A short wavelength pulsed laser

Abstract

The application relates to the technical field of lasers, and discloses a short-wavelength pulse laser, which comprises an external cavity semiconductor laser for outputting first pulse laser with a preset central wavelength; a modulator for performing chopping modulation on the first pulse laser output by the external cavity semiconductor laser according to a chopping modulation signal output by a control unit, and outputting second pulse laser, wherein the pulse width of the first pulse laser is greater than the pulse width of the second pulse laser; the control unit is used for controlling the external cavity semiconductor laser to output the first pulse laser and controlling the modulator to perform chopping modulation on the first pulse laser; and a frequency doubling device is used for frequency doubling the second pulse laser to obtain short-wavelength pulse laser. The short-wavelength pulse laser with narrow line width, time-domain stability and high power can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a short wavelength pulse laser. BACKGROUND

[0002] At present, there are two implementation ways for nanosecond pulse short wavelength laser, mainly including solid scheme and optical fiber scheme, wherein the solid scheme has more and more complex spatial devices due to its structural characteristics, and has relatively poor stability, and it is difficult to realize the scheme of more than 100W. In order to realize high frequency conversion efficiency, the spectral width of the signal light source is generally required to be narrow in the optical fiber MOPA scheme, which is related to the small allowed bandwidth of the nonlinear crystal. Generally, the wider the fundamental frequency spectrum is, the greater the phase mismatch is, and the lower the frequency conversion efficiency is.

[0003] In the related art, a technical scheme is proposed based on super fluorescent fiber light source (Superfluorescent fiber sources, SFSs) to output narrow-band pulse light by narrow-band filtering and using its low time coherence. This scheme has an advantage over the DFB scheme in that its cost is simpler, but its time-domain pulse stability is relatively general, and there is a certain pulse amplitude jitter. Such amplitude jitter may affect the process effect in actual use.

[0004] In summary, there is an urgent need for a laser suitable for generating short wavelength pulses to solve the technical problem of insufficient time-domain amplitude stability of the output short wavelength pulses. SUMMARY

[0005] Therefore, the present application provides a short wavelength pulse laser to solve or partially solve the technical problem of insufficient time-domain amplitude stability of the output pulse laser in the related art.

[0006] The technical scheme provided by the present application is as follows:

[0007] The short-wavelength pulsed laser provided by the application comprises: an external cavity semiconductor laser, which comprises an F-P semiconductor laser and a low-reflection narrow-band grating, the F-P semiconductor laser is used for outputting first pulsed laser, and the low-reflection narrow-band grating is used for partially reflecting the first pulsed laser with a set center wavelength within a first spectral linewidth and forming a stable laser oscillation mode, and the first pulsed laser with a preset center wavelength is output; a modulator, which is used for chopping and modulating the first pulsed laser output by the external cavity semiconductor laser according to a chopping and modulation signal output by a control unit, and outputting second pulsed laser, wherein the pulse width of the first pulsed laser is greater than the pulse width of the second pulsed laser; the control unit, which is used for controlling the external cavity semiconductor laser to output the first pulsed laser and controlling the modulator to chop and modulate the first pulsed laser; and a frequency doubling device, which is used for frequency doubling the second pulsed laser to obtain the short-wavelength pulsed laser.

[0008] The short-wavelength pulsed laser provided by the application comprises: an external cavity semiconductor laser, which comprises an F-P semiconductor laser and a low-reflection narrow-band grating, the F-P semiconductor laser is used for outputting first pulsed laser, and the low-reflection narrow-band grating is used for partially reflecting the first pulsed laser with a set center wavelength within a first spectral linewidth and forming a stable laser oscillation mode, and the first pulsed laser with a preset center wavelength is output; a modulator, which is used for chopping and modulating the first pulsed laser output by the external cavity semiconductor laser according to a chopping and modulation signal output by a control unit, and outputting second pulsed laser, wherein the pulse width of the first pulsed laser is greater than the pulse width of the second pulsed laser; the control unit, which is used for controlling the external cavity semiconductor laser to output the first pulsed laser and controlling the modulator to chop and modulate the first pulsed laser; and a frequency doubling device, which is used for frequency doubling the second pulsed laser to obtain the short-wavelength pulsed laser.

