CN112117634A - Semiconductor sodium beacon laser - Google Patents

Semiconductor sodium beacon laser Download PDF

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Publication number
CN112117634A
CN112117634A CN202011012223.1A CN202011012223A CN112117634A CN 112117634 A CN112117634 A CN 112117634A CN 202011012223 A CN202011012223 A CN 202011012223A CN 112117634 A CN112117634 A CN 112117634A
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laser
beacon laser
sodium beacon
semiconductor
sodium
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CN112117634B (en
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李志永
赵莉莉
谭荣清
田俊涛
刘松阳
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Aerospace Information Research Institute of CAS
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Aerospace Information Research Institute of CAS
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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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1028—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the temperature
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/105—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
    • H01S3/1053—Control by pressure or deformation
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
    • H01S3/137—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity for stabilising of frequency
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1691—Solid materials characterised by additives / sensitisers / promoters as further dopants

Abstract

The present disclosure provides a semiconductor sodium beacon laser, comprising: the laser comprises an external cavity semiconductor laser, a beam torsion system, an optical isolator, a focusing mirror and a resonant cavity which are sequentially arranged along the same direction; the resonant cavity includes: the laser comprises a first plane mirror, a second plane mirror M2, a third plane mirror M3, a fourth plane mirror M4, a concave mirror M5, a magnesium-doped periodically poled lithium niobate crystal, a crystal temperature control furnace, piezoelectric ceramics and a Faraday filter, wherein a light reflection channel among the first plane mirror, the second plane mirror M2, the third plane mirror M3 and the fourth plane mirror M4 forms an 8-shaped resonant cavity channel, and the Faraday filter comprises: the Faraday filter comprises a first polarization light splitting cube, a sodium vapor chamber, a second polarization light splitting cube and a half-wave plate which are sequentially arranged along the same direction, and further comprises a Helmholtz coil which is wound on the side surface of the sodium vapor chamber.

Description

Semiconductor sodium beacon laser
Technical Field
The disclosure relates to laser technology and the application field thereof, in particular to a semiconductor sodium beacon laser.
Background
The development of the external cavity technology and the epitaxial wafer etching grating technology enables a semiconductor Laser (LD) to be greatly developed in the aspects of narrow line width, precise wavelength regulation and the like, and a high-power narrow line width LD with the average power of kilowatt level and the line width of 10GHz level can be realized at present, so that the LD is expected to become a next-generation sodium beacon Laser source. At present, the main technical solutions of the sodium beacon laser include: 1, all-solid-state laser sum frequency technology; and 2, fiber Raman laser frequency doubling technology. Both schemes adopt semiconductor laser pump laser crystal, and then generate sodium beacon laser through nonlinear crystal. The sodium beacon laser can resonate with sodium atoms of an atmosphere ionized layer to generate a sodium beacon, and has important application value in the fields of remote sensing, aerospace, astronomical observation and the like.
However, in the prior art, since a solid-state laser, a fiber laser, etc. usually adopt a semiconductor laser pump, from the quantum efficiency point of view, the process is "2 high-energy semiconductor laser photons pump a gain medium to generate 2 low-energy photons, and then the 2 low-energy photons are phase-matched to synthesize 1 high-energy photon". The quantum defect introduced by this physical process is large.
Therefore, in the course of implementing the disclosed concept, the inventors found that there are at least the following problems in the related art: the frequency doubling technology adopted by the prior art has low quantum conversion efficiency, needs multi-stage amplification, has high technical difficulty and faces the problem of laser damage.
Disclosure of Invention
In view of this, the present disclosure provides a semiconductor sodium beacon laser.
The present disclosure provides a semiconductor sodium beacon laser, comprising: the laser comprises an external cavity semiconductor laser, a beam torsion system, an optical isolator, a focusing mirror and a resonant cavity which are sequentially arranged along the same direction.
According to an embodiment of the present disclosure, a resonant cavity includes: the laser comprises a first plane mirror M1, a second plane mirror M2, a third plane mirror M3, a fourth plane mirror M4, a concave mirror M5, a magnesium-doped periodically poled lithium niobate crystal, a crystal temperature control furnace, piezoelectric ceramics and a Faraday filter, wherein light reflection channels among the first plane mirror M1, the second plane mirror M2, the third plane mirror M3 and the fourth plane mirror M4 form an 8-shaped resonant cavity channel.
