prior art, the technical scheme of the invention has the following beneficial effects: the invention provides a wavelength locker and a tunable laser assembly, wherein the wavelength locker comprises a beam splitting unit, a first photoelectric detector and a second photoelectric detector, wherein the beam splitting unit comprises a light incident surface, a first light emergent surface and a second light emergent surface; the light incident surface and the first light emergent surface are plated with a reflecting medium film layer with the same reflectivity so as to form a reflecting cavity mirror of the etalon; the beam splitting unit is used for splitting the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, the first linearly polarized light is received by the first photoelectric detector after being emitted from the first light emitting surface, and the second linearly polarized light is received by the second photoelectric detector after being emitted from the second light emitting surface; wherein the ratio of the electrical signals generated by the first photodetector and the second photodetector forms a frequency discrimination signal.
In the invention, the light splitting function and the etalon are integrated, the structure is simple, the layout is compact, the size is small, and the device is very suitable for being integrated in the miniaturized package of a nanometer ultra-compact tunable laser component (Nano ITLA).
On the other hand, the wavelength locking range is equivalent to that of the conventional structure, and the locking sensitivity is higher.
Drawings
FIG. 1 is a schematic diagram of a prior art wavelength locker;
FIG. 2 is a schematic structural diagram of a first wavelength locker provided in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a second wavelength locker provided in an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a third wavelength locker provided in an embodiment of the present invention;
FIG. 5 is a schematic diagram of a fourth wavelength locker according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a fifth wavelength locker provided in an embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a sixth wavelength locker provided in an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a seventh wavelength locker according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a wavelength locking scheme according to an embodiment of the present invention;
fig. 10 is a schematic diagram of another wavelength locking principle provided by an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are for convenience only to describe the present invention without requiring the present invention to be necessarily constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1:
in this embodiment, a wavelength locker is provided, where the wavelength locker includes a beam splitting unit, a first photodetector and a second photodetector, and the beam splitting unit includes a light incident surface, a first light emitting surface and a second light emitting surface; the light incident surface and the first light emergent surface are plated with a reflection medium film layer with the same reflectivity so as to form a reflection cavity mirror of the etalon.
In practical use, the beam splitting unit is configured to split the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, where the first linearly polarized light is received by the first photodetector after being emitted from the first light emitting surface, and the second linearly polarized light is received by the second photodetector after being emitted from the second light emitting surface.
The ratio of the electric signals generated by the first photoelectric detector and the second photoelectric detector forms a frequency discrimination signal, wherein the first linearly polarized light is received by the first photoelectric detector after passing through a reflecting cavity of an etalon formed by the light incident surface and the first light emergent surface, and the electric signal generated by the first photoelectric detector is related to the wavelength and the optical power of the laser; the electrical signal generated by the second photodetector is only related to the light output power of the laser, and the frequency discrimination signal generated by the ratio of the two signals is used for controlling the laser to adjust the wavelength output by the laser so as to stabilize the wavelength to the required wavelength.
Further, the wavelength locker further comprises a half-wave plate disposed adjacent to the light incident surface, and the half-wave plate can be rotated around an axis of the light path to adjust a splitting ratio of the beam splitting unit. The process of adjusting the splitting ratio is as follows: in the manufacturing process of the wavelength locker, the half-wave plate is rotated around the axis of the optical path, and in the rotation process of the half-wave plate, the polarization state of the output light wave of the semiconductor laser is changed, and the light intensity ratio of the first linearly polarized light and the second linearly polarized light formed by polarizing and splitting through the beam splitting unit is changed.
In the embodiment, the light splitting function and the etalon are integrated, so that the structure is simple, the layout is compact, the size is small, and the Nano ultra-compact tunable laser module (Nano ITLA) is very suitable for being integrated in miniaturized packaging of Nano ITLA.
The specific structure of the wavelength locker is described in detail in the following embodiments 2 to 8.
Example 2:
referring to fig. 2, the present embodiment provides a wavelength locker, where the wavelength locker includes a beam splitting unit 1, a first photodetector 2, and a second photodetector 3, where 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 emergent surface B are plated with reflection medium film layers with the same reflectivity so as to form a reflection cavity mirror of the etalon.
The beam splitting unit 1 includes a first prism 11 and a second prism 12, wherein one inclined plane of the first prism 11 is glued with one inclined plane of the second prism 12 to form a first glued surface D, the first glued surface D is plated with a polarization beam splitting dielectric film, and the polarization beam splitting dielectric film is used for splitting linearly polarized light into first linearly polarized light and 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 emitting surface B, one surface of the second prism 12 is configured as the second light emitting surface C, and an antireflection film is plated on the second light emitting surface C.