[0009] In some optional embodiments, the pulse width of the first pulsed laser is 100 ns to 200 ns.

[0010] In the pulse width range, the first pulsed laser output by the external cavity semiconductor laser has a good wavelength locking effect, and the pulse width range meets the duty cycle requirement under the pulse modulation of the semiconductor laser.

[0011] In some optional embodiments, the modulator is an electro-optic modulator or an acousto-optic modulator.

[0012] In this mode, the electro-optic modulator or the acousto-optic modulator can realize fast response and high modulation precision.

[0013] In some optional embodiments, the F-P semiconductor laser, the low-reflection narrow-band grating, and the modulator are all polarization maintaining devices.

[0014] In this way, the F-P semiconductor laser, the low-reflection narrow-band grating, and the modulator are all polarization maintaining devices, which can effectively maintain the polarization state of the laser and reduce the influence of polarization state change on the performance of the laser. This helps to improve the stability of the laser and the quality of the output light beam.

[0015] In some optional embodiments, the preset central wavelength is 1030 nm or 1064 nm, and the first spectral line width is 0.1 nm to 0.5 nm.

[0016] In some optional embodiments, the short-wavelength pulsed laser further comprises a first isolator, which is arranged between the low-reflection narrow-band grating and the modulator.

[0017] In this way, the first isolator arranged between the low-reflection narrow-band grating and the modulator can effectively prevent the interference of light reflection on the resonant cavity of the laser, thereby improving the stability of the laser and the quality of the output light beam.

[0018] In some optional embodiments, the short-wavelength pulsed laser further comprises a step-by-step amplifier, an input end of the step-by-step amplifier is connected with an output end of the modulator, and an output end of the step-by-step amplifier is connected with the frequency doubling device.

[0019] In this way, the step-by-step amplifier can amplify the second pulsed laser after modulation step by step, thereby improving the power of the laser and meeting the application requirements of high-power short-wavelength pulsed laser.

[0020] In some optional embodiments, the step-by-step amplifier comprises a plurality of power amplifiers connected in series, each power amplifier comprises a pump source, a beam combiner, and an active optical fiber, one input end of the beam combiner is connected with the output end of the modulator, the other input end of the beam combiner is connected with the pump source, and the output end of the beam combiner is connected with one end of the active optical fiber.

[0021] In this way, efficient energy conversion and power amplification can be realized, and the output power of the laser can be further improved through the cascade of multiple power amplifiers.

[0022] In some optional embodiments, a second isolator is arranged between the first power amplifier connected in series and the modulator, and a third isolator is arranged between each power amplifier.

[0023] In this way, the isolators arranged between the first power amplifier and the modulator and between each power amplifier can effectively isolate the reverse light reflection and reduce the influence of light feedback on the performance of the laser.

[0024] In some optional embodiments, the control unit is further configured to control the pulse width of the second pulsed laser by controlling the pulse width or time delay of the first pulsed laser and / or the chopping modulation signal.

[0025] In this way, the pulse width of the second pulsed laser can be flexibly controlled by adjusting the pulse width or time delay of the first pulsed laser and / or the chopping modulation signal, thereby improving the flexibility and applicability of the output short-wavelength pulsed laser. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly express the technical solutions of the embodiments of the present application, the drawings needed for the description of the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0027] Figure 1 Fig. 1 is a structural schematic diagram of a short-wavelength pulsed laser in an embodiment of the present application;

[0028] Figure 2 Fig. 2 is a spectral schematic diagram of different pulse widths in an embodiment of the present application;

[0029] Figure 3 Fig. 3 is a modulation schematic diagram of a second pulsed laser in an embodiment of the present application;

[0030] Figure 4 Fig. 4 is a comparative schematic diagram of time-domain waveforms of a second pulsed laser and a pulsed laser generated based on an ultra-fluorescent fiber light source in an embodiment of the present application;

[0031] Fig. 1 is a structural schematic diagram of a short-wavelength pulsed laser in an embodiment of the present application; DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of protection of the present application.

