920nm femtosecond pulse fiber laser system based on neodymium-doped fiber

Abstract

The invention relates to the technical field of laser control, and discloses a 920nm femtosecond pulse fiber laser system based on a neodymium-doped fiber. The system comprises a seed laser source system, a pre-chirp system, an amplification system and a compression system, the output end of the seed laser source system is connected with the input end of the pre-chirp system, the output end of the pre-chirp system is connected with the input end of the amplification system, and the output end of the amplification system is connected with the input end of the compression system. Through a pre-chirp management method, the seed pulse can simultaneously realize the improvement of the pulse energy and the violent broadening of the spectrum in the amplification process. And a wider spectrum can obtain a narrower pulse width after being subjected to time domain compression. The narrower the width of the pulse means that the energy is more concentrated, so that the peak power of the laser pulse output after compression is higher, and the problem that narrow pulse width and high energy output cannot be simultaneously realized in the 920nm wave band in the existing fiber laser technology is solved.

Description

Technical Field

[0001] The present application relates to the field of laser control technology, and in particular, to a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber. Background Art

[0002] Ultrafast lasers are widely used in scientific research, industrial production, medical treatment and other fields. Wavelength, as one of the important parameters of lasers, determines the application field of lasers to a certain extent. Among them, femtosecond pulses with narrow pulse width, high energy and wide spectrum at a wavelength of 920nm have important applications in biomedical imaging, terahertz wave generation, single quantum dot light sources and other fields. At present, the most widely used laser in the 920nm band is titanium sapphire solid laser, but titanium sapphire solid laser and most fiber laser systems in this band have problems of insufficient compactness and stability. Moreover, the fiber laser system in this band cannot meet the requirements of achieving high single pulse energy output under narrow pulse width conditions. Therefore, how to realize a fiber laser system with compact structure, good stability, narrow pulse width and high single pulse energy in the 920nm band is a difficulty in the current laser field. Summary of the invention

[0003] The present application provides a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0004] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by the practice of the present application.

[0005] According to one aspect of an embodiment of the present application, a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber is proposed, wherein the 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber comprises: a seed laser source system, a pre-chirp system, an amplification system, and a compression system; the output end of the seed laser source system is connected to the input end of the pre-chirp system, the output end of the pre-chirp system is connected to the input end of the amplification system, and the output end of the amplification system is connected to the input end of the compression system;

[0006] Wherein, the seed laser source system is used to output a seed pulse to the pre-chirp system, the pre-chirp system is used to add a pre-chirp amount to the seed pulse, and output the seed pulse with the pre-chirp amount added to the amplification system, so that the amplification system performs spectral broadening and energy amplification on the seed pulse with the pre-chirp amount added, and inputs the spectrally broadened and energy-amplified seed pulse into the compression system, so that the compression system compresses the spectrally broadened and energy-amplified seed pulse in the time domain and emits a laser pulse.

[0007] In one embodiment of the present application, based on the above scheme, the pre-chirp system includes a first chirped fiber Bragg grating and a circulator, the first end of the circulator is connected to the output end of the seed laser source system, the second end of the circulator is connected to the input end of the first chirped fiber Bragg grating, and the third end of the circulator is connected to the input end of the amplification system;

[0008] The first end of the circulator receives a seed pulse output from the seed laser source system, and inputs the seed pulse to the first chirped fiber Bragg grating through the second end of the circulator. The first chirped fiber Bragg grating adds the pre-chirp amount to the received seed pulse, and outputs the seed pulse after the pre-chirp amount is added to the amplification system through the third end of the circulator.