Further, the wavelength locker further comprises a half-wave plate 4, the half-wave plate 4 is disposed adjacent to the light incident surface a, and the half-wave plate 4 can be rotated around the axis of the light path to adjust the splitting ratio of the beam splitting unit 1. The process of adjusting the splitting ratio is as follows: in the manufacturing process of the wavelength locker, the half-wave plate 4 is rotated around the axis of the optical path, and during the rotation process of the half-wave plate 4, the polarization state of the output light wave of the semiconductor laser is changed, so that the ratio of the light intensity of the first linearly polarized light and the second linearly polarized light formed by polarizing and splitting by the beam splitting unit 1 is changed.
Specifically, the first prism 11 is a quadrangular prism, two surfaces of the quadrangular prism are parallel to each other, the two parallel surfaces are set as the light incident surface a and the first light passing surface, and the second prism 12 is a triangular prism. For example, the quadrangular prism may be a parallelogram prism or a trapezoid prism, and the quadrangular prism may be a parallelogram prism as an example for explanation.
The beam splitting unit 1 is formed by gluing an inclined plane of a parallelogram prism and an inclined plane of a triangular prism, two opposite non-glued surfaces of the parallelogram prism are parallel to each other and are plated with partial reflecting dielectric films with the same reflectivity, and a reflecting cavity mirror of the Fabry-Perot etalon is formed.
Namely, two opposite non-cemented 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 are both plated with partial reflection dielectric films with the same reflectivity, so as to form a reflection cavity mirror of the fabry-perot etalon. Compared with the optical path structure of the wavelength locker shown in fig. 1, the beam splitting unit 1 of the present embodiment integrates functions of a beam splitter and an etalon at the same time, and has a compact structure, and compared with the F-P etalon filter separately arranged in fig. 1, the thickness of the equivalent etalon formed between the light incident surface a and the first light emitting surface B of the present embodiment is significantly reduced.
The parallelogram prism and the triangular prism are glued to form a first gluing surface D, and a polarization beam splitting dielectric film is plated on the first gluing surface D and can split a beam of incident light in any polarization state into a first linearly polarized light (S polarized light) and a second linearly polarized light (P polarized light) which are orthogonal in polarization state and distributed up and down.
The optical length of a propagation path from the light incident surface A- > the first bonding surface D- > the light transmitting surface opposite to the first bonding surface D- > the first light emitting surface B is equivalent to the optical thickness of F-P Etalon.
One surface of the triangular prism is configured as a second light emitting surface C, and the second linearly polarized light formed by the polarizing beam splitting of the first bonding surface D is directly projected into the second photodetector 3 through the second light emitting surface C of the triangular prism. In a preferred embodiment, the second light emitting surface C is coated with an antireflection film for reducing the intensity of reflected light and avoiding an etalon effect with the light incident surface a of the parallelogram prism.
In this embodiment, the first photodetector 2 and the second photodetector 3 are disposed corresponding to two orthogonal polarization states of linearly polarized light polarized and split by the beam splitting unit 1, and respectively receive the first linearly polarized light and the second linearly polarized light, and the first photodetector 2 and the second photodetector 3 convert the received optical signals into frequency discrimination signals required for wavelength locking.
A variant of the embodiment shown in fig. 2 is different from fig. 2 in that the first light exit surface B is arranged on a triangular prism and the second light exit surface C is arranged on a parallelogram prism.
Specifically, two surfaces of the parallelogram prism are respectively configured as an incident surface A and a second emergent surface C, one surface of the triangular prism is configured as a first emergent surface B, namely, the incident surface A of the parallelogram prism and the first emergent surface B of the triangular prism are parallel to each other and are plated with reflecting medium films with the same reflectivity, and a reflecting cavity mirror of the Fabry-Perot etalon is formed. And the second light-emitting surface C of the parallelogram prism is plated with an antireflection film.
In the present embodiment, the electrical signal generated by the second photodetector 3 that receives the second linearly polarized light (P-polarized light) is related to the wavelength and optical power of the laser; the electrical signal generated by the first photodetector 2 receiving the first linearly polarized light (S-polarized light) 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, so as to adjust and stabilize the wavelength to the required wavelength.
