Laser pulse train time domain profile modulation device and method

Abstract

The application provides a laser pulse train time domain appearance modulation device and method, wherein the device comprises a laser source, a control module, a gain compensation cycle module and a fiber coupler; the laser source is used for generating an initial laser pulse train to be modulated; the control module is used for sending a radio frequency signal for controlling the working state of the gain compensation cycle module and delivering the radio frequency signal to the gain compensation cycle module; the gain compensation cycle module is used for improving the energy of each sub-pulse in the first laser pulse train and making the sub-pulse after energy improvement coincide with the corresponding sub-pulse in the initial laser pulse train in the time domain; and the fiber coupler is used for coupling each superimposed sub-pulse according to a preset coupling ratio and outputting the first laser pulse train and the modulated second laser pulse train. The gain pre-compensation technology and the pulse time domain superposition technology are used to control the energy of each sub-pulse in the envelope one by one, so that the time domain appearance modulation of the laser pulse train is realized.

Description

Technical Field

[0001] This application relates to the field of pulsed fiber laser technology, and in particular to a laser pulse train temporal topography modulation device and method. Background Technology

[0002] Pulse train lasers refer to pulse sequences with a defined pulse envelope morphology in the time domain, and the number of pulses within the envelope is adjustable. This mode of laser has demonstrated significant advantages in the field of precision materials processing due to its lower thermal effects and higher processing efficiency. In addition, laser pulse trains also have important applications in numerous other fields such as space ablation propulsion, fluid measurement, high-speed imaging diagnostics, high-speed optical communication, and laser ranging.

[0003] Currently, the main methods for obtaining high-energy laser pulse trains are solid-state amplification and fiber amplification. However, due to gain saturation, the temporal envelope of the pulse train undergoes morphological distortion during amplification, lowering the nonlinear threshold of the laser system and hindering the increase in output energy. Simultaneously, the amplifier's front-end devices may be damaged, affecting system stability. Therefore, to mitigate the adverse effects of gain saturation on the amplification process, the temporal morphology of the laser pulse train must be modulated before amplification. Thus, how to achieve modulation of the pulse train's temporal morphology has become a pressing problem to be solved. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a laser pulse train temporal topography modulation device and method.

[0005] According to a first aspect of the embodiments of this application, a laser pulse train temporal topography modulation device is provided, the device comprising a laser source, a control module, a gain compensation loop module, and an optical fiber coupler; wherein:

[0006] The laser source is used to generate the initial laser pulse train to be modulated;

[0007] The control module is used to send a radio frequency signal to control the working state of the gain compensation loop module and transmit it to the gain compensation loop module; wherein, the radio frequency signal is matched in the time domain with the envelope signal of the initial laser pulse train;

[0008] The gain compensation loop module is used to increase the energy of each sub-pulse in the first laser pulse train and make the sub-pulse with increased energy coincide with the corresponding sub-pulse in the initial laser pulse train in the time domain; wherein, the first laser pulse train is a pulse train transmitted to the gain compensation loop module by the fiber coupler;

[0009] The fiber coupler is used to couple the superimposed sub-pulses according to a preset coupling ratio, and output the first laser pulse train and the modulated second laser pulse train; wherein, the superimposed sub-pulses are obtained by superimposing the sub-pulses output by the gain compensation loop module with the corresponding sub-pulses in the initial laser pulse train.

[0010] In some embodiments of this application, the fiber coupler includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal; wherein the first input terminal is connected to the laser source, the second input terminal is connected to the output terminal of the gain compensation loop module, the first output terminal is used to output the second laser pulse train, and the second output terminal is connected to the input terminal of the gain compensation loop module.

[0011] As one possible implementation, the gain compensation loop module includes an optical fiber amplifier, an optical transmission delay structure, and an optical modulation switch; wherein:

[0012] The fiber amplifier is used to increase the energy of each sub-pulse in the first laser pulse train; the input end of the fiber amplifier is connected to the output end of the fiber coupler.

[0013] The optical transmission delay structure is used to extend the overall optical length of the gain compensation loop module to delay the optical transmission time, so that the sub-pulse after energy enhancement coincides with the corresponding sub-pulse in the initial laser pulse in the time domain; the input end of the optical transmission delay structure is connected to the output end of the fiber amplifier.

[0014] The optical modulation switch is used to control the switching state of the output terminal based on the radio frequency signal; the input terminal of the optical modulation switch is connected to the output terminal of the optical transmission delay structure, and the output terminal of the optical modulation switch is connected to the input terminal of the fiber optic coupler.

