WO2020155250A1 - 单频激光光源 - Google Patents

单频激光光源 Download PDF

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Publication number
WO2020155250A1
WO2020155250A1 PCT/CN2019/076149 CN2019076149W WO2020155250A1 WO 2020155250 A1 WO2020155250 A1 WO 2020155250A1 CN 2019076149 W CN2019076149 W CN 2019076149W WO 2020155250 A1 WO2020155250 A1 WO 2020155250A1
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Prior art keywords
reflection
unit
filtering
laser light
light source
Prior art date
Application number
PCT/CN2019/076149
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English (en)
French (fr)
Inventor
文侨
孙志豪
Original Assignee
深圳大学
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN201920182140.3U external-priority patent/CN209448210U/zh
Priority claimed from CN201910099065.9A external-priority patent/CN111509543A/zh
Priority claimed from CN201910099035.8A external-priority patent/CN111509535A/zh
Priority claimed from CN201920182151.1U external-priority patent/CN209448209U/zh
Application filed by 深圳大学 filed Critical 深圳大学
Publication of WO2020155250A1 publication Critical patent/WO2020155250A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/083—Ring lasers
    • 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
    • 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

Definitions

  • This application belongs to the field of optical technology, and particularly relates to a single-frequency laser light source.
  • Precision interferometry mainly uses laser wavelength as a "ruler", and uses the principle of interference to measure various parameters, such as acceleration, displacement, angular displacement, and so on. Since the wavelength of light is on the order of nm, its resolution accuracy is unmatched by electrical and magnetic components.
  • the laser interferometer has been widely used in the field of precision and ultra-precision length measurement due to its unique advantages of large measurement range, high resolution and high measurement accuracy.
  • the distance and interference quality of precision interferometry are closely related to the line width of the laser. In order to further increase the measurement accuracy in the actual design, the laser linewidth is required to be less than 1kHz.
  • the sonar pulse ranging system composed of fiber laser hydrophone array has entered the engineering test stage.
  • Fiber laser hydrophone is the core equipment of underwater sound detection equipment. Its minimum resolvable longitudinal strain is determined by the line width of the fiber laser. The narrower the laser linewidth, the higher the sound pressure resolution of the hydrophone, and the better it can meet the detection of weak signals.
  • the fiber laser resonator Since the length of the fiber laser resonator usually reaches the order of tens of centimeters or even meters, adding the laser to work in a single-frequency operation state, the fiber laser can obtain good monochromaticity and coherence, which greatly improves the performance of the optoelectronic system and Upgrade and obtain great economic and social benefits. Therefore, the single-frequency narrow-linewidth fiber laser has very high practical value.
  • One of the mainstream single-frequency lasers currently in use is a short straight cavity single-frequency fiber laser.
  • the long linear cavity creates a spatial hole in the gain medium due to the standing wave effect, which will cause the laser to produce multi-mode oscillations and broaden the output spectral linewidth.
  • the cavity length is inversely proportional to the longitudinal mode interval. As the resonant cavity length becomes shorter, the cavity longitudinal mode interval increases. As shown in Figure 1, when the gain reaches the laser threshold S0 or more, When the distance between adjacent longitudinal modes L1 is greater than the reflection spectrum bandwidth L2 of the cavity mirror or the gain spectrum width of the active fiber, the laser can achieve single-frequency operation and realize single-frequency narrow linewidth laser output.
  • the longitudinal mode interval is inversely proportional to the cavity length.
  • the bandwidth can usually be controlled to several tens of nanometers.
  • the bandwidth is usually It can be controlled within a few hundred picometers, so a narrow bandwidth single-frequency light source is usually realized through the latter scheme.
  • the narrowband fiber grating 01 and broadband fiber grating 02 are used as cavity mirrors.
  • the reflection spectrum bandwidth of the overall cavity mirror mainly depends on the narrowband fiber grating 01.
  • the cavity length of the resonant cavity is only a few The centimeter length can ensure that the longitudinal mode spacing exceeds the reflection spectrum bandwidth L3 of the narrowband fiber grating 01.
  • the narrowband fiber grating reflection spectrum bandwidth L3 is larger, the cavity length needs to be shorter.
  • the shortening of the cavity length has a great limit on the output power.
  • the narrowband fiber grating 01 that is, the reflection spectrum bandwidth L3 is required to be narrower, and the process is more difficult. Therefore, for the short straight cavity single-frequency fiber laser light source, the mutual restriction between the narrow-band fiber grating and the output power becomes a difficult problem.
  • the purpose of this application is to provide a single-frequency laser light source, including but not limited to solving the technical problems of traditional single-frequency laser light sources that require high fiber gratings and limited output power.
  • a single frequency laser light source including
  • Resonant cavity used to absorb pump light and obtain single frequency laser
  • the resonant cavity includes:
  • the first reflection filtering unit is used to filter and reflect the laser light in the resonant cavity
  • the second reflection filtering unit is used to filter and reflect the laser light in the resonant cavity
  • the first reflection filter unit and the second reflection filter unit constitute at least two ends of the resonant cavity, the filter ranges of the first reflection filter unit and the second reflection filter unit partially overlap, and the excitation light After filtering by the first reflection filtering unit and the second reflection filtering unit, a single longitudinal mode output is realized to obtain a single frequency laser.
  • the single-frequency light source uses a first reflection filter unit and a second reflection filter unit to form a laser resonant cavity, uses a gain medium, a first reflection filter unit and a second reflection filter unit to generate laser light, and uses the first reflection filter unit
  • the filtering effect of the second reflection filtering unit and the second reflection filtering unit on the laser frequency selects the laser in the overlapping area of the two filtering, and then obtains a single longitudinal mode output.
  • Figure 1 is a schematic diagram of single-frequency laser single longitudinal mode operation
  • Figure 2 is a working principle diagram of a traditional narrow linewidth single frequency light source
  • Fig. 3 is a working principle diagram of a single-frequency laser light source provided by an embodiment of the present application.
  • FIG. 4 is a schematic diagram of wavelength tuning of a single-frequency laser light source provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of bandwidth tuning of a single-frequency laser light source provided by an embodiment of the present application.
  • FIG. 6 is a schematic diagram of adjusting the edge slope of the overlapping area of a single-frequency laser light source according to an embodiment of the present application
  • FIG. 7 is a schematic structural diagram of a first reflection filtering unit and a second reflection filtering unit provided by an embodiment of the present application;
  • FIG. 8 is a schematic diagram of another structure of the first reflection filter unit and the second reflection filter unit provided by an embodiment of the present application.
  • FIG. 9 is a schematic diagram of the structure of a single-frequency laser light source provided by the first embodiment of the present application.
  • FIG. 10 is a structural diagram of a single-frequency laser light source provided by a second embodiment of the present application.
  • FIG. 11 is another structural diagram of the single-frequency laser light source provided by the second embodiment of the present application.
  • FIG. 12 is a structural diagram of a single-frequency laser light source provided by a third embodiment of the present application.
  • FIG. 13 is a structural diagram of a single-frequency laser light source provided by a fourth embodiment of the present application.
  • FIG. 14 is a structural diagram of a single-frequency laser light source provided by a fifth embodiment of the present application.
  • 15 is a structural diagram of a single-frequency laser light source provided by a sixth embodiment of the present application.
  • 16 is a structural diagram of a single-frequency laser light source provided by a seventh embodiment of the present application.
  • FIG. 17 is a structural diagram of a single-frequency laser light source provided by an eighth embodiment of the present application.
  • FIG. 18 is a schematic diagram of a spectrum of a single-frequency laser light source provided by an embodiment of the present application.
  • 20 is a schematic diagram of the output line width of a laser based on a single-frequency laser light source provided by an embodiment of the present application.
  • an embodiment of the present application provides a single-frequency laser light source, which includes at least a pumping unit 10 and a resonant cavity 20.
  • the pumping unit 10 is used to output pump light; the resonant cavity 20 is provided in the pumping unit 10. On the output light path of, it is used to absorb pump light, and the gain medium in the resonant cavity 20 is excited by the pump light to obtain excitation light.
