WO2025237359A1 - 扫频激光器系统及扫频方法及谐振式光移频滤波器 - Google Patents

扫频激光器系统及扫频方法及谐振式光移频滤波器

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Publication number
WO2025237359A1
WO2025237359A1 PCT/CN2025/095031 CN2025095031W WO2025237359A1 WO 2025237359 A1 WO2025237359 A1 WO 2025237359A1 CN 2025095031 W CN2025095031 W CN 2025095031W WO 2025237359 A1 WO2025237359 A1 WO 2025237359A1
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Prior art keywords
frequency
optical
laser
sweeping
cavity
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French (fr)
Inventor
刘庆文
何祖源
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Shanghai Jiao Tong University
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Shanghai Jiao Tong University
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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
    • H01S3/08—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
    • H01S3/08018—Mode suppression
    • H01S3/08022—Longitudinal modes
    • 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
    • H01S3/08018—Mode suppression
    • H01S3/08022—Longitudinal modes
    • H01S3/08027—Longitudinal modes by a filter, e.g. a Fabry-Perot filter is used for wavelength setting
    • 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
    • H01S3/08018—Mode suppression
    • H01S3/08022—Longitudinal modes
    • H01S3/08031—Single-mode emission

Definitions

  • This invention relates to the field of laser technology, specifically to a swept-frequency laser system and sweep-frequency method, and a resonant optical frequency-shifting filter.
  • Narrow linewidth, wide tuning range swept lasers have wide applications in fields such as spectral analysis, lidar, environmental gas monitoring, laser communication, and biomedicine.
  • the frequency of laser light emitted by a laser depends on both the gain spectral shape within the cavity and the longitudinal mode frequency of the laser resonator.
  • the gain spectral shape and the wavelength of the output laser can be altered by changing the filter's center frequency.
  • the number of longitudinal modes also changes, and the switching between longitudinal modes produces phase jumps, resulting in strong frequency and phase noise in the output swept laser.
  • a Chinese patent application with publication number CN103151703B discloses a Littrow structure tunable external cavity laser and its mode-hopping-free frequency sweep adjustment method, comprising a semiconductor laser, a liquid crystal spatial light modulator, and a blazed grating.
  • the method involves passing a laser beam emitted from the semiconductor laser through the liquid crystal spatial light modulator and then incident on the blazed grating.
  • the first-order diffracted light returning along the original path after passing through the blazed grating resonates between the inner and outer cavities of the tunable external cavity laser, and finally exits from the zero-order of the blazed grating.
  • the blazed grating is rotated around axis point O, while simultaneously changing the voltage of the liquid crystal spatial light modulator to adjust its refractive index. During the tuning process of rotating the blazed grating, mode-hopping-free frequency sweep adjustment of the tunable external cavity laser is achieved.
  • the existing main technical solution is to use a grating as a wavelength tuning element.
  • a grating By mechanically rotating the grating or a mirror, the center wavelength of the filter and the cavity length of the laser are changed synchronously, so that the longitudinal mode frequency of the laser changes synchronously with the center wavelength of the filter, and the laser always works in the same longitudinal mode, achieving a wide range of frequency sweep output without mode hopping.
  • the mechanical motion device has a complex structure, requires very high precision in processing and motion control, and the mechanical tuning speed is relatively slow, which needs to be improved.
  • the purpose of this invention is to provide a swept-frequency laser system, a swept-frequency method, and a resonant optical frequency-shifting filter.
  • a swept-frequency laser system includes a laser resonant cavity, wherein an optical amplifier, an optical frequency shifting module, and a tunable optical filter module are disposed within the laser resonant cavity; the optical amplifier amplifies the light wave within the laser resonant cavity, providing gain; the optical frequency shifting module modulates the light wave, causing changes in the frequency and phase of the light wave; the tunable optical filter module performs bandpass filtering on the light wave within the laser resonant cavity, ensuring low loss for a selected frequency and high loss for other frequencies; the time taken for the light wave to circulate once within the laser resonant cavity is denoted as T, and the total frequency shift during one cycle is denoted as F; the passband of the tunable optical filter module is defined by a rate...
  • the regular changes in the frequency output result in a frequency-sweeping laser with a sweep rate of K.
  • it also includes one or more mirrors that do not affect the working principle of the swept laser, used to change the shape of the optical path or to couple part of the light out of the laser cavity, so as to obtain the output light of the laser and the optical wave information in the laser resonant cavity.
  • one or more mirrors that do not affect the working principle of the swept laser, used to change the shape of the optical path or to couple part of the light out of the laser cavity, so as to obtain the output light of the laser and the optical wave information in the laser resonant cavity.
  • the time it takes for light to circulate once within the laser resonant cavity is denoted as T, and the total frequency shift experienced during one cycle is denoted as F.
  • Each light wave that satisfies the above conditions is called a swept longitudinal mode of the resonant cavity, distinguished by the longitudinal mode order N. All swept longitudinal modes are linear swept light waves; light that does not satisfy the conditions cannot oscillate in the resonant cavity.
  • the tunable optical filter module By controlling the tunable optical filter module, its passband center frequency is swept at a rate K, and the center frequency is the same as the frequency of a selected sweeping longitudinal mode of order n. This allows the sweeping longitudinal mode to oscillate in the laser resonant cavity with low loss, while other sweeping longitudinal modes cannot oscillate due to high loss, thus realizing single-mode sweeping laser output.
  • a tunable optical frequency shifter is used to replace the optical frequency shifter module and the tunable optical filter module.
  • the tunable optical frequency shifter simultaneously performs the functions of both the optical frequency shifter module and the tunable optical filter module.
  • two or more of the tunable optical frequency shifters can be combined to ensure that the optical frequency shifting function and the optical filtering function do not interfere with each other.
  • the laser resonant cavity includes a composite cavity structure, and the light wave has at least two partially overlapping closed loop paths within the laser resonant cavity.
  • the delay T3 of any closed loop path and the total optical frequency shift F3 experienced on that path satisfy the following relationship:
  • multiple gain media with different operating wavelengths can be placed to expand the sweep frequency range of the laser.
  • a frequency sweeping method for a frequency-sweeping laser system includes the following steps: setting the frequency shift amount of each optical frequency shifting module in the laser resonant cavity, such that the ratio of the time delay T experienced by the light wave on any possible closed loop path in the resonant cavity to the total frequency shift F + is equal to K + .