[0015] As another possible implementation, the gain compensation loop module further includes:

[0016] An optical fiber isolator is used to enable unidirectional transmission of the first laser pulse train in the gain compensation loop module; the input end of the optical fiber isolator is connected to the output end of the optical fiber coupler, and the output end of the optical fiber isolator is connected to the input end of the optical fiber amplifier.

[0017] As an example, the optical transmission delay structure includes a passive matching fiber and an tunable optical delay line; wherein:

[0018] The passive matching fiber is used to make up for the optical length required to compensate for the optical transmission time delay of the gain compensation loop module;

[0019] The adjustable optical delay line is used to precisely adjust the optical length of the gain compensation loop module.

[0020] In some embodiments of this application, the optical modulation switch is an optical modulation device or an acousto-optic modulation device.

[0021] In one possible implementation, the control module includes a photodetector and a radio frequency signal generator, wherein:

[0022] The photodetector is used to convert the received initial laser pulse train signal into an electrical signal and transmit the electrical signal to the radio frequency signal generator; the input terminal of the photodetector is connected to the laser source, and the output terminal of the photodetector is connected to the input terminal of the radio frequency signal generator.

[0023] The radio frequency signal generator is used to generate the radio frequency signal based on the electrical signal and send it to the optical modulation switch.

[0024] In some other embodiments of this application, the radio frequency signal emitted by the control module matches the target morphology.

[0025] According to a second aspect of the embodiments of this application, a laser pulse train temporal topography modulation method is provided, applied to the laser pulse train temporal topography modulation apparatus described in the first aspect above, comprising:

[0026] Based on the laser source, an initial laser pulse train is generated;

[0027] Based on the control module, an radio frequency signal is issued to control the working state of the gain compensation loop module and sent to the gain compensation loop module; wherein, the radio frequency signal is matched in the time domain with the envelope signal of the initial laser pulse train;

[0028] Based on the gain compensation loop module, the energy of each sub-pulse in the first laser pulse train is increased, and the sub-pulse with increased energy coincides with the corresponding sub-pulse in the initial laser pulse train in the time domain; wherein, the first laser pulse train is the pulse train transmitted to the gain compensation loop module by the fiber coupler;

[0029] Based on the fiber coupler, the superimposed sub-pulses are coupled according to a preset coupling ratio to output the first laser pulse train and the modulated second laser pulse train; wherein, the superimposed sub-pulses are obtained by superimposing the sub-pulses output by the gain compensation loop module with the corresponding sub-pulses in the initial laser pulse train.

[0030] The radio frequency signal emitted by the control module corresponds to the target shape.

[0031] According to the technical solution of this application, the energy of each sub-pulse in the pulse train output by the fiber coupler is increased by a gain compensation loop module, and the sub-pulses with increased energy coincide with the corresponding sub-pulses in the initial laser pulse train emitted by the laser source in the time domain. The superimposed sub-pulses are split into two paths by the fiber coupler according to a preset coupling ratio. One path continues to be input to the gain compensation loop module, and the other path is directly used as the output of the modulated pulse train. This solution utilizes gain compensation and pulse time-domain superposition in the gain compensation loop module to individually control the energy of each sub-pulse within the envelope, thereby realizing the morphological modulation of the laser pulse train in the time domain, while greatly reducing energy loss during the modulation process.

[0032] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0033] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0034] Figure 1 This is a structural block diagram of a laser pulse train temporal topography modulation device provided in an embodiment of this application;

[0035] Figure 2 This is a timing diagram of various signals in the laser pulse train temporal topography modulation device according to an embodiment of this application;

[0036] Figure 3 This is a structural block diagram of another laser pulse train temporal topography modulation device provided in an embodiment of this application;

[0037] Figure 4 This is a schematic diagram of the modulation principle of the laser pulse train temporal topography modulation device provided in the embodiments of this application;

[0038] Figure 5 This is a structural block diagram of another laser pulse train temporal topography modulation device provided in the embodiments of this application;

[0039] Figure 6 An example diagram showing the moduliable morphology of the laser pulse train temporal morphology modulation device provided in the embodiments of this application;

[0040] Figure 7 This is a flowchart of a laser pulse train temporal topography modulation method provided in an embodiment of this application. Detailed Implementation

[0041] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0042] It should be noted that pulse train mode lasers refer to pulse sequences with a specific pulse envelope morphology in the time domain, and the number of pulses within the envelope is adjustable. This mode of laser has demonstrated significant advantages in the field of precision materials processing due to its lower thermal effects and higher processing efficiency. In addition, laser pulse trains also have important applications in numerous fields such as space ablation propulsion, fluid measurement, high-speed imaging diagnostics, high-speed optical communication, and laser ranging.

