Apparatus and method for multi-seed source modulation to suppress stimulated brillouin scattering

Abstract

This application discloses a device and method for suppressing stimulated Brillouin scattering (SBS) using multiple sub-source modulation. The device includes a main seed source, at least one secondary seed source, an optical beam combiner, and a drive control module. The main seed source is a multi-longitudinal-mode semiconductor laser, driven by a pulsed current to output a broadband pulsed substrate light. The secondary seed source is a single-longitudinal-mode semiconductor laser, outputting a narrow-linewidth seed light. The output light from the secondary seed source is coupled into the resonant cavity of the main seed source via the optical beam combiner. The drive control module independently regulates the waveform, amplitude, and timing of the driving currents of the main and secondary seed sources, adjusting the power of the injected secondary seed light to match the gain of the main seed source. This causes longitudinal-mode competition within the main seed cavity to achieve spectral quenching, and the original pulse of the main seed source is truncated by the depletion of transient upper-level particles. This invention can simultaneously obtain narrow-linewidth, sub-nanosecond ultrashort pulse seed light, suppressing stimulated Brillouin scattering in fiber optic links from both the frequency and time domains.

Description

Technical Field

[0001] This invention relates to narrow-linewidth high-power fiber laser seed source technology, specifically to a device and method for suppressing stimulated Brillouin scattering by modulating multiple seed sources. Background Technology

[0002] Stimulated Brillouin scattering (SBS) is an inherent third-order nonlinear optical effect in fiber laser amplification links. When the intensity and coherence duration of the laser light transmitted in the fiber meet the conditions for the establishment of the phonon field, strong backscattered light will be generated. The backscattered light will consume the forward laser energy, which not only limits the output power of the fiber laser, but also damages the front-end seed source and amplification devices in severe cases. Therefore, suppressing SBS is a core problem that must be solved in the development of high-power narrow-linewidth fiber laser systems.

[0003] In existing technologies, there are two main approaches to suppressing the SBS effect in fiber optic amplification links. The first approach uses an external phase modulator to modulate the seed light, artificially broadening the laser spectral linewidth and disrupting the coherent resonance condition of the phonon field, thereby weakening the SBS effect. However, this approach relies on external devices to introduce random phase perturbations, which degrades the beam coherence and quality of the output laser, significantly limiting its application in scenarios such as lidar and quantum sensing where laser coherence is critical.

[0004] The second approach suppresses SBS by compressing the seed pulse width, making the pulse duration shorter than the Brillouin phonon lifetime, thereby preventing the phonon field from fully establishing in the time domain. This approach typically uses narrow pulses to drive semiconductor lasers to achieve short pulse output. However, semiconductor lasers have an inherent physical lower limit to their carrier establishment time, making it difficult to stably generate seed pulses with pulse widths less than 1 ns. At the same time, under narrow pulse pumping conditions, lasers are prone to relaxation oscillations, resulting in severe distortion of the output pulse waveform and a significant increase in gain medium spontaneous emission (ASE) noise.

[0005] To improve the waveform quality of narrow pulse output, existing research has proposed injection-locking techniques, which use narrow-linewidth auxiliary light sources to inject and lock the main laser to compress the pulse. However, traditional injection-locking schemes only consider steady-state spectral matching conditions for optical path design, without taking into account the transient dynamic changes of charge carriers in the cavity under pulsed operating conditions. This results in defects such as narrow pulse tunability, pulse leading and trailing edge distortion, and the inability to filter out multi-longitudinal mode spontaneous emission, making it impossible to simultaneously achieve narrow-linewidth, ultrashort pulse, and low-noise seed light output.

[0006] In addition, the currently disclosed dual-seed source composite injection architecture has a single function, and can only output a seed pulse with a single fixed waveform. It lacks the ability to independently control the rising edge, flat top segment, and falling edge of the pulse, and cannot generate multi-morphology programmable custom pulses. It is difficult to adapt to the differentiated use needs of seed light with complex time-domain waveforms in emerging fields such as laser spectral analysis, airborne lidar, and quantum precision sensing.

[0007] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0008] The purpose of this invention is to provide a device and method for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources, so as to solve the above-mentioned technical problems.

[0009] To achieve the above objectives, a first aspect of this application provides a device for suppressing stimulated Brillouin scattering using multiple sub-source modulation, comprising:

[0010] The main seed source is a multi-longitudinal-mode semiconductor laser that outputs broadband pulsed seed light.

[0011] At least one secondary seed source, wherein the secondary seed source is a single longitudinal mode semiconductor laser that outputs narrow linewidth seed light;

[0012] In the optical beam combining device, the output optical path of each secondary seed source is connected to the corresponding input channel of the optical beam combining device, and the output light of the secondary seed source is coupled and injected into the resonant cavity of the main seed source through the optical beam combining device.

[0013] The drive control module is electrically connected to the main seed source and each sub-seed source. The drive control module can independently output the drive current waveform, output amplitude, pulse width, repetition frequency and relative timing corresponding to the main seed source and each sub-seed source.