Example 3:
different from the foregoing embodiment 2, referring to fig. 3, the beam splitting unit 1 further includes a first compensation plate 13, the first compensation plate 13 is glued with the second prism 12 to form a second gluing surface E, and an antireflection film is plated on the second gluing surface E.
The light emitting surface of the first compensation plate 13 is configured as the second light emitting surface C, and the second light emitting surface C is plated with a reflection medium film layer which is the same as the light incident surface a, so as to form a reflection cavity mirror of the etalon.
Specifically, the exit light-passing surface of the triangular prism and the incident light-passing surface of the first compensation plate 13 are parallel to each other, and the two are mutually glued to form a second gluing surface E, wherein an antireflection film is plated on the second gluing surface E, and the purpose of plating the antireflection film is to reduce the intensity of reflected light and avoid forming an additional etalon effect.
In this embodiment, the second light emitting surface C of the first compensation plate 13 is parallel to the light incident surface a of the parallelogram prism, and is plated with a partially reflective dielectric film with the same reflectivity, so as to form a reflective cavity mirror of the fabry-perot etalon. The second linearly polarized light formed by the polarized beam splitting of the first bonding surface D is repeatedly reflected between the light incident surface a of the parallelogram prism and the second light emitting surface C of the first compensation plate 13 to form multi-beam interference, and the optical length of the propagation path from the light incident surface a- > the first bonding surface D- > the second bonding surface E- > the second light emitting surface C is equivalent to the optical thickness of F-P Etalon through which the second linearly polarized light passes.
In practical use, the first compensation plate 13 is preferably made of the same material as that of the triangular prism, and the thickness of the first compensation plate 13 is set according to the following principle:
the optical thickness deltas of the equivalent F-P Etalon passed by the first linearly polarized light and the optical thickness deltap of the equivalent F-P Etalon passed by the second linearly polarized light are different by lambda/4, wherein lambda 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 nearly the same Free Spectral Range (FSR).
In an actual application scenario, the actual thickness of the first compensation plate 13 has a certain tolerance, and the optical thickness difference of the first linearly polarized light and the second linearly polarized light passing through the corresponding F-P Etalon can be adjusted on line by adjusting the angle of the incident light.
Different from the foregoing embodiment 2, the wavelength locker of the present embodiment can effectively improve the wavelength locking sensitivity without greatly increasing the product size, and the specific locking difference is detailed in the principle analysis below.
Example 4:
in contrast to embodiments 2 and 3, referring to fig. 4, in this embodiment, the beam splitting unit 1 further includes a third prism (not shown), the third prism is a triangular prism, the third prism and the second prism 12 are arranged opposite to the parallelogram prism, and an inclined surface of the triangular prism is glued to another inclined surface of the parallelogram prism.
In this embodiment, the shape of the beam splitting unit 1 is more regular, which facilitates clamping, so as to reduce the risk of damage to the beam splitting unit 1 during the manufacturing of the wavelength locker.
Example 5:
different from the foregoing embodiment 2, referring to fig. 5, in this embodiment, the first prism 11 and the second prism 12 are both triangular prisms, and the triangular prisms are isosceles right-angle triangular prisms, inclined surfaces of the two triangular prisms are mutually glued to form a first gluing surface D, two right-angle surfaces of the first prism 11 are respectively configured as a light incident surface a and a first light emitting surface B, and one right-angle surface of the second prism 12 is configured as a second light emitting surface C. The rest of the coating methods and the working principles are basically the same as those of embodiment 2, and are not described herein again.
Example 6:
different from embodiment 5, referring to fig. 6, in this embodiment, the beam splitting unit 1 further includes a first compensation plate 13, the first compensation plate 13 is glued to the second prism 12 to form a second gluing surface E, and an antireflection film is plated on the second gluing surface E. The light emitting surface of the first compensation plate 13 is configured as the second light emitting surface C, and the second light emitting surface C is plated with a reflection medium film layer which is the same as the light incident surface a, so as to form a reflection cavity mirror of the etalon.
Example 7:
referring to fig. 7, in the present embodiment, a wavelength locker is provided, where the wavelength locker includes a beam splitting unit 1, a first photodetector 2, and a second photodetector 3, and 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 emergent surface B are plated with reflection medium film layers with the same reflectivity so as to form a reflection cavity mirror of the etalon.