[0033] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the communication inside two elements, it can be wireless connection, or wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0035] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as there is no conflict between them.

[0036] At present, there are two ways to realize nanosecond pulse short wavelength laser, mainly divided into solid scheme and optical fiber scheme, wherein one of the schemes for realizing nanosecond short wavelength laser based on optical fiber scheme is to directly modulate the DFB semiconductor laser and then amplify, due to the single longitudinal mode structure characteristics of the DFB semiconductor laser, the spectral width of its direct output is generally hundreds of KHZ to several GHZ, and its spectrum cannot be naturally broadened. Thus, in the amplification process, serious SBS effect will be produced, which can only be used for narrow pulse width (below 5ns) amplification, which limits the final output pulse energy.

[0037] There is another way of DFB semiconductor laser plus phase modulation, this scheme is complex, and the cost is expensive due to the use of electro-optic phase modulator 3 and other devices, so it cannot be used on a large scale.

[0038] In the related art, a technical scheme is proposed for outputting narrow-band pulse light based on super-fluorescent fiber sources (Superfluorescent fiber sources, SFSs) through narrow-band filtering and using its low time coherence, which has one advantage over the DFB scheme, that is, its cost is simpler, but its time-domain pulse stability is relatively general, and there is a certain pulse amplitude jitter, which may affect the process effect in actual use.

[0039] However, the light source itself is composed of many incoherent different frequency wavelength components, and the different components form optical beat noise, also known as excess intensity noise. In the case of narrow-band filtering, the optical beat noise increases with the decrease of the bandwidth of the filter, thereby affecting the stability of the time-domain signal of the final filtered output. That is, it affects the time-domain amplitude stability of the final modulated pulse. Generally, the smaller the bandwidth of the narrow-band filter, the more serious the output pulse peak jitter. Therefore, for the superfluorescent fiber laser scheme, when outputting a narrow-bandwidth pulse laser, there is a relatively serious jitter and insufficient time-domain stability.

[0040] Therefore, an embodiment of the present application provides a short-wavelength pulse laser capable of outputting a pulse seed light source with a narrow linewidth spectrum, good time-domain stability and adjustable pulse width.

[0041] As shown in Figure 1 An embodiment of the present application provides a short-wavelength pulse laser, which comprises:

[0042] An external-cavity semiconductor laser, which comprises an F-P semiconductor laser 1 and a low-reflection narrow-band grating 2. The F-P semiconductor laser 1 is used to output first pulse laser. The low-reflection narrow-band grating 2 is used to partially reflect the first pulse laser with a set center wavelength within a first spectral linewidth and form a stable laser oscillation mode, and output first pulse laser with a preset center wavelength. A modulator 3 is used to perform chopper modulation on the first pulse laser output by the external-cavity semiconductor laser according to a chopper modulation signal output by a control unit 4, and output second pulse laser. The pulse width of the first pulse laser is greater than the pulse width of the second pulse laser, so that the pulse width of the first pulse laser is wider. The control unit 4 is used to control the external-cavity semiconductor laser to output the first pulse laser and control the modulator 3 to perform chopper modulation on the first pulse laser. A frequency doubling device 5 is used to frequency double the second pulse laser to obtain short-wavelength pulse laser.

[0043] Specifically, the external-cavity semiconductor laser (ECSL) is mainly composed of an F-P semiconductor laser 1 and a low-reflection narrow-band grating 2. The first pulse laser within the first spectral linewidth is output by direct electrical modulation, and the first pulse laser is subjected to external pulse modulation with a specific time delay with the chopper modulation signal of the external modulator 3, so as to output the second pulse laser with a narrow linewidth spectrum, good time-domain stability and adjustable pulse width.

[0044] It should be understood that a general semiconductor laser will form a laser resonant cavity by cleaving the front and back of the chip active layer. In the laser resonant cavity, only the longitudinal mode with gain greater than loss can stably oscillate to form laser output due to gain saturation mode competition. The free-running semiconductor laser has a relatively flat gain curve and a large number of carrier spontaneous emissions, so the semiconductor laser often operates in a multi-longitudinal mode, resulting in a relatively wide spectral width of the output.

