CN108598856B - Femtosecond laser - Google Patents
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- CN108598856B CN108598856B CN201810187215.7A CN201810187215A CN108598856B CN 108598856 B CN108598856 B CN 108598856B CN 201810187215 A CN201810187215 A CN 201810187215A CN 108598856 B CN108598856 B CN 108598856B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1106—Mode locking
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
- H01S3/10023—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by functional association of additional optical elements, e.g. filters, gratings, reflectors
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Abstract
The utility model relates to a laser instrument field provides a femto second laser instrument, its characterized in that includes: the optical fiber loop is used for transmitting the first laser signal and the second laser signal; the optical fiber beam splitter is connected with the optical fiber loop and used for receiving the first laser signal and the second laser signal and changing the phase difference between the first laser signal and the second laser signal so as to enable the femtosecond laser to be self-mode-locked; and the free space optical path is connected with the optical fiber beam splitter and used for reflecting the received laser signal to the optical fiber beam splitter. The self-mode-locking method of the femtosecond laser is realized, the repetition frequency of the output laser pulse is improved, the system noise is reduced, and the robustness of the system is improved.
Description
Technical Field
The disclosure relates to the technical field of lasers, in particular to a femtosecond laser.
Background
The femtosecond laser is a core component of the optical frequency comb, the time domain output of the femtosecond laser is an ultra-narrow laser pulse sequence with a certain time interval, and the frequency domain of the femtosecond laser is a frequency comb with a certain frequency interval. The mode-locked femtosecond laser is used as a core component in a femtosecond optical frequency comb, and has two controlled frequency quantities, namely a repetition frequency and a carrier phase frequency. Because the two frequency controlled quantities are both in the microwave band, the femtosecond optical frequency comb can directly connect the light wave band and the microwave band to realize the direct measurement of the optical frequency. The emergence of the femtosecond optical frequency comb brings breakthrough development for the fields of precision spectroscopy, optical frequency standard, optical clock and the like.
The performance of the femtosecond laser is directly related to the performance index and reliability of the optical frequency comb: on one hand, the strength and phase noise level of the femtosecond laser determine the system stability of the optical frequency comb; on the other hand, the environmental sensitivity of the femtosecond laser determines the reliability (environmental adaptability) of the optical frequency comb. Aiming at the application research requirements of the optical frequency comb in the precise physical measurement and related fields, increasing the longitudinal mode interval of the femtosecond laser, reducing the system noise level of the femtosecond laser and improving the system robustness of the femtosecond laser are important research contents which are paid attention to by researchers.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
An object of the present disclosure is to provide a femtosecond laser, thereby overcoming, at least to some extent, one or more of the problems due to the limitations and disadvantages of the related art.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
According to an aspect of the present disclosure, there is provided a femtosecond laser including:
the optical fiber loop is used for transmitting the first laser signal and the second laser signal;
the optical fiber beam splitter is connected with the optical fiber loop and used for receiving the first laser signal and the second laser signal and changing the phase difference between the first laser signal and the second laser signal so as to enable the femtosecond laser to be self-mode-locked;
and the free space optical path is connected with the optical fiber beam splitter and used for reflecting the received laser signal to the optical fiber beam splitter.
In an exemplary embodiment of the present disclosure, the fiber loop includes a polarization maintaining erbium doped gain fiber, a single mode polarization maintaining fiber, and a wavelength division multiplexer.
In an exemplary embodiment of the present disclosure, the polarization maintaining erbium-doped gain fiber is located at an asymmetric position of the fiber loop for generating a nonlinear phase difference between the first laser signal and the second laser signal.
In an exemplary embodiment of the present disclosure, the fiber beam splitter includes a first fiber collimator, a second fiber collimator, a first half-wave plate, a second half-wave plate, a first polarization splitting prism, a second polarization splitting prism, and a non-reciprocal phase shifter.
In an exemplary embodiment of the present disclosure, the non-reciprocal phase shifter is located between the first polarization splitting prism and the second polarization splitting prism.
In an exemplary embodiment of the present disclosure, the non-reciprocal phase shifter includes a faraday rotator and an eighth-wave plate.