[0009] In one embodiment of the present application, based on the above scheme, the seed laser source system includes a second chirped fiber Bragg grating, a single-mode 808nm laser diode, an 808nm isolator, an 808 / 920nm wavelength division multiplexer, a single-mode neodymium-doped fiber, a first 920nm isolator, an optical coupler and a non-reciprocal phase shifter; the output end of the 808 / 920nm wavelength division multiplexer is connected to one end of the single-mode neodymium-doped fiber, the other end of the single-mode neodymium-doped fiber is connected to the first end of the optical coupler, and the second end of the optical coupler is connected to the input end of the second chirped fiber Bragg grating; the output end of the second chirped fiber Bragg grating is connected to the first 920nm isolator. The input end of the non-reciprocal phase shifter is connected to the input end of the 808 / 920nm wavelength division multiplexer, and the input end of the 808 / 920nm wavelength division multiplexer is also connected to the output end of the 808nm isolator; the input end of the 808nm isolator is connected to the output end of the single-mode 808nm laser diode; the single-mode 808nm laser diode is used as a pump source, and the fourth end of the optical coupler is used as a detection end.

[0010] In one embodiment of the present application, based on the aforementioned scheme, the amplification system includes a pre-amplification unit and a main amplification unit, the input end of the pre-amplification unit is connected to the third end of the circulator, and the output end of the pre-amplification unit is connected to the input end of the main amplification unit; the output end of the main amplification unit is connected to the input end of the compression system.

[0011] In one embodiment of the present application, based on the aforementioned scheme, the pre-amplification unit includes a first multi-mode 808nm laser diode, a first beam combiner, a double-clad W-type neodymium-doped optical fiber, a first pump power stripping device and a second 920nm isolator; the input end of the first beam combiner is connected to the input end of the first multi-mode 808nm laser diode and the third end of the circulator, the output end of the first beam combiner is connected to the input end of the first pump power stripping device through the double-clad W-type neodymium-doped optical fiber, the output end of the first pump power stripping device is connected to the input end of the second 920nm isolator, and the output end of the second 920nm isolator is connected to the main amplification unit.

[0012] In one embodiment of the present application, based on the aforementioned scheme, the main amplification unit includes a second multi-mode 808nm laser diode, a second beam combiner, a 20 / 80 neodymium-doped optical fiber and a second pump power stripping device; the input end of the second beam combiner is connected to the output end of the second 920nm isolator and the output end of the second multi-mode 808nm laser diode; the output end of the second beam combiner is connected to the input end of the second pump power stripping device through the 20 / 80 neodymium-doped optical fiber, and the output end of the second pump power stripping device is connected to the input end of the compression system.

[0013] In one embodiment of the present application, based on the above scheme, the compression system includes a collimator, a first reflector, a second reflector, a dichroic mirror and a transmission grating pair, the collimator, the dichroic mirror, the second reflector, the transmission grating pair and the first reflector are arranged in sequence, and the input end of the collimator is connected to the output end of the second pump power stripping device;

[0014] The seed pulse output from the output end of the second pump power stripping device passes through the collimator, the dichroic mirror, the transmission grating pair, the first reflector, the transmission grating pair and the second reflector in sequence, and is emitted from the second reflector.

[0015] Beneficial effects of this application:

[0016] The present application can output a seed pulse to the pre-chirp system through a seed laser source system, and add a pre-chirp amount to the seed pulse through the pre-chirp system, and output the seed pulse with the pre-chirp amount added to the amplification system, thereby realizing spectral broadening and energy amplification of the seed pulse with the pre-chirp amount added in the amplification system.

[0017] Under the condition of spectrum broadening, according to the Fourier transform relationship between spectrum width and pulse width, the wider the spectrum width, the narrower the pulse width obtained after compression in the time domain. The narrower the pulse width, the more concentrated the energy. Therefore, by compressing the seed pulse in the time domain by the compression system, a seed pulse with narrow pulse width and high peak power can be obtained, thereby solving the technical problem that the existing fiber laser technology cannot achieve high single pulse energy output under the condition of narrow pulse width in the 920nm band. At the same time, the system compactness and stability of the 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber proposed in this application are relatively high. Therefore, the system can provide a better light source for scientific research and practical applications in the fields of biomedical imaging, terahertz wave generation, single quantum dot light source, etc.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0020] Figure 1 A specific schematic diagram of a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber provided in an embodiment of the present application;

[0021] Figure 2 An overall schematic diagram of a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber provided in an embodiment of the present application;

[0022] Figure 3 This is a comparison diagram of the intensity distribution of the seed pulse output by the amplification system before compression and the laser pulse output after compression provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] Example embodiments are now described more fully in conjunction with reference to the accompanying drawings, wherein the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; on the contrary, these embodiments are provided so that this application will be more comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art.