[0014] The drive control module is configured to adjust the output optical power of the secondary seed source so that the injected optical power of the secondary seed source matches the gain of the main seed source. The longitudinal mode competition occurs in the resonant cavity of the main seed source to achieve spectral quenching. At the same time, the gain medium in the cavity experiences transient upper energy level particle depletion, which cuts off the original pulse of the main seed source.

[0015] In a further technical solution, only one secondary seed source is set up, and the drive control module controls the secondary seed source to continuously output continuous light and constantly inject narrowband light into the resonant cavity of the main seed source. Through spectral quenching, the large pulse with wide pulse width and time domain is divided into multiple small pulses with narrow pulse width and time domain.

[0016] In a further technical solution, the secondary seed source is configured with two or more channels, each of which outputs narrow-linewidth continuous light with a different center wavelength. The drive control module divides a single pulse period of the main seed source into several independent fine time slots. In a single time slot, only one secondary seed source is activated to inject narrowband light into the resonant cavity of the main seed source, while the other secondary seed sources are in a closed or silent state below the lasing threshold. The wavelength of the injected light participating in mode competition in the cavity of the main seed source is changed in a time-division manner, and the center wavelength of the secondary seed sources activated in different time slots is respectively matched with different target longitudinal modes in the resonant cavity of the main seed source.

[0017] In a further technical solution, the drive control module includes a main seed source current drive circuit, an FPGA core main control unit, and a secondary seed source current drive circuit. The FPGA core main control unit is electrically connected to the main seed source current drive circuit and each secondary seed source current drive circuit. The output terminal of the main seed source current drive circuit is electrically connected to the main seed source, and the output terminal of each secondary seed source current drive circuit is individually electrically connected to a corresponding secondary seed source.

[0018] In a further technical solution, the drive control module stores preset standard pulse envelope data. The drive control module compares the real-time acquired waveform and spectral data with the preset standard pulse envelope, and dynamically fine-tunes the driving current amplitude, timing offset, and pulse width of the main seed source and each sub-seed source in the next pulse cycle to form a closed-loop correction.

[0019] In a further technical solution, the device also includes a monitoring beam splitting component, which is set at the output end of the main optical path. The monitoring beam splitting component includes a beam splitting coupler and a light detection and acquisition unit. The beam splitting coupler splits a portion of the optical signal from the total output optical path and transmits it to the light detection and acquisition unit. The waveform and spectral data acquired by the light detection and acquisition unit are transmitted back to the drive control module to form a closed-loop signal path.

[0020] In a further technical solution, the secondary seed source outputs a narrow-linewidth pulsed seed light; the driving control module synchronously matches the pulse timing of the main seed source with that of the secondary seed source, and drives the output pulsed light of the secondary seed source to inject into the resonant cavity of the main seed source during the falling edge period of the main seed source pulse, thereby depleting the residual upper energy level particles in the cavity and cutting off the falling edge tail of the main seed source pulse.

[0021] According to a second aspect of this application, a method for suppressing stimulated Brillouin scattering using multiple sub-source modulation is provided, applied to the apparatus described above, comprising the following steps:

[0022] S1. Power-on initialization timing control: First, turn on the secondary seed source and keep it in continuous light operation state. After the wavelength of the secondary seed source is stable and the injected light power matches the power of the main seed source, turn on the pulse current drive of the main seed source.

[0023] S2. Intracavity injection matching control: The drive control module independently adjusts the output optical power of the secondary seed source so that the injected narrowband optical power matches the gain of the main seed source. After the narrowband light is injected into the resonant cavity of the main seed source, the spectral quenching is completed through intracavity longitudinal mode competition. The original pulse of the main seed source is cut off by the depletion of the upper energy level particles in the gain medium.

[0024] S3, graded power-off timing control: After receiving the shutdown signal, the main seed source pulse drive is first cut off, and the residual photons in the main seed source cavity are delayed for a period of time to decay. Then, the continuous drive current of each auxiliary seed source is turned off in sequence, and finally the temperature control unit is turned off.

[0025] In a further technical solution, S2 also includes time-division multi-wavelength modulation: when there are two or more secondary seed sources, a single main pulse period is divided into multiple time slots, and only one secondary seed source injects narrowband light into the main seed source resonant cavity in each time slot. Different secondary seed sources are switched in different time slots to participate in the mode competition within the main seed source resonant cavity.

[0026] According to a third aspect of this application, a method for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources is provided, applied to the apparatus described above, comprising the following steps:

[0027] T1, the drive control module outputs periodic pulse drive current to the main seed source, driving the main seed source to output broadband pulse seed light;

[0028] T2. The drive control module synchronously matches the pulse timing of the main seed source with the pulse drive timing of the secondary seed source, aligning the secondary seed pulse to the starting time of the falling edge of the main seed source pulse.

[0029] T3. At the beginning of the falling edge of the main seed source pulse, the secondary seed source is driven to output a narrow-linewidth pulse seed light. The narrow-linewidth pulse seed light is coupled into the main seed source resonant cavity through an optical beam combiner. The injected narrow-band pulse light matches the target longitudinal mode corresponding energy level of the main seed resonant cavity, preempts the remaining upper energy level carriers in the cavity, and achieves spectral quenching through longitudinal mode competition, thus cutting off the damping tail of the falling edge of the main seed source pulse.