In an exemplary embodiment of the disclosure, the laser signal reflected by the free space optical path passes through the eighth wave plate to form a third laser signal and a fourth laser signal, and the phase difference between the third laser signal and the fourth laser signal is
The third laser signal and the fourth laser signal pass through the optical fiber loop and then pass through the eighth wave plate again to form a fifth laser signal and a sixth laser signal, and the phase difference between the fifth laser signal and the sixth laser signal is
In an exemplary embodiment of the present disclosure, the fifth laser signal and the sixth laser signal form a seventh laser signal in the second polarization beam splitter prism in an interference manner, a part of the seventh laser signal is reflected by the second polarization beam splitter prism to form output laser, and a part of the seventh laser signal is transmitted through the polarization beam splitter prism and enters the free space optical path.
In an exemplary embodiment of the present disclosure, the free-space optical path includes a laser mirror.
In an exemplary embodiment of the present disclosure, the free-space optical path includes an electro-optic modulation crystal, a laser mirror, and a piezo ceramic driver.
According to the technical scheme, the femtosecond laser in the exemplary embodiment of the disclosure has at least the following advantages and positive effects:
the femtosecond laser device comprises an optical fiber loop, an optical fiber beam splitter and a free space optical path, wherein the optical fiber beam splitter receives laser signals output from two output ends of the optical fiber loop and changes the phase difference between the two laser signals; meanwhile, the optical fiber beam splitter receives the laser signal reflected by the free space optical path. According to the method, on one hand, the phase difference between laser signals is changed, so that the femtosecond laser realizes self mode locking; on the other hand, the robustness of the femtosecond laser system is improved and the output of high repetition frequency pulse laser is realized through a nonlinear optical fiber amplification ring mirror formed by an optical fiber loop and an optical fiber beam splitter; in addition, the femtosecond laser device has the advantages of compact structure, simple packaging and stable operation.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.
Fig. 1 shows a schematic structural diagram of a femtosecond laser in an exemplary embodiment of the present disclosure;
FIG. 2 shows a schematic structural diagram of a femtosecond laser in an exemplary embodiment of the present disclosure;
FIG. 3 shows a schematic diagram of a non-reciprocal phase shifter in an exemplary embodiment of the present disclosure;
FIG. 4 illustrates a reflectivity curve of a non-linear amplifying fiber ring mirror in an exemplary embodiment of the present disclosure;
fig. 5 shows a mode-locked spectrum of a femtosecond laser in an exemplary embodiment of the present disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.
The terms "a," "an," "the," and "said" are used in this specification to denote the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first" and "second", etc. are used merely as labels, and are not limiting on the number of their objects.
Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities.
The initial optical frequency comb in the field was a system based on a titanium sapphire solid-state femtosecond laser, which has the advantages of low noise, capability of generating high-repetition-frequency comb teeth, and the like, but the system is large, the maintenance cost is high, the environmental adaptability of the system is poor, and the requirements of various application fields cannot be met. In recent years, with the progress of fiber laser technology, an optical frequency comb system constructed based on an ultrashort pulse fiber laser has characteristics of compact structure, high conversion efficiency, long-term stable operation and the like, and is widely applied to a plurality of application research fields, wherein application research of an erbium-doped fiber femtosecond laser is the most typical application research.
The mode locking techniques commonly used in erbium-doped fiber femtosecond lasers include saturable absorber mode locking, nonlinear polarization rotation mode locking, nonlinear fiber amplification ring mirror mode locking and the like, and have great influence on output mode locking pulse characteristics and laser system parameters.
In the femtosecond laser based on mode locking of the saturable absorber, the saturable absorber is made of several different materials such as a semiconductor saturable absorber mirror (SESAM), graphene, a carbon nano tube and the like. Because the saturable absorbers have slow saturable absorption characteristics, the output pulse of the laser is often in the picosecond order, and the noise level of the laser based on the mode locking mechanism of the saturable absorber is high. In addition, too high pump power can break down and damage the saturable absorber material, limiting the output power and pulse energy of femtosecond lasers based on mode locking of the saturable absorber.