[0024] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the present application.

[0025] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or micro-control node devices.

[0026] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0027] It should be noted that the "multiple" mentioned in this article refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0028] The following is a detailed introduction to the technical background of the embodiments of the present application:

[0029] Ultrafast lasers are widely used in scientific research, industrial production, medical treatment and other fields. Wavelength, as one of the important parameters of lasers, determines the application field of lasers to a certain extent. Among them, femtosecond pulses with narrow pulse width, high energy and wide spectrum at a wavelength of 920nm have important applications in biomedical imaging, terahertz wave generation, single quantum dot light source and other fields. At present, the most widely used laser in the 920nm band is titanium sapphire solid laser. In fiber laser systems, wavelength conversion technology and direct use of neodymium-doped optical fiber can also obtain femtosecond pulses with a wavelength of 920nm. Wavelength conversion technology uses high-power femtosecond pulses in the 1.0μm and 1.5μm bands to perform nonlinear spectral broadening to obtain femtosecond pulses of 920nm, or frequency-doubles 1840nm femtosecond pulses to obtain femtosecond pulses of 920nm; direct use of neodymium-doped optical fiber relies on the three-level transition of neodymium ions to generate femtosecond pulses of 920nm.

[0030] In the process of studying the prior art, the inventor of the present invention found that the current titanium sapphire solid laser and most 920nm fiber laser systems have the problems of insufficient compactness and stability. In addition, in the 920nm band, the fiber laser system cannot simultaneously meet the conditions of pulse width less than 100fs and single pulse energy greater than 10nJ. Therefore, how to realize a 920nm fiber laser system with compact structure, good stability, narrow pulse width and high single pulse energy is a difficulty in the current laser field.

[0031] The implementation details of the technical solution of the embodiment of the present application are described in detail below:

[0032] According to one aspect of the embodiments of the present application, a 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber is provided. Figure 1 The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber provided in the embodiment of the present application is Figure 2 The overall block diagram of the 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber provided in the embodiment of the present application is as follows:

[0033] The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber includes: a seed laser source system, a pre-chirp system, an amplification system and a compression system; the output end of the seed laser source system is connected to the input end of the pre-chirp system, the output end of the pre-chirp system is connected to the input end of the amplification system, and the output end of the amplification system is connected to the input end of the compression system;

[0034] Wherein, the seed laser source system is used to output a seed pulse to the pre-chirp system, the pre-chirp system is used to add a pre-chirp amount to the seed pulse, and output the seed pulse with the pre-chirp amount added to the amplification system, so that the amplification system performs spectral broadening and energy amplification on the seed pulse with the pre-chirp amount added, and inputs the spectrally broadened and energy-amplified seed pulse into the compression system, so that the compression system compresses the spectrally broadened and energy-amplified seed pulse in the time domain and emits a laser pulse.

[0035] Specifically, the seed laser source system outputs a seed pulse to the pre-chirp system, and adds a pre-chirp amount to the seed pulse through the pre-chirp system, and outputs the seed pulse with the pre-chirp amount added to the amplification system. After the seed pulse with the pre-chirp amount added enters the amplification system, under the combined effect of the nonlinear effect and the additional pre-chirp amount, a strong broadening of the seed pulse spectrum can be achieved. At the same time, the amplification system also excites the double-clad W-type neodymium-doped fiber and the 20 / 80 neodymium-doped fiber through the first multi-mode 808nm laser diode and the second multi-mode 808nm laser diode to increase the energy of the seed pulse.

