Short-wavelength pulse laser

Abstract

The invention relates to the technical field of short-wavelength lasers, and discloses a short-wavelength pulse laser, which comprises a super-fluorescence optical fiber light source used for outputting first laser of which the spectral width range is a first width range; the narrow-band filter is used for performing narrow-band filtering on the first laser to obtain second laser of which the spectral width range is a second width range, and the second width range is smaller than the first width range; the filtering and amplifying unit is used for carrying out narrow-band filtering and power amplification on the second laser to obtain third laser of which the spectral width range is a third width range, and the third width range is smaller than the second width range; the light modulator is used for modulating the third laser and outputting target pulse laser; and the frequency multiplication device is used for carrying out frequency multiplication on the target pulse laser to obtain short-wavelength pulse laser. According to the invention, the narrow spectral width can still be maintained after amplification, the output short-wavelength pulse laser is stable, and the frequency doubling efficiency of 50-60% can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of short-wavelength lasers, and in particular to a short-wavelength pulse laser. Background Art

[0002] Currently, there are two ways to implement nanosecond pulse short-wavelength lasers, mainly divided into solid-state solutions and optical fiber solutions. Among them, the solid-state solution has more and more complex spatial devices due to its structural characteristics, and its stability is relatively poor. In general, solutions above 100W are difficult to implement.

[0003] Another fiber solution has the advantages of high stability and good heat dissipation. In order to achieve a higher frequency doubling efficiency, the spectral width of the signal light source is generally required to be narrower, which is related to the small allowable bandwidth of the nonlinear crystal. Generally, the wider the fundamental frequency spectrum, the greater the phase mismatch and the lower the frequency doubling efficiency.

[0004] Therefore, one of the current solutions to realize nanosecond short-wavelength lasers based on fiber solutions is to use a fiber resonant cavity composed of high and low reflection narrowband gratings to output narrowband continuous lasers and then cut the waves based on an external modulator to produce pulsed light. Due to the use of narrowband gratings, the continuous light in the continuous resonant cavity is unstable and prone to generating chaotic self-pulses, resulting in uneven pulse light output after cutting, large fluctuations in pulse sequence, and unstable pulse light, which affects the performance of the laser and limits the development of this type of pulsed laser. That is, the narrowband light source output by the resonant cavity has sub-pulses, which are prone to sub-pulse spikes and are not suitable for outputting stable pulsed light.

[0005] In summary, there is an urgent need for a laser that is suitable for generating short-wavelength pulses to solve the technical problem of unstable output pulse light. Summary of the invention

[0006] In view of this, the present invention provides a short-wavelength pulse laser to solve or partially solve the technical problem of unstable output pulse light of the existing laser.

[0007] The technical solution proposed by the present invention is as follows:

[0008] The first aspect of the present invention provides a short-wavelength pulse laser, comprising: a super-fluorescent fiber light source (SFS), used to output a first laser with a spectral width range of a first width range; a narrow-band filter, used to perform narrow-band filtering on the first laser to obtain a second laser with a spectral width range of a second width range, the second width range being smaller than the first width range; a filtering and amplifying unit, used to perform narrow-band filtering and power amplification on the second laser to obtain a third laser with a spectral width range of a third width range, the third width range being smaller than the second width range; an optical modulator, used to modulate the third laser to output a target pulse laser; and a frequency doubling device, used to perform frequency doubling on the target pulse laser to obtain a short-wavelength pulse laser.

[0009] The short-wavelength pulse laser of the embodiment of the present invention utilizes the unstable and random phase relationship of the spectrum of the superfluorescent fiber light source, so that the spectrum components per unit width in the spectrum are correspondingly more stable in the time domain than the laser output by the ordinary laser resonant cavity, and there will be no violent sub-pulse phenomenon due to mode interference. The superfluorescent fiber light source is used as a pulse seed light source, and the first laser output by the superfluorescent fiber light source is filtered in sequence through a narrowband filter and a filter amplifier unit to obtain a second laser and a third laser with successively reduced spectrum widths, and then pulse modulated by an optical modulator to output a pulse laser with a narrow line width and a high side mode suppression ratio, and finally the target pulse laser is frequency-doubled by a frequency doubling device to obtain a high-power short-wavelength pulse laser. The present invention can achieve that a relatively narrow spectrum width can be maintained after amplification, the output short-wavelength pulse laser is stable, and a frequency doubling efficiency of up to 50%-60% can be achieved.