Further, the wavelength locker further comprises a half-wave plate 4, the half-wave plate 4 is disposed adjacent to the light incident surface a, and the half-wave plate 4 can be rotated around the axis of the light path to adjust the splitting ratio of the beam splitting unit 1. The process of adjusting the splitting ratio is as follows: in the manufacturing process of the wavelength locker, the half-wave plate 4 is rotated around the axis of the optical path, and during the rotation process of the half-wave plate 4, the polarization state of the output light wave of the semiconductor laser is changed, so that the ratio of the light intensity of the first linearly polarized light and the second linearly polarized light formed by polarizing and splitting by the beam splitting unit 1 is changed.
The beam splitting unit 1 comprises a birefringent crystal 14, and the birefringent crystal 14 is used for splitting linearly polarized light into the first linearly polarized light and the second linearly polarized light with orthogonal polarization states; one of the faces of the birefringent crystal 14 is configured as the light incident face a, and the other face of the birefringent crystal 14 is divided into a first portion (an upper portion in fig. 7) configured as the first light emitting face B and a second portion (a lower portion in fig. 7). The second part is configured as the second light emitting surface C, and an antireflection film is plated on the second light emitting surface C.
Specifically, the optical axis of the birefringent crystal 14 is parallel to the optical main cross section, the main axis forms an acute angle with the light incident surface a, the light incident surface a is parallel to the first light emergent surface B, and the light incident surface a and the first light emergent surface B are plated with the reflective dielectric film with the same reflectivity, so as to form the reflective cavity mirror of the fabry-perot etalon.
The birefringent crystal 14 can decompose a beam of incident light in any polarization state into a first linearly polarized light (P-polarized light) and a second linearly polarized light (S-polarized light) which are vertically distributed and have orthogonal polarization states by using the birefringence characteristics of the crystal.
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 respectively receive energy of light in corresponding polarized states, and the first photodetector 2 and the second photodetector 3 convert received optical signals into frequency discrimination signals required by wavelength locking.
There is a variant of 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 portion (upper portion in fig. 7) and a second portion (lower portion in fig. 7), which is configured as the first light exit face B. The first part is configured as the second light emitting surface C, and an antireflection film is plated on the second light emitting surface C.
In the present embodiment, the electrical signal generated by the second photodetector 3 that receives the second linearly polarized light (S-polarized light) is correlated with the wavelength and optical power of the laser; the electrical signal generated by the first photodetector 2 receiving the first linearly polarized light (P-polarized light) 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, so as to adjust and stabilize the wavelength to the required wavelength.
Example 8:
different from the foregoing embodiment 7, referring to fig. 8, the beam splitting unit 1 further includes a second compensation plate 15, the second compensation plate 15 is glued to the second portion to form a third glued surface F, and an antireflection film is plated on the third glued surface F;
the light emitting surface of the second compensation plate 15 is configured as the second light emitting surface C, and the second light emitting surface C is plated with a reflection medium film layer which is the same as the light incident surface a, so as to form a reflection cavity mirror of the etalon.
Specifically, the exit light-passing surface of the birefringent crystal 14 and the incident light-passing surface of the second compensation plate 15 are parallel to each other, and the two are glued to each other to form a third gluing surface F, and the third gluing surface F is plated with an antireflection film for the purpose of reducing the intensity of reflected light and avoiding the formation of an additional etalon effect.
In this embodiment, the second light-emitting surface C of the second compensation plate 15 is parallel to the light-incident surface a of the birefringent crystal 14, and is plated with a partially reflective dielectric film with the same reflectivity, so as to form a reflective cavity mirror of the fabry-perot etalon. 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 emitting surface B of the polarization beam splitting birefringent crystal 14 to form multi-beam interference, and the optical length of a propagation path between the light incident surface a- > the first light emitting surface B is equivalent to the optical thickness of F-P Etalon through which the first linearly polarized light passes. The second linearly polarized light formed by the polarized beam splitting of the birefringent crystal 14 is repeatedly reflected between the light incident surface a of the birefringent crystal 14 and the second light emitting surface C of the second compensation plate 15 to form multi-beam interference, and the optical length of the propagation path from the light incident surface a- > the third bonding surface F- > the second light emitting surface C is equivalent to the optical thickness of F-P Etalon through which the second linearly polarized light passes.
In practical use, 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 principle:
the optical thickness deltap of the equivalent F-P Etalon passed by the first linearly polarized light and the optical thickness deltas of the equivalent F-P Etalon passed by the second linearly polarized light are different by lambda/4, wherein lambda 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 nearly the same Free Spectral Range (FSR).