[0043] Currently, the main methods for obtaining high-energy laser pulse trains are solid-state amplification and fiber amplification. However, due to gain saturation, the temporal envelope of the pulse train undergoes morphological distortion during amplification, lowering the nonlinear threshold of the laser system and hindering the increase in output energy. Simultaneously, the amplifier's front-end devices may be damaged, affecting system stability. Therefore, to mitigate the adverse effects of gain saturation on the amplification process, the temporal morphology of the laser pulse train can be modulated before amplification. Thus, how to achieve modulation of the pulse train's temporal morphology has become a pressing problem to be solved.

[0044] In related technologies, optical modulation is the mainstream method for achieving editable temporal morphology of pulse trains. This involves controlling the diffraction efficiency of the optical modulation switch in the laser system for different optical pulses by changing the temporal waveform of the analog drive signal, thereby regulating the temporal morphology of the pulse train. Essentially, this method adjusts the magnitude of optical loss, and the insertion loss of the devices themselves is relatively large, leading to a significant reduction in the energy of the modulated pulse train. Therefore, multi-stage amplification is required to achieve high-energy pulse train output, increasing the complexity of laser system design and construction. Furthermore, due to the rise / fall time limitations of the optical modulation switch and driver, for pulse train modes with high sub-pulse repetition frequencies (on the order of GHz), the leading and trailing edges of the temporal envelope suffer greater energy loss during modulation, making precise morphology control difficult.

[0045] To address the aforementioned issues, this application provides a laser pulse train temporal topography modulation device and method.

[0046] Figure 1 This is a structural block diagram of a laser pulse train temporal topography modulation device provided in an embodiment of this application. Figure 1As shown, the device includes a laser source 101, a control module 102, a gain compensation loop module 103, and an optical fiber coupler 104. The laser source 101 is connected to the input end of the optical fiber coupler 104, and both the input and output ends of the optical fiber coupler 104 are connected to the gain compensation loop module 103. The control module 102 is connected to both the laser source 101 and the gain compensation loop module 103.

[0047] In some embodiments of this application, the laser source 101 is used to generate an initial laser pulse train to be modulated. The laser source 101 can be a semiconductor laser with fiber-coupled output, a solid-state laser, or an all-fiber laser. The output optical pulses are in pulse train mode, that is, a pulse sequence with a certain envelope morphology in the time domain, and the number of pulses within the envelope is adjustable. The repetition frequency of the time-domain envelope can be on the order of kHz to MHz, the time width on the order of ns to ms, the repetition frequency of the sub-pulses within the envelope can be on the order of MHz to GHz, the pulse width on the order of ps to fs, and the energy of each sub-pulse within the envelope is equal.

[0048] As an example, laser source 101 can be a 1064nm picosecond pulse train laser source, with single-mode fiber coupling output, fiber core diameter of 6μm, and an average maximum output power of 200mW. The generated pulse train envelope time width t B The envelope repetition frequency f is adjustable in the range of 5ns-1μs. B Adjustable within the range of 100kHz-1MHz; repetition frequency f of the sub-pulses within the envelope. p It is adjustable from 1MHz to 1GHz, and the number of sub-pulses N can be adjusted from 5 to 1000.

[0049] In some embodiments of this application, the control module 102 is used to send an radio frequency (RF) signal controlling the operating state of the gain compensation loop module 103 and transmit it to the gain compensation loop module 103; wherein the RF signal is time-domain matched with the envelope signal of the initial laser pulse train. The control module 102 receives the initial laser pulse train emitted by the laser source 101 and sends an RF signal that matches the time domain of the envelope signal of the initial laser pulse train to control the operating state of the gain compensation loop module 103.

[0050] As an example, the control module 102 may include a photodetector and a radio frequency (RF) signal generator. The photodetector is used to generate the initial laser pulse train from the laser source 101 and converts it into an electrical signal, which is then transmitted as a clock signal to the RF signal generator. The RF signal generator, based on the clock signal, emits an RF signal to control the operating state of the gain compensation loop module 103. Figure 2As shown, the radio frequency signal can be a high or low level signal. When the signal is high, the gain compensation loop module 103 is turned on, and when the signal is low, the gain compensation loop module 103 is turned off. The high and low level signals are matched with the envelope signal of the initial laser pulse train in the time domain. That is, the start time of each envelope signal of the radio frequency signal is consistent with the start time of the envelope signal of the initial laser pulse train, and the time width of each envelope signal of the radio frequency signal is consistent with the time width of the envelope signal of the initial laser pulse train.