According to an embodiment of the present disclosure, an external cavity semiconductor laser includes: semiconductor laser, fast axis collimating lens, slow axis collimating lens, volume Bragg grating.
According to an embodiment of the present disclosure, an external cavity semiconductor laser is used to output semiconductor fundamental frequency light.
According to the embodiment of the disclosure, the beam torsion system is used for homogenizing the beam quality factor of the semiconductor fundamental frequency light, so as to obtain the homogenized semiconductor fundamental frequency light.
According to the embodiment of the disclosure, the optical isolator is used for injecting the homogenized semiconductor fundamental frequency light into the focusing mirror to obtain the first focusing semiconductor fundamental frequency light and the second focusing semiconductor fundamental frequency light, and the optical isolator is also used for blocking a channel for transmitting the semiconductor fundamental frequency light to the external cavity semiconductor laser.
According to the embodiment of the present disclosure, the first plane mirror M1 is used to inject the first focused semiconductor fundamental frequency light into the magnesium-doped periodically poled lithium niobate crystal to generate the first sodium beacon laser.
According to an embodiment of the present disclosure, the second flat mirror M2 is used to reflect the first sodium beacon laser to the third flat mirror M3.
According to an embodiment of the present disclosure, the third flat mirror M3 is used to reflect the first sodium beacon laser light reflected by the second flat mirror M2 into the faraday filter.
According to the embodiment of the disclosure, the faraday filter is used for performing frequency stabilization on the first sodium beacon laser to generate the third sodium beacon laser and the fourth sodium beacon laser.
According to an embodiment of the present disclosure, the fourth flat mirror M4 is used to reflect the trisodium beacon laser to the first flat mirror M1 so as to retain the trisodium beacon laser in the "8" shaped cavity channel, the fourth sodium beacon laser being output through the fourth flat mirror M4.
According to an embodiment of the present disclosure, a faraday filter includes: the Faraday filter comprises a first polarization light splitting cube, a sodium vapor chamber, a second polarization light splitting cube and a half-wave plate which are sequentially arranged along the same direction, the Faraday filter further comprises a Helmholtz coil, the Helmholtz coil surrounds the side face of the sodium vapor chamber, the direction in which the first polarization light splitting cube points to the second polarization light splitting cube is a forward propagation channel of first sodium beacon laser, and the direction in which the second polarization light splitting cube points to the first polarization light splitting cube is a backward propagation channel of the first sodium beacon laser.
According to the embodiment of the disclosure, the difference between the polarization plane of the first polarization light splitting cube and the polarization plane of the second polarization light splitting cube is 45 degrees, the helmholtz coil is used for generating a magnetic field parallel to the direction of the first sodium beacon laser, under the action of the magnetic field, the forward propagation direction of the first sodium beacon laser is in a conducting state, and the backward propagation channel of the first sodium beacon laser is in a non-conducting state.
According to an embodiment of the present disclosure, the sodium beacon laser according to claim 3, the sodium vapor chamber is used to stabilize the frequency of the first sodium beacon laser.
According to an embodiment of the present disclosure, a magnesium-doped periodically poled lithium niobate crystal is used to achieve a non-linear change in the frequency of the first sodium beacon laser.
According to the embodiment of the disclosure, the temperature of the magnesium-doped periodically poled lithium niobate crystal is controlled by a crystal temperature control furnace.
According to an embodiment of the present disclosure, a piezo ceramic is connected to the third flat mirror M3, and the piezo ceramic is used to adjust the position of the third flat mirror M3.
According to the embodiment of the present disclosure, the concave mirror M5 is configured to reflect the second focusing semiconductor fundamental frequency light incident to the second flat mirror M2, the second flat mirror M2 is configured to inject the second focusing semiconductor fundamental frequency light into the magnesium-doped periodically poled lithium niobate crystal, and the magnesium-doped periodically poled lithium niobate crystal is configured to generate the second disodium beacon laser.
According to the embodiment of the disclosure, the first sodium beacon laser and the second sodium beacon laser are frequency doubled light of the semiconductor fundamental frequency light, and the spectral line widths of the first sodium beacon laser and the second sodium beacon laser are both smaller than the spectral line width of the semiconductor fundamental frequency light.
According to an embodiment of the present disclosure, the optical isolator is configured to block a channel through which the first sodium beacon laser and the second sodium beacon laser transmit to the external cavity semiconductor laser.