  • the resonant cavity 20 is a main unit for obtaining single-frequency laser light, which at least includes: a first reflection filter unit 21, a second reflection filter unit 22, and a gain medium 23 in between.
  • the single-frequency laser light outputs the resonant cavity 20 through the first reflection filter unit 21 or the second reflection filter unit 22 or the cavity side end.
  • the first reflection filter unit 21 and the second reflection filter unit 22 constitute the cavity of the laser resonator 20, that is, at least can form two-end cavity mirrors, and also have a filtering function. See FIG. 3, first The reflection filter unit 21 and the second reflection filter unit 22 have filter bandwidths L6 and L7, respectively, and the filter bandwidths L6 and L7 have an overlapping frequency band L8.
  • the filtering described in this embodiment is all frequency filtering.
  • the first reflection filtering unit 21 is at least used to filter the laser light in the resonant cavity 20 and reflect the light intensity; specifically, the first reflection filtering unit 21 means that the unit at least includes Among them, the laser light intensity is reflected; the first reflection filtering unit 21 also includes a module capable of frequency "screening" (ie filtering) the laser light incident therein, and then selectively reflecting or transmitting part of the frequency light, after filtering
  • the obtained laser is the necessary basis for the formation of single-frequency laser.
  • the two modules may be the same module structure capable of performing the dual functions of reflected light intensity and filtering, or may be two independent module structures respectively used for reflected light intensity and filtering.
  • the second reflection filtering unit 22 is used for filtering the laser light in the resonant cavity 20 and reflecting the light intensity; specifically, the second reflection filtering unit 22 at least includes a module capable of reflecting the light intensity of the laser light incident therein.
  • the module is used as the reflection end of the resonant cavity 20, and also includes a module capable of frequency "screening" (ie, filtering) the incident laser light, and then selectively reflecting or transmitting part of the frequency laser light, and the laser light obtained after filtering is formed into a single unit.
  • the necessary foundation for frequency laser Similarly, the two modules can also be an integral structure or independent structures.
  • the filtering ranges of the above-mentioned first reflection filtering unit 21 and the second reflection filtering unit 22 partially overlap.
  • the pump light enters the cavity 20, excites the gain medium 23 to generate laser light, and the laser light is reflected between the first reflection filter unit 21 and the second reflection filter unit 22, and passes through the first reflection filter unit 21 and the second reflection filter unit 22 After filtering, the generated laser frequency band is located in the overlapping area of the filtering range.
  • a suitable filtering range to make the overlapping frequency band extremely narrow a single longitudinal mode output can be obtained, that is, a single frequency laser can be obtained.
  • the single-frequency laser light source provided by the embodiment of the application has the following effects: the first reflection filter unit 21 and the second reflection filter unit 22 are used to form the laser resonant cavity 20, and the first reflection filter unit 21 is used to reflect light intensity and the second reflection.
  • the filter unit 22 forms an active resonant cavity for the reflective gain medium with light intensity to obtain laser light, and uses the filtering effect of the first reflection filter unit 21 and the second reflection filter unit 22 on the laser frequency to select the laser in the overlapping area of the two filters, and then obtain the single For longitudinal mode output, the bandwidth of the single longitudinal mode output can be less than 1KHz.
  • the single-frequency light source does not need to be equipped with extremely narrow-band fiber gratings.
  • the bandwidth requirements of the reflection filter unit 22 are not high, and are not limited by the extremely narrow filtering range requirements of a single narrow-band filter grating, and can be composed of a grating with lower parameters, which greatly reduces the process difficulty.
  • the reflection bandwidth of the narrow-band grating must be smaller than the longitudinal mode interval.
  • the cavity length is shorter.
  • the output power will be lost, and the traditional single-frequency light source has the mutual restriction of narrow-band grating performance and output power.
  • the single-frequency light source of this embodiment does not completely depend on the filter bandwidth of either end of the filter unit, that is, no filter bandwidth is required.
  • the single-frequency laser light source further includes a tuning unit 80, through which the center wavelength and bandwidth of the single-frequency laser can be flexibly adjusted.
  • the tuning unit 80 is used to adjust the center wavelength and/or filter bandwidth of the first reflection filter unit 21 and/or the second reflection filter unit 22, and specifically includes: adjusting the first reflection filter unit 21 or the second reflection filter unit 22; adjust the filter bandwidth of the first reflection filter unit 21 or the second reflection filter unit 22; adjust the center wavelength and filter bandwidth of the first reflection filter unit 21 or the second reflection filter unit 22; adjust the first reflection filter unit 21 and the center wavelength of the second reflection filter unit 22; adjust the filter bandwidth of the first reflection filter unit 21 and the second reflection filter unit 22; adjust the center wavelength and filter bandwidth of the first reflection filter unit 21 and the second reflection filter unit 22 ; Adjust the center wavelength and filter bandwidth of the first reflection filter unit 21 and the second reflection filter unit 22 ; Adjust the center wavelength of the first reflection filter unit 21 and the filter bandwidth of the second reflection filter unit 22; adjust the filter bandwidth of the first reflection filter unit 21 and the center wavelength of the
  • this embodiment only connects the tuning unit 80 to the first reflection filter unit 21 or the second reflection filter unit 22 that needs to be adjusted.
  • a tuning unit 80 is provided on the first reflection filtering unit 21 and the second reflection filtering unit 22 respectively.
  • p m ( ⁇ i ) and p m-1 ( ⁇ i ) are the power before and after the light source with the wavelength ⁇ i makes a round trip (m-th round trip) in the cavity.
  • R 1 ( ⁇ i ) and R 2 ( ⁇ i ) are the reflectivities of the two filters in the resonant cavity to the wavelength ⁇ i .
  • the power difference of two different wavelengths ⁇ i and ⁇ j is
  • the input of pump light and the output of single-frequency laser have various forms.
  • the pump light enters the resonant cavity 20 through one of the two ends of the resonant cavity 20, and the single-frequency laser is output through the first reflection filtering unit 21 or the second reflection filtering unit 22 of the resonant cavity 20.
  • the first reflection filtering unit 21 is a partial reflection filtering unit for transmitting pump light, filtering the laser light in the resonator 20 and partially reflecting the light intensity, and outputting single-frequency laser light;
  • the second reflection filtering unit 22 It is a total reflection filter unit, used for filtering the laser light in the resonant cavity 20 and totally reflecting the light intensity.
  • the pump light enters the resonant cavity 20 through one of the two ends of the resonant cavity 20, and the single-frequency laser is output to the resonant cavity 20 through somewhere in the resonant cavity 20, that is, does not pass through the first reflection filter unit 21 or The second reflection filter unit 22 outputs.
  • the first reflection filtering unit 21 is a total reflection filtering unit for transmitting pump light, filtering the laser light in the resonant cavity 20, and totally reflecting the light intensity
  • the second reflection filtering unit 22 is a total reflection filtering unit, It is used to filter the laser light in the resonant cavity 20 and totally reflect the light intensity
  • an output unit 30 is provided in the resonant cavity 20 to output the single-frequency laser light from the side end of the resonant cavity 20.
  • a pump light coupling unit 40 can also be provided between the pump unit 10 and the resonant cavity 20.
  • the pump light enters the resonant cavity 20 through the side end of the resonant cavity 20, and the single-frequency laser light is output to the resonant cavity 20 through a place in the cavity 20.
  • the first reflection filter unit 21 and the second reflection filter unit 22 are both total reflection filter units for filtering the laser light in the resonant cavity 20 and totally reflecting the light intensity;
  • the resonant cavity 20 is provided with pump light The coupling unit 40 and the output unit 30.
  • the pump light coupling unit 40 is used to couple pump light into the resonant cavity 20, and the output unit 30 is used to output the single-frequency laser light from the side end of the resonant cavity 20.
  • a circulator 50 can also be arranged outside the resonant cavity 20 and connected to the output unit 30. On the one hand, it can be used to output single-frequency laser; The frequency laser is transmitted back to the cavity 20.
  • the pump light enters the resonant cavity 20 through the side end of the resonant cavity 20, and the single-frequency laser light outputs the resonant cavity 20 through the first reflection filter unit 21 or the second reflection filter unit 22 of the resonator 20.