  • the passband frequency of the tunable optical filter module is adjusted to select one of the sweeping longitudinal modes, so that the selected sweeping longitudinal mode always passes through the tunable optical filter module with minimal loss, while the other sweeping longitudinal modes have high losses and cannot oscillate in the cavity, so that only one sweeping longitudinal mode can oscillate in the cavity, and the output is a linear sweeping laser with a sweep rate of K + .
  • the center frequency of the tunable optical filter module is changed, a new sweeping longitudinal mode is re-selected and tracked, and the above process is repeated.
  • a frequency sweeping method for a frequency sweeping laser system includes the following steps:
  • each optical frequency shifting module within the laser resonant cavity is set such that the ratio of the time delay T experienced by the light wave on any possible closed loop path within the resonant cavity to the total frequency shift F is equal to the same constant K: Set the passband frequency of the tunable optical filter module so that its center frequency changes according to the sweep rate K.
  • the frequency shift of one or more optical frequency shifters is changed so that the ratio of the time delay T′ experienced by the light wave on any possible closed loop path within the resonant cavity to the total frequency shift F′ is equal to another constant K′:
  • the frequency sweep rate of the passband frequency of the synchronously adjusted tunable optical filter module is K′.
  • the center frequency of the passband tracks the frequency of the sweeping longitudinal mode in the cavity, and the output sweeping laser has a sweep rate of K′, so that the power and phase of the output laser remain continuous without abrupt changes during the process of the sweep rate changing from K to K′.
  • a resonant optical frequency shifter includes: inserting an optical frequency shifting module into a linear or ring optical resonant cavity, wherein the circulation time of the light wave in the optical resonant cavity is T2, and the total frequency shift experienced by the light wave in one cycle is F2, thereby enabling light waves of a specific frequency to pass through with low loss, while light waves of other frequencies have high loss.
  • the frequency of the light that can pass through the resonant optical frequency shifter with low loss changes with time at a rate of... change.
  • the present invention has the following beneficial effects:
  • This invention changes the optical frequency by frequency shifting within the laser resonant cavity.
  • the sweep rate of the output laser is determined by the amount of frequency shift and the cycle time within the cavity. It has good sweep linearity and no mode skipping.
  • the sweep speed and direction can be changed by altering the magnitude and direction of the frequency shift. It is not affected by mechanical inertia and can achieve fast and wide-range sweep optical operation.
  • the present invention provides an optical frequency increment in laser frequency sweeping through an intracavity frequency shifter.
  • the optical frequency increment is independent of the sweeping range. Only a very small frequency increment is needed to achieve a very large laser frequency sweeping range, and it is no longer limited by devices such as the working band of the grating, so that laser frequency sweeping operation can be carried out over a wider range.
  • Figure 1 is a schematic diagram of the basic structure of the sweeping laser mainly embodied in this invention
  • Figure 2 is a schematic diagram illustrating the working principle of the sweeping laser resonant cavity and the resonant optical frequency shifter of the present invention.
  • Figure 3 is a schematic diagram illustrating the spectral variation of the tunable filtering module over time, which is the main feature of this invention.
  • Figure 4 is a schematic diagram of a swept-frequency laser with a composite cavity, which mainly embodies the second variation of the present invention.
  • Figure 5 is a schematic diagram of a swept-frequency laser structure with multiple gain media, which mainly embodies the third variation of the present invention.
  • Figure 6 is a schematic diagram of the sweep laser structure with a resonant optical frequency shifter, which is the main embodiment of the fourth variation of the present invention.
  • a swept-frequency laser system includes a laser resonant cavity, within which are disposed an optical amplifier, an optical frequency shifting module 301, and a tunable optical filter module 401.
  • the optical amplifier amplifies the light wave within the laser resonant cavity, providing gain; that is, the optical amplifier serves as the gain medium 201.
  • the optical frequency shifting module 301 modulates the light wave, causing changes in its frequency and phase.
  • the tunable optical filter module 401 performs bandpass filtering on the light wave within the laser resonant cavity, ensuring low loss for a selected frequency and high loss for other frequencies.
  • the gain coefficient of the gain medium 201, the frequency and phase changes of the optical frequency shifting module 301, and the center frequency of the tunable optical filter can be changed as needed.
  • T be the time it takes for the light wave to complete one cycle within the laser resonant cavity
  • F be the total frequency shift experienced during one cycle.
  • the passband of the tunable optical filter module 401 is expressed as a rate of The regular changes in the frequency output result in a frequency-sweeping laser with a sweep rate of K.
  • it also includes one or more optical reflectors 101 that do not affect the working principle of the swept laser, used to change the shape of the optical path or to couple part of the light out of the laser cavity in order to obtain the output light of the laser and the optical wave information in the laser resonant cavity.
  • one or more optical reflectors 101 that do not affect the working principle of the swept laser, used to change the shape of the optical path or to couple part of the light out of the laser cavity in order to obtain the output light of the laser and the optical wave information in the laser resonant cavity.
  • a laser resonant cavity is formed by two optical reflectors 101.
  • the laser resonant cavity contains an optical amplifier, an optical frequency shifter module 301, and a tunable optical filter module 401.
  • the optical amplifier, optical frequency shifter module 301, and tunable optical filter module 401 are all two-port devices, and their connection order can be arbitrarily changed.
  • the optical reflector 101 can be a partial reflector, used to couple part of the light out of the laser cavity to obtain the laser's output light and intracavity light wave information.
  • the devices involved in this application mainly refer to functional classifications. Two or more functions can be performed by the same device, and each function can also be implemented by a combination of one or more devices.
  • Each light wave that meets the above conditions is called a swept longitudinal mode of the resonant cavity, distinguished by the longitudinal mode order N. All swept longitudinal modes are linear swept light waves; light that does not meet the conditions cannot oscillate in the resonant cavity.
  • the tunable optical filter module 401 By controlling the tunable optical filter module 401, its passband center frequency is swept at a rate K, and the center frequency is the same as the frequency of a selected sweeping longitudinal mode of order n. This allows the sweeping longitudinal mode to oscillate in the laser resonant cavity with low loss, while other sweeping longitudinal modes cannot oscillate due to high loss, thereby realizing single longitudinal mode sweeping laser output.