[0010] Further, the first width ranges from 10nm to 40nm, the second width ranges from 1nm to 2nm, and the third width ranges from 0.01nm to 0.5nm.

[0011] In this method, the 10nm-40nm laser output by the superfluorescent fiber light source is modulated into a narrow-band light source of 1nm-2nm for the first time, and then modulated into a narrow-band light source in the range of 0.01nm-0.5nm for the second time. It can be pulse-modulated by an optical modulator to output a pulse seed light with a narrow linewidth and a high side mode suppression ratio in the range of 0.01nm-0.5nm, thereby suppressing the nonlinear spectrum broadening as much as possible during the amplification process, and finally maintaining a narrow output spectrum while obtaining a large pulse energy, making it very suitable as a fundamental frequency light source for nonlinear frequency conversion, and obtaining a higher frequency doubling efficiency and more stable laser output, thereby improving the power and stability of short-pulse lasers.

[0012] Furthermore, the central wavelength of the first laser is 1030 nm or 1064 nm.

[0013] In this method, by setting the central wavelength of the first laser to 1030nm or 1064nm, green light pulses can be output after subsequent frequency doubling, which can be widely used in various industrial scenarios.

[0014] Furthermore, the superfluorescent fiber light source includes a first active optical fiber, a first wavelength division multiplexer and a first pump source, one end of the first active optical fiber is provided with an anti-return light end face with a preset tilt angle, the other end of the first active optical fiber is connected to the wavelength division multiplexer, the first pump source is used to input the first pump light to the first active optical fiber through the first wavelength division multiplexer, and the output end of the wavelength division multiplexer is connected to the narrowband filter.

[0015] In this manner, by providing an anti-return light end face with a preset tilt angle at one end of the first active optical fiber and inputting the first pump light using the first pump source, laser can be effectively generated and amplified, thereby achieving efficient laser output.

[0016] Furthermore, the superfluorescent fiber light source further includes a first isolator, which is arranged between the output end of the first wavelength division multiplexer and the narrowband filter.

[0017] In this manner, by adding the first isolator, the reverse propagating light can be reduced, the internal components of the laser can be protected, and the stability of the system and the quality of the laser output can be improved.

[0018] Furthermore, the filtering and amplifying unit includes an optical fiber circulator, a second active optical fiber, a second wavelength division multiplexer, a second pump source and a narrowband high-reflection grating. The first end of the optical fiber circulator is connected to the narrowband filter, the second end of the optical fiber circulator is connected to one end of the second active optical fiber, and the other end of the second active optical fiber is connected to the wavelength division multiplexer. The second pump source is used to input the second pump light to the second active optical fiber through the second wavelength division multiplexer. The narrowband high-reflection grating is used to narrow-band filter the laser output by the second wavelength division multiplexer and reflect it back to the second wavelength division multiplexer, and enter the second active optical fiber through the second wavelength division multiplexer.

[0019] In this way, through the design of a fiber circulator, a second active fiber, a second wavelength division multiplexer, a second pump source and a narrowband high-reflection grating, narrowband filtering and power amplification of the laser are achieved, the power of the laser is increased and the spectral width range is further reduced.

[0020] Further, the optical modulator includes an acousto-optic modulator or an electro-optic modulator.

[0021] In this method, two modulation modes are provided for selection, and a suitable modulator can be selected according to different application requirements, thereby improving the flexibility of the system.

[0022] Furthermore, the short-wavelength pulse laser further includes a second isolator, which is arranged between the optical modulator and the frequency doubling device.