The femtosecond laser based on the nonlinear polarization rotation mode locking mechanism generates nonlinear phase shift related to light intensity in an optical fiber, realizes mode locking through selection of a polarization state, can realize pulse output with dozens of femtosecond magnitude by carrying out dispersion management on an optical cavity, and has low noise. However, since the mode locking state of the femtosecond laser based on the nonlinear polarization rotation mode locking mechanism is close to the polarization state of the laser, the change of the mode locking state and even the unlocking can be caused by the change of the environment temperature, the vibration, the change of the fiber bending and the like. In addition, the femtosecond laser based on the nonlinear polarization rotation mode locking mechanism needs to search the mode locking state through the adjustment of a polarization device, and has no self-unlocking function.
The femtosecond laser based on the nonlinear amplification ring mirror mode locking generally adopts the design of a full polarization maintaining optical fiber, and has the advantages of high reliability, miniaturization and easy practicability. The laser has a self-unlocking function by adding the phase modulator in the optical cavity. The femtosecond laser based on nonlinear amplification ring mirror mode locking generally adopts a 8-shaped structure, and the 8-shaped structure is composed of an interference loop and an optical transmission loop and is an all-fiber structure. However, in the manufacturing process of the 8-shaped laser, various optical fiber devices are needed to be welded, the repetition frequency of general pulses is low, and a full-optical-fiber structure is adopted, so that a frequency control element is difficult to be added into a laser cavity.
In view of the problems of the femtosecond laser in the art, the present disclosure provides a femtosecond laser, fig. 1 shows a schematic structural diagram of the femtosecond laser, as shown in fig. 1, a femtosecond laser 100 includes an optical fiber loop 101, an optical fiber beam splitter 102, and a free space optical path 103, the optical fiber loop 101 is used for transmitting a first laser signal and a second laser signal; the optical fiber beam splitter 102 is connected to the optical fiber loop 101, and is configured to receive the first laser signal and the second laser signal and change a phase difference between the first laser signal and the second laser signal, so that the femtosecond laser 100 is self-mode-locked; the free space optical path 103 is connected to the optical fiber splitter 102, and is configured to reflect the received laser signal to the optical fiber splitter 102.
The optical fiber beam splitter in the femtosecond laser can change the phase difference between the first laser signal and the second laser signal output by the optical fiber loop, and meanwhile, the free space optical path can reflect the laser signal transmitted by the optical fiber beam splitter into the optical fiber beam splitter to form laser oscillation. The femtosecond laser realizes self mode locking on one hand, and the fiber loop and the fiber beam splitter form a nonlinear fiber amplification ring mirror light path on the other hand, so that the repetition frequency of output laser pulses is improved, and the performance of the femtosecond laser is further improved.
In an exemplary embodiment of the present disclosure, fig. 2 shows a schematic structural diagram of a femtosecond laser, and as shown in fig. 2, an optical fiber loop 101 includes a polarization-maintaining erbium-doped gain fiber 201, a single-mode polarization-maintaining fiber 202, and a wavelength division multiplexer 203. Wherein, the polarization-maintaining erbium-doped gain fiber 201 and the wavelength division multiplexer 203 are connected through a single-mode polarization-maintaining fiber 202; the polarization-maintaining erbium-doped gain fiber 201 is positioned at an asymmetric position in the fiber loop 101 and used for generating a nonlinear phase difference and maintaining a laser mode locking state; the wavelength division multiplexer 203 is configured to connect the pump source 204, transmit the pump laser to the polarization maintaining erbium-doped gain fiber 201 to generate laser, and specifically, the pump source 204 may emit pump laser with a wavelength of 980nm, and the erbium ions in the polarization maintaining erbium-doped gain fiber 201 absorb energy of the pump laser to implement energy level transition, and spontaneously radiate laser with a wavelength of 1550nm, and transmit the laser along the single-mode polarization maintaining fiber 202. The present disclosure can further improve the robustness of the femtosecond laser system by forming the femtosecond laser using the full polarization maintaining fiber structure.