[0036] Under the condition that the spectrum (frequency domain) of the seed pulse is broadened, the seed pulse is input into the compression system. According to the Fourier transform relationship between the spectrum width (frequency domain) and the pulse width (time domain), a wider spectrum width can be compressed in the time domain to obtain a narrower pulse width. The narrower the pulse width, the more concentrated the energy. Therefore, by compressing the seed pulse in the time domain through the compression system, a seed pulse with a narrow pulse width and high peak power can be obtained, thereby solving the technical problem that the existing fiber laser technology cannot achieve high single pulse energy output under the condition of narrow pulse width in the 920nm band. At the same time, the 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber proposed in this application has high system compactness and stability.

[0037] Please refer to Figure 3 As shown, Figure 3 The left side shows the intensity distribution of the seed pulse output by the amplification system before compression. Figure 3 The right side is the intensity distribution diagram of the laser pulse output after compression. By comparison, it can be seen that the seed pulse output by the amplification system has a wider pulse width, so the energy is more dispersed; the compressed seed pulse has a narrower pulse width, so the energy is more concentrated. Therefore, the seed pulse output by the amplification system can achieve a narrow pulse width and high peak power pulse output after being compressed by the compression system.

[0038] Therefore, the system can provide a better light source for scientific research and practical applications in the fields of biomedical imaging, terahertz wave generation, and single quantum dot light sources.

[0039] In one embodiment of the present application, the pre-chirp system includes a first chirped fiber Bragg grating and a circulator, wherein a first end of the circulator is connected to an output end of the seed laser source system, a second end of the circulator is connected to an input end of the first chirped fiber Bragg grating, and a third end of the circulator is connected to an input end of the amplification system;

[0040] The first end of the circulator receives a seed pulse output from the seed laser source system, and inputs the seed pulse to the first chirped fiber Bragg grating through the second end of the circulator. The first chirped fiber Bragg grating adds the pre-chirp amount to the received seed pulse, and outputs the seed pulse after the pre-chirp amount is added to the amplification system through the third end of the circulator.

[0041] Specifically, the first end of the circulator can be specifically Figure 1 The circulator e end in the circulator, the second end of the circulator can be specifically Figure 1 The circulator f end in the circulator, the third end of the circulator can be specifically Figure 1 The output end of the seed laser source is connected to the e end of the circulator, the f end of the circulator is connected to the input end of the first chirped fiber Bragg grating, and the g end of the circulator serves as the output of the pre-chirp system.

[0042] The circulator allows the seed pulse output by the seed laser source system to be transmitted unidirectionally in the pre-chirp system. The seed pulse enters from the e end of the circulator, is input to the first chirped fiber Bragg grating through the f end of the circulator, and is output to the amplification system from the g end of the circulator after the first chirp fiber Bragg grating is additionally chirped. The first chirp fiber Bragg grating is used to introduce additional chirp. The seed pulse enters the first chirp fiber Bragg grating through the f end of the circulator. After the first chirp fiber Bragg grating introduces negative chirp, the seed pulse is reflected back to the circulator and output to the amplification system from the g end of the circulator.

[0043] In one embodiment of the present application, the seed laser source system includes a second chirped fiber Bragg grating, a single-mode 808nm laser diode, an 808nm isolator, an 808 / 920nm wavelength division multiplexer, a single-mode neodymium-doped fiber, a first 920nm isolator, an optical coupler and a non-reciprocal phase shifter; the output end of the 808 / 920nm wavelength division multiplexer is connected to one end of the single-mode neodymium-doped fiber, the other end of the single-mode neodymium-doped fiber is connected to the first end of the optical coupler, and the second end of the optical coupler is connected to the input end of the second chirped fiber Bragg grating; the output end of the second chirped fiber Bragg grating is connected to the input end of the first 920nm isolator. The input end of the non-reciprocal phase shifter is connected to the third end of the optical coupler, the output end of the non-reciprocal phase shifter is connected to the input end of the 808 / 920nm wavelength division multiplexer, and the input end of the 808 / 920nm wavelength division multiplexer is also connected to the output end of the 808nm isolator; the input end of the 808nm isolator is connected to the output end of the single-mode 808nm laser diode; the single-mode 808nm laser diode is used as a pump source, and the fourth end of the optical coupler is used as a detection end.