According to the embodiment of the disclosure, the sodium beacon laser has the spectrum selection characteristic based on the volume Bragg grating, and the spectrum selection of a high-power semiconductor laser can be realized.
According to the embodiment disclosed by the invention, the semiconductor laser can be directly subjected to frequency doubling through the magnesium-doped periodically-polarized lithium niobate crystal, the quantum deficiency of the semiconductor laser is reduced, the utilization efficiency of the sodium beacon laser is improved, and the transition of the generated sodium beacon laser, namely the frequency doubling light, is obviously enhanced under the action of a magnetic field and the Faraday optical rotation effect under the action of the sodium vapor chamber. The invention realizes the detection and optimization of the temperature of the magnesium-doped periodically poled lithium niobate crystal through the crystal temperature control furnace, can determine the optimal poling period of the magnesium-doped periodically poled lithium niobate crystal through temperature regulation and control, and can stabilize the frequency of sodium beacon laser through the Faraday filter.
According to the embodiment of the disclosure, the spectrum selection is performed on the generated frequency doubling light by using the sodium vapor chamber, only the required frequency doubling light is reserved, the uncertainty of the semiconductor laser caused by the complicated multi-stage amplification process is avoided, the technical difficulty is reduced, and the required laser with kilowatt-level power can be obtained easily. In addition, the piezoelectric ceramic of the sodium beacon laser is connected with the third plane mirror M3, the position of the third plane mirror M3 is adjusted by moving the piezoelectric ceramic, the oscillation frequency of the sodium beacon laser is automatically locked at the position of an absorption peak, the frequency selection of the sodium beacon laser is realized, and the practicability of the sodium beacon laser is improved.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:
FIG. 1 schematically illustrates a schematic diagram of a sodium beacon laser of the present disclosure;
fig. 2 schematically shows polarization periodograms of the magnesium-doped periodically poled lithium niobate crystals of the present disclosure at different temperatures.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
Where a convention analogous to "A, B, at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a device having at least one of A, B and C" would include but not be limited to devices having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a convention analogous to "A, B or at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a device having at least one of A, B or C" would include but not be limited to devices having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
Embodiments of the present disclosure provide a sodium beacon laser, comprising: the laser comprises an external cavity semiconductor laser, a beam torsion system, an optical isolator, a focusing mirror and a resonant cavity which are sequentially arranged along the same direction; a resonant cavity, comprising: a light reflection channel among a first plane mirror M1, a second plane mirror M2, a third plane mirror M3, a fourth plane mirror M4, a concave mirror M5, magnesium-doped periodically poled lithium niobate crystals, a crystal temperature control furnace, piezoelectric ceramics and a Faraday filter forms an 8-shaped resonant cavity channel;
the external cavity semiconductor laser is used for outputting semiconductor fundamental frequency light;
the beam torsion system is used for homogenizing beam quality factors of the semiconductor fundamental frequency light to obtain homogenized semiconductor fundamental frequency light;
the optical isolator is used for emitting the homogenized semiconductor fundamental frequency light into the focusing lens to obtain first focusing semiconductor fundamental frequency light and second focusing semiconductor fundamental frequency light;
the first plane mirror M1 is used for injecting the first focusing semiconductor fundamental frequency light into the magnesium-doped periodically-polarized lithium niobate crystal to generate a first sodium beacon laser; the second flat mirror M2 is used to reflect the first sodium beacon laser to the third flat mirror M3; the third flat mirror M3 is used for reflecting the first sodium beacon laser light reflected by the second flat mirror M2 into the faraday filter;
the Faraday filter is used for performing frequency stabilization treatment on the first sodium beacon laser to generate a third sodium beacon laser and a fourth sodium beacon laser; the fourth plane mirror M4 is used to reflect the trisodium beacon laser to the first plane mirror M1 so that the trisodium beacon laser remains in the "8" cavity channel, the fourth sodium beacon laser being output through the fourth plane mirror M4.
Fig. 1 schematically illustrates a schematic diagram of a sodium beacon laser of the present disclosure.
As shown in fig. 1, the LD is a semiconductor laser, the FAC is a fast axis collimating mirror, the SAC is a slow axis collimating mirror, the VBG is a volume bragg grating, the BTS is a beam torsion system, the mirror M1 is a first plane mirror M1, the mirror M2 is a second plane mirror M2, the mirror M3 is a third plane mirror M3, the mirror M4 is a fourth plane mirror M4, the mirror M5 is a concave mirror M5, and MgO: PPLN is a magnesium-doped periodically-polarized lithium niobate crystal, the temperature control is a crystal temperature control furnace, PBS1 is a first polarization light-splitting cube, and PBS2 is a second polarization light-splitting cube.