Further, the dispersion in the optical cavity can be managed by polarization maintaining erbium doped gain fiber 201 and single mode polarization maintaining fiber 202. The polarization maintaining erbium doped gain fiber 201 can not only provide the required energy for the femtosecond laser 100, but also provide normal dispersion in the communication band (for example, 1550nm band), and the single mode polarization maintaining fiber 202 can provide anomalous dispersion in the communication band. According to the dispersion coefficients of the polarization-maintaining erbium-doped gain fiber 201 and the single-mode polarization-maintaining fiber 202, the dispersion in the laser oscillation cavity of the femtosecond laser 100 can be made to be 0 by adjusting the length ratio between the polarization-maintaining erbium-doped gain fiber 201 and the single-mode polarization-maintaining fiber 202, and the dispersion management of the cavity of the femtosecond laser 100 is realized.
In an exemplary embodiment of the present disclosure, as shown in fig. 2, the fiber beam splitter 102 includes a first fiber collimator 205, a second fiber collimator 206, a first half-wave plate 207, a second half-wave plate 208, a first polarization splitting prism 209, a second polarization splitting prism 210, and a non-reciprocal phase shifter 211, wherein the first fiber collimator 205 and the output end O of the fiber loop 1011Connected to the output O of the fiber loop 101 is a second fiber collimator 2062Connecting; the first half-wave plate 207 is positioned between the first fiber collimator 205 and the first polarization splitting prism 209, and the second half-wave plate 208 is positioned between the second fiber collimator 206 and the first polarization splitting prism 209; the non-reciprocal phase shifter 211 is located between the first polarization splitting prism 209 and the second polarization splitting prism 210. The fiber splitter 102 has two output ends O3And O4Wherein the output terminal O3Connected to the free space optical path 103 and having an output terminal O4For outputting laser pulses.
In an exemplary embodiment of the present disclosure, the free-space optical path 103 comprises a laser mirror, the free-space optical path 103 and the output end O of the fiber splitter 1023And a connection for reflecting the laser signal transmitted from the fiber beam splitter 102 into the fiber beam splitter 102 to form laser oscillation.
In an exemplary embodiment of the present disclosure, as shown in fig. 2, the free space optical path 103 includes an electro-optic modulation crystal 212, a laser mirror 213, and a piezoceramic driver 214, and the free space optical path 103 is in communication with an optical fiberOutput O of beam splitter 1023And (4) connecting. The electro-optical modulation crystal 212 is located at the transmission end of the second polarization beam splitter prism 210, the refractive index of the electro-optical modulation crystal can be changed along with the change of the loading voltage, and the optical path length in the free space optical path can be changed rapidly in a small range; the length of the piezoelectric ceramic driver 214 is controlled by the driving voltage, and the length of the optical path of the free space optical path 103 is changed at low speed in a large range; the electro-optic modulation crystal 212 and the piezoelectric ceramic driver 214 are simultaneously used as feedback elements for locking the laser repetition frequency, so that the laser pulse output by the femtosecond laser 100 can keep constant frequency, and the performance of the femtosecond laser is improved.
In an exemplary embodiment of the present disclosure, fig. 3 shows a schematic structural diagram of a non-reciprocal phase shifter, and as shown in fig. 3, the non-reciprocal phase shifter 211 includes a faraday rotator 301 and an eighth-wave plate 302, wherein the faraday rotator 301 is disposed near the first polarization splitting prism 209 and the eighth-wave plate 302 is disposed near the second polarization splitting prism 210.