[0044] Specifically, the first end of the optical coupler can be specifically Figure 1 The optical coupler a end in the optical coupler, the second end of the optical coupler can be specifically Figure 1 The third end of the optical coupler can be specifically Figure 1 The fourth end of the optical coupler can be specifically Figure 1 The d end of the optocoupler.

[0045] Specifically, through the light splitting effect of the optical coupler, the d-end of the optical coupler can detect the working state of the seed laser source system, and thereby determine whether the seed laser source system works normally.

[0046] Specifically, the seed laser source system is a laser built based on a nonlinear amplifying loop mirror (NALM). A single-mode 808nm laser diode is used as a pump source; an 808nm isolator prevents back-reflected light from damaging the laser diode; a single-mode neodymium-doped fiber is used as a gain medium; an optical coupler is used to redistribute the optical power; the second chirped fiber Bragg grating controls the dispersion in the laser cavity and also acts as a bandpass filter; the first 920nm isolator prevents back-reflected light from affecting the laser cavity; a non-reciprocal phase shifter is used to enable the laser cavity to self-start better; by adjusting the output power of the single-mode 808nm pump source, the laser can be operated in a mode-locked state and achieve single pulse output.

[0047] In one embodiment of the present application, the amplification system includes a pre-amplification unit and a main amplification unit, the input end of the pre-amplification unit is connected to the third end of the circulator, and the output end of the pre-amplification unit is connected to the input end of the main amplification unit; the output end of the main amplification unit is connected to the input end of the compression system.

[0048] Specifically, the amplification system composed of the pre-amplification unit and the main amplification unit can effectively broaden the spectrum and increase the energy of the seed pulse. The function of the amplification system is to achieve spectral broadening and energy amplification of the signal pulse, and the pre-amplification unit and the main amplification unit can achieve double spectral broadening and secondary energy amplification of the signal pulse.

[0049] In one embodiment of the present application, the pre-amplification unit includes a first multi-mode 808nm laser diode, a first beam combiner, a double-clad W-type neodymium-doped optical fiber, a first pump power stripping device and a second 920nm isolator; the input end of the first beam combiner is connected to the input end of the first multi-mode 808nm laser diode and the third end of the circulator, the output end of the first beam combiner is connected to the input end of the first pump power stripping device through the double-clad W-type neodymium-doped optical fiber, the output end of the first pump power stripping device is connected to the input end of the second 920nm isolator, and the output end of the second 920nm isolator is connected to the main amplification unit.

[0050] In one embodiment of the present application, the main amplification unit includes a second multi-mode 808nm laser diode, a second beam combiner, a 20 / 80 neodymium-doped optical fiber and a second pump power stripping device; the input end of the second beam combiner is connected to the output end of the second 920nm isolator and the output end of the second multi-mode 808nm laser diode; the output end of the second beam combiner is connected to the input end of the second pump power stripping device through the 20 / 80 neodymium-doped optical fiber, and the output end of the second pump power stripping device is connected to the input end of the compression system.

[0051] Specifically, the first multimode 808nm laser diode and the second multimode 808nm laser diode are used as pump sources; the first beam combiner and the second beam combiner are used to couple the pump light emitted by the pump source and the signal light from the seed pulse; the double-clad W-type neodymium-doped fiber and the 20 / 80 neodymium-doped fiber are used as gain media; the second 920nm isolator is used to eliminate the influence of back-reflected light on the pre-amplification unit; the first pump power stripping device and the second pump power stripping device are used to strip the pump light that is not absorbed by the gain fiber, so the spectrum broadening and energy improvement of the signal light can be achieved through the amplification system.