  • the first reflection filtering unit 21 is a partial reflection filtering unit for filtering the laser light in the resonant cavity 20, partially reflecting the light intensity, and outputting single-frequency laser;
  • the second reflection filtering unit 22 is a total reflection filtering unit , Used for filtering the laser light in the resonant cavity 20 and totally reflecting the light intensity.
  • a pump light coupling unit 40 is provided in the resonant cavity 20 for coupling the pump light into the resonant cavity 20.
  • the single-frequency light source may include an isolation unit 60 arranged on the output path of the single-frequency laser, for isolating the reverse laser light and protecting the single-frequency light source.
  • the gain medium 23 is used as a medium for realizing particle beam inversion, preferably a full-gain fiber, and both ends are connected to the first reflection filter unit 21 and the second reflection filter unit 22 respectively.
  • the pump light coupling unit 40 couples the pump light into the resonant cavity 20, realizes the particle beam inversion of the full-gain fiber in the resonant cavity 20, and obtains laser light, which passes through the first reflection filter unit 21 and the second reflection filter unit 22 It has a filtering function, which has a very small line width range and emits single-frequency laser.
  • the gain medium 23 may also be a block-shaped gain crystal.
  • the gain crystal may be independently arranged in the resonant cavity 20, or may be connected to the first reflection filter unit 21 and the second reflection filter unit 21 through a non-gain fiber or a gain fiber. Filtering unit 22.
  • both the total reflection filter unit and the partial reflection filter unit can adopt an integrated structure or a combined structure of two independent modules.
  • the integrated structure is a structure capable of performing dual functions of reflected light intensity and filtering.
  • the combined structure is specifically as follows: the first reflection filter unit 21 includes a first mirror 211, and a The first filter module 212 in the reflection direction.
  • the second reflection filtering unit 22 includes a second reflection mirror 221 and a second filtering module 222 disposed in the reflection direction of the second reflection mirror 221.
  • the first reflector 221 or the second reflector 222 can be designed in a form of total reflection or partial reflection.
  • the first reflection filtering unit 21 is a partial reflection filtering unit
  • the second reflection filtering unit 22 is a total reflection filtering unit.
  • the pump light is input from the partial reflection filter unit, and the single-frequency laser is output from the partial reflection filter unit.
  • the single-frequency light source includes a pump unit 10 and a resonant cavity 20, and may further include a pump light coupling unit 40.
  • the pump unit 10 is used to output pump light;
  • the pump light coupling unit 40 is arranged between the pump unit 10 and the resonant cavity 20, and is used to couple the pump light into the resonant cavity 20 and output the single unit of the resonant cavity 20. Frequency laser output.
  • the resonant cavity 20 is arranged at one end of the pump light coupling unit 40, and is used to absorb pump light, excite the gain medium 23 in the resonant cavity 20 by the pump light to obtain excitation light, and obtain single-frequency laser light through filtering and reflection of the resonant cavity
  • the single-frequency laser is emitted from the cavity 20 and then output through the other end of the pump light coupling unit 40.
  • the partial reflection filter unit and the total reflection filter unit form the cavity of the laser resonator 20, that is, at least it can form two-end cavity mirrors, and also has a filtering function.
  • the partial reflection filter unit and the total reflection filter unit have filter bandwidths L6 and L7, respectively.
  • the filter bandwidths L6 and L7 have an overlapping frequency band L8.
  • the pump light enters the resonant cavity 20 through the partial reflection filter unit, and the gain medium 23 is excited to generate excitation light.
  • the excitation light is reflected between the partial reflection filter unit and the total reflection filter unit, and passes through the partial reflection filter unit and the total reflection filter unit.
  • the generated laser frequency band is located in the overlapping area of the filtering range.
  • the Bragg fiber grating can be directly written on the fiber to form a grating cavity mirror, so the compatibility with the doped active fiber is very good, not only the connection loss is very small, but also the complicated optical structure is avoided , Facilitate the integration and miniaturization of fiber lasers, so that fiber lasers have better stability and reliability, and are especially suitable for workplaces with very harsh environmental conditions. Therefore, the fiber laser based on the linear cavity 20 structure preferably uses an ultrashort linear cavity structure to obtain a single-frequency narrow linewidth laser output. In this embodiment, it is preferable to use an integrated grating cavity mirror formed by directly writing Bragg fiber gratings on the optical fiber as the partial reflection filter unit and the total reflection filter unit. The structure is compact, the length of the entire resonant cavity 20 is short, and the light source volume small.
  • the pump unit 10 and the pump light coupling unit 40 can be connected by an optical fiber 70, and the pump light coupling unit 40 and the partial reflection filter unit of the resonator 20 can be connected by an optical fiber 70, so that an all-optical fiber can be realized.
  • Single frequency light source
  • the pump unit 10 and the pump light coupling unit 40 can be connected by an optical fiber 70, and the pump light coupling unit 40 and the partial reflection filter unit of the resonant cavity 20 can transmit light through free space, which can be realized Single-frequency light source of partial fiber.
  • the pump unit 10 and the pump light coupling unit 40 can transmit light through free space, and the pump light coupling unit 40 and the partial reflection filter unit of the resonator 20 can transmit light through the optical fiber 70. Realize the single-frequency light source of partial fiber.
  • the pump unit 10 and the pump light coupling unit 40 can transmit light through free space, and the pump light coupling unit 40 and the partially reflective filter unit of the resonator 20 can also transmit light through free space. In this way, a single-frequency light source with full free space transmission can be realized.
  • a tuning unit 80 is further included.
  • the first reflection filter unit 21 is connected to a tuning unit 80, and the second reflection filter unit 22 is connected to another tuning unit 80.
  • the tuning unit 80 can adjust the center wavelength and/or bandwidth of the first reflection filter unit 21 and the second reflection filter unit 22 . It is also possible to adjust the slope of the edge of the filter area of the first reflection filter unit 21, while adjusting the slope of the edge of the filter area of the second reflection filter unit 22, thereby adjusting the overlap of the first reflection filter unit 21 and the second reflection filter unit 22. The slope of the edge of the area.
  • the pump light enters the resonant cavity 20 through the partial reflection filter unit, and the gain medium 23 is excited to generate excitation light.
  • the excitation light is reflected between the partial reflection filter unit and the total reflection filter unit, and passes through the partial reflection filter unit and the total reflection filter unit. After filtering, the generated laser frequency band is located in the overlapping area of the filtering range. By selecting a suitable filtering range to make the overlapping frequency band extremely narrow, a single longitudinal mode output can be obtained.
  • the first reflection filtering unit 21 and the second reflection filtering unit are adjusted by the tuning unit 80.
  • the central wavelength and/or bandwidth of 22 and/or the slope of the edge of the overlap area can obtain a tunable single-frequency laser.
  • tuning unit 80 may also be connected to only the first reflection filtering unit 21 or the second reflection filtering unit 22.
  • the partial reflection filter unit is composed of two independent modules that can partially reflect light intensity and filter.
  • the total reflection filter unit is composed of two independent modules for total reflection light intensity and filtering.
  • the partially reflective filter unit includes a first partially reflective mirror 213, as an end mirror of the resonator 20, used to transmit the pump light, partially reflect the light intensity of the laser light, and output single-frequency laser light, and also includes The first filter module 214 in the reflection direction of the first part of the mirror 213 is used to filter the laser light, and the first filter module 214 is connected to a tuning unit 80.
  • the total reflection filter unit includes a first total reflection mirror 223, and a second filter module 224 arranged in the reflection direction of the first total reflection mirror 223 for filtering laser light.
  • the second filter module 224 is connected to a tuning unit. 80.
  • the first total reflection mirror 223 serves as the other end mirror of the resonant cavity 20.
  • the first filter module 214 and the second filter module 224 are both transmissive filters, and the filtering ranges of the two overlapped and the center wavelength and bandwidth of the overlapped range can be adjusted through the adjustment of the tuning unit 80.
  • the specific adjustment is The method can be the adjustment of the center wavelength, the bandwidth, or the slope of the edge of the overlapping area as described in the first embodiment.
  • tuning unit may be provided on the first filter module 214 or the second filter module 224.
  • the partial reflection filter unit is composed of two independent modules that can partially reflect light intensity and filter.