The invention provides a sodium beacon laser, which comprises: the laser comprises an external cavity semiconductor laser, a beam torsion system, an optical isolator, a focusing mirror and a resonant cavity which are sequentially arranged along the same direction.
According to an embodiment of the present disclosure, an external cavity semiconductor laser includes: semiconductor Laser (LD), fast axis collimating mirror (FAC), slow axis collimating mirror (SAC), Volume Bragg Grating (VBG).
According to the embodiment of the disclosure, the external cavity semiconductor laser has the spectrum selection characteristic based on the volume Bragg grating, the spectrum selection of the high-power semiconductor laser can be realized, and the output of semiconductor fundamental frequency light is realized.
According to an embodiment of the present disclosure, the external cavity semiconductor laser may optionally output 1178nm narrow linewidth semiconductor fundamental light with typical values of beam quality factors in fast and slow axis directions of 1 and 1500 or more.
According to the embodiment of the disclosure, optionally, the semiconductor laser is a high-power cm-bar laser with an end face coated with an antireflection film, when an external cavity is not added, the laser does not output laser, the fluorescence spectrum width of the laser is 15nm, the central wavelength of the fluorescence spectrum is 1178nm, and the laser has the capability of continuously outputting 25W of power.
According to the embodiment of the present disclosure, optionally, the fast axis collimating lens may adopt a short focal length aspheric cylindrical lens to collimate the laser light of the semiconductor laser in the fast axis direction, and a typical value of the focal length may be set to 0.9 mm.
According to the embodiment of the present disclosure, optionally, the slow-axis collimating mirror is composed of a cylindrical lens array, and the slow axes of the LD light-emitting elements are collimated respectively. The number of lenticular arrays is typically 19, with each lenticular having a focal length of 1.81 mm.
According to embodiments of the present disclosure, optionally, the bulk bragg grating provides narrow linewidth laser feedback to the semiconductor laser. A temperature control component and a platinum resistor temperature sensor are added in a clamping base of the volume Bragg grating, the feedback wavelength of the grating to the semiconductor laser can be changed by controlling the temperature of the volume Bragg grating, and the narrow-linewidth tunable laser output of the semiconductor laser is realized.
According to an embodiment of the present disclosure, the clamping base of the volume bragg grating may be optionally made of red copper.
According to an embodiment of the present disclosure, optionally, the temperature control assembly within the clamping base may utilize a nickel-chromium heater wire to achieve matching of the pump source with the center wavelength of the rubidium vapor absorption line. The central wavelength of the volume Bragg grating is controlled by a nickel-chromium heating wire, so that the tuning range of the volume Bragg grating covers 1177.5-1178.5 nm. The typical central wavelength of the volume Bragg grating is 1178nm, the bandwidth is less than 2GHz, and the external cavity semiconductor laser can output continuously tunable semiconductor fundamental frequency light with the power of more than 22W.
According to the embodiment of the disclosure, the beam torsion system is used for homogenizing the beam quality factor of the semiconductor fundamental frequency light, so as to obtain the homogenized semiconductor fundamental frequency light.
According to the embodiment of the present disclosure, the beam twisting system is an optical element group composed of lenses for homogenizing the beam quality factor of the semiconductor laser in the fast axis direction and the slow axis direction, wherein the fast axis direction is a direction parallel to the semiconductor PN junction, and the slow axis direction is a direction perpendicular to the semiconductor PN junction. After the light beam quality factors of the semiconductor laser in the fast and slow axis directions are homogenized, the light beam quality factors of the semiconductor laser in the direction parallel to the semiconductor PN junction and the direction vertical to the semiconductor PN junction are approximately equal, the light beam torsion system can realize the homogenization of the light beam quality factors of the fast and slow axes, and the ratio of the light beam quality factors of the fast and slow axes is less than 1.2.
According to the embodiment of the disclosure, the optical isolator is used for injecting the homogenized semiconductor fundamental frequency light into the focusing mirror to obtain the first focusing semiconductor fundamental frequency light and the second focusing semiconductor fundamental frequency light, and the optical isolator is also used for blocking a channel for transmitting the semiconductor fundamental frequency light to the external cavity semiconductor laser.