[0023] In this manner, the optical path between the optical modulator and the frequency doubling device can be further isolated, interference and reflection in the optical path can be reduced, and the stability and efficiency of the laser can be improved.

[0024] Furthermore, the short-wavelength pulse laser also includes a power amplifier, the input end of the power amplifier is connected to the second isolator, and the output end of the power amplifier is connected to the frequency doubling device.

[0025] In this way, by adding a power amplifier, the output power of the laser can be further improved to meet the needs of high-power applications such as industrial processing and medical surgery.

[0026] Furthermore, the superfluorescent fiber light source, narrowband filter, filter amplifier unit, optical modulator and frequency doubling device are all polarization-maintaining devices.

[0027] In this method, each device uses a polarization-maintaining device, which can output a high-peak, high-energy, narrow-spectrum polarization-maintaining fundamental frequency laser. Through a suitable frequency doubling module, the pulse light output can meet a maximum frequency doubling efficiency of 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly express the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a schematic diagram of the structure of a short-wavelength pulse laser in an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the structure of another short-wavelength pulse laser in an embodiment of the present invention;

[0031] Figure 3 is a schematic diagram of the spectrum of the first laser in an embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of the spectrum of the second laser in an embodiment of the present invention;

[0033] Figure 5 is a schematic diagram of the spectrum of the third laser in an embodiment of the present invention;

[0034] Figure numerals: 11, superfluorescent fiber light source; 12, narrowband filter; 13, fiber circulator; 14, optical modulator; 15, second isolator; 16, power amplifier; 17, frequency doubling device; 18, spectroscope; 19, output mirror; 21, second active fiber; 22, second wavelength division multiplexer; 23, narrowband high-reflection grating; 24, second pump source; 111, anti-return light end face; 112, first active fiber; 113, first wavelength division multiplexer; 114, first pump source; 115, first isolator. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", 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 intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] Currently, there are two ways to implement nanosecond pulse short-wavelength lasers, mainly divided into solid-state solutions and fiber-optic solutions.

[0040] The optical fiber solution has the advantages of high stability and good heat dissipation. In order to achieve a higher frequency doubling efficiency, the spectral width of the signal light source is generally required to be narrower, which is related to the smaller allowable bandwidth of the nonlinear crystal. Generally, the wider the fundamental frequency spectrum, the greater the phase mismatch and the lower the frequency doubling efficiency.

[0041] Therefore, one of the current solutions for realizing nanosecond short-wavelength lasers based on fiber solutions is based on direct modulation of DFB semiconductor lasers for amplification. Due to the single longitudinal mode structural characteristics of DFB semiconductor lasers, the spectral width of its direct output is generally in the order of hundreds of KHZ to several GHZ, which is 0.01nm when converted to nm units, and its spectrum cannot be naturally widened. Even under short pulse width modulation, its spectral width remains at the order of 0.01nm, and its spectrum will not be significantly widened by amplification of about 3dB, and it has very strong longitudinal mode control capabilities. Therefore, a serious SBS effect will occur during the amplification process, and it can generally only be used for narrow pulse width (less than 5ns) amplification, which limits the final output pulse energy. The pulse energy is low.

[0042] There is another method of adding phase modulation to the DFB semiconductor laser. This solution is complex and expensive because it requires devices such as electro-optical phase modulators, so it cannot be used on a large scale.

[0043] In addition, there is a method of using a fiber resonant cavity composed of high and low reflection narrowband gratings to output narrowband continuous lasers and then chopping based on an external modulator to produce pulsed light. Due to the use of narrowband gratings, the continuous light in the continuous resonant cavity is unstable and prone to generating random self-pulses, resulting in uneven pulse light output after chopped wave, large fluctuations in pulse sequence, and unstable pulse light, which affects the performance of the laser and limits the development of this type of pulsed laser. That is, the narrowband light source output by the resonant cavity has sub-pulses, which are prone to sub-pulse spikes and are not suitable for outputting stable pulsed light.

[0044] In view of this, an embodiment of the present invention provides a short-wavelength pulse laser.