  • the total reflection filter unit is an integrated unit that can perform the dual functions of total reflection light intensity and filtering. structure.
  • the partial reflection filter unit includes a second partial reflection mirror 215 for transmitting the pump light, partially reflecting the light intensity of the laser light, and outputting single-frequency laser light, and also includes a reflection set on the second partial reflection mirror 215
  • the third filtering module 216 of the direction is used to perform transmission filtering on the laser.
  • the total reflection filter unit selects the grating cavity mirror formed by directly writing the Bragg fiber grating on the optical fiber, which is used for reflection filtering and total reflection of light intensity.
  • the third filter module 216 is connected to a tuning unit 80, and the total reflection filter unit is connected to a tuning unit 80. It is also possible to connect only one tuning unit 80 to the third filter module 216, or to connect only one tuning unit 80 to the total reflection filter unit.
  • the adjustment of the tuning unit 80 can realize the adjustment of the center wavelength and the bandwidth of the overlap range, and the specific adjustment method may be the adjustment of the center wavelength, the bandwidth or the slope of the edge of the overlap area as described in the first embodiment.
  • the partial reflection filter unit is a structure that can perform the dual functions of partial reflection light intensity and filtering.
  • the total reflection filter unit is composed of two independent modules that can fully reflect light intensity and filter. .
  • the partial reflection filter unit selects a grating cavity mirror formed by directly writing Bragg fiber gratings on the optical fiber, which is used to transmit the pump light, partially reflect the light intensity of the laser, filter and output the single-frequency laser.
  • the total reflection filter unit includes a second total reflection mirror 225, and further includes a fourth filter module 226 disposed in the reflection direction of the second total reflection mirror 225, for transmitting and filtering the laser light.
  • the fourth filter module 226 is connected to a tuning unit 80, and the partial reflection filter unit is connected to a tuning unit 80. It is also possible to connect only one tuning unit 80 to the fourth filter module 226, or connect one tuning unit 80 to only part of the reflection filter unit.
  • the adjustment of the tuning unit 80 can realize the adjustment of the center wavelength and the bandwidth of the overlap range, and the specific adjustment method may be the adjustment of the center wavelength, the bandwidth or the slope of the edge of the overlap area as described in the first embodiment.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • This embodiment adopts the basic structure of the second embodiment described above.
  • the difference from the second to fifth embodiments described above is that the pump light is input from the partial reflection filter unit, and the single-frequency laser is output from the side end of the resonant cavity.
  • the first reflection filtering unit 21 is a total reflection filtering unit
  • the second reflection filtering unit 22 is a total reflection filtering unit.
  • the partial reflection filter unit and the total reflection filter unit are each connected to a tuning unit 80, and a tuning unit 80 can also be connected to one of the two.
  • the specific tuning method may be the adjustment of the center wavelength, the bandwidth, or the slope of the edge of the overlapping area as described in the first embodiment.
  • the total reflection filter unit is a structure capable of performing dual functions of total reflection light intensity and filtering.
  • a pump light coupling unit 40 is provided outside the resonant cavity, and an output unit 30 is provided in the resonant cavity for outputting single-frequency laser light from the side end of the resonant cavity without affecting the transmission of laser light in the cavity.
  • the output unit 30 can select a coupler.
  • a circulator 50 may be provided in the output path of the single-frequency laser.