  • the present invention also provides a frequency sweeping method for a frequency sweeping laser system. Based on the above-described frequency sweeping laser system, the frequency sweeping method includes:
  • the frequency shift of the optical frequency shift module 301 in the laser resonant cavity is set such that the ratio of the time delay T experienced by the light wave during one cycle in the laser resonant cavity to the frequency shift F is equal to K:
  • the laser resonant cavity can support a series of swept longitudinal modes that satisfy the phase condition.
  • the sweep rate of each swept longitudinal mode is K
  • the frequency interval between each swept longitudinal mode is K.
  • one of the sweep frequency longitudinal modes is selected and its frequency is tracked in real time.
  • the phase change caused by intracavity dispersion and environmental disturbance is compensated so that the selected sweep frequency longitudinal mode always passes through the tunable optical filter module 401 with minimal loss, while the other sweep frequency longitudinal modes have high losses and cannot oscillate in the cavity, so that only one sweep frequency longitudinal mode can oscillate in the cavity.
  • the center frequency of the tunable optical filter module 401 is controlled to re-select and track a new sweeping longitudinal mode, and the above process is repeated.
  • the laser resonator of this application may have two or more optical frequency shifting modules 301 to achieve a more flexible frequency shifting range, and two or more tunable optical filtering modules 401 to further narrow the operating linewidth of the linear sweep laser.
  • the frequency sweeping method of the sweeping laser system in this application can achieve reverse frequency sweeping by changing the direction of the frequency shift F and correspondingly changing the sweeping direction of the tunable optical filter module 401.
  • the frequency shift F By setting the frequency shift F to 0 and aligning the center frequency of the tunable optical filter module 401 with a certain longitudinal mode, fixed-frequency operation at any wavelength within the working range of the laser can be achieved.
  • This application changes the optical frequency by intracavity frequency shifting to output a highly coherent swept laser.
  • the sweep rate of the laser is determined by the intracavity frequency shift and the intracavity cycle time.
  • a wide range of mode-hopping-free linear sweep can be achieved without mechanical motion devices.
  • the sweep range is only limited by the operating bandwidth of the optical amplifier and other optical devices used, and the sweep rate is flexibly adjustable.
  • a sweep laser system uses a tunable optical frequency shifter filter 501 to replace the optical frequency shifter module 301 and the tunable optical filter module.
  • the tunable optical frequency shifter filter 501 simultaneously performs the functions of both the optical frequency shifter module 301 and the tunable optical filter module.
  • two or more tunable optical frequency shifters 501 can be combined, ensuring that the optical frequency shifting function and the optical filtering function do not interfere with each other, which helps to achieve single-mode sweep operation with a wide range of adjustable sweep rates.
  • a swept-frequency laser system includes a laser resonant cavity with a composite cavity structure.
  • the light wave has at least two partially overlapping closed-loop paths within the laser resonant cavity.
  • the delay T2 of any closed-loop path and the total optical frequency shift F2 experienced along that path satisfy the following relationship:
  • the composite cavity structure can increase the frequency spacing between each longitudinal mode without affecting the laser sweep rate, making it easy to achieve single longitudinal mode operation.
  • an optical beam splitter 109 is inserted into the laser resonant cavity to form a composite cavity structure.
  • the cavity There are two partially overlapping optical loop closed circuits in the cavity, namely the main cavity: optical mirror 101-gain medium 201-tunable optical frequency shifter 501-optical beam splitter 109-tunable optical frequency shifter 501-gain medium 201-optical mirror 101; and the auxiliary cavity: optical mirror 101-tunable optical frequency shifter 501-optical beam splitter 109-optical mirror 101-optical beam splitter 109-tunable optical frequency shifter 501-optical mirror 101.
  • Each optical closed loop contains a device with optical frequency shifting function. Let the cycle times of the two closed optical paths be T1 and T2, respectively. Let the total frequency shifts F1 and F2 of the two closed optical paths be set to satisfy the following formula:
  • the passband frequencies of the tunable optical frequency shifter 501 in the two optical closed loops are controlled so that their passband frequencies sweep at a rate K.
  • the relative phase of the two tunable optical frequency shifter filters 501 is adjusted so that the frequency of the sweeping longitudinal mode of the auxiliary cavity is aligned with a certain sweeping longitudinal mode of the main cavity, achieving single-mode operation.
  • fiber couplers are used to replace some of the mirrors in free-space lasers, and the two achieve equivalent functions.
  • This invention provides a frequency sweeping method for a frequency-sweeping laser system.
  • the frequency sweeping method includes the following steps: setting the frequency shift amount of each frequency shift module in the laser resonant cavity, such that the ratio of the time delay T experienced by the light wave on all possible closed loop paths in the resonant cavity to the frequency shift magnitude F + is equal to K + .
  • each tunable optical frequency shifter 501 is adjusted to select one of the sweeping longitudinal modes and its frequency is tracked in real time to compensate for the phase changes caused by intracavity dispersion and environmental disturbances. This ensures that the selected sweeping longitudinal mode always passes through each tunable optical frequency shifter 501 with minimal loss, while other sweeping longitudinal modes have high losses and cannot oscillate in the cavity. This ensures that only one sweeping longitudinal mode can oscillate in the cavity, outputting a sweeping laser with a sweep rate of K + . The sweep rate can be changed by simultaneously changing the frequency of each tunable optical frequency shifter 501.
  • the center frequency of the tunable optical frequency shift filter 501 is controlled to re-select and track a new sweeping optical mode, and the above process is repeated.
  • this application proposes a composite cavity swept-frequency laser system with two gain media 201.
  • the main cavity is: optical mirror 101 - gain media 201 - tunable optical frequency shifter 501 - optical beam splitter 109 - tunable optical frequency shifter 501 - optical mirror 101 - tunable optical frequency shifter 501 - optical beam splitter 109 - tunable optical frequency shifter 501 - gain media 201 - optical mirror 101;
  • the auxiliary cavity is: optical mirror 101 - gain media 201 - tunable optical frequency shifter 501 - optical beam splitter 109 - tunable optical frequency shifter 501 - optical mirror 101 - tunable optical frequency shifter 501 - optical beam splitter 109 - tunable optical frequency shifter 501 - gain media 201 - optical mirror 101.