[0045] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, an embodiment of the present invention provides a short-wavelength pulse laser, including:

[0046] A super fluorescent fiber light source 11, used for outputting a first laser with a spectral width range of a first width range;

[0047] A narrowband filter 12 is used to perform narrowband filtering on the first laser to obtain a second laser with a spectrum width range of a second width range, where the second width range is smaller than the first width range;

[0048] A filtering and amplifying unit, used for performing narrow-band filtering and power amplification on the second laser to obtain a third laser with a spectrum width range of a third width range, wherein the third width range is smaller than the second width range;

[0049] The optical modulator 14 is used to modulate the third laser to output a target pulse laser;

[0050] The frequency doubling device 17 is used to double the frequency of the target pulse laser to obtain a short-wavelength pulse laser.

[0051] Specifically, the superfluorescent fiber light source 11 is characterized in that the light source is designed to have weak reflection on one side or both sides, in order to prevent it from forming a resonant cavity, so that the light generated is incoherent light or weakly coherent light, and exhibits weak temporal coherence. Its weak temporal coherence means that the electric field of this light source in the time domain has very fast random fluctuations, with very short coherence time and coherence length. Although the spectrum of the superfluorescent fiber light source 11 is continuous and covers different wavelengths within a certain range, it does not have a stable phase relationship in time.

[0052] Due to the unstable and random phase relationship, the spectral components per unit width in the spectrum of the superfluorescent fiber light source 11 are more stable in the time domain than the laser output by the ordinary laser resonant cavity, and there will be no violent sub-pulse phenomenon due to mode interference.

[0053] Furthermore, since the superfluorescent fiber light source 11 has a random, continuous, and low coherence phase, even if a narrow spectrum is output after spectral filtering, its original spectral components can still meet the broadening of nonlinear spectral modulation after amplification. Therefore, its SBS threshold will gradually increase with the spectrum broadening and will not become the minimum threshold nonlinear effect that hinders system amplification.

[0054] Therefore, the embodiment of the present invention uses a continuous superfluorescent fiber based on narrowband filtering combined with an optical modulator 14 as a pulse seed light source to achieve a narrow spectral width after amplification and ultimately achieve a frequency doubling efficiency of up to 50%-60%.

[0055] Furthermore, after the superfluorescent fiber light source 11 outputs the first laser, in order to further reduce the spectral width, the first laser is narrow-band filtered by the narrowband filter 12 to obtain a second laser with a spectral width range of a second width range, and then the second laser is narrow-band filtered and power amplified by the filtering and amplifying unit to obtain a third laser with a spectral width range of a third width range, wherein the second width range is smaller than the first width range, and the third width range is smaller than the second width range. The output narrow-band filtering is performed step by step, so that the output third laser is modulated by the optical modulator 14 to output a pulse laser with a narrow linewidth and a high side mode suppression ratio. The pulse laser serves as a pulse seed light, and can suppress nonlinear spectral broadening as much as possible during the amplification process, and finally maintains a relatively narrow output spectrum while obtaining a large pulse energy. The obtained pulse laser is very suitable as a fundamental frequency light source for nonlinear frequency conversion (i.e., frequency doubling) and obtains a higher frequency doubling efficiency.

[0056] The optical modulator 14 includes an acousto-optic modulator 14 (AOM) or an electro-optic modulator 14 (EOM). A suitable modulator can be selected according to different application requirements, thereby improving the flexibility of the system.

[0057] The frequency doubling device 17 can be a nonlinear crystal such as a frequency doubling crystal, and can specifically realize functions such as double frequency and quadruple frequency, and the number of frequency doubling can be determined according to the required laser frequency. For example, a pulsed laser with a wavelength of 1064nm red light can be frequency-doubled to obtain a pulsed laser with a wavelength of 532nm green light.