  • This embodiment adopts the basic structure of the second embodiment.
  • the difference from the first to fourth embodiments is that the pump light is input from the side end of the resonator 20, and the single-frequency laser is output from the partial reflection filter unit.
  • the first reflection filtering unit 21 is a partial reflection filtering unit
  • the second reflection filtering unit 22 is a total reflection filtering unit.
  • the partial reflection filter unit and the total reflection filter unit are each connected to a tuning unit 80, and a tuning unit 80 can also be connected to one of the two.
  • the specific tuning method can be the adjustment of the center wavelength, bandwidth, or edge of the overlap region as described in Example 1.
  • a pump light coupling unit 40 is provided in the resonant cavity 20 to couple the pump light into the resonant cavity without affecting the transmission of laser light in the cavity.
  • the pump light coupling unit 40 can be a wavelength division multiplexer.
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • This embodiment adopts the basic structure of the second embodiment above.
  • the difference from the second to fifth embodiments above is that the pump light is input from the side end of the resonant cavity, and the single-frequency laser light is output from the side end of the resonant cavity.
  • the first reflection filtering unit 21 and the second reflection filtering unit 22 are total reflection filtering units.
  • Each of the two total reflection filter units is connected to a tuning unit 80, and one of them can also be connected to a tuning unit 80.
  • the specific tuning method may be the adjustment of the center wavelength, bandwidth or the slope of the edge of the overlapping area as described in the first embodiment.
  • a pump light coupling unit 40 is provided in the resonant cavity to couple the pump light into the resonant cavity without affecting the transmission of laser light in the cavity, and an output unit 30 is also provided to send the single-frequency laser light from the cavity side Terminal output without affecting the laser transmission in the cavity.
  • the pump light coupling unit 40 can be a wavelength division multiplexer.
  • the output unit 30 can select a coupler.
  • a circulator 50 may be provided on the output path of the single frequency laser outside the cavity.
  • the pump unit 10, the resonant cavity 20, the pump light coupling unit 40, the isolation unit 60 and other devices may be connected by the optical fiber 70 to realize an all-fiber single-frequency light source. It is also possible to connect some devices through the optical fiber 70 to realize a partial optical fiber single-frequency light source. Or they all transmit light through free space.

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Abstract

本申请提供了单频激光光源，包括泵浦单元，谐振腔，谐振腔包括第一反射滤波单元，第二反射滤波单元，增益介质，其中第一反射滤波单元与第二反射滤波单元至少构成谐振腔的两端，第一反射滤波单元和第二反射滤波单元的滤波范围部分重叠，激发光经过第一反射滤波单元和第二反射滤波单元的滤波后实现单纵模输出，获得单频激光。本申请采用第一、第二反射滤波单元构成激光谐振腔，利用第一反射滤波单元和第二反射滤波单元对激光频率的滤波作用选择二者滤波重叠区域的激光，进而获得单纵模输出，不受单个窄带滤波光栅的极窄滤波范围要求所限，降低了工艺难度，避免滤波带宽大小的性能和输出功率相互制约。

Description

单频激光光源
本申请要求于2019年1月31日提交中国专利局，申请号为201910099035.8，发明名称为“一种单频光源”、于2019年1月31日提交中国专利局，申请号为201920182151.1，发明名称为“一种单频光源”、于2019年1月31日提交中国专利局，申请号为201910099065.9，发明名称为“单频激光光源”、于2019年1月31日提交中国专利局，申请号为201920182140.3，发明名称为“单频激光光源”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于光学技术领域，特别涉及一种单频激光光源。
背景技术
在现代激光技术的发展基础上，精密干涉测量、激光传感技术和光通信技术等领域得到了飞速的发展。精密干涉测量主要以激光波长作为“尺子”，利用干涉原理来测定各种参量，如加速度、位移、角位移等等。由于光波长为nm数量级，因此其分辨精度是电学、磁学元件无法比拟的。激光干涉仪以其特有的大测量范围、高分辨率和高测量精度等优点，在精密和超精密测长领域获得了广泛的应用。而精密干涉测量的距离和干涉质量与激光的线宽紧密相关。实际设计中为了进一步增加测量精度，要求激光线宽要小于lkHz。
在激光传感技术中，由于深海油气开发和国防发展的需要，水声探测装备越来越得到了世界各国的重视。由光纤激光水听器阵列构成的声呐脉冲测距系统，己进入工程试验阶段，光纤激光水听器是水声探测装备的核心设备，其最小可分辨纵向应变量由光纤激光器的线宽决定，激光器线宽越窄，水听器的声压分辨率就越高，就更能满足对微弱信号的探测。
而对于光通信，随着互联网的普及，如何提高系统传输速率成为了光通信领域的重要研究目标。在高速传输速率的光通信系统中，为了满足误码的要求，调制格式下，激光线宽需要进一步缩窄。
从以上的分析可知，高单色性、高相干性的激光光源拥有极大的需求，这也要求激光器输出的单模光谱线宽要窄，而且必须工作在稳定的单纵模状态。而这也使得光纤激光器通过必要模式选择和控制措施，如谐振腔结构改进或利用非线性二波混频等，使谐振腔内只存在一个纵模振荡，即工作在单纵模或单频运转状态。
由于光纤激光器谐振腔长通常会达到几十厘米甚至米的量级，加入激光器工作在单频运转状态，光纤激光器就能获得良好单色性、相干性，使光电系统的性能得到极大改善和 提升，获得极大的经济效益和社会效益。因此单频窄线宽光纤激光器具有非常高的实用价值。