According to the embodiment of the disclosure, the focusing mirror improves the power density of the semiconductor fundamental frequency optical beam.
According to an embodiment of the present disclosure, an optical isolator is used to isolate semiconductor fundamental frequency light that is reused.
According to the embodiment of the disclosure, optionally, the focal length value of the lens can be selected to be 75mm, the size of a light spot at a focused position is 0.8mm, the rayleigh distance is 2.8mm, and the focusing lens focuses a light beam output by the external cavity semiconductor laser and subjected to homogenization treatment, so as to improve the power density of the fundamental frequency light.
According to an embodiment of the present disclosure, a resonant cavity includes: the laser comprises a first plane mirror M1, a second plane mirror M2, a third plane mirror M3, a fourth plane mirror M4, a concave mirror M5, a magnesium-doped periodically poled lithium niobate crystal, a crystal temperature control furnace, piezoelectric ceramics and a Faraday filter, wherein light reflection channels among the first plane mirror M1, the second plane mirror M2, the third plane mirror M3 and the fourth plane mirror M4 form an 8-shaped resonant cavity channel.
According to the embodiment of the present disclosure, the first plane mirror M1 is configured to inject the included first focused semiconductor fundamental frequency light into the magnesium-doped periodically-polarized lithium niobate crystal to generate a first sodium beacon laser;
according to the embodiment of the present disclosure, optionally, for the first flat mirror M1, when the incident angle of the first focused semiconductor fundamental frequency light and the second focused semiconductor fundamental frequency light is 45 degrees, the first flat mirror M1 is highly reflective to 589nm frequency doubled light, highly transmissive to 1178nm frequency doubled light, the reflectivity of 589nm frequency doubled light is higher than 99.5%, the transmissivity of 1178nm frequency doubled light is higher than 99.0%, and the first flat mirror M1 may be used to realize the coupling of the semiconductor fundamental frequency light and the frequency doubled light.
According to the embodiment of the present disclosure, the incident angle of the first focusing semiconductor fundamental frequency light and the second focusing semiconductor fundamental frequency light to the first plane mirror M1 may also be other angles. When the incident angle is other angles, the dielectric film of the first plane mirror M1 needs to be highly reflective to 589nm frequency-doubled light and highly transmissive to 1178nm semiconductor fundamental frequency light at the angle.
The second flat mirror M2 is used to reflect the first sodium beacon laser to the third flat mirror M3;
according to the embodiment of the present disclosure, optionally, for the second flat mirror M2, when the incident angle of the light beam is 45 degrees, the second flat mirror M2 is highly reflective to the frequency-doubled light beam of 589nm, highly transparent to the semiconductor fundamental frequency light beam of 1178nm, the reflectivity of the frequency-doubled light of 589nm is higher than 99.5%, and the transmittance of the semiconductor fundamental frequency light of 1178nm is higher than 99.0%.
According to the embodiment of the present disclosure, the incident angle of the first focusing semiconductor fundamental frequency light and the second focusing semiconductor fundamental frequency light to the first plane mirror M1 may also be other angles. When the incident angle is other angles, the dielectric film of the first plane mirror M1 needs to be highly reflective to 589nm frequency-doubled light and highly transmissive to 1178nm semiconductor fundamental frequency light at the angle.
According to the embodiment of the present disclosure, optionally, the third plane mirror M3 is highly reflective to the frequency-doubled light beam of 589nm and highly transparent to the base-frequency semiconductor light beam of 1178nm, the reflectivity of the frequency-doubled light of 589nm is higher than 99.5%, and the transmissivity of the base-frequency semiconductor light beam of 1178nm is higher than 99.0%.
According to the embodiment of the present disclosure, the third flat mirror M3 is used to reflect the first sodium beacon laser light reflected by the second flat mirror M2 into the faraday filter;
according to an embodiment of the present disclosure, a piezo ceramic is connected to the third flat mirror M3, and the piezo ceramic is used to adjust the position of the third flat mirror M3 by moving.
According to the embodiment of the disclosure, the piezoelectric ceramic is used for driving the third plane mirror M3, and the position of the third plane mirror M3 is adjusted through the piezoelectric ceramic, so that the oscillation frequency of the sodium beacon laser is automatically locked at the position of an absorption peak, the frequency selection of the sodium beacon laser is realized, and the practicability of the sodium beacon laser is improved.