[0030] The apparatus and method for suppressing stimulated Brillouin scattering by various sub-source modulation provided in this application have the following technical effects:

[0031] By coupling a narrow-linewidth secondary seed source into the resonant cavity of the primary seed source, and driving the control module to match the secondary seed injection power with the primary cavity gain, the spectral quenching and transient upper-level particle depletion truncation of the original pulse are achieved through intracavity longitudinal mode competition. This simultaneously realizes narrow-linewidth output and pulse width compression to below 1 ns, thereby disrupting the formation conditions of stimulated Brillouin scattering in the fiber link from both the frequency and time domains. This significantly increases the SBS threshold, removes the constraint of the SBS effect on the output power of the fiber laser amplification system, and filters out multi-longitudinal mode spontaneous emission, reducing ASE noise and improving the coherence quality of the output beam.

[0032] The drive control module can independently adjust the drive current waveform, amplitude, and timing of the main and secondary seed sources. When multiple secondary seed sources are configured, it can time-division switching of different wavelength narrowband light to participate in intracavity mode competition, segmentally control the gain consumption process of each stage of the pulse, and flexibly generate programmable pulse waveforms with different time-domain profiles to adapt to the differentiated seed light waveform requirements of various devices such as lidar, quantum sensing, and spectral detection. When a single secondary seed source is configured, the secondary seed source can be activated only briefly during the falling edge of the main seed source pulse to output narrow-linewidth pulse light. Relying on photons of the matched energy level to quickly consume residual charge carriers in the cavity, it can quickly eliminate the damping tail of the main seed source pulse, shorten the output pulse time-domain width and narrow the output spectrum, and improve the stimulated Brillouin scattering suppression capability of the fiber optic link. Attached Figure Description

[0033] Figure 1 This is a structural diagram and corresponding waveform of the device in Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of energy level transitions in Embodiment 1 of the present invention;

[0035] Figure 3 This is a possible module diagram of Embodiment 1 of the present invention;

[0036] Figure 4 This is a structural diagram and corresponding waveform of the device in Embodiment 2 of the present invention;

[0037] Figure 5 This is a schematic diagram of the energy level transition corresponding to Embodiment 2 of the present invention;

[0038] Figure 6 This is a possible module diagram of Embodiment 2 of the present invention;

[0039] Figure 7 This is a structural diagram and corresponding waveform of the device in Embodiment 3 of the present invention;

[0040] Wherein: 1-Main seed source; 2-Secondary seed source; 21-First secondary seed source; 22-Secondary seed source; 4-Optical beam combining device; 5-Optical isolator; 6-Drive control module; 71-Optical splitter coupler; 72-Optical detection and acquisition unit. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0043] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.

[0044] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0045] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the case.

[0046] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.

[0047] Example 1: See Figure 1 This application provides a device for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources, including a main seed source 1, a secondary seed source 2, a light beam combining device 4, an optical isolator 5, a monitoring and splitting component, and a drive control module 6.

[0048] The main seed source 1 is a multi-longitudinal-mode FP (Fabry-Perot) semiconductor laser. The drive control module 6 internally houses the main seed source current drive circuit, which continuously outputs periodic pulsed current to the main seed source 1. Under pulse pumping, the FP laser outputs broadband pulsed substrate light. The FP laser itself has multiple sub-levels with different energies within its gain bandwidth. Electrons simultaneously transition between multiple levels, naturally generating a single-envelope pulse with a wide pulse width and a large spectral range. Figure 1 The waveform shown in the upper left corner.

[0049] The secondary seed source 2 is a single-longitudinal-mode DFB (Distributed Feedback) semiconductor laser. In this embodiment, only one secondary seed source 2 is provided. The drive control module 6 includes an FPGA core control unit, a main seed source current drive circuit, and a secondary seed source current drive circuit. The FPGA core control unit and the main and secondary seed source current drive circuits are electrically connected. The secondary seed source current drive circuit continuously outputs a DC current with a constant amplitude to supply the secondary seed source 2, so that the secondary seed source 2 always maintains a continuous light output state and continuously emits narrow-linewidth single-longitudinal-mode seed light. Figure 1 The continuous pulse waveform below.

[0050] The narrowband light output from the secondary seed source 2 first passes through the optical isolator 5, and then is connected to the corresponding input channel of the optical beam combiner 4 (e.g., a wavelength division multiplexer); such as Figure 3 As shown, in this embodiment, an optical isolator 5 is also provided. The optical isolator 5 is arranged between the secondary seed source 2 and the optical beam combiner 4. It only allows the narrowband light of the secondary seed source 2 to be transmitted in the forward direction to the optical beam combiner 4, which can block the broadband stray light back from the resonant cavity of the main seed source 1 and avoid damage to the DFB secondary seed source by the reverse strong light. In this embodiment, a wavelength division multiplexer is used as the optical beam combiner 4 to couple the narrow linewidth continuous light output from the secondary seed source 2 into the resonant cavity of the main seed source 1. The narrowband light directly participates in the cavity oscillation process of the main laser.