[0045] The embodiment of the present application adds a low-reflection narrow-band grating 2 in the output direction of the F-P semiconductor laser 1 to form an external cavity semiconductor laser. The laser output by the F-P semiconductor laser 1 will be partially reflected by the low-reflection narrow-band grating 2 in the reflection bandwidth of the low-reflection narrow-band grating 2, and fed back into the internal cavity of the F-P semiconductor laser 1, causing the mode loss in the corresponding range to be reduced. The gain greater than loss effect in this bandwidth range is enhanced to form stable laser oscillation, and other waveband modes are suppressed, thereby realizing wavelength locking and spectral line narrowing.

[0046] In some embodiments, the reflectivity of the low-reflection narrow-band grating 2 is between 2% and 10%, the first spectral line width is between 0.1 nm and 0.5 nm, and the preset center wavelength is 1030 nm or 1064 nm, so as to output the first pulsed laser with a narrow line width and a high side mode suppression ratio.

[0047] In particular, the locking effect is related to the working state of the F-P semiconductor laser 1, that is, the output spectrum is related to the actual working state.

[0048] When the external cavity semiconductor laser is in a continuous working state, the internal cavity can continuously receive feedback from the external low-reflection narrow-band grating 2, and due to the effect of mode competition, only the signal wavelength component within the reflection peak bandwidth of the external low-reflection narrow-band grating 2 can form stable oscillation and eventually output a single longitudinal mode with extremely narrow line width, which can be used for single-frequency laser related applications. In this case, due to the extremely narrow spectral line width and extremely high side mode suppression ratio, the SBS effect threshold is low during amplification, and it cannot be directly used as a seed source for high-power or high-energy pulse after external modulation.

[0049] As Figure 2As shown, when the external cavity semiconductor laser is in a pulse modulation state, the intensity and time of the feedback of the internal cavity by the low-reflection narrow-band grating 2 is related to the actual pulse modulation time. When the pulse width is too narrow (less than 2 ns), the internal active region of the seed source is limited by the feedback of the external low-reflection narrow-band grating 2, and the actual wavelength locking effect is not obvious. At this time, the output spectrum is still close to the state of the free running of the semiconductor. With the increase of the pulse width, the feedback intensity of the external grating on the internal cavity is also increased, the output spectrum width is narrowed accordingly, the wavelength locking effect is more obvious, and the side mode suppression ratio is also increased accordingly, so that the relatively narrow spectrum output can be maintained when the high-power amplification is performed.

[0050] The embodiment of the present application utilizes the property of the external cavity semiconductor laser. The external cavity semiconductor laser is directly modulated to output a first pulse laser with a specific pulse width. The pulse width of the first pulse laser needs to meet the following requirements:

[0051] On the one hand, the pulse width of the first pulse laser needs to obtain a good wavelength locking effect, so the pulse width cannot be too narrow. On the other hand, the duty cycle requirement under the pulse modulation of the semiconductor laser is limited (a too high duty cycle will affect the service life or damage the semiconductor laser. Generally, the duty cycle cannot be greater than 25%. That is, if the modulated pulse width is 500 ns, the maximum adjustable pulse frequency is 500 kHz, because (500*10 -9 )s*500*10 3 =0.25 s, that is, the actual light emission time of the seed source per second is 0.25 seconds), and the adjustable range of the modulated pulse frequency cannot be too small (to meet the requirement of high-frequency application, generally, the pulse repetition frequency adjustable needs to meet 2 MHz or less), so the modulated pulse width cannot be too wide.

[0052] In an embodiment, the pulse width of the first pulse laser is 100 ns to 200 ns.

[0053] For example, the pulse width of the first pulse laser is 100 ns, 150 ns, 200 ns, etc.

[0054] In this pulse width range, the first pulse laser output by the external cavity semiconductor laser has a good wavelength locking effect, and the pulse width range meets the duty cycle requirement under the pulse modulation of the semiconductor laser.