According to the embodiment of the present disclosure, optionally, the fourth plane mirror M4 partially transmits the frequency-doubled light beam of 589nm, and the transmittance is 40%.
According to the embodiment of the disclosure, the Faraday filter is used for performing frequency stabilization on the first sodium beacon laser to generate a third sodium beacon laser and a fourth sodium beacon laser;
according to an embodiment of the present disclosure, the fourth flat mirror M4 is used to reflect the trisodium beacon laser to the first flat mirror M1 so as to retain the trisodium beacon laser in the "8" shaped cavity channel, the fourth sodium beacon laser being output through the fourth flat mirror M4.
According to the embodiment of the present disclosure, the first plane mirror M1, the second plane mirror M2, the third plane mirror M3, and the fourth plane mirror M4 form an "8" -shaped resonator channel, wherein the third plane mirror M3 and the fourth plane mirror M4 form a traveling wave resonator transmission channel, and the traveling wave resonator transmission channel opens to the sodium beacon laser that passes through the faraday filter after being reflected by the third plane mirror M3.
According to the embodiment of the present disclosure, the concave mirror M5 is configured to reflect the second focusing semiconductor fundamental frequency light incident to the second flat mirror M2, the second flat mirror M2 is configured to inject the second focusing semiconductor fundamental frequency light into the magnesium-doped periodically poled lithium niobate crystal, and the magnesium-doped periodically poled lithium niobate crystal is further configured to generate the second disodium beacon laser.
According to the embodiment of the disclosure, the sodium beacon laser realizes secondary utilization of the semiconductor fundamental frequency light output by the external cavity semiconductor laser through the concave mirror M5.
According to an embodiment of the present disclosure, the optical isolator is used to isolate the second focused semiconductor fundamental frequency light from interfering with the operating state of the external cavity semiconductor laser.
According to the embodiment of the disclosure, the first sodium beacon laser and the second sodium beacon laser are frequency doubled light of the semiconductor fundamental frequency light, and the spectral line widths of the first sodium beacon laser and the second sodium beacon laser are both smaller than the spectral line width of the semiconductor fundamental frequency light.
According to the embodiment of the disclosure, relative to the semiconductor laser for the first-level narrowing of the line width of the semiconductor fundamental frequency light, the spectral line widths of the first sodium beacon laser and the second sodium beacon laser are both smaller than the spectral line width of the semiconductor fundamental frequency light, the resonant cavity can realize the second-level narrowing of the line width of the frequency doubling light, obtain the frequency doubling light with narrow spectral width, and can effectively inhibit the output of the frequency doubling light in a high-order mode.
According to an embodiment of the present disclosure, the optical isolator is further configured to block a channel through which the first sodium beacon laser and the second sodium beacon laser are transmitted to the external cavity semiconductor laser.
According to the embodiment of the disclosure, the optical isolator prevents the first sodium beacon laser and the second sodium beacon laser from interfering the working state of the external cavity semiconductor laser, ensures the working performance of the external cavity semiconductor laser, and avoids the problem of laser damage.
According to an embodiment of the present disclosure, a faraday filter includes: the Faraday filter comprises a first polarization light splitting cube, a sodium vapor chamber, a second polarization light splitting cube and a half-wave plate which are sequentially arranged along the same direction, the Faraday filter further comprises a Helmholtz coil, the Helmholtz coil surrounds the side face of the sodium vapor chamber, the direction in which the first polarization light splitting cube points to the second polarization light splitting cube is a forward propagation channel of first sodium beacon laser, and the direction in which the second polarization light splitting cube points to the first polarization light splitting cube is a backward propagation channel of the first sodium beacon laser.
According to the embodiment of the disclosure, the difference between the polarization plane of the first polarization light splitting cube and the polarization plane of the second polarization light splitting cube is 45 degrees, the helmholtz coil is used for generating a magnetic field parallel to the direction of the first sodium beacon laser, under the action of the magnetic field, the forward propagation channel of the first sodium beacon laser is in a conducting state, and the backward propagation channel of the first sodium beacon laser is in a non-conducting state.
According to the embodiment of the disclosure, the frequency of the sodium beacon laser can be stabilized through the Faraday filter, the forward propagation channel of the first sodium beacon laser is protected to be always conducted, and a stable 8-shaped resonant cavity channel is established for the first sodium beacon laser.
According to embodiments of the present disclosure, optionally, the magnetic field in the faraday filter may also be generated by a permanent magnet.