[0051] In a possible embodiment, a three-port optical circulator can be used on the single-path secondary seed branch to simultaneously replace the wavelength division multiplexer and the optical isolator 5. The output optical path of the secondary seed source 2 is connected to the first port of the optical circulator, the optical coupling input terminal of the resonant cavity of the main seed source 1 is connected to the second port of the optical circulator, and the third port of the optical circulator serves as the final output port. Light can only be transmitted unidirectionally from the first port to the second port. The narrow-linewidth seed light output from the secondary seed source 2 is coupled into the resonant cavity of the main seed source 1 through the circulator, realizing the optical path beam combining function of the original wavelength division multiplexer. The back-reflected light generated by the resonant cavity of the main seed source 1 enters the circulator from the second port and cannot flow back to the first port to damage the secondary seed source 2. It can only be output from the third port, simultaneously realizing the unidirectional anti-reflection function of the original optical isolator 5.

[0052] In this embodiment, the drive control module 6 is specifically an FPGA (Field Programmable Gate Array) drive control module. The drive control module 6 establishes electrical connections with the main seed source 1 and the single-channel secondary seed source 2. The FPGA core main control unit can independently control the current waveform, output amplitude, pulse repetition frequency, and relative timing of the outputs of the main seed source 1 and the secondary seed source 2. The drive control module 6 adjusts the output optical power of the secondary seed source 2 in real time so that the narrowband optical power injected into the main cavity matches the cavity gain of the main seed source 1.

[0053] When the narrowband light from the secondary seed source 2 is continuously injected into the resonant cavity of the FP main seed source 1, combined with the attached... Figure 2 The energy level structure can be intuitively understood for microscopic processes: the narrowband light from the secondary seed source 2 corresponds to a single, definite upper energy level (a sub-level of E2). ’ 2. Continuous stimulation causes electrons in this energy level to rapidly transition downwards and emit light. The total number of upper-level electrons within the gain medium is limited. The energy level corresponding to the matched wavelength will compete for the vast majority of inverted particle number resources, leaving other energy levels unable to obtain enough charge carriers to complete stimulated emission, resulting in spectral quenching and a significant narrowing of the output spectrum. Simultaneously, the electrons in the matched energy level are rapidly consumed, causing the cavity gain to drop instantaneously below the lasing threshold. The originally wide pulse from the main seed source 1 is rapidly truncated, generating a narrow pulse sequence with a pulse width of less than 1 ns based on the transient upper-level particle depletion effect. At this time, the driving current of the main seed source 1 continues to rise, and then is again quenched by the secondary seed source 2's spectral quenching stage. Ultimately, the large pulse with a wide pulse width and time domain of the seed source is divided into multiple small pulses with narrow pulse widths and narrow time domains, corresponding to the secondary seed source 2's spectral quenching stage. Figure 1 The output waveform in the upper right corner.

[0054] like Figure 3 As shown, the monitoring beam splitting component is located at the end of the main output optical path of the entire device, consisting of a beam splitting coupler 71 and a light detection and acquisition unit 72. The beam splitting coupler 71 splits a small amount of output light and sends it to the light detection and acquisition unit 72. The light detection and acquisition unit 72 captures the output pulse waveform and spectral data in real time and transmits the acquired data back to the drive control module 6, forming a complete closed-loop signal path. The drive control module 6 stores standard pulse envelope data in advance and compares the real-time acquired waveform and spectrum with the preset standard envelope. Before the next pulse cycle arrives, it dynamically fine-tunes the amplitude and timing offset of the pulse current of the main seed source 1 and the CW (Continuous Wave) drive current of the secondary seed source 2, continuously correcting the waveform and spectral state of the output light.

[0055] In this embodiment, the main seed source 1 is a 1550nm multimode FP semiconductor laser, which outputs a wide-spectrum pulse with a pulse time-domain width of approximately 10ns when driven only by pulsed current and without secondary seed light injection. The secondary seed source 2 is a single-mode DFB semiconductor laser in the same wavelength band, driven by constant DC CW, and continuously outputs narrow-linewidth continuous seed light. The drive control module 6 adjusts the output optical power of the secondary seed source 2 to match the injected optical power with the saturation gain threshold of the main seed source 1.

[0056] After the narrow-linewidth continuous light emitted by the secondary seed source 2 is continuously coupled into the resonant cavity of the main seed source 1, the charge carriers of the target upper energy level are rapidly consumed under stimulated emission. Relying on the transient upper energy level particle depletion effect, the original 10ns original pulse is truncated multiple times. The device eventually outputs multiple modulated pulses with a stable time-domain width of less than 1ns, for example, the steady-state output pulse width is 0.7ns.