In an actual application scenario, the actual thickness of the second compensation plate 15 has a certain tolerance, and the optical thickness difference of the first linearly polarized light and the second linearly polarized light passing through the corresponding F-P Etalon can be adjusted on line by adjusting the angle of the incident light.
Different from the foregoing embodiment 7, the wavelength locker of the present embodiment can effectively improve the wavelength locking sensitivity without greatly increasing the product size, and the specific locking difference is detailed in the principle analysis below.
In a practical application scenario, a tunable laser module is further provided, where the tunable laser module includes the wavelength locker described in any of the foregoing embodiments.
The wave-lock principle of embodiments 2, 4, 5 and 7 is further explained below with reference to fig. 9. As previously described, the first photodetector 2 receives the F-P etalon transmission spectrum and the resulting electrical signal (PIN1) varies 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. In order to eliminate the effect of power fluctuations of the tunable laser, the ratio of these two signals (PIN1/PIN2) is usually used to generate a frequency discrimination signal, and the relationship between the frequency discrimination signal (PIN1/PIN2) and the frequency of the laser input light is shown as a solid line trace 1. trace2 is the target value ([ xi ]) of the frequency discrimination signal maintained in the lock wave. the intersection point (PIN1/PIN2 ═ ξ) of trace1 and trace2 is the target light frequency point for laser locking. The difference in slope sign of trace1 at the lock frequency point can be divided into: the working principle of the positive locking and the negative locking is basically the same, and the positive locking is taken as an example and already described. When the measured frequency discrimination signal is larger than a target value xi (PIN1/PIN2> xi), the frequency of the laser is larger, and the control parameter of the laser needs to be adjusted to enable the wavelength of the laser to move to the long wavelength; if the frequency discrimination signal is smaller than the target value xi (PIN1/PIN2< xi), it indicates that the laser frequency is small, and the control parameter of the laser needs to be adjusted to make the wavelength of the laser move to short wavelength. The frequency discrimination signal is used for discriminating the wavelength change of the laser, the drive control of the laser is adjusted in time, the ratio of the two detection signals PIN1 and PIN2 is maintained as a fixed value xi, and the frequency stabilization of the laser is realized.
The wave-lock principle of embodiments 3, 6 and 8 is further explained below with reference to fig. 10. . As described above, the first photodetector 2 receives the transmission spectrum of the first linearly polarized light equivalent F-P etalon, and the second photodetector 3 receives the transmission spectrum of the second linearly polarized light equivalent F-P etalon; the two equivalent F-P etalons differ in optical thickness by λ/4 and therefore have transmission spectra that are complementary to each other, as shown in fig. 10, with the peak point optical frequency and the valley point optical frequency of the equivalent F-P etalon transmission spectrum trace3 corresponding to the valley point optical frequency and the peak point optical frequency, respectively, of the other equivalent F-P etalon transmission spectrum trace 4. The light intensity ratio detected by the two paths of photoelectric detectors is used as a frequency discrimination signal, and the stable frequency output of the laser is realized by maintaining the ratio signal as a fixed value. Meanwhile, in order to obtain better sensitivity, it is recommended to set the target frequency locking point to be the rising edge or the falling edge of the curve of trace3/trace4, when the frequency discrimination signal deviates from the locking value, that is, the wavelength of the laser deviates from the target frequency, the two-path photodetector detection signal will change in different directions (one path signal becomes larger and the other path becomes smaller, or one path signal becomes smaller and the other path becomes larger), so compared with the scheme without adding the compensation plate, the same frequency change, the frequency discrimination signal has a larger change amplitude, and has higher locking precision.
Here, it should be noted that, the ratio of the detection signals of the two photodetectors is used as a frequency discrimination signal, and the intensities of the two detection signals at the target frequency point cannot differ too much, otherwise, the detection accuracy of the frequency discrimination signal is affected. The half-wave plate 4 is arranged at the input end of the light path, the polarization state of the semiconductor laser can be changed by rotating the half-wave plate 4, and the amplitudes of the two paths of detection signals are dynamically adjusted, so that the intensities of the two paths of detection signals under a target frequency point are consistent as much as possible.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A wavelength locker is characterized by comprising a beam splitting unit (1), a first photoelectric detector (2) and a second photoelectric detector (3), wherein the beam splitting unit (1) comprises a light incident surface, a first light emitting surface and a second light emitting surface;
the light incident surface and the first light emergent surface are plated with a reflecting medium film layer with the same reflectivity so as to form a reflecting cavity mirror of the etalon;
the beam splitting unit (1) is used for splitting the received linearly polarized light into a first linearly polarized light and a second linearly polarized light, the first linearly polarized light is received by the first photoelectric detector (2) after being emitted from the first light emitting surface, and the second linearly polarized light is received by the second photoelectric detector (3) after being emitted from the second light emitting surface;
wherein the ratio of the electrical signals generated by the first photodetector (2) and the second photodetector (3) forms a frequency discrimination signal.