According to an embodiment of the present disclosure, a sodium vapor chamber is used to stabilize the frequency of the first sodium beacon laser.
According to the embodiment of the disclosure, the sodium vapor chamber can realize frequency stabilization of the first sodium beacon laser, and effectively prevent frequency drift of the first sodium beacon laser.
According to the embodiment of the disclosure, optionally, the frequency sampling may be performed on the third sodium beacon laser and the fourth sodium beacon laser output by the sodium vapor chamber, and if there is a drift in the sampled laser frequency, a feedback device may feed back a control signal to control the movement of the piezoelectric ceramic connected to the third plane mirror M3, so as to adjust the position of the third plane mirror M3, and further stabilize the frequency of the first sodium beacon laser.
According to the embodiment of the disclosure, the spectrum selection is performed on the generated frequency doubling light by using the sodium vapor chamber, only the required frequency doubling light is reserved, the uncertainty of the semiconductor laser caused by the complicated process of multi-stage amplification is avoided, the technical difficulty is reduced, and the required laser with kilowatt-level power can be obtained.
According to an embodiment of the present disclosure, a magnesium-doped periodically poled lithium niobate crystal is used to achieve a non-linear change in the frequency of the first sodium beacon laser.
According to the embodiment of the disclosure, the magnesium-doped periodically-polarized lithium niobate crystal is a quasi-phase matching crystal and has a high effective nonlinear coefficient, the fundamental frequency light and the frequency doubling light can be transmitted in the magnesium-doped periodically-polarized lithium niobate crystal in a coaxial manner, the fundamental frequency light can generate nonlinear frequency conversion through the magnesium-doped periodically-polarized lithium niobate crystal, the process of frequency summation of the fundamental frequency light beam is realized, the magnesium-doped periodically-polarized lithium niobate crystal can directly carry out frequency doubling on a semiconductor laser, the quantum loss of the semiconductor laser is reduced, and the utilization efficiency of the sodium beacon laser is improved.
According to the embodiment of the present disclosure, optionally, the magnesium-doped periodically poled lithium niobate crystal may perform a sum frequency process on the first focused semiconductor fundamental frequency light with a wavelength of 1178nm and the first focused semiconductor fundamental frequency light with another wavelength of 1178nm to generate 589nm of first sodium beacon laser or second sodium beacon laser.
According to the embodiment of the disclosure, the temperature of the magnesium-doped periodically poled lithium niobate crystal is controlled by a crystal temperature control furnace.
Fig. 2 schematically shows polarization periodograms of the magnesium-doped periodically poled lithium niobate crystals of the present disclosure at different temperatures.
According to the embodiment of the disclosure, as shown in fig. 2, according to the fact that the magnesium-doped periodically poled lithium niobate crystal has a poling period at different temperatures, and the different temperatures have a one-to-one correspondence with the poling period of the magnesium-doped periodically poled lithium niobate crystal, the temperature of the magnesium-doped periodically poled lithium niobate crystal is detected and determined according to the one-to-one correspondence, the optimal poling period of the magnesium-doped periodically poled lithium niobate crystal can be determined through temperature regulation, and the conversion efficiency of fundamental frequency light to frequency-doubled light is remarkably improved.
Those skilled in the art will appreciate that various combinations and/or combinations of features recited in the various embodiments and/or claims of the present disclosure can be made, even if such combinations or combinations are not expressly recited in the present disclosure. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present disclosure may be made without departing from the spirit or teaching of the present disclosure. All such combinations and/or associations are within the scope of the present disclosure.
The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.