[0055] From the above analysis, it can be seen that the pulse width of the first pulsed laser cannot be too small, and a too narrow pulse width cannot obtain a good wavelength locking effect, while a too large pulse width will result in a too low pulse peak power of the final output, which cannot meet the requirements of the process processing effect. Therefore, by adding the modulator 3, the first pulsed laser output by the external cavity semiconductor laser is subjected to secondary chopping modulation, and the relative time delay of the two or the pulse width of the chopping modulation signal is controlled by the control unit 4, so that the second pulsed laser with a smaller pulse width can be obtained in the overlapping part of the two. The pulse width of the second pulsed laser is smaller than the pulse width of the first pulsed laser, for example, the pulse width of the second pulsed laser is 10 ns, 5 ns, 2 ns, etc.

[0056] It should be understood that the control unit 4 can be a central processing unit, a network processing unit or a combination thereof. The control unit 4 can further include a hardware chip. The hardware chip can be an application specific integrated circuit, a programmable logic device or a combination thereof. The programmable logic device can be a complex programmable logic device, a field programmable gate array (FPGA), a general array logic or any combination thereof.

[0057] As shown in Figure 4 The second pulsed laser output by the short wavelength pulsed laser of the embodiment of the present application has good stability in the time domain relative to the pulsed laser output by the super fluorescent fiber light source, and at the same time, it has the advantages of narrow linewidth and high side mode suppression ratio as the first pulsed laser. After being doubled by the frequency doubling device 5, the highest green light, purple light and other short wavelength pulsed laser with a frequency doubling efficiency of 70% can be output.

[0058] After the second pulsed laser is doubled by the frequency doubling device 5, green light pulses of 515 nm or 532 nm are output, and finally green light pulses with a linewidth of 0.1 nm to 0.5 nm can be output, which have wide application value in the fields of industrial processing, medical treatment and scientific research, etc.

[0059] The short-wavelength pulse laser of the embodiment of the present application utilizes the F-P semiconductor laser 1 and the low-reflection narrow-band grating 2 for direct modulation, and outputs the first pulse laser with narrow spectral line width within the first spectral line width. For the external cavity semiconductor laser mainly composed of the F-P semiconductor laser 1 and the low-reflection narrow-band grating 2, as the pulse width increases, the feedback intensity of the low-reflection narrow-band grating 2 to the internal cavity is also increased, the spectral width of the output light is narrowed accordingly, and the side mode suppression ratio is also increased accordingly. Therefore, the pulse width of the first pulse laser output by the external cavity semiconductor laser is greater than that of the second pulse laser, which helps to output the first pulse laser with narrow spectral line width, high side mode suppression ratio and stable time domain. The first pulse laser is chopped and modulated by the modulator 3 as the polarization maintaining pulse seed light, and the second pulse laser with adjustable pulse width is output. The second pulse laser has the same characteristics as the first pulse laser, that is, narrow spectral line width, high side mode suppression ratio and stable time domain. When high-power amplification is performed, the spectral output can still be relatively narrow. After frequency doubling, the second pulse laser can obtain short-wavelength pulse laser with narrow spectral line width, stable time domain and high power.

[0060] In some embodiments, the modulator 3 is an electro-optic modulator or an acousto-optic modulator.

[0061] In an example, the modulator 3 is an electro-optic modulator, the control unit 4 is connected with the electro-optic modulator, and the chopping modulation signal of the electro-optic modulator is time-delayed with the first pulse laser output by the F-P semiconductor laser 1, so as to obtain the second pulse laser with adjustable pulse width, narrow spectral line width and high side mode suppression ratio. By using the electro-optic modulator or the acousto-optic modulator, fast response and high modulation accuracy can be achieved.

[0062] Further, the F-P semiconductor laser 1, the low-reflection narrow-band grating 2 and the modulator 3 are all polarization maintaining devices.

[0063] In this mode, the F-P semiconductor laser 1, the low-reflection narrow-band grating 2 and the modulator 3 are all polarization maintaining devices, which can effectively maintain the polarization state of the laser, reduce the influence of the change of the polarization state on the performance of the laser, and can achieve a relatively narrow spectral width after amplification, and the output short-wavelength pulse laser is stable.