  • the gain medium 201 in the auxiliary cavity has a different operating band than the gain medium 201 in the main cavity.
  • the effective gain band of the laser is the sum of the operating bands of
  • the present invention also provides a resonant optical frequency shifter 601, applicable to the sweep laser system proposed in the invention.
  • the structure of the resonant optical frequency shifter 601 includes inserting an optical frequency shifter within a linear or ring optical resonant cavity.
  • the cycle time of the light wave within this optical resonant cavity is T2, and the total frequency shift experienced by the light wave in one cycle is F2.
  • T2 The cycle time of the light wave within this optical resonant cavity
  • F2 the total frequency shift experienced by the light wave in one cycle.
  • the frequency of the light that can pass through the resonant optical frequency shifter 601 with low loss changes with time at a rate...
  • the resonant optical frequency shifter 601 can allow light waves with a sweep rate of K and a specific initial frequency to pass through with low loss, while light waves of other frequencies have high loss.
  • the optical beam splitter 109, the optical reflector 101, and the optical frequency shifting module 301 work together to form a resonant optical frequency shifting filter 601.
  • This resonant optical frequency shifting filter 601 together with the optical frequency shifting module 301, the optical reflector 101, the gain medium 201, the optical reflector 101, and the optical isolator 701, constitute a ring cavity structure sweeping laser that outputs a linear sweeping laser.
  • the resonant optical frequency shifter 601 includes two optical beam splitters 109, two optical reflectors 101, and an optical frequency shifting module 301.
  • the optical beam splitters 109, optical reflectors 101, optical frequency shifting module 301, optical reflectors 101, optical beam splitters 109, and optical beam splitters 109 together form a closed loop to constitute the resonant optical frequency shifter 601.
  • the resonant optical frequency shifter 601, optical frequency shifting module 301, optical reflectors 101, gain medium 201, optical reflectors 101, and optical isolator 701 together constitute a ring cavity structure swept laser, outputting a linear swept laser.
  • the frequency sweeping method includes the following steps: setting the frequency shift amount of each optical frequency shifting module 301 in the laser resonant cavity, such that the ratio of the time delay T experienced by the light wave on all possible closed loop paths in the resonant cavity to the frequency shift magnitude F + is equal to K + .
  • the passband frequency of the tunable optical filter module 401 is adjusted to select one sweeping longitudinal mode. This selected sweeping longitudinal mode always passes through the tunable optical filter module 401 with minimal loss, while other sweeping longitudinal modes suffer high losses and cannot oscillate within the cavity. This ensures that only one sweeping longitudinal mode can oscillate within the cavity, outputting a linear sweeping laser with a sweep rate of K + . Once the optical frequency of the selected sweeping optical mode reaches the set value, the center frequency of the tunable optical filter module 401 is changed to reselect and track a new sweeping longitudinal mode, and the above process is repeated.