[0057] The control methods corresponding to the above-mentioned devices are as follows:

[0058] S1. Power-on Initialization Timing Control: After the system powers on, the drive control module 6 prioritizes enabling the CW drive mode of the secondary seed source 2, maintaining continuous light output from the secondary seed source 2. After a waiting period of at least 10ms, the DFB laser undergoes thermal equilibrium and wavelength locking. Once the wavelength of the secondary seed source 2 is confirmed to be stable and the injected light power and the gain of the main seed source 1 are matched, a pulsed current is output to drive the main seed source 1 to begin operation. This timing control avoids spectral degradation caused by transient loss of lock.

[0059] S2. Intracavity injection matching control: The drive control module 6 continuously and independently adjusts the output optical power of the secondary seed source 2, continuously injecting stable narrowband light into the resonant cavity of the main seed source 1. The spectral quenching is completed by relying on the competition of longitudinal mode in the cavity. At the same time, the original wide pulse of the main seed source 1 is truncated by the depletion effect of the transient upper energy level particles of the gain medium, and the narrow linewidth and ultrashort pulse seed light output is realized simultaneously.

[0060] For example, in this embodiment, the drive control module 6 collects pulse waveform data fed back by the monitoring beam splitter every 200μs, fine-tunes the DC drive current of the secondary seed source 2 with a minimum step size of 0.75mA, and simultaneously corrects the narrowband optical power injected into the main cavity with a step size of 0.015mW, so as to stably control the output pulse width in the range of 0.6~0.9ns.

[0061] Specifically, if the output pulse is widened to 0.95ns, it indicates that the cavity gain is not matched enough; the drive control module 6 increases the drive current of the secondary seed source 2 by 0.75mA, the injected optical power increases by 0.015mW, the particle depletion speed in the cavity accelerates, and the pulse drops back to 0.7ns;

[0062] If it is detected that the output pulse is as narrow as 0.5 ns and the waveform has a sag, it indicates that the injection power of the secondary seed is too high; the drive control module 6下调 the drive current of the secondary seed source 2 by 0.75 mA, and the injected optical power decreases by 0.015 mW, thereby stably maintaining the width of each small pulse in the range of 0.6~0.9 ns.

[0063] The narrow linewidth output can weaken the phonon resonance coupling in the optical fiber link from the frequency domain. The pulse duration of less than 1 ns is shorter than the Brillouin phonon lifetime, which destroys the establishment conditions of the phonon field from the time domain, doubly raises the stimulated Brillouin scattering threshold, and greatly alleviates the limitation of the SBS effect on the output power of the optical fiber amplification system; meanwhile, the intracavity mode competition will continuously consume the carriers matching the longitudinal mode, inhibit the spontaneous emission behavior of other energy levels, reduce ASE noise, and improve the coherence quality of the output beam.

[0064] S3, Graded power-off sequence regulation: when the system receives a shutdown command and the safety alarm triggers the shutdown logic, the drive control module 6 will preferentially cut off the pulse drive signal of the main seed source 1, delay for no less than 5 ms, wait for the residual high-energy photons in the resonant cavity of the main seed source 1 to fully attenuate, then slowly turn off the CW drive current of the secondary seed source 2, and finally turn off the TEC temperature control unit matched with the laser. This graded sequence can prevent the residual light field in the main cavity from back-crosstalking the secondary seed source 2 at the moment of power failure, and reduce the risk of damage to optical devices.

[0065] Example 2: See Figure 4 , the difference between the device provided in this embodiment and Embodiment 1 is that two channels of secondary seed sources are provided, which are a first secondary seed source 21 and a second secondary seed source 22 respectively. Both two channels of secondary seed sources are single-longitudinal-mode DFB semiconductor lasers, and the central wavelengths of the output light of the two DFBs are different from each other, and the two wavelengths are respectively matched Figure 5 the sublevels E of two different target upper energy levels in the resonant cavity of the main seed source 1 ’ 2, E ’’ 2.

[0066] As shown in Figure 6 , in this embodiment, the optical beam combining device 4 is a multi-channel optical coupler, the first secondary seed source 21 and the second secondary seed source 22 are respectively configured with independent optical paths, each optical path is individually connected in series with a group of optical isolators 5, and the two optical paths are respectively connected to two groups of independent input channels of the optical beam combining device 4; the narrow-band light with different wavelengths output by the two channels of secondary seed sources is combined by the optical beam combining device 4 and then uniformly coupled and injected into the resonant cavity of the main seed source 1.

[0067] The drive control module 6 is provided with two groups of mutually independent current drive circuits for secondary seed sources, the FPGA core main control unit is electrically connected with the two groups of current drive circuits for secondary seed sources respectively, each current drive circuit for secondary seed source corresponds to the first secondary seed source 21 and the second secondary seed source 22 individually, and the output current amplitude and opening / closing sequence of the two groups of drive channels are completely independently adjustable.

[0068] In this embodiment, the FPGA core control unit divides a single complete pulse cycle of the main seed source 1 into three independent time slots: rising edge time slot, flat-top time slot, and falling edge time slot. Within the same time slot, the drive control module 6 outputs a constant CW drive current to only one of the secondary seed sources. This secondary seed source continuously outputs narrowband light to inject into the main cavity to participate in intracavity mode competition. The drive current of the other secondary seed source is lower than the laser lasing threshold, so there is no light output, and it remains silent. The time slots are seamlessly switched, and the two secondary seed sources are alternately activated to change the injected light wavelength participating in mode competition in the resonant cavity of the main seed source in a time-division manner.