[0064] In some embodiments, the short-wavelength pulse laser further comprises a first isolator 7, which is arranged between the low-reflection narrow-band grating 2 and the modulator 3.

[0065] Specifically, the first isolator 7 is an optical isolator (Optical Isolator, ISO), which is a passive optical device that only allows light to transmit in one direction and blocks the transmission of light in the opposite direction, thereby protecting the F-P semiconductor laser 1 and ensuring that the spectrum output by the F-P semiconductor laser 1 is not affected by back light.

[0066] In this mode, the first isolator 7 is arranged between the low reflection narrowband grating 2 and the modulator 3, which can effectively prevent the interference of light reflection on the laser resonant cavity, and improve the stability and output beam quality of the laser.

[0067] In some embodiments, the short-wavelength pulsed laser further comprises a step-by-step amplifier 6, an input end of the step-by-step amplifier 6 is connected with an output end of the modulator 3, and an output end of the step-by-step amplifier 6 is connected with the frequency doubling device 5.

[0068] Specifically, the step-by-step amplifier 6 comprises a plurality of power amplifiers 61 connected in series, each power amplifier 61 comprises a pump source, a beam combiner and an active optical fiber, one input end of the beam combiner is connected with the output end of the modulator 3, the other input end of the beam combiner is connected with the pump source, and the output end of the beam combiner is connected with one end of the active optical fiber.

[0069] The second pulsed laser passes through the beam combiner and enters the active optical fiber, and is amplified under the excitation of the pump energy of the pump source.

[0070] Exemplarily, the pump light output by the pump source has a wavelength of 975 nm or 915 nm, and can be forward pumping or backward pumping. Preferably, backward pumping can be used, which can reduce the spectral broadening caused by nonlinear effects.

[0071] In this mode, the step-by-step amplifier 6 can be added to step-by-step amplify the second pulsed laser after modulation, so as to improve the power of the laser and meet the application requirements of high-power short-wavelength pulsed laser.

[0072] Through the series connection of the plurality of power amplifiers 61, the power of the laser can be gradually increased, so that the laser can output pulsed laser with higher energy, which is suitable for applications requiring high-power laser, such as industrial processing, medical surgery, etc., while the spectral characteristics of the laser are maintained.

[0073] In some embodiments, a second isolator 8 is arranged between the first power amplifier 61 connected in series and the modulator 3, and a third isolator is arranged between each power amplifier 61.

[0074] The second isolator 8 and the third isolator are the same as the first isolator 7, and are optical isolators. By arranging the second isolator 8 between the power amplifier 61 connected in series and the modulator 3, and arranging the third isolator between each power amplifier 61, the reverse propagation and mutual interference of light can be prevented, and the stability of the output laser of the short-wavelength pulsed laser can be improved.

[0075] In some embodiments, the control unit 4 is further configured to control the pulse width or time delay of the first pulsed laser and / or the chopping modulation signal to control the pulse width of the second pulsed laser.

[0076] Specifically, as shown in FIG. 1, the control unit 4 is configured to control the pulse width of the first pulsed laser and / or the chopping modulation signal to control the pulse width of the second pulsed laser. Figure 3As shown, the second pulsed laser output after the chopper modulation is the overlapping part of the first pulsed laser and the chopper modulation signal, and therefore, when the output time delay is fixed, the overlapping width of the first pulsed laser and the chopper modulation signal can be changed by the pulse width of the first pulsed laser and / or the chopper modulation signal, so as to adjust the pulse width of the second pulsed laser. For example, the pulse width of the first pulsed laser is properly increased, so as to increase the pulse width of the second pulsed laser.

[0077] When the pulse width of the first pulsed laser and the chopper modulation signal is fixed, the overlapping width of the first pulsed laser and the chopper modulation signal can be changed by controlling the time delay, so as to adjust the pulse width of the second pulsed laser, for example, the time delay of the chopper modulation signal is reduced, so as to increase the pulse width of the second pulsed laser.

[0078] In this mode, by adjusting the pulse width or the time delay of the first pulsed laser and / or the chopper modulation signal, the pulse width of the second pulsed laser can be flexibly adjusted, and the flexibility and applicability of the output short-wavelength pulsed laser are improved.