  • the frequency sweeping method includes the following steps: setting the frequency shift amount of each optical frequency shifting module 301 in the laser resonant cavity, such that the ratio of the time delay T experienced by the light wave on any possible closed loop path in the resonant cavity to the total frequency shift F is equal to the same constant K: Set the passband frequency of the tunable optical filter module 401 so that its passband center frequency changes according to the sweep rate K.
  • the frequency sweep rate of the passband frequency of the synchronously adjusted tunable optical filter module 401 is K′.
  • the center frequency of the passband tracks the frequency of the sweeping longitudinal mode in the cavity, and the output sweeping laser has a sweeping rate of K′, so that the power and phase of the output laser remain continuous without abrupt changes during the process of the sweeping rate changing from K to K′.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

一种扫频激光器系统及扫频方法及谐振式光移频滤波器（601），包括激光谐振腔，激光谐振腔内设置有光放大器、光移频模块（301）以及可调谐光滤波模块（401）；光放大器放大激光谐振腔内的光波，提供增益；光移频模块（301）调制光波，使光波的频率和相位发生变化；可调谐光滤波模块（401）对激光谐振腔内的光波进行带通滤波，使选定频率的光波具有低损耗，而其他频率的光波具有高损耗。通过腔内移频的方式改变光频率，输出具有高相干性的扫频激光，激光的扫频速率由腔内的移频量和腔内循环时间决定，不需要机械运动装置即可实现大范围的无跳模扫频，扫频范围只受限于所用光放大器等光器件的工作带宽，扫频速率灵活可调。

Description

扫频激光器系统及扫频方法及谐振式光移频滤波器 技术领域
本发明涉及激光技术领域，具体地，涉及一种扫频激光器系统及扫频方法及谐振式光移频滤波器。
背景技术
窄线宽、大调谐范围的扫频激光器在光谱分析、激光雷达、环境气体监测、激光通信、生物医学等领域有着广泛的应用。
通常激光器所发出激光的频率同时取决于腔内的增益谱线形状和激光谐振腔的纵模频率。在激光谐振腔中插入中心频率可调谐的滤波器时，通过改变滤波器的中心频率可以改变腔内的增益谱线形状和输出激光的波长，但是激光的频率变化时其纵模模式数会发生变化，纵模之间的切换会产生相位跳变，导致输出的扫频激光存在很强的频率和相位噪声。
现有公开号为CN103151703B的中国专利申请文献，其公开了一种Littrow结构可调谐外腔式激光器及其无跳模扫频调节方法，包括半导体激光器、液晶空间光调制器和闪耀光栅；方法为使半导体激光器发射的激光束经过液晶空间光调制器后入射在闪耀光栅上，经闪耀光栅后原路返回的一级衍射光在所述可调谐外腔式激光器的内腔和外腔之间形成谐振，最后由闪耀光栅的零级出射；绕轴点O旋转闪耀光栅，并同时改变液晶空间光调制器的电压使液晶空间光调制器的折射率，在旋转闪耀光栅调谐的过程中，从而实现所述可调谐外腔式激光器的无跳模扫频调节。
现有技术中为了实现无跳模的相位连续扫频，现有主要技术方案是在采用光栅作为波长调谐元件，通过光栅或者反射镜的机械转动，实现滤波器中心波长和激光器腔长的同步改变，使得激光的纵模频率与滤波器中心波长同步变化，使得激光始终工作在同一个纵模内，实现无跳模的大范围扫频输出，但是机械运动装置结构复杂，对加工和运动控制精度要求非常高，而且机械调谐速度的速度较慢，存在待改进之处。
发明内容
针对现有技术中的缺陷，本发明的目的是提供一种扫频激光器系统及扫频方法及谐振式光移频滤波器。
根据本发明提供的一种扫频激光器系统,包括激光谐振腔，所述激光谐振腔内设置有光放大器、光移频模块以及可调谐光滤波模块；所述光放大器放大激光谐振腔内的光波，提供增益；所述光移频模块调制光波，使光波的频率和相位发生变化；所述可调谐光滤波模块对激光谐振腔内的光波进行带通滤波，使选定频率的光波具有低损耗，而其他频率的光波具有高损耗；所述光波在激光谐振腔内循环一周所用的时间记为T，循环一周所经历的总移频量记为F，所述可调谐光滤波模块的通带以速率的规律变化，输出扫频速率为K的扫频激光。
优选地，还包括不影响扫频激光器工作原理的一个或多个反射镜，用于改变光路的形状，或者将部分光耦合出激光器腔外，以得到激光器的输出光及激光谐振腔内的光波信息。
优选地，光在激光谐振腔内循环一周的时间记为T，循环一周时经历的总频移量记为F，根据激光振荡的相位条件，能够在谐振腔内起振的光波的瞬时频率f(t)需要满足如下形式：f(t)＝f0+Kt，其中f0为初始频率，满足N为任意正整数，代表纵模的级次，K为扫频速率，每一个满足上述条件的光波称为该谐振腔的一个扫频纵模，用纵模级次N区分，所有的扫频纵模均为线性扫频光波；而不满足该条件的光不能在谐振腔内起振；
通过控制可调谐光滤波模块，使其通带的中心频率以速率K进行扫频，且中心频率与筛选的某一个级次为n的扫频纵模的频率相同，从而使得该扫频纵模能够始终低损耗地在激光谐振腔内振荡，而其他频率的扫频纵模因损耗大而不能起振，从而实现单纵模扫频激光输出。
优选地，采用可调谐光移频滤波器替代光移频模块和可调谐光滤波器模块，所述可调谐光移频滤波器同时实现光移频模块和可调谐光滤波器模块的功能；且可以组合两个或多个所述可调谐光移频滤波器，使得光移频功能和光滤波功能互不干扰。
优选地，所述激光谐振腔包括复合腔结构，光波在激光谐振腔内具有至少两个部分重合的闭合循环路径，任一闭合循环路径的延时T3与该路径上经历的总光频移量F3均满足关系