[0069] The wavelengths of the secondary seed sources activated in different time slots are precisely matched to the different target longitudinal modes of the main cavity, and the electrons of the corresponding energy levels will preferentially complete the transition in the corresponding time slots: only the first secondary seed source 21 is activated in the rising time slot, corresponding to the energy level E ’ 2. Rapidly consume charge carriers to quickly establish an intracavity photon field, forming a steep, tailless pulse rising edge; switch the flat-top time slot to inject separately from the second seed source 22, corresponding to energy level E. ’’ 2. The intracavity gain is reduced, stabilizing the intracavity photon density and suppressing pulse top fluctuations caused by relaxation oscillations; the secondary seed source can be switched as needed during the falling edge time slot, controllably consuming remaining upper-level particles in the cavity, smoothly completing photon attenuation, and eliminating pulse bottom noise trailing. The output waveform after segmented modulation corresponds to... Figure 4 The modulated pulse sequence in the upper right corner.

[0070] like Figure 6 As shown, similar to Example 1, the monitoring and splitting component continuously collects output pulse waveforms and spectral information, and the collected data is transmitted back to the drive control module 6 in real time. The drive control module 6 compares the measured waveform with the internal preset standard pulse envelope, and dynamically corrects the current amplitude of the two secondary seed sources CW, the time slot switching timing offset, and the pulse current parameters of the main seed source 1 on a cycle-by-cycle basis to complete the closed-loop correction, compensate for the waveform and spectral shifts caused by environmental temperature drift and device aging, and ensure the output stability during long-term operation.

[0071] In this embodiment, two 1550nm band DFB secondary seed sources are selected. The center wavelengths of the first secondary seed source 21 and the second secondary seed source 22 are different. The first secondary seed source 21 is matched with the E in the main seed resonant cavity. ’ The longitudinal mode corresponding to the 2nd energy level, and the second seed source 22 matched E ’’ The longitudinal mode corresponding to the 2 energy levels; the CW drive current adjustment range of both secondary seed sources is 20mA to 50mA. The drive current and the output optical power are linearly related. 1mA drive current corresponds to 0.02mW output optical power. The laser lasing threshold current is 20mA. When the current is below 20mA, the secondary seed source has no light output and enters a silent state. The maximum output light intensity of the secondary seed source is controlled within 20dB.

[0072] The total duration of the complete pulse cycle of the main seed source is set to 10ns. In this embodiment, the drive control module 6 divides a single 10ns pulse cycle into three time slots: the rising edge time slot has a duration of 2ns, the flat top time slot has a duration of 5ns, and the falling edge time slot has a duration of 3ns.

[0073] The time-sharing power matching numerical control process is as follows:

[0074] Rising edge time slot (0-2ns): The drive control module 6 outputs only 33.5mACW drive current to the first seed source 21, corresponding to an output optical power of 0.27mW. This power matches the transient gain of the main seed during the pulse rising edge phase, rapidly consuming E. ’ Two energy level carriers are used to create a steep rising edge; the second seed source 22 is driven by a current of 15mA, which is below the 20mA lasing threshold, and remains silent with no output.

[0075] Flat-top time slot (2-7ns): The drive control module 6 cuts off the CW drive of the first seed source 21 and switches to output a constant DC current of 34.5mA to the second seed source 22, corresponding to an output optical power of 0.29mW, matching the steady-state intracavity gain during the flat-top phase of the pulse, and continuously consuming E ’’ Two energy level particles stabilize the photon density within the cavity; the driving current of the first seed source 21 drops back to 15mA to achieve quiescence.

[0076] Falling edge time slot (7-10ns): The drive control module 6 maintains the 32mACW drive current of the second seed source 22, outputs an optical power of 0.24mW, slowly consumes the remaining upper energy level particles in the cavity, smoothly completes photon decay, and eliminates the noise trailing at the bottom of the pulse.

[0077] After three time-division injection modulations, the width of each small pulse is less than 1 ns. During system operation, the drive control module 6 reads the waveform data fed back by the monitoring beam splitter every 200 μs, and adjusts the closed-loop correction parameter step size with a minimum current adjustment step size of 0.75 mA, simultaneously compensating the output amplitude of the two secondary seed sources with 0.015 mW of optical power. If fluctuations are detected at the top of the pulse, the drive control module 6 increases the drive current of the second secondary seed source 22 by 2.5 mA in the next flat-top time slot, and the output optical power increases by 0.05 mW to stabilize the pulse top profile. If the rising edge slope becomes slower, the drive current amplitude of the first secondary seed source 21 in the time slot is increased to improve the carrier consumption rate and maintain the preset pulse waveform standard.

[0078] The number of secondary seed sources can be expanded to three, four or more according to pulse shaping requirements. For each additional secondary seed source, an independent CW drive channel, an optical isolator 5, and an independent input channel for the optical beam combiner 4 are added simultaneously. The number of time slots in the drive control module 6 is also increased accordingly. The time-division switching logic is consistent with the two-channel secondary seed source implementation.