Claims (10)

1. A semiconductor sodium beacon laser, comprising: the laser comprises an external cavity semiconductor laser, a beam torsion system, an optical isolator, a focusing mirror and a resonant cavity which are sequentially arranged along the same direction;
wherein, the resonant cavity includes: a first plane mirror M1, a second plane mirror M2, a third plane mirror M3, a fourth plane mirror M4, a concave mirror M5, a magnesium-doped periodically poled lithium niobate crystal, a crystal temperature control furnace, piezoelectric ceramics and a Faraday filter, wherein light reflection channels among the first plane mirror M1, the second plane mirror M2, the third plane mirror M3 and the fourth plane mirror M4 form an 8-shaped resonant cavity channel;
the external cavity semiconductor laser is used for outputting semiconductor fundamental frequency light;
the beam torsion system is used for homogenizing beam quality factors of the semiconductor fundamental frequency light to obtain homogenized semiconductor fundamental frequency light;
the optical isolator is used for injecting the homogenized semiconductor fundamental frequency light into the focusing mirror to obtain first focusing semiconductor fundamental frequency light and second focusing semiconductor fundamental frequency light, and the optical isolator is also used for blocking a channel for transmitting the semiconductor fundamental frequency light to the external cavity semiconductor laser;
the first plane mirror M1 is configured to inject the first focused semiconductor fundamental frequency light into the magnesium-doped periodically-polarized lithium niobate crystal to generate a first sodium beacon laser;
the second flat mirror M2 is used to reflect the first sodium beacon laser to the third flat mirror M3;
the third flat mirror M3 is used for reflecting the first sodium beacon laser light reflected by the second flat mirror M2 into the Faraday filter;
the Faraday filter is used for performing frequency stabilization treatment on the first sodium beacon laser to generate a third sodium beacon laser and a fourth sodium beacon laser;
the fourth plane mirror M4 is used to reflect the trisodium beacon laser to the first plane mirror M1 so as to retain the trisodium beacon laser in the "8" cavity channel, the fourth sodium beacon laser being output through the fourth plane mirror M4.
2. The sodium beacon laser of claim 1, wherein the faraday filter comprises: first polarization beam splitting cube, sodium vapour room, second polarization beam splitting cube, the half wave plate that places in proper order along same direction, faraday's filter still includes helmholtz coil, helmholtz coil encircles the side of sodium vapour room, first polarization beam splitting cube points to the direction at second polarization beam splitting cube place does the forward direction of propagation of first sodium beacon laser, second polarization beam splitting cube points to the direction at first polarization beam splitting cube place does the reverse direction of propagation of first sodium beacon laser.
3. The sodium beacon laser as claimed in claim 2, wherein the polarization plane of the first polarization beam splitter cube is 45 degrees different from the polarization plane of the second polarization beam splitter cube, and the helmholtz coil is configured to generate a magnetic field parallel to the direction of the first sodium beacon laser, under the action of the magnetic field, the forward propagation channel of the first sodium beacon laser is in a conducting state, and the backward propagation channel of the first sodium beacon laser is in a non-conducting state.
4. The sodium beacon laser of claim 3, wherein the sodium vapor chamber is configured to stabilize a frequency of the first sodium beacon laser.
5. The sodium beacon laser of claim 1, the magnesium-doped periodically poled lithium niobate crystal being configured to effect a non-linear change in frequency of the first sodium beacon laser.
6. The sodium beacon laser of claim 1, wherein the temperature of the magnesium-doped periodically poled lithium niobate crystal is controlled by the crystal temperature controlled furnace.
7. The sodium beacon laser of claim 1, the piezo ceramic being connected to the third planar mirror M3, the piezo ceramic being used to adjust the position of the third planar mirror M3.
8. The sodium beacon laser of claim 1, said concave mirror M5 for reflecting said second focused semiconductor-based frequency light incident on said second flat mirror M2, said second flat mirror M2 for injecting said second focused semiconductor-based frequency light into said magnesium-doped periodically poled lithium niobate crystal for generating a second sodium beacon laser.
9. The sodium beacon laser of claim 8, wherein the first sodium beacon laser and the second sodium beacon laser are both frequency doubled with respect to the semiconductor fundamental frequency light, and wherein the spectral linewidths of the first sodium beacon laser and the second sodium beacon laser are both smaller than the spectral linewidth of the semiconductor fundamental frequency light.
10. The sodium beacon laser of claim 9, the optical isolator for blocking passage of the first and second sodium beacon lasers to the external cavity semiconductor laser.
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EP3096182B1 (en) * 2015-05-19 2020-01-01 Qioptiq Photonics GmbH & Co. KG Tunable, narrow linewidth single transversal mode light source using a quasi-incoherent broadband pump source
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CN102035136A (en) * 2009-09-29 2011-04-27 中国计量科学研究院 External cavity semiconductor laser
EP3096182B1 (en) * 2015-05-19 2020-01-01 Qioptiq Photonics GmbH & Co. KG Tunable, narrow linewidth single transversal mode light source using a quasi-incoherent broadband pump source
CN205543667U (en) * 2016-02-04 2016-08-31 福建中科晶创光电科技有限公司 Continuous ultraviolet laser of annular chamber single -frequency
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