[0058] The short-wavelength pulse laser of the embodiment of the present invention utilizes the unstable and random phase relationship of the spectrum of the superfluorescent fiber light source 11, so that the spectrum components per unit width in the spectrum are more stable in the time domain than the laser output by the ordinary laser resonant cavity, and there will be no violent sub-pulse phenomenon due to mode interference. The superfluorescent fiber light source 11 is used as a pulse seed light source, and the first laser output by the superfluorescent fiber light source 11 is filtered in sequence through the narrowband filter 12 and the filter amplifier unit to obtain the second laser and the third laser whose spectra are successively reduced, and then the pulse is modulated by the optical modulator 14 to output the pulse laser with narrow line width and high side mode suppression ratio, and finally the target pulse laser is frequency-doubled by the frequency doubling device 17 to obtain a high-power short-wavelength pulse laser. The present invention can achieve that the narrow spectrum width can still be maintained after amplification, the output short-wavelength pulse laser is stable, and the frequency doubling efficiency up to 50%-60% can be achieved.

[0059] In some embodiments, the superfluorescent fiber light source 11 includes a first active optical fiber 112, a first wavelength division multiplexer 113 and a first pump source 114, one end of the first active optical fiber 112 is provided with an anti-return light end face 111 with a preset tilt angle, the other end of the first active optical fiber 112 is connected to the wavelength division multiplexer, the first pump source 114 is used to input the first pump light to the first active optical fiber 112 through the first wavelength division multiplexer 113, and the output end of the wavelength division multiplexer is connected to the narrowband filter 12.

[0060] Specifically, the superfluorescent fiber light source 11 is a continuous broadband light source, the central wavelength can be in the 1030nm band or the 1064nm band, the spectrum width range is 10nm-40nm, and the power is generally in the range of 10mW-100mW.

[0061] The anti-return light end face 111 may be a beveled section or a fiber reflector. For example, a beveled section is provided at one end of the first active fiber 112, and the preset inclination angle is 4° to prevent the end face from returning light and forming self-radiation to increase the output power.

[0062] Alternatively, the oblique cut surface may be replaced by a broadband optical fiber reflector, the central wavelength of which may be 1030 nm or 1064 nm, and the reflection spectrum bandwidth may be 20 nm-30 nm.

[0063] After connecting the first active optical fiber 112, the first wavelength division multiplexer 113, and the first pump source 114, the first isolator 115 can be connected to prevent the return light from self-excitation, and the first isolator 115 is arranged between the output end of the first wavelength division multiplexer 113 and the narrowband filter 12. By adding the first isolator 115, the reverse propagation of light can be reduced, the internal components of the laser can be protected, and the stability of the system and the quality of the laser output can be improved.

[0064] In one example, the pump light output by the first pump source 114 is a laser with a central wavelength of 980 nm, and the pumping direction can be backward, forward, bidirectional, etc. Through the above settings, a super fluorescent fiber light source 11 with an output bandwidth range of about 10nm-20nm and an output power of about 10mW-100mW is obtained, that is, the bandwidth range of the first laser output by the super fluorescent fiber light source 11 is about 10nm-20nm, and the output power is about 10mW-100mW.

[0065] In this embodiment, by providing a seed at one end of the first active optical fiber 112 and inputting the first pump light using the first pump source 114 , laser light can be effectively generated and amplified, thereby achieving efficient output of laser light.

[0066] In some embodiments, the filtering and amplifying unit includes an optical fiber circulator 13, a second active optical fiber 21, a second wavelength division multiplexer 22, a second pump source 24 and a narrowband high-reflection grating 23. The first end of the optical fiber circulator 13 is connected to the narrowband filter 12, the second end of the optical fiber circulator 13 is connected to one end of the second active optical fiber 21, and the other end of the second active optical fiber 21 is connected to the wavelength division multiplexer. The second pump source 24 is used to input the second pump light to the second active optical fiber 21 through the second wavelength division multiplexer 22. The narrowband high-reflection grating 23 is used to narrow-band filter the laser output by the second wavelength division multiplexer 22 and reflect it back to the second wavelength division multiplexer 22, and enter the second active optical fiber 21 through the second wavelength division multiplexer 22.