[0079] By using multiple secondary seed sources for time-slot segmented modulation, the steepness of the rising edge, the width of the flat top, and the decay rate of the falling edge of the output pulse can be flexibly adjusted to generate programmable pulses with various differentiated time-domain profiles. This allows the device to adapt to the differentiated requirements of seed light waveforms in different application scenarios such as lidar, quantum sensing, and spectral analysis without changing the hardware structure, thus greatly improving the universal adaptability of the entire device.

[0080] Example 3: After the pulsed drive current is turned off, a large number of upper-level charge carriers remain in the gain medium of the main seed source 1. The slow recombination of these charge carriers and their luminescence will form an exponentially decaying pulse falling edge damped tail, lengthening the overall pulse time-domain width. During the tailing stage, multiple longitudinal modes oscillate continuously, resulting in a large output spectral width, such as... Figure 7 The waveform is shown in the upper left corner.

[0081] Therefore, in this embodiment, the secondary seed source is configured in pulse output mode. When using a pulsed secondary seed source, the drive control module 6 synchronously manages the pulse timing of the main seed source and the pulse timing of the secondary seed source. At the beginning of the falling edge of the pulse of the main seed source 1, a short-time pulse drive current is output to the secondary seed source, so that the secondary seed source outputs narrow-linewidth pulsed seed light, which is coupled into the resonant cavity of the main seed source 1 through the optical isolator 5 and the optical beam combiner 4.

[0082] The narrowband pulse light injected on the falling edge time slot precisely matches the energy level corresponding to the target longitudinal mode in the FP main cavity, instantly preempting all remaining upper energy level carriers in the cavity. Spectral quenching is achieved through longitudinal mode competition, and the residual carriers in the gain medium are transiently depleted, rapidly trunculating the originally slowly decaying damped tail of the main seed source 1. After the pulse tail is completely eliminated, the output pulse time domain width is significantly shortened, while only a single dominant longitudinal mode oscillation is retained in the cavity, resulting in a narrower output spectral width and effectively suppressing the stimulated Brillouin scattering effect in the fiber optic transmission link.

[0083] The control methods corresponding to this device include:

[0084] T1, the drive control module outputs periodic pulse drive current to the main seed source, driving the main seed source to output broadband pulse seed light;

[0085] In this embodiment, the complete pulse period of the main seed source is 2ns, of which the pulse body duration is 0.7ns and the tail damping tail accounts for 1.3ns;

[0086] T2. The drive control module synchronously matches the pulse timing of the main seed source with the pulse drive timing of the secondary seed source, aligning the secondary seed pulse to the starting time of the falling edge of the main seed source pulse.

[0087] In this embodiment, the drive control module 6 aligns the timing of the secondary seed pulse to the main pulse at 0.7ns (the starting point of the falling edge), and the peak output optical power of the secondary seed pulse is 0.27mW.

[0088] T3. At the beginning of the falling edge of the main seed source pulse, the secondary seed source is driven to output a narrow-linewidth pulse seed light. The narrow-linewidth pulse seed light is coupled into the main seed source resonant cavity through an optical beam combiner. The injected narrow-band pulse light matches the target longitudinal mode corresponding energy level of the main seed resonant cavity, preempts the remaining upper energy level carriers in the cavity, and achieves spectral quenching through longitudinal mode competition, thus cutting off the damping tail of the falling edge of the main seed source pulse.

[0089] In this embodiment, when the main pulse reaches 0.7 ns, the narrowband light of the pulse seed is injected into the main cavity, instantly depleting the remaining charge carriers in the cavity. The 1.3 ns damping tail is truncated, and the final output total pulse width is compressed to approximately 0.78 ns. Figure 7 The waveform is shown in the upper right corner.

[0090] In this embodiment, the secondary seed source is activated only briefly during the falling edge of the main seed source pulse to output narrow-linewidth pulsed light. Relying on photons from the matched energy level to rapidly consume residual carriers in the cavity, the damping tail of the main seed source pulse can be quickly eliminated, shortening the output pulse time-domain width and narrowing the output spectrum. The secondary seed source does not need to emit light continuously throughout the entire process, reducing the overall power consumption. In addition, real-time waveform and spectral closed-loop correction can adaptively compensate for waveform shifts caused by temperature and device aging, maintaining pulse shaping effect stably over the long term and improving the stimulated Brillouin scattering suppression capability of the fiber optic link.

[0091] In a possible embodiment, the main seed source 1 and all auxiliary seed sources are equipped with TEC temperature control units, and all of them are electrically connected to the drive control module 6. The drive control module 6 uniformly manages the power-on heating and power-off cooling sequence, and coordinates with the drive sequence of the main and auxiliary seed sources to further improve the operational stability of the entire system.