[0051] In other words, the control module 102 can control the gain compensation loop module 103 to turn off after the temporal topography of a single laser pulse train in the laser source 101 is modulated, and control the gain compensation loop module 103 to turn on again when the next pulse train is emitted. The control module 102 controls the gain compensation loop module to turn on and off cyclically, so as to avoid the laser pulse in the gain compensation loop module 103 being output to the coupler after the single pulse train is modulated and before the next pulse train is emitted, which would cause interference to the output modulated pulse train.

[0052] In some embodiments of this application, the gain compensation loop module 103 is used to increase the energy of each sub-pulse in the first laser pulse train and make the energy-enhanced sub-pulse coincide with the corresponding sub-pulse in the initial laser pulse train in the time domain; wherein, the first laser pulse train is a pulse train delivered to the gain compensation loop module 103 by the fiber coupler 104; the fiber coupler 104 is used to couple each superimposed sub-pulse according to a preset coupling ratio to output the first laser pulse train and the modulated second laser pulse train; wherein, the superimposed sub-pulse is obtained by superimposing the sub-pulse output by the gain compensation loop module 103 with the corresponding sub-pulse in the initial laser pulse train.

[0053] As one possible implementation, the fiber optic coupler 104 is a 2*2 type, that is, two input terminals and two output terminals, namely a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal is connected to the laser source 101, the second input terminal is connected to the output terminal of the gain compensation loop module 103, the first output terminal is used to output a second laser pulse train, and the second output terminal is connected to the input terminal of the gain compensation loop module 103.

[0054] In other words, the sub-pulse whose energy has been boosted by the gain compensation loop module 103 can completely overlap with the corresponding sub-pulse in the initial laser pulse train in the time domain. Therefore, the two can be directly superimposed, and the superimposed sub-pulse is split into two paths by the fiber coupler 104. One path is directly output as the modulated sub-pulse, and the other path enters the gain compensation loop module 103 again for energy boosting to modulate subsequent sub-pulses.

[0055] In some embodiments of this application, the gain compensation loop module 103 increases the energy of the corresponding sub-pulse by a preset gain. Simultaneously, the gain compensation loop module 103 can provide a certain optical length, generating a time delay so that the energy-enhanced sub-pulse can coincide in the time domain with the corresponding sub-pulse in the initial laser pulse train. As one implementation, the time delay of the gain compensation loop module 103 can be set so that the currently energy-enhanced sub-pulse coincides in the time domain with the next sub-pulse in the initial laser pulse train.

[0056] As an example, if the initial laser pulse train includes four sub-pulses, namely sub-pulse 1, sub-pulse 2, sub-pulse 3, and sub-pulse 4, and the fiber coupler 104 has a preset coupling ratio of 50:50, after sub-pulse 1 enters the fiber coupler 104, since the gain compensation loop module 103 has not yet output any sub-pulses, the fiber coupler 104 splits sub-pulse 1 into two paths. One path is directly output, and the other path enters the gain compensation loop module 103 for energy boosting. The boosted sub-pulse 1' can then be coupled with sub-pulse 2 in the initial laser pulse train. In the time domain, they completely overlap, so that subpulse 1' and subpulse 2 are superimposed when they enter the fiber coupler 104 and split into two paths. One path is directly output as the pulse modulated by atomic pulse 2, and the other path continues to enter the gain compensation loop module 103 for energy boosting to continue modulating subpulse 3 in the initial laser pulse train. This cycle continues until the modulation of subpulse 4 is completed, at which point the gain compensation loop module 103 is turned off. When the laser source 101 emits the next pulse train, the gain compensation loop module 103 is turned on again, and the above process is repeated. Figure 2 As shown, the morphology of the modulated second laser pulse train is obliquely upward.

[0057] According to the laser pulse train temporal topography modulation device of this application embodiment, the energy of each sub-pulse in the pulse train output by the fiber coupler is increased by a gain compensation loop module, and the sub-pulses with increased energy coincide with the corresponding sub-pulses in the initial laser pulse train emitted by the laser source in the time domain. The superimposed sub-pulses are split into two paths by the fiber coupler according to a preset coupling ratio. One path is input to the gain compensation loop module, and the other path is directly used as the output of the modulated pulse train. This scheme can use the gain compensation of the gain compensation loop module and the superposition of pulses in the time domain to adjust the energy of each sub-pulse within the envelope one by one, thereby realizing the temporal topography modulation of the laser pulse train, while greatly reducing the energy loss during the modulation process.