[0079] The short-wavelength pulsed laser of the embodiment of the present application has the following effects:

[0080] The short-wavelength pulsed laser of the embodiment of the present application has the following effects:

[0080] The short-wavelength pulsed laser of the embodiment of the present application has the following effects:

[0081] In combination with the modulator 3, by controlling the time delay or the pulse width of the F-P semiconductor laser 1 and the modulator 3, the polarized second pulsed laser with narrow line width and time-domain stability can be obtained, and through multi-stage amplification, the polarized base frequency pulsed laser with high peak value, high energy, narrow line width and high time-domain stability can be output, and after frequency doubling by the frequency doubling device 5, the short-wavelength pulsed laser with the highest frequency doubling efficiency of 70% can be output.

[0082] The application also avoids high cost of the phase modulator 3 in the DFB seed source plus phase modulation scheme, and can realize more stable time domain pulse output than the superfluorescent fiber source scheme, and can realize high nonlinear frequency conversion efficiency, so it is a low cost and high efficiency short wavelength laser realization scheme.

[0083] Although the example embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions and modifications to the embodiments without departing from the spirit of the application and the scope of protection defined, and such modifications and variations fall within the scope defined.

Claims

1. A short-wavelength pulsed laser, characterized in that, include: An external cavity semiconductor laser, comprising an FP semiconductor laser (1) and a low-reflection narrowband grating (2), wherein the FP semiconductor laser (1) is used to output a first pulse laser, and the low-reflection narrowband grating (2) is used to partially reflect the first pulse laser with a set center wavelength within a first spectral linewidth and form a stable laser oscillation mode, thereby outputting a first pulse laser with a preset center wavelength. Modulator (3) is used to chop and modulate the first pulse laser output by the external cavity semiconductor laser according to the chopping modulation signal output by the control unit (4) and output a second pulse laser, wherein the pulse width of the first pulse laser is greater than the pulse width of the second pulse laser. The control unit (4) is used to control the external cavity semiconductor laser to output a first pulse laser and to control the modulator (3) to chop and modulate the first pulse laser. The frequency doubling device (5) is used to double the frequency of the second pulse laser to obtain a short-wavelength pulse laser.

2. The short-wavelength pulsed laser according to claim 1, characterized in that, The pulse width of the first pulsed laser is 100ns to 200ns.

3. The short-wavelength pulsed laser according to claim 1, characterized in that, The modulator (3) is an electro-optic modulator (3) or an acousto-optic modulator (3).

4. The short-wavelength pulsed laser according to claim 1, characterized in that, The FP semiconductor laser (1), the low-reflection narrowband grating (2), and the modulator (3) are all polarization-maintaining devices.

5. The short-wavelength pulsed laser according to claim 1, characterized in that, The preset center wavelength is 1030nm or 1064nm, and the first spectral linewidth is 0.1nm to 0.5nm.

6. The short-wavelength pulsed laser according to claim 1, characterized in that, It also includes a first isolator (7), which is disposed between the low-reflection narrowband grating (2) and the modulator (3).

7. The short-wavelength pulsed laser according to claim 1, characterized in that, It also includes a step-by-step amplifier (6), the input of which is connected to the output of the modulator (3), and the output of which is connected to the frequency multiplier (5).

8. The short-wavelength pulsed laser according to claim 7, characterized in that, The step-by-step amplifier (6) includes a plurality of power amplifiers (61) connected in series. Each power amplifier (61) includes a pump source, a combiner and an active optical fiber. One input end of the combiner is connected to the output end of the modulator (3), the other input end of the combiner is connected to the pump source, and the output end of the combiner is connected to one end of the active optical fiber.

9. The short-wavelength pulsed laser according to claim 8, characterized in that, A second isolator (8) is provided between the first series-connected power amplifier (61) and the modulator (3), and a third isolator is provided between each of the power amplifiers (61).

10. The short-wavelength pulsed laser according to claim 1, characterized in that, The control unit (4) is also used to adjust the pulse width of the second pulse laser by controlling the pulse width or delay of the first pulse laser and / or the chopper modulation signal.

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