目前使用的主流单频激光器之一是短直腔单频光纤激光器。长线形腔由于驻波效应在增益介质中形成的空间烧孔，将导致激光器产生多模振荡，输出光谱线宽展宽。在腔内激光传播过程中，腔长同纵模间隔成反比，随着谐振腔长变短，腔内纵模间隔加大，如图1所示，在增益达到激光阈值S0以上的情况下，当相邻纵模间隔L1大于腔镜的反射光谱带宽L2或有源光纤的增益谱宽时，激光器就可获得单频运转，实现单频窄线宽激光输出。纵模间隔与腔长成反比，对于确定增益光谱带宽和光纤光栅反射光谱带宽的情况下，腔长越小，纵模间隔越大，越容易实现单模运转。通过缩短谐振腔长使纵模间隔超过增益谱宽的方案，通常带宽可控制在几十纳米，通过缩短谐振腔长使纵模间隔超过光纤光栅反射光谱带宽的方案，由于工艺所限，通常带宽可控制在几百皮米，因此通常通过后者方案实现窄带宽单频光源。
如图2，有一种窄线宽的单频光源，将窄带光纤光栅01和宽带光纤光栅02作为腔镜，整体腔镜反射光谱带宽主要取决于窄带光纤光栅01，谐振腔的腔长只有几个厘米长才能保证纵模间隔超过窄带光纤光栅01的反射光谱带宽L3。当窄带光纤光栅反射光谱带宽L3越大，腔长就需要越短，然而腔长缩短对输出功率有极大限制。若要保证较高的输出功率，就要提高对窄带光纤光栅01的要求，即要求其反射光谱带宽L3更窄，工艺难度就更大。因此，对于短直腔单频光纤激光光源，窄带光纤光栅和输出功率之间的相互制约成为难题。
技术问题
本申请的目的在于提供一种单频激光光源，包括但不限于解决传统单频激光光源对光纤光栅的要求较高以及输出功率受限的技术问题。
技术解决方案
为解决上述技术问题，本申请采用的技术方案是：单频激光光源，包括
泵浦单元，用于输出泵浦光；
谐振腔，用于吸收泵浦光并获得单频激光；
所述谐振腔包括：
第一反射滤波单元，用于对所述谐振腔内的激光进行滤波和反射；
第二反射滤波单元，用于对所述谐振腔内的激光进行滤波和反射；
增益介质，用于经所述泵浦光激发后获得激发光；
其中，所述第一反射滤波单元与所述第二反射滤波单元至少构成所述谐振腔的两端，所述第一反射滤波单元和第二反射滤波单元的滤波范围部分重叠，所述激发光经过所述第 一反射滤波单元和第二反射滤波单元的滤波后实现单纵模输出，获得单频激光。
有益效果
本申请实施例提供的单频光源采用第一反射滤波单元和第二反射滤波单元构成激光谐振腔，利用增益介质和第一反射滤波单元以及第二反射滤波单元产生激光，利用第一反射滤波单元和第二反射滤波单元对激光频率的滤波作用选择二者滤波重叠区域的激光，进而获得单纵模输出。
附图说明
图1是单频激光单纵模运转原理图；
图2是传统的一种窄线宽单频光源的工作原理图；
图3是本申请实施例提供的单频激光光源的工作原理图；
图4是本申请实施例提供的单频激光光源的波长调谐示意图；
图5是本申请实施例提供的单频激光光源的带宽调谐示意图；
图6是本申请实施例提供的单频激光光源的重叠区域边缘斜率调节示意图；
图7是本申请实施例提供的第一反射滤波单元和第二反射滤波单元的一种结构示意图；
图8是本申请实施例提供的第一反射滤波单元和第二反射滤波单元的另一种结构示意图；
图9是本申请第一种实施例提供的单频激光光源的结构示意图；
图10是本申请第二种实施例提供的单频激光光源的一种结构图；
图11是本申请第二种实施例提供的单频激光光源的另一种结构图；
图12是本申请第三种实施例提供的单频激光光源的结构图；
图13是本申请第四种实施例提供的单频激光光源的结构图；
图14是本申请第五种实施例提供的单频激光光源的结构图；
图15是本申请第六种实施例提供的单频激光光源的结构图；
图16是本申请第七种实施例提供的单频激光光源的结构图；
图17是本申请第八种实施例提供的单频激光光源的结构图；
图18是本申请实施例提供的一种单频激光光源的光谱示意图；
图19是本申请实施例提供的一种单频激光光源的滤波带宽随着谐振腔往返次数的关系曲线；
图20是基于本申请实施例提供的单频激光光源的激光器的输出线宽示意图。
本发明的实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本申请，并不用于限定本申请。
为了说明本申请所述的技术方案，以下结合具体附图及实施例进行详细说明。
请参阅图9，本申请实施例提供一种单频激光光源，至少包括泵浦单元10以及谐振腔20，其中，泵浦单元10用于输出泵浦光；谐振腔20设置在泵浦单元10的输出光路上，用于吸收泵浦光，通过泵浦光激发谐振腔20内的增益介质获得激发光。该谐振腔20是获取单频激光的主要单元，其至少包括：第一反射滤波单元21、第二反射滤波单元22以及介于二者之间的增益介质23。单频激光通过第一反射滤波单元21或者第二反射滤波单元22或者谐振腔侧端输出谐振腔20。
该单频激光光源中，第一反射滤波单元21和第二反射滤波单元22构成激光谐振腔20的腔体，即至少可以构成两端腔镜，同时还具有滤波功能，参见图3，第一反射滤波单元21和第二反射滤波单元22分别具有滤波带宽L6和L7，滤波带宽L6和L7具有交叠频带L8。本实施例所述的滤波均为频率滤波。
在该实施例中，该第一反射滤波单元21至少用于对谐振腔20内的激光进行滤波和对光强反射；具体而言，第一反射滤波单元21是指该单元至少包括能够对入射其中的激光光强进行反射的模块；第一反射滤波单元21还包括能够对入射其中的激光进行频率“筛选”(即滤波)的模块，进而选择性地反射或者透射部分频率的光，滤波后获得的激光是形成单频激光的必要基础。当然，该两个模块可以是能够进行反射光强和滤波双重功能的同一个模块结构，也可以是分别用于反射光强和滤波的两个独立模块结构。
该第二反射滤波单元22用于对谐振腔20内的激光进行滤波和对光强反射；具体而言，第二反射滤波单元22至少包括能够对入射其中的激光光强进行反射的模块，该模块用作谐振腔20的反射端，还包括能够对入射其中的激光进行频率“筛选”(即滤波)的模块，进而选择性地反射或者透射部分频率的激光，滤波后获得的激光是形成单频激光的必要基础。同样的，这两个模块也可以是一体结构或者是相互独立的结构。
进一步地，上述第一反射滤波单元21和第二反射滤波单元22的滤波范围部分重叠。泵浦光入射谐振腔20中，激发增益介质23产生激光，激光在第一反射滤波单元21和第二反射滤波单元22之间反射，并且通过第一反射滤波单元21和第二反射滤波单元22的滤波后，产生的激光频带位于滤波范围重叠区域，通过选择合适的滤波范围，使重叠频带极窄，可以获得单纵模输出，即获得单频激光。
本申请实施例提供的单频激光光源具有如下效果：采用第一反射滤波单元21和第二反射滤波单元22构成激光谐振腔20，利用第一反射滤波单元21对光强的反射和第二反射滤波单元22对光强的反射增益介质形成有源谐振腔获得激光，利用第一反射滤波单元21和第二反射滤波单元22对激光频率的滤波作用选择二者滤波重叠区域的激光，进而获得单纵模输出，该单纵模输出的带宽可以小于1KHz。
与采用窄带光纤光栅和宽带光纤光栅作为腔镜的单频光源(传统单频光源)相比，一方面，该单频光源不需设置极窄带光纤光栅，对第一反射滤波单元21和第二反射滤波单元22的带宽要求均不高，不被单个窄带滤波光栅的极窄滤波范围要求所限，可以用参数较低的光栅组成，极大的降低了工艺难度。
另一方面，传统单频光源为获得单频激光，还要满足窄带光栅的反射带宽小于纵模间隔，腔长越短纵模间隔越大，对窄带光栅的要求越低，然而腔长较短又会损失输出功率，进而传统单频光源存在窄带光栅性能和输出功率的相互制约，而本实施例的单频光源不完全依赖于任一端滤波单元的滤波带宽，即不需要使任一滤波带宽小于纵模间隔，进而解除对腔长的限制，避免第一反射滤波单元21和第二反射滤波单元22的滤波性能和输出功率相互制约，使第一反射滤波单元21和第二反射滤波单元22的选择以及谐振腔20的设计更加灵活。
作为本申请的进一步改进，参考图10和图11，该单频激光光源还包括调谐单元80，通过调谐单元80可以灵活调节单频激光的中心波长和带宽。具体地，调谐单元80，用于调节第一反射滤波单元21和/或第二反射滤波单元22的中心波长和/或滤波带宽，具体包括：调节第一反射滤波单元21或第二反射滤波单元22的中心波长；调节第一反射滤波单元21或第二反射滤波单元22的滤波带宽；调节第一反射滤波单元21或第二反射滤波单元22的中心波长和滤波带宽；调节第一反射滤波单元21和第二反射滤波单元22的中心波长；调节第一反射滤波单元21和第二反射滤波单元22的滤波带宽；调节第一反射滤波单元21和第二反射滤波单元22的中心波长和滤波带宽；调节第一反射滤波单元21的中心波长和第二反射滤波单元22的滤波带宽；调节第一反射滤波单元21的滤波带宽和第二反射滤波单元22的中心波长；调节第一反射滤波单元21的滤波区域边缘的斜率，调节第二反射滤波单元22的滤波区域边缘的斜率，进而调节二者重叠区域的斜率。
当只需对第一反射滤波单元21或第二反射滤波单元22进行调节时，本实施例仅在需要调节的第一反射滤波单元21或第二反射滤波单元22上连接调谐单元80，当需要同时调节第一反射滤波单元21和第二反射滤波单元22时，本实施例在第一反射滤波单元21和第二反射滤波单元22上各设置一个调谐单元80。
参见图4，采用调谐单元80对第一反射滤波单元21的中心波长λ1进行调节，而保持第二反射滤波单元22的中心波长λ2不变时，获得的单频激光的中心波长由λ01频移至λ02。参见图5，采用调谐单元80对第一反射滤波单元21和第二反射滤波单元22的滤波带宽进行调节时，单频激光的带宽由L01变化为L02。参见图6，采用调谐单元80对第一反射滤波单元21和第二反射滤波单元22的滤波重叠区域边缘的斜率进行调节时，单频激光的带宽由L01变化为L02。图4、图5和图6仅是示意了三种调谐情况，还可以进行其他方式的调谐，本实施例不进行一一赘述。通过设置调谐单元80,，可以获得可调谐的单纵模输出，应用领域更加广泛。
下面利用公式推导来说明两个滤波器在激光器谐振腔中对重叠区域的滤波效果。假如一光源在谐振腔中往返一周，只考虑滤波器滤波效果时，往返一周前、后其功率满足以下关系：