优选地，在复合腔结构光路不重合的部分，可以分别放置多个不同工作波段的增益介质，扩大激光器的扫频范围。
根据本发明提供的一种扫频激光器系统的扫频方法，扫频方法包括如下步骤：设置激光谐振腔内各光移频模块的移频量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T和总频移量F+的比值均等于K+：设置可调谐光滤波模块的通带频率，使其通带频率按照扫频速率K+变化；
调整可调谐光滤波模块的通带频率，筛选出其中一个扫频纵模，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块，而其他扫频纵模的损耗很大，无法在腔内起振，使得腔内只有一个扫频纵模可以起振，输出扫频速率为K+的线性扫频激光；
当被选中的扫频光模式的光频率达到设定值后，改变可调谐光滤波模块的中心频率，重新筛选并跟踪一个新的扫频纵模，并重复上述过程。
根据本发明提供的一种扫频激光器系统的扫频方法，扫频方法包括如下步骤：
设置激光谐振腔内各光移频模块的移频量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T和总频移量F的比值均等于同一个常数K：设置可调谐光滤波模块的通带频率，使其通带中心频率按照扫频速率K变化；
调整可调谐光滤波模块或者光移频模块，使得腔内的一个扫频纵模的频率与可调谐光滤波模块的通带频率相一致，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块，而其他扫频光模式的损耗很大，无法在腔内起振，使得腔内只有被选中的扫频纵模起振，输出扫频速率为K的扫频激光；
在激光器内有扫频速率为K的一个扫频纵模起振时，改变一个或同时改变多个光移频器的频移量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T′和总频移量F′的比值均等于另一个常数K′：同步调整可调谐光滤波模块的通带频率的扫频速度为K′，通带的中心频率跟踪腔内该扫频纵模的频率，输出扫频速率为K′的扫频激光，使得在扫频速率从K变为K′的过程中，输出激光的功率和光的相位保持连续而不发生突变；
按照一定的规律调整扫频速率，可以实现激光频率随时间以任意规律变化的扫频激光输出，包括任意固定频率的激光，频率随时间成三角波变化的光波，和频率随时间成锯齿波变化的光波。
根据本发明提供的一种谐振式光移频滤波器，谐振式光移频滤波器的结构包括：在线性或者环形光学谐振腔内插入光移频模块，光波在该光学谐振腔内的循环时间为T2，光波循环一周经历的总移频量为F2，从而使得特定频率的光波能够低损耗地通过，而其他频率的光波具有高损耗，且能够低损耗地通过该谐振式光移频滤波器的光的频率随时间以速率变化。
与现有技术相比，本发明具有如下的有益效果：
1、本发明通过激光谐振腔内移频的方式改变光频率，输出激光的扫频速率由腔内的移频量和腔内循环时间决定，具有良好的扫频线性度且没有跳模，扫频的速度和方向可以通过改变移频量的大小和方向而改变，不受机械惯性影响，可以实现快速、大范围的扫频光运转。
2、本发明通过腔内移频器提供的激光扫频中的光频率增量，光频增量与扫频范围无关，只需要很小的频率增量即可实现极大的激光频率扫频范围，而不再受到光栅的工作波段等器件的限制，可以更大范围的激光扫频运转。
附图说明
通过阅读参照以下附图对非限制性实施例所作的详细描述，本发明的其它特征、目的和优点将会变得更明显：
图1为本发明主要体现扫频激光器基本结构示意图；
图2为本发明主要体现扫频激光谐振腔以及谐振式光移频滤波器的工作原理示意；
图3为本发明主要体现可调光滤波模块的光谱随时间变化的示意图；
图4为本发明主要体现变化例二的具有复合腔的扫频激光器结构示意图；
图5为本发明主要体现变化例三的具有多个增益介质的扫频激光器结构示意图；
图6为本发明主要体现变化例四的具有谐振式光移频滤波器的扫频激光器结构示意图。
图中所示：
光反射镜101                     可调谐光滤波模块401
光分束镜109                     可调谐光移频滤波器501
增益介质201                     谐振式光移频滤波器601
光移频模块301                   光隔离器701
具体实施方式
下面结合具体实施例对本发明进行详细说明。以下实施例将有助于本领域的技术人员进一步理解本发明，但不以任何形式限制本发明。应当指出的是，对本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变化和改进。这些都属于本发明的保护范围。
实施例一
如图1所示，根据本发明提供的一种扫频激光器系统，包括激光谐振腔，激光谐振腔内设置有光放大器、光移频模块301以及可调谐光滤波模块401。光放大器放大激光谐振腔内的光波，提供增益，即光放大器作为增益介质201。光移频模块301调制光波，使光波的频率和相位发生变化。可调谐光滤波模块401对激光谐振腔内的光波进行带通滤波，使选定频率的光波具有低损耗，而其他频率的光波具有高损耗。增益介质201的增益系数、光移频模块301的频率和相位改变量、以及可调光滤波器的中心频率可以根据需要改变。
光波在激光谐振腔内循环一周所用的时间记为T，循环一周所经历的总移频量记为F，可调谐光滤波模块401的通带以速率的规律变化，输出扫频速率为K的扫频激光。
具体地，还包括不影响扫频激光器工作原理的一个或多个光反射镜101，用于改变光路的形状，或者将部分光耦合出激光器腔外，以得到激光器的输出光及激光谐振腔内的光波信息。
如图1所示，本申请提供一种可行的实施方式：由两个光反射镜101构成激光谐振腔，激光谐振腔内具有光放大器、光移频模块301以及可调谐光滤波模块401，且本申请技术方案中的光放大器、光移频模块301以及可调谐光滤波模块401均为两端口器件，连接的先后顺序可以任意改变。光反射镜101可以为部分反射镜，用于将部分光耦合出激光器腔外，以得到激光器的输出光及腔内光波信息。
需要说明的是，本申请涉及的器件主要是指功能上的分类，两个或多个功能可以由同一个器件完成，每个功能也可以由一个或多个器件的组合来实现。
本申请的扫频激光器系统的工作原理：光在激光谐振腔内循环一周的时间记为T，循环一周时经历的总频移量记为F，根据激光振荡的相位条件，能够在谐振腔内起振的光波的瞬时频率f(t)需要满足如下形式：f(t)＝f0+Kt，其中f0为初始频率，满足N为任意正整数，代表纵模的级次，K为扫频速率，每一个满足上述条件的光波称为该谐振腔的一个扫频纵模，用纵模级次N区分，所有的扫频纵模均为线性扫频光波；而不满足该条件的光不能在谐振腔内起振。
通过控制可调谐光滤波模块401，使其通带的中心频率以速率K进行扫频，且中心频率与筛选的某一个级次为n的扫频纵模的频率相同，从而使得该扫频纵模能够始终低损耗地在激光谐振腔内振荡，而其他频率的扫频纵模因损耗大而不能起振，从而实现单纵模扫频激光输出。
本发明还提供一种扫频激光器系统的扫频方法，基于上述的扫频激光器系统，扫频方法包括：
设置激光谐振腔内光移频模块301的移频量，使得光波在激光谐振腔内循环一周经历的时间延迟T和频移量F的比值等于K：
如图2所示，此时，激光谐振腔内可以支持一系列满足相位条件的扫频纵模，各扫频纵模的扫频速率均为K，而各扫频纵模之间的频率间隔均为设置可调谐光滤波模块401的通带频率，使其通带频率按照速率K变化，如图3所示。