In an exemplary embodiment of the present disclosure, the laser signal is linearly polarized light. The linearly polarized light entering the free space optical path 103 is reflected by the laser mirror 213 and passes through the output end O3The light is incident to the second polarization beam splitter 210 in the fiber beam splitter 102, and the light transmitted by the second polarization beam splitter 210 is vertically polarized light; rotating the eighth wave plate 302 to make the included angle between the fast axis of the eighth wave plate 302 and the vertical polarized light 45 degrees, and decomposing the vertical polarized light passing through the eighth wave plate 302 into a third linearly polarized light transmitted along the fast axis of the eighth wave plate and a fourth linearly polarized light transmitted along the slow axis, wherein the phase difference between the third linearly polarized light and the fourth linearly polarized light is
Then the horizontally polarized light is transmitted to the first polarization beam splitter prism 209 after passing through the Faraday rotator 301, the first polarization beam splitter prism 209 reflects the horizontally polarized light to enter the first collimator 205, and the vertically polarized light transmits to enter the second collimator 206; the first half-wave plate 207 is adjusted to make the horizontally polarized light parallel to the slow/fast axis of the first fiber collimator 205, and the second half-wave plate 208 is adjusted to make the vertically polarized lightThe polarized light is parallel to the slow/fast axis of the second fiber collimator 206; the horizontal polarized light enters the optical fiber loop 101 from the first optical fiber collimator 205, is transmitted to the second optical fiber collimator 206 after being wound for a circle, and the polarization state of the horizontal polarized light is changed into vertical polarization, so that the linearly polarized light which is incident on the first polarization splitting prism 209 again can be completely transmitted; similarly, the vertically polarized light enters the optical fiber loop 101 from the second optical fiber collimator 206, and is transmitted to the first optical fiber collimator 205 after being wound for a circle, and the polarization state of the vertically polarized light is changed into horizontal polarization, so that the linearly polarized light incident on the first polarization splitting prism 209 again can be totally reflected; two linearly polarized light beams oppositely transmitted in the optical fiber loop 101 are output by the first optical fiber collimator 205 and the second optical fiber collimator 206, then are collinearly transmitted again after passing through the first polarization beam splitter prism 209, and due to the nonreciprocity of the Faraday optical rotator 301, the phase difference of the two linearly polarized light beams is increased after passing through the eighth wave plate 302 again
Total phase difference of
The two linearly polarized lights interfere in the second polarization beam splitter prism 210 to form a third laser, and part of the third laser is reflected by the second polarization beam splitter prism 210 and passes through the output end O4Outputting; part of the third laser is transmitted through the second polarization beam splitter prism 210 and passes through the output end O3Into the free space optical path 103.
In the exemplary embodiment of the present disclosure, the fiber loop 101 and the fiber splitter 102 together form an interference loop of the femtosecond laser 100, and are also a nonlinear fiber amplification ring mirror optical path. When the nonlinear phase difference is zero, the reflectivity is not zero and the slope of the reflectivity curve is not zero, which are necessary conditions for realizing mode locking. Fig. 4 shows a reflectivity curve of the nonlinear fiber ring mirror, as shown in fig. 4, when the nonlinear phase difference is zero, the reflectivity is 1, that is, no laser pulse is output at the second polarization splitting prism 210, and the slope of the reflectivity curve at this position is zero, so that the femtosecond laser self-unlocking lock cannot be realized. While the present disclosure introduces non-mutually-distinct phase shifts in the interference loopThe reflectivity curve of the nonlinear fiber amplification ring mirror is correspondingly shifted to the right
When the nonlinear phase difference is zero, the reflectivity is 0.5, and the slope of the reflectivity curve is maximum, so that the femtosecond laser can automatically unlock the lock.
In an exemplary embodiment of the present disclosure, after the femtosecond laser unlocks the laser by reducing the pumping energy, the femtosecond laser may realize self-mode locking by increasing the pumping energy to the unlocking threshold; when the free space optical path is shielded to unlock the femtosecond laser, the shield can be removed to realize self-mode locking of the femtosecond laser.
As shown in fig. 2, the femtosecond laser of the present disclosure may be a "9" polarization-maintaining fiber mode-locked erbium-doped femtosecond laser composed of a fully polarization-maintaining fiber, which can increase the pulse repetition frequency of the pulse laser to 185MHz, increase the single-pulse energy to 0.03nJ, directly output pulse width less than 100fs, and output 3dB spectral width of 60nm, as shown in fig. 5, which is much larger than the output 3dB spectral width (less than 40nm) of the fully polarization-maintaining fiber mode-locked erbium-doped femtosecond laser in the related art. Meanwhile, compared with an 8-shaped cavity fully-polarization-maintaining optical fiber mode-locked erbium-doped femtosecond laser commonly used in the field, the 9-shaped cavity fully-polarization-maintaining optical fiber mode-locked erbium-doped femtosecond laser disclosed by the invention uses less optical fiber devices, and can greatly improve the repetition frequency of output laser pulses; and frequency control elements such as an electro-optic modulation crystal, a piezoelectric ceramic driver and the like can be easily added into a free space optical path, so that the system noise is reduced, and the robustness of the system is improved.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is to be limited only by the terms of the appended claims.