[0067] Specifically, the width of the narrowband high-reflection grating 23 is generally in the range of 0.01nm-0.5nm, the central wavelength is 1030nm or 1064nm, the pump light output by the second pump source 24 is a laser with a central wavelength of 980nm, and the pumping direction can be backward, forward, and bidirectional.

[0068] The light beam enters the second active optical fiber 21 from the optical fiber circulator 13, is amplified by the pump energy provided by the second pump source 24, and is transmitted to the narrow-band high-reflection grating 23 for filtering, and then is reflected back to the second active optical fiber 21. After being amplified again in the second active optical fiber 21, it is output from the optical fiber circulator 13. The laser output at this time is the third laser.

[0069] Through the design of the optical fiber circulator 13, the second active optical fiber 21, the second wavelength division multiplexer 22, the second pump source 24 and the narrowband high-reflection grating 23, a second-order narrowband filtering double-pass amplification structure can be constructed, which realizes the filtering and amplification of the laser again, improves the power of the laser and further reduces the spectral width range.

[0070] Furthermore, the short-wavelength pulse laser further includes a second isolator 15 , which is disposed between the optical modulator 14 and the frequency doubling device 17 .

[0071] Specifically, the second isolator 15 , like the first isolator 115 , is an optical isolator (ISO), which is a passive optical device that only allows light to be transmitted in one direction and blocks the transmission of light in the opposite direction.

[0072] By providing the second isolator 15, the optical path between the optical modulator 14 and the frequency doubling device 17 can be further isolated, thereby reducing interference and reflection in the optical path and improving the stability and efficiency of the laser.

[0073] Furthermore, the short-wavelength pulse laser further includes a power amplifier 16 , an input end of the power amplifier 16 is connected to the second isolator 15 , and an output end of the power amplifier 16 is connected to the frequency multiplication device 17 .

[0074] In one example, a plurality of power amplifiers 16 may be provided, for example, three power amplifiers 16 may be provided to implement multi-stage power amplification. The second isolator 15 and the frequency multiplication device 17 are connected by three cascaded power amplifiers 16, thereby achieving high-power output.

[0075] By adding the power amplifier 16, the output power of the laser can be further improved to meet the needs of high-power applications, such as industrial processing, medical surgery, etc.

[0076] Furthermore, the short-wavelength pulse laser also includes a beam splitter 18 and an output mirror 19. The beam splitter 18 is mainly used to separate the output mixed light beam. The component is generally coated with a dielectric beam splitter film to reflect the short-wavelength light beam and transmit the infrared light beam. Generally, in order to reduce loss, the component is coated with a short-wavelength high-reflection film and an infrared light beam high-transmittance film.

[0077] The output mirror 19 is mainly used to output short-wavelength lasers. This component is generally coated with a dielectric spectroscopic film to further filter out infrared beams.

[0078] In some embodiments, the first width ranges from 10 nm to 40 nm, the second width ranges from 1 nm to 2 nm, and the third width ranges from 0.01 nm to 0.5 nm.

[0079] Furthermore, the central wavelength of the first laser is 1030nm or 1064nm. By setting the central wavelength of the first laser to 1030nm or 1064nm, green light pulses can be output after subsequent frequency doubling, which can be widely used in various industrial scenarios.

[0080] In one example, the central wavelength of the first laser is 1064 nm, the bandwidth of the first laser output by the superfluorescent fiber light source 11 is in the range of about 10 nm-20 nm, and the output power is about 10 mW-100 mW.

[0081] The first laser is then filtered through a narrowband filter 12, preferably an optical fiber narrowband filter 12 with a bandpass width of 1nm-2nm, to obtain a second laser with a spectrum width of 1nm-2nm.

[0082] Then the spectrum is filtered and amplified again through the filtering and amplifying unit to obtain a third laser with a narrow band range of 0.01nm-0.5nm.