p m(λ i)dBm＝-10lg(p m-1(λ i)*R 1(λ i)*R 2(λ i)，    (1)
其中，p m(λ i)和p m-1(λ i)是波长为λ i的光源在谐振腔中往返一周(第m次往返)前、后的功率。R 1(λ i)和R 2(λ i)是谐振腔中两个滤波器对波长λ i为光的反射率。在谐振腔中，往返一周后，两个不同波长λ i和λ j光的功率差为
Δ＝p 1(λ i)-p 1(λ j)＝-10(lg(p 0(λ i)*R 1(λ i)*R 2(λ i)-lg(p 0(λ j)*R 1(λ j)*R 2(λ j))          (2)
为了使得考虑问题简单起见，假如入射光为白光源(即各波长光功率相等p 0(λ i)＝p 0(λ j),那么该白光源在谐振腔中往返N周后，其功率差值为
Figure PCTCN2019076149-appb-000001
由此，往返N周后，其不同波长光功率的差异变大，这说明了滤波单元在谐振腔中，其带宽随着往返周期的增加而逐渐减小。
在实验中采用了两个存在一定重叠区域的光纤布拉格光栅FBG1和FBG2作为滤波单元，其带宽分别为0.09nm和0.07nm，如图18中的线条L11和线条L12所示，采用这两个滤波器共同滤波，测量其带宽为0.024nm，如图18中的线条L13所示。根据上述推导，模拟出了两个滤波器在激光谐振腔中，其滤波带宽随着谐振腔往返次数N的关系。从图中可知道，往返100次后，其滤波带宽为0.0025nm，如图19所示。
在实验中，利用两个带宽分别为0.09nm和0.07nm的滤波器FBG1和FBG2在腔长为30cm的激光器中，获得输出带宽为941Hz的超窄带光纤激光器，如图20所示。
在该单频激光光源中，泵浦光的输入和单频激光的输出有多种形式。
第一种，参见图10至图14，泵浦光经谐振腔20两端之一进入谐振腔20，单频激光经谐振腔20的第一反射滤波单元21或者第二反射滤波单元22输出。具体地，第一反射滤波单元21为部分反射滤波单元，用于透射泵浦光、对谐振腔20内的激光进行滤波和对光强部分反射，以及输出单频激光；第二反射滤波单元22为全反射滤波单元，用于对谐振腔20内的激光进行滤波和对光强全反射。
第二种，参见图15，泵浦光经谐振腔20两端之一进入谐振腔20，单频激光经谐振腔20内的某处输出谐振腔20，即不经过第一反射滤波单元21或者第二反射滤波单元22输出。具体地，第一反射滤波单元21为全反射滤波单元，用于透射泵浦光、对谐振腔20内的激光进行滤波和对光强全反射；第二反射滤波单元22为全反射滤波单元，用于对谐振腔20内的激光进行滤波和对光强全反射；谐振腔20内设置有输出单元30，用于将单频激光从谐振腔20侧端输出。
在第一种和第二种情况的基础上，还可以在泵浦单元10和谐振腔20之间设置泵浦光耦合单元40。
第三种，参见图17，泵浦光经谐振腔20侧端进入谐振腔20，单频激光经谐振腔20内的某处输出谐振腔20。具体地，第一反射滤波单元21和第二反射滤波单元22均为全反射滤波单元，用于对谐振腔20内的激光进行滤波和对光强全反射；谐振腔20内设置有泵浦光耦合单元40和输出单元30，泵浦光耦合单元40用于将泵浦光耦合进入谐振腔20，输出单元30用于将单频激光从谐振腔20侧端输出。
在第二种和第三种情况的基础上，还可以在谐振腔20外设置一环形器50，与输出单元30连接，一方面，可以用于输出单频激光，另一方面，可以将单频激光回传至谐振腔20。
第四种，参见图16，泵浦光经谐振腔20侧端进入谐振腔20，单频激光经谐振腔20的第一反射滤波单元21或第二反射滤波单元22输出谐振腔20。具体地，第一反射滤波单元21为部分反射滤波单元，用于对谐振腔20内的激光进行滤波和对光强部分反射，以及输出单频激光；第二反射滤波单元22为全反射滤波单元，用于对谐振腔20内的激光进行滤波和对光强全反射。谐振腔20内设置有泵浦光耦合单元40，用于将泵浦光耦合进入谐振腔20。
在本申请实施例中，单频光源均可包括设置于单频激光的输出路径上的隔离单元60， 用于隔离反向激光，保护单频光源。
在本申请实施例中，增益介质23作为实现粒子束反转的介质，优选为全增益光纤，两端分别连接第一反射滤波单元21和第二反射滤波单元22。泵浦光耦合单元40将泵浦光耦合到谐振腔20内，在谐振腔20内实现全增益光纤的粒子束反转，获得激光，通过第一反射滤波单元21和第二反射滤波单元22的滤波作用，起振极小的线宽范围，出射单频激光。
在其他实施例中，增益介质23也可以为块状的增益晶体，增益晶体可以独立设置于谐振腔20内，也可以通过非增益光纤或增益光纤连接于第一反射滤波单元21和第二反射滤波单元22。
进一步地，全反射滤波单元和部分反射滤波单元均可采用一体结构或者两个独立模块的组合结构。参见图7，一体结构为能够进行反射光强和滤波双重功能的结构，参见图8，组合结构具体为：第一反射滤波单元21包括第一反射镜211，以及设置于第一反射镜211的反射方向的第一滤波模块212。第二反射滤波单元22包括第二反射镜221以及设置于第二反射镜221的反射方向的第二滤波模块222。根据全反射与部分反射的需求，将第一反射镜221或第二反射镜222设计为全反射或者部分反射的形式即可。
以下提供几种具体的实施例：
实施例一：
参考图9，第一反射滤波单元21是部分反射滤波单元、第二反射滤波单元22是全反射滤波单元。泵浦光从部分反射滤波单元输入，单频激光从部分反射滤波单元输出。
具体地，该单频光源包括泵浦单元10以及谐振腔20，可以进一步包括泵浦光耦合单元40。泵浦单元10用于输出泵浦光；泵浦光耦合单元40设置于泵浦单元10和谐振腔20之间，用于将泵浦光耦合进入谐振腔20，并将谐振腔20输出的单频激光输出。谐振腔20设置在泵浦光耦合单元40的一端，用于吸收泵浦光，通过泵浦光激发谐振腔20内的增益介质23获得激发光，并通过滤波以及谐振腔的反射获得单频激光；该单频激光射出谐振腔20后通过泵浦光耦合单元40的另一端输出。部分反射滤波单元和全反射滤波单元构成激光谐振腔20的腔体，即至少可以构成两端腔镜，同时还具有滤波功能，部分反射滤波单元和全反射滤波单元分别具有滤波带宽L6和L7，滤波带宽L6和L7具有交叠频带L8。
泵浦光经过部分反射滤波单元入射谐振腔20中，激发增益介质23产生激发光，激发光在部分反射滤波单元和全反射滤波单元之间反射，并且通过部分反射滤波单元和全反射滤波单元的滤波后，产生的激光频带位于滤波范围重叠区域，通过选择合适的滤波范围，使重叠频带极窄，可以获得单纵模输出，获得单频激光。单频激光通过部分反射滤波单元输出谐振腔20。
作为本实施例的优选方案，布拉格光纤光栅可在光纤上直接写入而形成光栅腔镜，因此与掺杂有源光纤的兼容性非常好，不仅连接损耗非常小，而且避免了复杂的光学结构，便于光纤激光器的集成和小型化，使光纤激光器具有更好的稳定性和可靠性，尤其适合环境条件非常恶劣的工作场所。因此基于线形谐振腔20结构的光纤激光器优选使用超短线形腔结构来获得单频窄线宽激光输出。在本实施例中，优选采用在光纤上直接写入布拉格光纤光栅而形成的一体结构的光栅腔镜作为部分反射滤波单元和全反射滤波单元，结构紧凑，整个谐振腔20长度较短，光源体积小。
进一步地，泵浦单元10和泵浦光耦合单元40之间可以通过光纤70连接，泵浦光耦合单元40和谐振腔20的部分反射滤波单元之间可以通过光纤70连接，这样可以实现全光纤单频光源。
进一步地，泵浦单元10和泵浦光耦合单元40之间可以通过光纤70连接，泵浦光耦合单元40和谐振腔20的部分反射滤波单元之间可以通过自由空间进行光传输，这样可以实现部分光纤的单频光源。或者，泵浦单元10和泵浦光耦合单元40之间可以通过自由空间进行光传输，泵浦光耦合单元40和谐振腔20的部分反射滤波单元之间可以通过光纤70进行传输，这样也可以实现部分光纤的单频光源。
进一步地，泵浦单元10和泵浦光耦合单元40之间可以通过自由空间进行光传输，泵浦光耦合单元40和谐振腔20的部分反射滤波单元之间也可以通过自由空间进行光传输，这样可以实现全自由空间传输的单频光源。
实施例二：
参考图10和图11，在上述实施例一的基础上，进一步包括调谐单元80。
第一反射滤波单元21连接一调谐单元80，第二反射滤波单元22连接另一调谐单元80，调谐单元80可以调节第一反射滤波单元21和第二反射滤波单元22的中心波长和/或带宽。也可以调节第一反射滤波单元21的滤波区域的边缘的斜率，同时调节第二反射滤波单元22的滤波区域的边缘的斜率，进而调节第一反射滤波单元21和第二反射滤波单元22的重叠区域边缘的斜率。泵浦光经过部分反射滤波单元入射谐振腔20中，激发增益介质23产生激发光，激发光在部分反射滤波单元和全反射滤波单元之间反射，并且通过部分反射滤波单元和全反射滤波单元的滤波后，产生的激光频带位于滤波范围重叠区域，通过选择合适的滤波范围，使重叠频带极窄，可以获得单纵模输出，通过调谐单元80调节第一反射滤波单元21和第二反射滤波单元22的中心波长和/或带宽和/或重叠区域边缘的斜率，即获得可调谐的单频激光。
可以理解，还可以仅在第一反射滤波单元21或第二反射滤波单元22上连接调谐单元80。
实施例三：
在采用上述实施例二的基本结构基础上，部分反射滤波单元是由可以部分反射光强和滤波的两个独立模块构成的。全反射滤波单元是由分别进行全反射光强和用于滤波的两个独立模块构成。
参考图12，具体地，部分反射滤波单元包括第一部分反射镜213，作为谐振腔20的一个端镜，用于透射泵浦光、部分反射激光的光强以及输出单频激光，还包括设置于第一部分反射镜213的反射方向的第一滤波模块214，用于对激光进滤波，第一滤波模块214连接有一调谐单元80。同样的，全反射滤波单元包括第一全反射镜223，以及设置于第一全反射镜223的反射方向的用于对激光进行滤波的第二滤波模块224，第二滤波模块224连接有一调谐单元80，该第一全反射镜223作为谐振腔20的另一端镜。在本实施例中，第一滤波模块214和第二滤波模块224均为透射式滤波，二者滤波范围重叠且通过调谐单元80的调节可实现重叠范围的中心波长和带宽可调，具体的调节方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。激光在谐振腔20内经过第一滤波模块214和第二滤波模块224的滤波后，仅处于二者滤波范围重叠区域内的频带的激光可以输出，通过合理的设计二者滤波范围，可以获得可调谐的单纵模输出。