Claims (6)
1. A femtosecond laser comprising:
the optical fiber loop is used for transmitting the first laser signal and the second laser signal;
the optical fiber beam splitter comprises a first optical fiber collimator, a second optical fiber collimator, a first half wave plate, a second half wave plate, a first polarization splitting prism, a second polarization splitting prism and a non-reciprocal phase shifter, is connected with the optical fiber loop, and is used for receiving the first laser signal and the second laser signal and changing the phase difference between the first laser signal and the second laser signal so as to enable the femtosecond laser to be in self-mode locking;
the free space optical path comprises an electro-optic modulation crystal, a laser mirror and a piezoelectric ceramic driver, is connected with the optical fiber beam splitter and is used for reflecting a received laser signal to the optical fiber beam splitter;
wherein the non-reciprocal phase shifter comprises a Faraday rotator and an eighth-wave plate; the laser signal reflected by the free space optical path passes through the eighth wave plate to form a third laser signal and a fourth laser signal, and the phase difference between the third laser signal and the fourth laser signal is
The third laser signal and the fourth laser signal pass through the optical fiber loop and then pass through the eighth wave plate again to form a fifth laser signal and a sixth laser signal, and the phase difference between the fifth laser signal and the sixth laser signal is
2. The femtosecond laser according to claim 1, wherein the fiber loop comprises a polarization maintaining erbium-doped gain fiber, a single-mode polarization maintaining fiber, and a wavelength division multiplexer.
3. The femtosecond laser according to claim 2, wherein the polarization-maintaining erbium-doped gain fiber is located at an asymmetric position of the fiber loop for generating a nonlinear phase difference between the first laser signal and the second laser signal.
4. A femtosecond laser according to claim 1, wherein the non-mutually exclusive phase shifter is positioned between the first polarization splitting prism and the second polarization splitting prism.
5. A femtosecond laser as claimed in claim 1, wherein the fifth laser signal and the sixth laser signal interfere in the second polarization beam splitter prism to form a seventh laser signal, and the seventh laser signal is partially reflected by the second polarization beam splitter prism to form output laser light and partially transmitted through the polarization beam splitter prism into the free-space optical path.
6. A femtosecond laser according to claim 1, wherein the free-space optical path comprises a laser mirror.
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| CN112104429B (en) * | 2020-09-17 | 2021-08-17 | 电子科技大学 | Femtosecond laser-based underwater frequency transmission system and method |
| CN113300203B (en) * | 2021-07-26 | 2021-10-08 | 济南量子技术研究院 | Rapid mode locking method and system for optical frequency comb |
| CN116487984B (en) * | 2023-05-15 | 2024-08-23 | 密尔医疗科技(深圳)有限公司 | Nonreciprocal phase shifter and laser |
| CN117578173A (en) * | 2023-10-27 | 2024-02-20 | 北京大学长三角光电科学研究院 | Full polarization-maintaining O-shaped ultrashort pulse mode-locked fiber laser |
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| CN104035101B (en) * | 2014-06-12 | 2016-03-30 | 中国科学院上海技术物理研究所 | Based on the Synthetic Aperture Laser Radar system of intensity coding |
| CN107565354B (en) * | 2017-07-13 | 2020-01-17 | 西安电子科技大学 | High-power Kerr lens self-mode-locking laser of LD (laser diode) pump |
| CN107565358A (en) * | 2017-10-27 | 2018-01-09 | 西安电子科技大学 | A kind of high power kerr lenses self mode-locked laser of optical fiber laser pump |
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