[0058] Figure 3 This is a structural block diagram of another laser pulse train temporal topography modulation device provided in an embodiment of this application. Figure 3As shown, the device includes a laser source 310, a control module 320, a gain compensation loop module 330, and an optical fiber coupler 340.

[0059] In some embodiments of this application, the gain compensation loop module 330 includes an optical fiber amplifier 331, an optical transmission delay structure 332, and an optical modulation switch 333. The optical fiber amplifier 331 is used to boost the energy of each sub-pulse in the first laser pulse train; the input end of the optical fiber amplifier 331 is connected to the output end of the optical fiber coupler. The optical transmission delay structure 332 is used to extend the overall optical length of the gain compensation loop module to achieve a delay in optical transmission time, so that the boosted sub-pulse coincides with the corresponding sub-pulse in the initial laser pulse in the time domain; the input end of the optical transmission delay structure 332 is connected to the output end of the optical fiber amplifier 331. The optical modulation switch 333 is used to control the switching state of the output end based on a radio frequency signal; the input end of the optical modulation switch 333 is connected to the output end of the optical transmission delay structure 332, and the output end of the optical modulation switch 333 is connected to the input end of the optical fiber coupler 340.

[0060] In one possible implementation, the fiber amplifier 331 includes a pump / signal combiner, a pump source, and a gain fiber. The pump / signal combiner couples the pump light and the pulse train signal light into the gain fiber; the pump source generates photons of a specific energy to excite the gain fiber; the gain fiber is used to achieve population inversion and increase the energy of the sub-pulses. The gain fiber can be a single / double-clad fiber doped with Yb, Er, Ho, or Tm, with a core diameter of 6–20 μm. The specific doping ion type, core diameter, and fiber length of the gain fiber need to be matched to the wavelength and pulse energy of the initial laser pulse train output by the laser source 310.

[0061] The pump source can be a semiconductor laser with fiber-coupled output, with an output mode of continuous wave or pulse and an output wavelength of 915nm to 1550nm. The pumping method can be forward, reverse, or bidirectional pumping. The specific pump light parameters and pumping method must be matched with the initial laser pulse train output by the laser source 310 and the gain fiber parameters. In the case of pulse pumping, the time width and repetition frequency of the pump pulse must be matched with the corresponding parameters of the envelope of the initial laser pulse train.

[0062] As one possible implementation, the optical transmission delay structure 332 includes a passive matching fiber and an adjustable optical delay line. The passive matching fiber is used to compensate for the optical transmission time delay required by the gain compensation loop module 330, and the adjustable optical delay line is used to precisely adjust the optical length of the gain compensation loop module 330. The passive matching fiber can be a single / double-clad fiber with a core diameter of 6–20 μm. Specific parameters such as the fiber core diameter and length need to be matched to the wavelength and pulse energy of the initial laser pulse train, the gain fiber parameters, and the length requirements of the gain compensation loop system based on the pulse train morphology modulation.

[0063] As an example, an adjustable optical delay line can be a fiber-coupled output device based on a spatial interferometer structure, which adjusts the optical transmission delay by precisely controlling the optical path difference of the interferometer using a micrometer or motor.

[0064] As another example, adjustable optical delay lines can also be piezoelectric ceramics wound with passive optical fiber. The length of the wound passive optical fiber can be controlled by adjusting the expansion and contraction of the piezoelectric ceramics using voltage, thereby adjusting the optical transmission delay. It should be noted that the adjustment precision of adjustable optical delay lines is at least on the picosecond level.

[0065] The optical modulation switch 333 can be an optical modulation device or an acousto-optic modulation device. The rise / fall time of the optical modulation switch 333 does not exceed 15ns, and the on / off extinction ratio is greater than 50dB, so as to achieve fast and effective on and off.

[0066] In some embodiments of this application, the control module 320 includes a photodetector 321 and a radio frequency (RF) signal generator 322. The photodetector 321 converts the received initial laser pulse train signal into an electrical signal and transmits the electrical signal to the RF signal generator. The input terminal of the photodetector 321 is connected to the laser source 310, and the output terminal of the photodetector 321 is connected to the input terminal of the RF signal generator 322. The RF signal generator 322 emits an RF signal based on the electrical signal and transmits it to the optical modulation switch 333.