[0083] Then, through an online optical modulator 14, such as an acousto-optic modulator AOM or an electro-optic modulator EOM, the desired pulse waveform can be modulated, and then amplified step by step through a power amplifier 16 to output a polarization-maintaining fundamental frequency pulse laser with a high peak value, high energy, and narrow linewidth. After being frequency-doubled by a suitable frequency doubling device 17, a pulse green light output with a frequency doubling efficiency of up to 60% (generally above 50%) can be achieved, thereby realizing high-power fiber pulse rate light output.

[0084] In the embodiment of the present invention, the 10nm-40nm laser output by the superfluorescent fiber light source 11 is modulated into a narrow-band light source of 1nm-2nm for the first time, and then modulated into a narrow-band light source in the range of 0.01nm-0.5nm for the second time, so that it can be pulse-modulated by the optical modulator 14 to output a pulse seed light with a narrow linewidth and a high side mode suppression ratio in the range of 0.01nm-0.5nm, thereby suppressing the nonlinear spectrum broadening as much as possible during the amplification process, and finally maintaining a narrow output spectrum while obtaining a large pulse energy, so that it is very suitable as a fundamental frequency light source for nonlinear frequency conversion, and obtains a higher frequency doubling efficiency and a more stable laser output, thereby improving the power and stability of short pulse lasers.

[0085] The short-wavelength pulse laser of the embodiment of the present invention has the following effects:

[0086] The short-wavelength pulse laser of the embodiment of the present invention utilizes the spectrum of the superfluorescent fiber light source 11 to have an unstable and random phase relationship, so that the spectrum components per unit width in the spectrum are correspondingly more stable in the time domain than the laser output by the ordinary laser resonant cavity, and there will be no violent sub-pulse phenomenon due to mode interference. The superfluorescent fiber light source 11 is used as a pulse seed light source, and the first laser output by the superfluorescent fiber light source 11 is filtered in sequence through the narrowband filter 12 and the filter amplifier unit to obtain the second laser and the third laser with successively reduced spectrum widths, and then the pulse is modulated by the optical modulator 14 to output a pulse laser with a narrow line width and a high side mode suppression ratio, and finally the target pulse laser is frequency-doubled by the frequency doubling device 17 to obtain a high-power short-wavelength pulse laser. The devices used in the short-wavelength pulse laser are all polarization-maintaining devices, which can achieve a narrow spectrum width after amplification, and the output short-wavelength pulse laser is stable, and a frequency doubling efficiency of up to 50%-60% can be achieved.

[0087] In order to meet the requirement of smaller allowable bandwidth of nonlinear crystal, the spectral range of the first laser output by the superfluorescent fiber light source 11 is designed to be 10nm-40nm, and the spectral width is relatively narrow, so as to achieve higher frequency doubling efficiency in subsequent frequency doubling work. And a narrowband filter 12, a filter amplifier unit and an optical modulator 14 are used to modulate the 10nm-40nm laser output by the superfluorescent fiber light source 11 into a narrowband light source of 1nm-2nm for the first time, and then into a narrowband light source in the range of 0.01nm-0.5nm for the second time, so that it can be pulse modulated by the optical modulator 14 to output a pulse seed light with a narrow line width and a high side mode suppression ratio in the range of 0.01nm-0.5nm, and then the nonlinear spectrum broadening can be suppressed as much as possible during the amplification process, and finally a relatively narrow output spectrum can be maintained while obtaining a large pulse energy. The obtained pulse seed light is very suitable as a fundamental frequency light source for nonlinear frequency conversion, and obtains a higher frequency doubling efficiency, and realizes high-power short-wavelength pulse light output.

[0088] The present invention does not require expensive devices such as DFB lasers and electro-optic phase modulators, and can achieve a relatively ideal frequency doubling efficiency effect. The solutions of the embodiments of the present invention use mature optical passive devices, and the overall cost is less than 1 / 3 to 1 / 4 of the existing solutions using DFB lasers and electro-optic phase modulators. In addition, since high-speed phase modulators are not used, high-speed modulation devices have very high requirements for non-interference, so the anti-interference stability of the embodiments of the present invention is also better.