调节可调谐光滤波模块401的通带频率或者光移频模块301的频率和相位，筛选出其中一个扫频纵模，并实时跟踪其频率，补偿因腔内色散、环境扰动导致的相位变化，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块401，而其他扫频纵模的损耗很大，无法在腔内起振，使得腔内只有一个扫频纵模可以起振。
当被选中的扫频纵模的光频率达到设定值后，控制可调谐光滤波模块401的中心频率，重新筛选并跟踪一个新的扫频纵模，并重复上述过程。
需要说明的是，本申请的激光谐振腔内可以具有两个或以上的光移频模块301实现更加灵活的移频范围，两个或以上的可调谐光滤波模块401用于进一步压窄线性扫频激光器的工作线宽。
更需要说明的是，本申请的扫频激光器系统的扫频方法，可以通过改变频移F的方向，并相应改变可调谐光滤波模块401的扫频方向，可以实现反向扫频。可以通过将频移F设为0，并使可调谐光滤波模块401的中心频率对准某个纵模，则可实现激光的工作范围内任意波长处定频运转。
本申请通过腔内移频的方式改变光频率，输出具有高相干性的扫频激光，激光的扫频速率由腔内的移频量和腔内循环时间决定，不需要机械运动装置即可实现大范围的无跳模线性扫频，扫频范围只受限于所用光放大器等光器件的工作带宽，扫频速率灵活可调。
变化例一
基于实施例一，根据本发明提供的一种扫频激光器系统，如图1所示，采用可调谐光移频滤波器501替代光移频模块301和可调谐光滤波器模块，可调谐光移频滤波器501同时实现光移频模块301和可调谐光滤波器模块的功能。且可以组合两个或多个可调谐光移频滤波器501，使得光移频功能和光滤波功能互不干扰，有助于实现扫频速率大范围可调的单纵模扫频运转。
变化例二
基于实施例一或变化例一，根据本发明提供的一种扫频激光器系统，如图4所示，激光谐振腔包括复合腔结构，光波在激光谐振腔内具有至少两个部分重合的闭合循环路径，任一闭合循环路径的延时T2与该路径上经历的总光频移量F2均满足关系复合腔结构可以增加各纵模之间的频率间隔而不影响激光的扫频速率，以易于实现单纵模运转。
具体地，在激光谐振腔内插入光分束镜109，形成复合腔结构，在腔内有两个部分重合的光循环闭合回路，分别是主腔：光反射镜101-增益介质201-可调谐光移频滤波器501-光分束镜109-可调谐光移频滤波器501-增益介质201-光反射镜101；附腔：光反射镜101-可调谐光移频滤波器501-光分束镜109-光反射镜101-光分束镜109-可调谐光移频滤波器501-光反射镜101。
每个光闭合回路内均包含具有光移频功能的器件，记上述两个闭合光路的循环时间分别为T1和T2,设置两闭合光路循环一周受到的总频移量F1和F2使其满足如下公式：
同时，控制两个光闭合回路中的可调谐光移频滤波器501的通带频率，使得其通带频率以速率K扫频。并调整两个可调谐光移频滤波器501的相对相位，使附腔的扫频纵模的频率对准主腔的某个扫频纵模，实现单纵模运转。
需要说明的是，在光纤激光器系统中，采用光纤耦合器代替自由空间激光器中部分反射镜，两者实现的功能是等价的。
本发明提供一种扫频激光器系统的扫频方法，扫频方法包括如下步骤：设置激光谐振腔内各移频模块的移频量，使得光波在谐振腔内的所有可能的闭合循环路径上经历的时间延迟T和频移大小F+的比值均等于K+：设置各可调谐光移频滤波器501的通带频率，使其通带频率按照速率K+变化。
调整各可调谐光移频滤波器501的通带频率，筛选出其中一个扫频纵模，并实时跟踪其频率，补偿因腔内色散、环境扰动导致的相位变化，使得被选中的扫频纵模始终以最小损耗通过各可调谐光移频滤波器501，而其他扫频纵模的损耗很大，无法在腔内起振，使得腔内只有一个扫频纵模可以起振，输出扫频速率为K+的扫频激光，且扫频速率可以通过同时改变各可调谐移频滤波器501的频率而改变；
当被选中的扫频光模式的光频率达到设定值后，控制可调谐光移频滤波器501的中心频率，重新筛选并跟踪一个新的扫频光模式，并重复上述过程。
变化例三
基于变化例二，根据本发明提供的一种扫频激光器系统，在复合腔结构光路不重合的部分，如图5所示，可以分别放置多个不同工作波段的增益介质201，扩大激光器的扫频范围。
具体地，本申请提出一种具有两个增益介质201的复合腔扫频激光器系统，主腔为：光反射镜101-增益介质201-可调谐光移频滤波器501-光分束镜109-可调谐光移频滤波器501-光反射镜101-可调谐光移频滤波器501-光分束镜109-可调谐光移频滤波器501-增益介质201-光反射镜101；附腔为：光反射镜101-增益介质201-可调谐光移频滤波器501-光分束镜109-可调谐光移频滤波器501-光反射镜101-可调谐光移频滤波器501-光分束镜109-可调谐光移频滤波器501-增益介质201-光反射镜101。附腔中的增益介质201与主腔中的增益介质201的工作波段不同，激光器有效增益波段是两个增益介质201的工作波段的和，能够实现更大的扫频范围。
变化例四
基于实施例一、变化例二、变化例三或变化例四，本发明还提供一种谐振式光移频滤波器601，适用于发明提出的扫频激光器系统，谐振式光移频滤波器601的结构包括在线性或者环形光学谐振腔内插入光移频器，光波在该光学谐振腔内的循环时间为T2，光波循环一周经历的总移频量为F2，从而使得特定频率的光波能够低损耗地通过，而其他频率的光波具有高损耗，且能够低损耗地通过该谐振式光移频滤波器601的光的频率随时间以速率变化。则该谐振式光移频滤波器601可以使扫频速率为K、具有特定初始频率的光波低损耗地通过，而其他频率的光波具有高损耗。
如图6所示，具体地，光分束镜109、光反射镜101以及光移频模块301配合构成了一个谐振式光移频滤波器601，该谐振式光移频滤波器601与光移频模块301、光反射镜101、增益介质201、光反射镜101以及光隔离器701一起构成一个环形腔结构的扫频激光器，输出线性扫频激光。
进一步地，本申请提供一种可行的实施方式为：谐振式光移频滤波器601包括两个光分束镜109、两个光反射镜101以及一个光移频模块301，光分束镜109-光反射镜101-光移频模块301-光反射镜101-光分束镜109-光分束镜109形成闭环构成谐振式光移频滤波器601。谐振式光移频滤波器601-光移频模块301、光反射镜101、增益介质201、光反射镜101以及光隔离器701-谐振式光移频滤波器601一起构成一个环形腔结构的扫频激光器，输出线性扫频激光。
需要说明的是，各变化例记载的技术方案与实施例一相比，仅仅只是对扫频激光器系统的结构进行了改变，工作原理是相同的。
本发明还提供一种扫频激光器系统的扫频方法，以实施例一的系统为例，扫频方法包括如下步骤：设置激光谐振腔内各光移频模块301的移频量，使得光波在谐振腔内的所有可能的闭合循环路径上经历的时间延迟T和频移大小F+的比值均等于K+：设置可调谐光滤波模块401的通带频率，使其通带频率按照速率K+变化。
调整可调谐光滤波模块401的通带频率，筛选出其中一个扫频纵模，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块401，而其他扫频纵模的损耗很大，无法在腔内起振，使得腔内只有一个扫频纵模可以起振，输出扫频速率为K+的线性扫频激光。当被选中的扫频光模式的光频率达到设定值后，改变可调谐光滤波模块401的中心频率，重新筛选并跟踪一个新的扫频纵模，并重复上述过程。