[0067] As an example, the optical modulation switch 333 can be an acousto-optic modulator with an operating frequency of 200MHz, a rise / fall time of 10ns, and an on / off extinction ratio greater than 50dB. The operating state of the acousto-optic modulator is changed based on the radio frequency signal output by the radio frequency signal generator 322 in the control module 320. The characteristics of the radio frequency signal output by the radio frequency signal generator 322 include: (1) a video pulse sequence with a repetition frequency of f1, which is set to f1 = 200MHz to match the operating frequency of the acousto-optic modulator; (2) a signal amplitude of 3.5V-5V and a rise time of 10ns; (3) the output of m pulse sequences with a repetition frequency of f1 to form a pulse envelope sequence with a repetition frequency of f2, and f2 is consistent with the envelope repetition frequency of the initial laser pulse train. The total time width T of the m video pulse signals is consistent with the envelope time width of the initial laser pulse train, where f2 = 1MHz and T = 40ns. The generated video signal is input as a synchronization signal to the optical modulation switch, which is then used as a drive signal to control the optical modulation switch, thereby controlling the working state of the gain compensation loop system.

[0068] The working principle of the laser pulse train temporal topography modulation device in the embodiments of this application will be described in detail below with examples. Figure 4 As shown, the modulation process of a single initial laser pulse train is described as an example. This initial laser pulse train includes four sub-pulses, which are sub-pulses a, b, c, and d from beginning to end. The repetition frequency of the sub-pulses within the train is 100MHz, the time interval between two adjacent sub-pulses is Δt = 10ns, the energy of a single sub-pulse is E0, and the pulse train time width is t. B =40ns, pulse train repetition frequency f B =1MHz. The coupling ratio of the fiber optic coupler 340 is 50:50. Sub-pulse a enters the fiber optic coupler 340 from the first input terminal. If the coupling loss is not ignored, the fiber optic coupler 340 splits it into two sub-pulses a', each with a capability of E0 / 2. One of them is directly output from the first output terminal, and the other is input to the gain compensation loop module 330 from the second output terminal. Ignoring the gain and loss changes of the gain compensation loop module 330 for signal pulses with different capabilities, and setting the amplification factor of the gain compensation loop module 330 to α (α>1), the energy of the amplified sub-pulse a” becomes αE0 / 2.

[0069] By designing the optical transmission delay structure 332, the transmission time of the entire gain compensation loop module 330 is ΔT = Δt = 10ns, corresponding to an optical length of ΔL = c·ΔT / n = 2m. After one gain compensation loop, the sub-pulse a” enters the fiber coupler 340 through the second output terminal, and coincides in the time domain with the second sub-pulse b within the incident initial laser pulse train. The two pulses superimpose to form a new sub-pulse. After beam splitting by the coupler, the energy of both output sub-pulses b' is (E0 + αE0 / 2) / 2, thus completing one loop.

[0070] One of the sub-pulses b' after beam splitting re-enters the gain loop module 330 for a second loop process, resulting in an amplified sub-pulse b” with energy of (1+α / 2)αE0 / 2. This sub-pulse b” is then superimposed in the time domain with the third sub-pulse c in the initial laser pulse train and output as a sub-pulse c' after being split by the fiber coupler 340, with energy of [1+(1+α / 2)α / 2]E0 / 2.

[0071] Similarly, after the third cycle, the energy of the sub-pulse d' output by the fiber coupler 340 is {1+[1+(1+α / 2)α / 2]α / 2}E0 / 2. The energy of each sub-pulse in the final output second laser pulse train increases sequentially from beginning to end, meaning the pulse train's temporal shape is modulated into an upward-sloping line. After the temporal shape of a single laser pulse train is modulated, the optical modulation switch 333 immediately turns off, terminating the cycle. When the next pulse train from the laser source 310 is emitted, the optical modulation switch turns on again, restarting the cycle.

[0072] In other embodiments of this application, the gain compensation loop module further includes an optical fiber isolator.