可以理解，还可以仅在第一滤波模块214或第二滤波模块224上设置一个调谐单元。
实施例四：
在采用上述实施例二的基本结构基础上，部分反射滤波单元是由可部分反射光强和滤波的两个独立模块构成的，全反射滤波单元为能够进行全反射光强和滤波双重功能的一体结构。
参考图13，具体地，部分反射滤波单元包括第二部分反射镜215，用于透射泵浦光、部分反射激光的光强以及输出单频激光，还包括设置于第二部分反射镜215的反射方向的第三滤波模块216，用于对激光进行透射滤波。全反射滤波单元选择在光纤上直接写入布拉格光纤光栅而形成的光栅腔镜，用于反射滤波和对光强进行全反射。第三滤波模块216连接一调谐单元80，全反射滤波单元连接一调谐单元80。还可以仅在第三滤波模块216连接一调谐单元80，或者仅在全反射滤波单元连接一调谐单元80。通过调谐单元80的调节可实现重叠范围的中心波长和带宽可调，具体的调节方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。
实施例五：
在采用上述实施例二的基本结构基础上，部分反射滤波单元为能够进行部分反射光强和滤波双重功能的结构，全反射滤波单元是由可全部反射光强和滤波的两个独立模块构成 的。
参考图14，具体地，部分反射滤波单元选择在光纤上直接写入布拉格光纤光栅而形成的光栅腔镜，用于透射泵浦光、部分反射激光的光强、滤波以及输出单频激光。全反射滤波单元包括第二全反射镜225，还包括设置于第二全反射镜225的反射方向的第四滤波模块226，用于对激光进行透射滤波。第四滤波模块226连接一调谐单元80，部分反射滤波单元连接一调谐单元80。还可以仅在第四滤波模块226连接一调谐单元80，或者仅在部分反射滤波单元连接一调谐单元80。通过调谐单元80的调节可实现重叠范围的中心波长和带宽可调，具体的调节方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。
实施例六：
本实施例采用上述实施例二的基本结构，与上述实施例二至五不同的是，泵浦光从部分反射滤波单元输入，单频激光从谐振腔侧端输出。
参考图15，该实施例中，第一反射滤波单元21是全反射滤波单元、第二反射滤波单元22是全反射滤波单元。部分反射滤波单元和全反射滤波单元各连接一调谐单元80，还可在二者之一上连接调谐单元80。具体的调谐方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。
具体地，全反射滤波单元为能够进行全反射光强和滤波双重功能的结构。在谐振腔外设有泵浦光耦合单元40，在谐振腔中设有输出单元30，用于将单频激光从谐振腔侧端输出，同时不影响腔内激光的传输。该输出单元30可以选择耦合器。
进一步地，还可以在单频激光的输出路径上述设置环形器50。
实施例七：
本实施例采用上述实施例二的基本结构，与上述实施例一至四不同的是，泵浦光从谐振腔20侧端输入，单频激光从部分反射滤波单元输出。
如图16，具体地，第一反射滤波单元21是部分反射滤波单元、第二反射滤波单元22是全反射滤波单元。部分反射滤波单元和全反射滤波单元各连接一调谐单元80，还可在二者之一上连接调谐单元80，具体的调谐方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。在谐振腔20中设有泵浦光耦合单元40，用于将泵浦光耦合进入谐振腔，同时不影响腔内激光的传输。该泵浦光耦合单元40可以选择波分复用器。
实施例八：
本实施例采用上述实施例二的基本结构，与上述实施例二至五不同的是，泵浦光从谐振腔侧端输入，单频激光从谐振腔侧端输出。
参考图17，具体地，第一反射滤波单元21和第二反射滤波单元22是全反射滤波单元。两个全反射滤波单元各连接一调谐单元80，还可在二者之一上连接调谐单元80，具体的调谐方式可以是实施例一所述的调节中心波长、带宽或者重叠区域边缘的斜率。在谐振腔中设有泵浦光耦合单元40，用于将泵浦光耦合进入谐振腔，同时不影响腔内激光的传输，还设有输出单元30，用于将单频激光从谐振腔侧端输出，同时不影响腔内激光的传输。该泵浦光耦合单元40可以选择波分复用器。该输出单元30可以选择耦合器。
进一步地，还可以在腔外单频激光的输出路径上设置环形器50。在上述各实施例中，泵浦单元10、谐振腔20、泵浦光耦合单元40、隔离单元60等器件之间可以通过光纤70连接，实现全光纤单频光源。也可以部分器件之间通过光纤70连接，实现部分光纤单频光源。或者均通过自由空间进行光传输。
以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (15)

  1. 单频激光光源，其特征在于，包括
    泵浦单元，用于输出泵浦光；
    谐振腔，用于吸收泵浦光并获得单频激光；
    所述谐振腔包括：
    第一反射滤波单元，用于对所述谐振腔内的激光进行滤波和反射；
    第二反射滤波单元，用于对所述谐振腔内的激光进行滤波和反射；
    增益介质，用于经所述泵浦光激发后获得激发光；
    其中，所述第一反射滤波单元与所述第二反射滤波单元至少构成所述谐振腔的两端，所述第一反射滤波单元和第二反射滤波单元的滤波范围部分重叠，所述激发光经过所述第一反射滤波单元和第二反射滤波单元的滤波后实现单纵模输出，获得单频激光。
  2. 如权利要求1所述的单频激光光源，其特征在于，所述单频激光光源还包括调谐单元，用于调节所述第一反射滤波单元和/或第二反射滤波单元的中心波长和/或滤波带宽。
  3. 如权利要求1所述的单频激光光源，其特征在于，所述单频激光光源还包括调谐单元，用于调节第一反射滤波单元和第二反射滤波单元的重叠区域的边缘的斜率。
  4. 如权利要求1所述的单频激光光源，其特征在于，所述调谐单元的数量为一个，与所述第一反射滤波单元或第二反射滤波单元连接；
  5. 如权利要求1所述的单频激光光源，其特征在于，所述调谐单元的数量为两个，其中一个调谐单元与所述第一反射滤波单元连接，另一个调谐单元与所述第二反射滤波单元连接。
  6. 如权利要求1所述的单频激光光源，其特征在于，所述第一反射滤波单元为部分反射滤波单元，用于透射泵浦光、对所述谐振腔内的激光进行滤波和部分反射光强，以及输出所述单频激光；所述第二反射滤波单元为全反射滤波单元，用于对所述谐振腔内的激光进行滤波和全反射光强。
  7. 如权利要求1所述的单频激光光源，其特征在于，所述第一反射滤波单元为全反射滤波单元，用于透射泵浦光、对所述谐振腔内的激光进行滤波和全反射光强；所述第二反射滤波单元为全反射滤波单元，用于对所述谐振腔内的激光进行滤波和全反射光强；
    所述单频光源还包括位于所述谐振腔内的输出单元，用于在所述谐振腔侧端输出所述 单频激光。
  8. 如权利要求7所述的单频激光光源，其特征在于，在所述输出单元的输出路径上还设有环形器，用于输出单频激光或者将所述单频激光回传至所述谐振腔并经过所述第一反射滤波单元或第二反射滤波单元输出。
  9. 如权利要求1所述的单频激光光源，其特征在于，所述单频光源还包括泵浦光耦合单元，用于将所述泵浦光耦合进入所述谐振腔。
  10. 如权利要求1所述的单频激光光源，其特征在于，所述单频光源还包括设置于所述单频激光的输出路径上的隔离单元。
  11. 如权利要求1所述的单频激光光源，其特征在于，所述第一反射滤波单元为能够对所述激光进行滤波和反射的一体结构。
  12. 如权利要求1所述的单频激光光源，其特征在于，所述第一反射滤波单元包括第一反射镜，以及设置于所述第一反射镜的反射方向的第一滤波模块。
  13. 如权利要求1所述的单频激光光源，其特征在于，所述第二反射滤波单元为能够对所述激光进行反射和滤波的一体结构。
  14. 如权利要求1所述的单频激光光源，其特征在于，所述第二反射滤波单元包括第二反射镜，以及设置于所述第二反射镜的反射方向的第二滤波模块。
  15. 如权利要求1所述的单频激光光源，其特征在于，所述增益介质为全增益光纤；或者所述增益介质为块状的增益晶体，所述增益晶体两侧为自由空间或者光纤。
PCT/CN2019/076149 2019-01-31 2019-02-26 单频激光光源 WO2020155250A1 (zh)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101483304A (zh) * 2009-02-25 2009-07-15 中国科学院上海光学精密机械研究所 基于相移光纤光栅的分布式布拉格反射型单频光纤激光器
CN102104229A (zh) * 2010-12-29 2011-06-22 上海华魏光纤传感技术有限公司 一种单频激光器的波长控制装置及控制方法
CN103825167A (zh) * 2014-02-12 2014-05-28 华南理工大学 一种连续可调谐单频光纤激光器

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101483304A (zh) * 2009-02-25 2009-07-15 中国科学院上海光学精密机械研究所 基于相移光纤光栅的分布式布拉格反射型单频光纤激光器
CN102104229A (zh) * 2010-12-29 2011-06-22 上海华魏光纤传感技术有限公司 一种单频激光器的波长控制装置及控制方法
CN103825167A (zh) * 2014-02-12 2014-05-28 华南理工大学 一种连续可调谐单频光纤激光器

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