本申请扫频激光器系统的扫频方法的另一种实施方式为：扫频方法包括如下步骤：设置激光谐振腔内各光移频模块301的移频量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T和总频移量F的比值均等于同一个常数K：设置可调谐光滤波模块401的通带频率，使其通带中心频率按照扫频速率K变化；
调整可调谐光滤波模块401或者光移频模块301，使得腔内的一个扫频纵模的频率与可调谐光滤波模块的通带频率相一致，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块401，而其他扫频光模式的损耗很大，无法在腔内起振，使得腔内只有被选中的扫频纵模起振，输出扫频速率为K的扫频激光；
在激光器内有扫频速率为K的一个扫频纵模起振时，改变一个或同时改变多个光移频器的频移量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T′和总频移量F′的比值均等于另一个常数K′：同步调整可调谐光滤波模块401的通带频率的扫频速度为K′，通带的中心频率跟踪腔内该扫频纵模的频率，输出扫频速率为K′的扫频激光，使得在扫频速率从K变为K′的过程中，输出激光的功率和光的相位保持连续而不发生突变；
按照一定的规律调整扫频速率，可以实现激光频率随时间以任意规律变化的扫频激光输出，包括任意固定频率的激光，频率随时间成三角波变化的光波，和频率随时间成锯齿波变化的光波。
在本申请的描述中，需要理解的是，术语“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。
以上对本发明的具体实施例进行了描述。需要理解的是，本发明并不局限于上述特定实施方式，本领域技术人员可以在权利要求的范围内做出各种变化或修改，这并不影响本发明的实质内容。在不冲突的情况下，本申请的实施例和实施例中的特征可以任意相互组合。

Claims (9)

  1. 一种扫频激光器系统，其特征在于，包括激光谐振腔，所述激光谐振腔内设置有光放大器、光移频模块以及可调谐光滤波模块；
    所述光放大器放大激光谐振腔内的光波，提供增益；
    所述光移频模块调制光波，使光波的频率和相位发生变化；
    所述可调谐光滤波模块对激光谐振腔内的光波进行带通滤波，使选定频率的光波具有低损耗，而其他频率的光波具有高损耗；
    所述光波在激光谐振腔内循环一周所用的时间记为T，循环一周所经历的总移频量记为F，所述可调谐光滤波模块的通带以速率的规律变化，输出扫频速率为K的扫频激光。
  2. 如权利要求1所述的扫频激光器系统，其特征在于，还包括不影响扫频激光器工作原理的一个或多个反射镜，用于改变光路的形状，或者将部分光耦合出激光器腔外，以得到激光器的输出光及激光谐振腔内的光波信息。
  3. 如权利要求1所述的扫频激光器系统，其特征在于，光在激光谐振腔内循环一周的时间记为T，循环一周时经历的总频移量记为F，根据激光振荡的相位条件，能够在谐振腔内起振的光波的瞬时频率f(t)需要满足如下形式：f(t)＝f0+Kt，其中f0为初始频率，满足N为任意正整数，代表纵模的级次，K为扫频速率，
    每一个满足上述条件的光波称为该谐振腔的一个扫频纵模，用纵模级次N区分，所有的扫频纵模均为线性扫频光波；而不满足该条件的光不能在谐振腔内起振；
    通过控制可调谐光滤波模块，使其通带的中心频率以速率K进行扫频，且中心频率与筛选的某一个级次为n的扫频纵模的频率相同，从而使得该扫频纵模能够始终低损耗地在激光谐振腔内振荡，而其他频率的扫频纵模因损耗大而不能起振，从而实现单纵模扫频激光输出。
  4. 如权利要求1所述的扫频激光器系统，其特征在于，采用可调谐光移频滤波器替代光移频模块和可调谐光滤波模块，所述可调谐光移频滤波器同时实现光移频模块和可调谐光滤波模块的功能；
    且可以组合两个或多个所述可调谐光移频滤波器，使得光移频功能和光滤波功能互不干扰。
  5. 如权利要求1所述的扫频激光器系统，其特征在于，所述激光谐振腔包括复合腔结构，光波在激光谐振腔内具有至少两个部分重合的闭合循环路径，任一闭合循环路径的循环延时T3与该路径上经历的总光频移量F3均满足关系
  6. 如权利要求5所述的扫频激光器系统，其特征在于，在复合腔结构光路不重合的部分，可以分别放置多个不同工作波段的增益介质，扩大激光器的扫频范围。
  7. 一种扫频激光器系统的扫频方法，其特征在于，采用权利要求1-6任一项所述的扫频激光器系统，扫频方法包括如下步骤：
    设置激光谐振腔内各光移频模块的移频量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T和总频移量F+的比值均等于K+：设置可调谐光滤波模块的通带频率，使其通带频率按照扫频速率K+变化；
    调整可调谐光滤波模块的通带频率，筛选出其中一个扫频纵模，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块，而其他扫频纵模的损耗很大，无法在腔内起振，使得腔内只有一个扫频纵模可以起振，输出扫频速率为K+的线性扫频激光；
    当被选中的扫频光模式的光频率达到设定值后，改变可调谐光滤波模块的中心频率，重新筛选并跟踪一个新的扫频纵模，并重复上述过程。
  8. 一种扫频激光器系统的扫频方法，其特征在于，采用权利要求1-6任一项所述的扫频激光器系统，扫频方法包括如下步骤：
    设置激光谐振腔内各光移频模块的移频量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T和总频移量F的比值均等于同一个常数K：设置可调谐光滤波模块的通带频率，使其通带中心频率按照扫频速率K变化；
    调整可调谐光滤波模块或者光移频模块，使得腔内的一个扫频纵模的频率与可调谐光滤波模块的通带频率相一致，使得被选中的扫频纵模始终以最小损耗通过可调谐光滤波模块，而其他扫频光模式的损耗很大，无法在腔内起振，使得腔内只有被选中的扫频纵模起振，输出扫频速率为K的扫频激光；
    在激光器内有扫频速率为K的一个扫频纵模起振时，改变一个或同时改变多个光移频器的频移量，使得光波在谐振腔内的任意一个可能的闭合循环路径上经历的时间延迟T′和总频移量F′的比值均等于另一个常数K′：同步调整可调谐光滤波模块的通带频率的扫频速度为K′，通带的中心频率跟踪腔内该扫频纵模的频率，输出扫频速率为K′的扫频激光，使得在扫频速率从K变为K′的过程中，输出激光的功率和光的相位保持连续而不发生突变；
    按照一定的规律调整扫频速率，可以实现激光频率随时间以任意规律变化的扫频激光输出，包括任意固定频率的激光，频率随时间成三角波变化的光波，频率随时间成指数变化的光波和频率随时间成锯齿波变化的光波。
  9. 一种谐振式光移频滤波器，其特征在于，可以用于权利要求1-6任一项所述的扫频激光器系统，谐振式光移频滤波器的结构包括：在线性或者环形光学谐振腔内插入光移频模块，光波在该光学谐振腔内的循环时间为T2，光波循环一周经历的总移频量为F2，从而使得特定频率的光波能够低损耗地通过，而其他频率的光波具有高损耗，且能够低损耗地通过该谐振式光移频滤波器的光的频率随时间以速率变化。
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