2. The wavelength locker according to claim 1, wherein the beam splitting unit (1) comprises a first prism (11) and a second prism (12), one inclined surface of the first prism (11) is glued with one inclined surface of the second prism (12) to form a first gluing surface, and the first gluing surface is plated with a polarization beam splitting medium film;
the polarization beam splitting dielectric film is used for decomposing linearly polarized light into first linearly polarized light and second linearly polarized light with orthogonal polarization states;
two faces of the first prism (11) are configured as the light incident face and the first light emergent face.
3. The wavelength locker according to claim 2, characterized in that one of the faces of the second prism (12) is configured as the second light-emitting face, which is coated with an antireflection coating.
4. The wavelength locker according to claim 2, wherein the beam splitting unit (1) further comprises a first compensation plate (13), the first compensation plate (13) is glued with the second prism (12) to form a second gluing surface, and the second gluing surface is plated with an antireflection film;
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 plated with a reflection medium film layer which is the same as the light incident surface so as to form a reflection cavity mirror of the etalon.
5. The wavelength locker according to any one of claims 2 to 4, wherein the first prism (11) is a quadrangular prism, two surfaces of which are parallel to each other, two surfaces which are parallel to each other are provided as the light incident surface and the first light passing surface, and the second prism (12) is a triangular prism; or the like, or, alternatively,
the first prism (11) and the second prism (12) are both triangular prisms.
6. The wavelength locker according to claim 1, characterized in that the beam splitting unit (1) comprises a birefringent crystal (14), the birefringent crystal (14) being adapted to split linearly polarized light into the first linearly polarized light and the second linearly polarized light of orthogonal polarization states;
one of the faces of the birefringent crystal (14) is configured as the light-in face, and the other face of the birefringent crystal (14) is divided into a first portion configured as the first light-out face and a second portion.
7. The wavelength locker of claim 6, wherein the second portion is configured as the second light emitting surface, and the second light emitting surface is coated with an antireflection film.
8. The wavelength locker according to claim 6, wherein the beam splitting unit (1) further comprises a second compensation plate (15), the second compensation plate (15) is glued with the second part to form a third gluing surface, and the third gluing surface is plated with an antireflection film;
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 plated with a reflection medium film layer which is the same as the light incident surface so as to form a reflection cavity mirror of the etalon.
9. The wavelength locker of claim 1, further comprising a half-wave plate (4), the half-wave plate (4) being disposed adjacent to the light incident surface, the half-wave plate (4) being rotatable about an axis of the light path.
10. A tunable laser module comprising a wavelength locker as claimed in any one of claims 1 to 9.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011144159.2A CN112271551A (en) | 2020-10-23 | 2020-10-23 | Wavelength locker and adjustable laser component |
| PCT/CN2020/135491 WO2022082965A1 (en) | 2020-10-23 | 2020-12-10 | Wavelength locker and tunable laser component |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011144159.2A CN112271551A (en) | 2020-10-23 | 2020-10-23 | Wavelength locker and adjustable laser component |
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| CN112271551A true CN112271551A (en) | 2021-01-26 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202011144159.2A Pending CN112271551A (en) | 2020-10-23 | 2020-10-23 | Wavelength locker and adjustable laser component |
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| CN (1) | CN112271551A (en) |
| WO (1) | WO2022082965A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114204411A (en) * | 2021-11-03 | 2022-03-18 | 武汉光迅科技股份有限公司 | Laser equipment |
| CN114498277A (en) * | 2021-12-31 | 2022-05-13 | 中国科学院空天信息创新研究院 | Narrow linewidth pulse laser frequency stabilizer |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115657075B (en) * | 2022-05-25 | 2023-07-14 | 北京一径科技有限公司 | Beam combining device and method for manufacturing the same |
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Also Published As
| Publication number | Publication date |
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| WO2022082965A1 (en) | 2022-04-28 |
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