[0089] In terms of volume, since the phase modulator system used in the related technology is complex and requires a certain volume and space, the embodiment of the present invention uses the above-mentioned first active optical fiber 112, the first wavelength division multiplexer 113 and the first pump source 114 to realize the optical fiber integrated narrow-band filtered super fluorescent optical fiber light source 11, which can utilize the bendable characteristics of the optical fiber for integrated packaging to reduce the volume of the short-wavelength pulse laser.

[0090] Although example embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and modifications to these embodiments without departing from the spirit and defined scope of the present invention, and such modifications and variations are all within the defined scope.

Claims

1. A short wavelength pulse laser, characterized in that: include: A superfluorescent fiber light source (11) is used to output a first laser with a spectrum width range in a first width range; A narrowband filter (12) is used to perform narrowband filtering on the first laser to obtain a second laser having a spectral width range of a second width range, wherein the second width range is smaller than the first width range; a filtering and amplifying unit, configured to perform narrow-band filtering and power amplification on the second laser to obtain a third laser having a spectrum width range of a third width range, wherein the third width range is smaller than the second width range; An optical modulator (14) is used to modulate the third laser to output a target pulse laser; The frequency doubling device (17) is used for doubling the frequency of the target pulse laser to obtain a short-wavelength pulse laser.

2. The short-wavelength pulse laser according to claim 1, characterized in that: The first width ranges from 10 nm to 40 nm, the second width ranges from 1 nm to 2 nm, and the third width ranges from 0.01 nm to 0.5 nm.

3. The short-wavelength pulse laser according to claim 2, characterized in that: The central wavelength of the first laser is 1030 nm or 1064 nm.

4. The short-wavelength pulse laser according to claim 1, characterized in that: The superfluorescent fiber light source (11) comprises a first active fiber (112), a first wavelength division multiplexer (113) and a first pump source (114); one end of the first active fiber (112) is provided with an anti-return light end face (111) with a preset tilt angle; the other end of the first active fiber (112) is connected to the wavelength division multiplexer; the first pump source (114) is used to input a first pump light into the first active fiber (112) through the first wavelength division multiplexer (113); and the output end of the wavelength division multiplexer is connected to the narrowband filter (12).

5. The short-wavelength pulse laser according to claim 4, characterized in that: The superfluorescent fiber light source (11) further comprises a first isolator (115), wherein the first isolator (115) is arranged between the output end band filters of the multiplexer.

6. The short-wavelength pulse laser according to claim 1, characterized in that: The filtering and amplifying unit comprises an optical fiber circulator (13), a second active optical fiber (21), a second wavelength division multiplexer (22), a second pump source (24) and a narrowband high-reflection grating (23); a first end of the optical fiber circulator (13) is connected to the narrowband filter (12); a second end of the optical fiber circulator (13) is connected to one end of the second active optical fiber (21); the other end of the second active optical fiber (21) is connected to the wavelength division multiplexer; the second pump source (24) is used to input a second pump light to the second active optical fiber (21) through the second wavelength division multiplexer (22); and the narrowband high-reflection grating (23) is used to perform narrowband filtering on the laser output by the second wavelength division multiplexer (22), and then reflect the laser back to the second wavelength division multiplexer (22), and enter the second active optical fiber (21) through the second wavelength division multiplexer (22).

7. The short-wavelength pulse laser according to claim 1, characterized in that: The optical modulator (14) comprises an acousto-optic modulator (14) or an electro-optic modulator (14).

8. The short-wavelength pulse laser according to claim 1, characterized in that: It also includes a second isolator (15), which is arranged between the optical modulator (14) and the frequency multiplying device (17).

9. The short-wavelength pulse laser according to claim 8, characterized in that: It also includes a power amplifier (16), wherein the input end of the power amplifier (16) is connected to the second isolator (15), and the output end of the power amplifier (16) is connected to the frequency multiplication device (17).

10. The short-wavelength pulse laser according to claim 1, characterized in that: The superfluorescent fiber light source (11), the narrowband filter (12), the filter amplification unit, the light modulator (14) and the frequency doubling device (17) are all polarization-maintaining devices.

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