[0073] Figure 5 This is a structural block diagram of another laser pulse train temporal topography modulation device provided in an embodiment of this application. Figure 5 As shown, based on the above embodiment, the gain compensation loop module 330 in this device also includes an optical fiber isolator 501. The second output end of the optical fiber coupler 340 is connected to the input end of the optical fiber isolator 501, and the output end of the optical fiber isolator 501 is connected to the input end of the optical fiber amplifier 331. The optical fiber isolator 501 is used to ensure unidirectional transmission of the first laser pulse train in the gain compensation loop module 330, to prevent reverse-transmitted light from damaging the laser source, and to ensure the orderliness and stability of the pulse loop superposition. The functions and connection methods of other components in this device are consistent with the above embodiment and will not be repeated here.

[0074] According to the laser pulse train temporal topography modulation device of this application embodiment, the gain compensation loop module includes an optical fiber amplifier, an optical transmission delay structure, and an optical modulation switch. This increases the energy of the sub-pulses entering the gain compensation loop module. Simultaneously, the optical transmission delay structure ensures that the output sub-pulses coincide with the corresponding sub-pulses in the initial laser pulse train in the time domain, thereby achieving topography modulation of the initial laser sub-pulses and avoiding energy loss. Furthermore, the optical fiber isolator in the gain compensation loop module ensures unidirectional pulse transmission, preventing damage to the laser source from back-propagating light.

[0075] In some embodiments of this application, the radio frequency (RF) signal emitted by the control module of the laser pulse train temporal topography modulation device is matched with the target topography. The target topography is the topography to be modulated. That is, the RF signal emitted by the control module can be a square wave signal to control the operating state of the gain compensation loop module, or other analog modulation signals to control the opening degree of the optical modulation switch. For example, various correspondences between topography and RF signal waveforms can be preset. Figure 6 As shown, the shapes can include upward sloping lines, downward sloping lines, M-shapes, roof shapes, etc. In practical applications, the waveform of the RF signal transmitter can be adjusted using editable logic devices based on actual needs to achieve modulation of the target shape, thereby achieving the goal of editable pulse train shapes.

[0076] To achieve the above embodiments, this application also provides a laser pulse train temporal topography modulation method.

[0077] Figure 7 This is a flowchart illustrating a laser pulse train temporal topography modulation method provided in an embodiment of this application. It should be noted that this method is applied to the laser pulse train temporal topography modulation device in the above embodiments. Figure 7 As shown, the method may include the following steps:

[0078] Step 701: Generate an initial laser pulse train based on the laser source.

[0079] Step 702: Based on the control module, an RF signal is sent to control the working state of the gain compensation loop module and then transmitted to the gain compensation loop module; wherein, the RF signal is matched in the time domain with the envelope signal of the initial laser pulse train.

[0080] Step 703: Based on the gain compensation loop module, increase the energy of each sub-pulse in the first laser pulse train, and make the sub-pulses with increased energy coincide with the corresponding sub-pulses in the initial laser pulse train in the time domain; wherein, the first laser pulse train is the pulse train sent to the gain compensation loop module by the fiber coupler.

[0081] Step 704: Based on the fiber coupler, the superimposed sub-pulses are coupled according to a preset coupling ratio to output a first laser pulse train and a modulated second laser pulse train; wherein, the superimposed sub-pulses are obtained by superimposing the sub-pulses output by the gain compensation loop module with the corresponding sub-pulses in the initial laser pulse train.

[0082] In some embodiments of this application, the video signal emitted by the control module corresponds to the target shape.

[0083] It should be noted that the foregoing explanation of the embodiment of the laser pulse train temporal topography modulation device also applies to the embodiment of the laser pulse train temporal topography modulation method, and will not be repeated here.

[0084] According to the laser pulse train temporal topography modulation method of this application, a gain compensation loop module is used to enhance the energy of each sub-pulse in the pulse train output by the fiber coupler, and the enhanced sub-pulses coincide with the corresponding sub-pulses in the initial laser pulse train emitted by the laser source in the time domain. The superimposed sub-pulses are split into two paths by the fiber coupler according to a preset coupling ratio. One path is input to the gain compensation loop module, and the other path is directly used as the output of the modulated pulse train. This scheme can utilize the gain compensation of the gain compensation loop module and the superposition of pulses in the time domain to achieve individual control of the energy of each sub-pulse within the envelope, thereby realizing the temporal topography modulation of the laser pulse train and reducing energy loss during the modulation process.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0087] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0088] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0089] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0090] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0091] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc.