[0052] In one embodiment of the present application, the compression system comprises a collimator, a first reflector, a second reflector, a dichroic mirror and a transmission grating pair, wherein the collimator, the dichroic mirror, the second reflector, the transmission grating pair and the first reflector are sequentially arranged at intervals, and an input end of the collimator is connected to an output end of the second pump power stripping device;

[0053] The seed pulse output from the output end of the second pump power stripping device passes through the collimator, the dichroic mirror, the transmission grating pair, the first reflector, the transmission grating pair and the second reflector in sequence, and is emitted from the second reflector.

[0054] Specifically, the optical path of the seed pulse output from the output end of the second pump power stripping device is: collimator→dichroic mirror→transmission grating pair→first reflector→transmission grating pair→second reflector, and finally the second reflector emits a high-energy, narrow-pulse-width laser pulse.

[0055] Specifically, the function of the compression system is to perform dispersion compensation to obtain high-quality compressed pulses. The collimator is used to introduce the light of the seed pulse into space; the dichroic mirror is used to filter out the amplified spontaneous radiation with a wavelength of 1064nm; the transmission grating pair is used for dispersion compensation; the first reflector and the second reflector are used to change the direction of the spatial light path. According to the Fourier transform relationship, the wider the spectrum of the seed pulse is, the narrower the pulse width is after compression in the time domain. The narrower the pulse width means that the energy is more concentrated. Therefore, the compression system can achieve femtosecond-level narrow pulse width and high peak power pulse output. It should be noted that in the embodiments of the present application, all optical fibers (20 / 80 neodymium-doped optical fiber, single-mode neodymium-doped optical fiber, double-clad W-type neodymium-doped optical fiber) and optical fiber devices are fusion-coupled.

[0056] In summary, by means of the above structure, the embodiment of the present application has the following beneficial effects:

[0057] 1. The embodiment of the present application adopts a seed laser source system, a pre-chirp system and an amplification system with a fully polarization-maintaining all-fiber structure, which improves the compactness and stability of the system and realizes the miniaturization and practicality of a femtosecond pulse fiber laser system in the 920nm band.

[0058] 2. This technical solution improves the upper limit of the pulse energy of the fiber laser system in the 920nm band with a pulse width of less than 100fs, while meeting the conditions of a pulse width of less than 100fs and a single pulse energy higher than 10nJ, providing a better quality laser source for scientific research and practical applications in the fields of biomedical imaging, terahertz wave generation, and single quantum dot light sources.

[0059] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application; unless otherwise clearly specified and limited, the terms "install", "connect", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediary medium, and it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0060] The device includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device; in the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or device that includes the elements.

[0061] The above description is only a specific implementation mode of the present application, which is convenient for those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in this article can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in this article, but will conform to the widest scope consistent with the principles and novel features of the application in this article.

Claims

1. A 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber, characterized in that: include: Seed laser source system, pre-chirp system, amplification system and compression system; The output end of the seed laser source system is connected to the input end of the pre-chirp system, the output end of the pre-chirp system is connected to the input end of the amplification system, and the output end of the amplification system is connected to the input end of the compression system; Wherein, the seed laser source system is used to output a seed pulse to the pre-chirp system, the pre-chirp system is used to add a pre-chirp amount to the seed pulse, and output the seed pulse with the pre-chirp amount added to the amplification system, so that the amplification system performs spectral broadening and energy amplification on the seed pulse with the pre-chirp amount added, and inputs the spectrally broadened and energy-amplified seed pulse into the compression system, so that the compression system compresses the spectrally broadened and energy-amplified seed pulse in the time domain and emits a laser pulse.

2. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 1, characterized in that: The pre-chirp system comprises a first chirped fiber Bragg grating and a circulator, wherein a first end of the circulator is connected to an output end of the seed laser source system, a second end of the circulator is connected to an input end of the first chirped fiber Bragg grating, and a third end of the circulator is connected to an input end of the amplification system; The first end of the circulator receives a seed pulse output from the seed laser source system, and inputs the seed pulse to the first chirped fiber Bragg grating through the second end of the circulator. The first chirped fiber Bragg grating adds the pre-chirp amount to the received seed pulse, and outputs the seed pulse added with the pre-chirp amount to the amplification system through the third end of the circulator.

3. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 2, characterized in that: The seed laser source system comprises a second chirped fiber Bragg grating, a single-mode 808nm laser diode, an 808nm isolator, an 808 / 920nm wavelength division multiplexer, a single-mode neodymium-doped fiber, a first 920nm isolator, an optical coupler and a non-reciprocal phase shifter; the output end of the 808 / 920nm wavelength division multiplexer is connected to one end of the single-mode neodymium-doped fiber, the other end of the single-mode neodymium-doped fiber is connected to the first end of the optical coupler, and the second end of the optical coupler is connected to the input end of the second chirped fiber Bragg grating; the output end of the second chirped fiber Bragg grating is connected to the input end of the first 920nm isolator, and the output end of the second chirped fiber Bragg grating is connected to the input end of the first 920nm isolator. The output end of the first 920nm isolator is connected to the first end of the circulator as the output end of the seed laser source system; the input end of the non-reciprocal phase shifter is connected to the third end of the optical coupler, the output end of the non-reciprocal phase shifter is connected to the input end of the 808 / 920nm wavelength division multiplexer, and the input end of the 808 / 920nm wavelength division multiplexer is also connected to the output end of the 808nm isolator; the input end of the 808nm isolator is connected to the output end of the single-mode 808nm laser diode; the single-mode 808nm laser diode is used as a pump source, and the fourth end of the optical coupler is used as a detection end.

4. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 3 is characterized in that: The amplification system includes a pre-amplification unit and a main amplification unit, the input end of the pre-amplification unit is connected to the third end of the circulator, the output end of the pre-amplification unit is connected to the input end of the main amplification unit; the output end of the main amplification unit is connected to the input end of the compression system.

5. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 4, characterized in that: The pre-amplification unit includes a first multi-mode 808nm laser diode, a first beam combiner, a double-clad W-type neodymium-doped optical fiber, a first pump power stripping device, and a second 920nm isolator; the input end of the first beam combiner is connected to the input end of the first multi-mode 808nm laser diode and the third end of the circulator, the output end of the first beam combiner is connected to the input end of the first pump power stripping device through the double-clad W-type neodymium-doped optical fiber, the output end of the first pump power stripping device is connected to the input end of the second 920nm isolator, and the output end of the second 920nm isolator is connected to the main amplification unit.

6. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 5, characterized in that: The main amplification unit includes a second multi-mode 808nm laser diode, a second beam combiner, a 20 / 80 neodymium-doped optical fiber and a second pump power stripping device; the input end of the second beam combiner is connected to the output end of the second 920nm isolator and the output end of the second multi-mode 808nm laser diode; the output end of the second beam combiner is connected to the input end of the second pump power stripping device through the 20 / 80 neodymium-doped optical fiber, and the output end of the second pump power stripping device is connected to the input end of the compression system.

7. The 920nm femtosecond pulse fiber laser system based on neodymium-doped fiber according to claim 6, characterized in that: The compression system comprises a collimator, a first reflector, a second reflector, a dichroic mirror and a transmission grating pair, wherein the collimator, the dichroic mirror, the second reflector, the transmission grating pair and the first reflector are sequentially arranged at intervals, and an input end of the collimator is connected to an output end of the second pump power stripping device; The seed pulse output from the output end of the second pump power stripping device passes through the collimator, the dichroic mirror, the transmission grating pair, the first reflector, the transmission grating pair and the second reflector in sequence, and is emitted from the second reflector.

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