[0092] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A laser pulse train temporal topography modulation device, characterized in that, It includes a laser source, a control module, a gain compensation loop module, and an optical fiber coupler; among which: The laser source is used to generate the initial laser pulse train to be modulated; The control module is used to send an radio frequency signal to control the working state of the gain compensation loop module and transmit it to the gain compensation loop module; wherein, the radio frequency signal is matched in the time domain with the envelope signal of the initial laser pulse train; The gain compensation loop module is used to increase the energy of each sub-pulse in the first laser pulse train and make the sub-pulse with increased energy coincide with the corresponding sub-pulse in the initial laser pulse train in the time domain; wherein, the first laser pulse train is a pulse train transmitted to the gain compensation loop module by the fiber coupler; The fiber coupler is used to couple the superimposed sub-pulses according to a preset coupling ratio, and output the first laser pulse train and the modulated second laser pulse train; wherein, the superimposed sub-pulses are obtained by superimposing the sub-pulses output by the gain compensation loop module with the corresponding sub-pulses in the initial laser pulse train; The gain compensation loop module includes an optical fiber amplifier, an optical transmission delay structure, and an optical modulation switch; wherein: The fiber amplifier is used to increase the energy of each sub-pulse in the first laser pulse train; the input end of the fiber amplifier is connected to the output end of the fiber coupler. The optical transmission delay structure is used to extend the overall optical length of the gain compensation loop module to delay the optical transmission time, so that the sub-pulse after energy enhancement coincides with the corresponding sub-pulse in the initial laser pulse in the time domain; the input end of the optical transmission delay structure is connected to the output end of the fiber amplifier. The optical modulation switch is used to control the switching state of the output terminal based on the radio frequency signal; the input terminal of the optical modulation switch is connected to the output terminal of the optical transmission delay structure, and the output terminal of the optical modulation switch is connected to the input terminal of the fiber optic coupler.

2. The apparatus according to claim 1, characterized in that, The fiber coupler includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal; wherein, the first input terminal is connected to the laser source, the second input terminal is connected to the output terminal of the gain compensation loop module, the first output terminal is used to output the second laser pulse train, and the second output terminal is connected to the input terminal of the gain compensation loop module.

3. The apparatus according to claim 1, characterized in that, The gain compensation loop module also includes: An optical fiber isolator is used to enable unidirectional transmission of the first laser pulse train in the gain compensation loop module; the input end of the optical fiber isolator is connected to the output end of the optical fiber coupler, and the output end of the optical fiber isolator is connected to the input end of the optical fiber amplifier.

4. The apparatus according to claim 1, characterized in that, The optical transmission delay structure includes a passive matched fiber and an adjustable optical delay line; wherein: The passive matching fiber is used to make up for the optical length required to compensate for the optical transmission time delay of the gain compensation loop module; The adjustable optical delay line is used to precisely adjust the optical length of the gain compensation loop module.

5. The apparatus according to claim 1, characterized in that, The optical modulation switch is an optical modulation device or an acousto-optic modulation device.

6. The apparatus according to claim 1, characterized in that, The control module includes a photodetector and a radio frequency signal generator, wherein: The photodetector is used to convert the received initial laser pulse train signal into an electrical signal and transmit the electrical signal to the radio frequency signal generator; the input terminal of the photodetector is connected to the laser source, and the output terminal of the photodetector is connected to the input terminal of the radio frequency signal generator. The radio frequency signal generator is used to generate the radio frequency signal based on the electrical signal and send it to the optical modulation switch.

7. The apparatus according to any one of claims 1-6, characterized in that, The radio frequency signal emitted by the control module matches the target shape.

8. A method for temporal topography modulation of laser pulse trains, characterized in that, The laser pulse train temporal topography modulation apparatus applied to any one of claims 1 to 7 comprises: Based on the laser source, an initial laser pulse train is generated; Based on the control module, an radio frequency signal is issued to control the working state of the gain compensation loop module and sent to the gain compensation loop module; wherein, the radio frequency signal is matched in the time domain with the envelope signal of the initial laser pulse train; Based on the gain compensation loop module, the energy of each sub-pulse in the first laser pulse train is increased, and the sub-pulse with increased energy coincides with the corresponding sub-pulse in the initial laser pulse train in the time domain; wherein, the first laser pulse train is the pulse train transmitted to the gain compensation loop module by the fiber coupler; Based on the fiber coupler, the superimposed sub-pulses are coupled according to a preset coupling ratio to output the first laser pulse train and the modulated second laser pulse train; wherein, the superimposed sub-pulses are obtained by superimposing the sub-pulses output by the gain compensation loop module with the corresponding sub-pulses in the initial laser pulse train.

9. The method according to claim 8, characterized in that, The radio frequency signal emitted by the control module corresponds to the target shape.

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