[0092] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A device for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources, characterized in that, include: The main seed source is a multi-longitudinal-mode semiconductor laser that outputs broadband pulsed seed light. At least one secondary seed source, wherein the secondary seed source is a single longitudinal mode semiconductor laser that outputs narrow linewidth seed light; In the optical beam combining device, the output optical path of each secondary seed source is connected to the corresponding input channel of the optical beam combining device, and the output light of the secondary seed source is coupled and injected into the resonant cavity of the main seed source through the optical beam combining device. The drive control module is electrically connected to the main seed source and each sub-seed source. The drive control module can independently output the drive current waveform, output amplitude, pulse width, repetition frequency and relative timing corresponding to the main seed source and each sub-seed source. The drive control module includes a main seed source current drive circuit, an FPGA core main control unit, and a secondary seed source current drive circuit. The FPGA core main control unit is electrically connected to the main seed source current drive circuit and each secondary seed source current drive circuit. The output terminal of the main seed source current driving circuit is electrically connected to the main seed source, and the output terminal of each auxiliary seed source current driving circuit is individually electrically connected to a corresponding auxiliary seed source. The drive control module stores preset standard pulse envelope data. The drive control module compares the real-time acquired waveform and spectral data with the preset standard pulse envelope, and dynamically fine-tunes the driving current amplitude, timing offset and pulse width of the main seed source and each sub-seed source in the next pulse cycle to form a closed-loop correction. The drive control module is configured to adjust the output optical power of the secondary seed source so that the injected optical power of the secondary seed source matches the gain of the main seed source. The longitudinal mode competition occurs in the resonant cavity of the main seed source to achieve spectral quenching. At the same time, the gain medium in the cavity experiences transient upper energy level particle depletion, which cuts off the original pulse of the main seed source.

2. The apparatus for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources according to claim 1, characterized in that, Only one secondary seed source is set up. The drive control module controls the secondary seed source to continuously output continuous light and constantly inject narrowband light into the resonant cavity of the main seed source. Through spectral quenching, the large pulse with wide pulse width and time domain is divided into multiple small pulses with narrow pulse width and time domain.

3. The apparatus for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources according to claim 1, characterized in that, The secondary seed source is configured with two or more channels, each channel outputting narrow-linewidth continuous light with a different center wavelength. The drive control module divides a single pulse period of the main seed source into several independent fine time slots. In a single time slot, only one secondary seed source is activated to inject narrowband light into the resonant cavity of the main seed source, while the other secondary seed sources are in a closed or silent state below the lasing threshold. The module time-division changes the wavelength of the injected light participating in mode competition in the cavity of the main seed source, and the center wavelength of the secondary seed sources activated in different time slots is respectively matched with different target longitudinal modes in the resonant cavity of the main seed source.

4. The apparatus for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources according to claim 1, characterized in that, It also includes a monitoring beam splitting component, which is set at the output end of the main optical path. The monitoring beam splitting component includes a beam splitting coupler and a light detection and acquisition unit. The beam splitting coupler splits a portion of the optical signal from the total output optical path and transmits it to the light detection and acquisition unit. The waveform and spectral data acquired by the light detection and acquisition unit are transmitted back to the drive control module to form a closed-loop signal path.

5. The apparatus for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources according to claim 1, characterized in that, The secondary seed source outputs narrow-linewidth pulsed seed light; The drive control module synchronously matches the timing of the main seed source pulse and the timing of the secondary seed source pulse. During the falling edge of the main seed source pulse, it drives the output pulse light of the secondary seed source to be injected into the resonant cavity of the main seed source, exhausting the residual upper energy level particles in the cavity and cutting off the falling edge tail of the main seed source pulse.

6. A method for suppressing stimulated Brillouin scattering using multiple sub-source modulation, applied to the apparatus as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Power-on initialization timing control: First, turn on the secondary seed source and keep it in continuous light operation state. After the wavelength of the secondary seed source is stable and the injected light power matches the power of the main seed source, turn on the pulse current drive of the main seed source. S2. Intracavity injection matching control: The drive control module independently adjusts the output optical power of the secondary seed source so that the injected narrowband optical power matches the gain of the main seed source. After the narrowband light is injected into the resonant cavity of the main seed source, the spectral quenching is completed through intracavity longitudinal mode competition. The original pulse of the main seed source is cut off by the depletion of the upper energy level particles in the gain medium. S3, graded power-off timing control: After receiving the shutdown signal, the main seed source pulse drive is first cut off, and the residual photons in the main seed source cavity are delayed for a period of time to decay. Then, the continuous drive current of each auxiliary seed source is turned off in sequence, and finally the temperature control unit is turned off.

7. The method for suppressing stimulated Brillouin scattering by modulation of multiple sub-sources according to claim 6, characterized in that, S2 also includes time-division multi-wavelength modulation: when there are two or more secondary seed sources, a single main pulse period is divided into multiple time slots. In each time slot, only one secondary seed source injects narrowband light into the main seed source resonant cavity. Different secondary seed sources are switched in different time slots to participate in the mode competition within the main seed source resonant cavity.

8. A method for suppressing stimulated Brillouin scattering using multiple sub-source modulation, applied to the apparatus as described in claim 5, characterized in that, Includes the following steps: T1, the drive control module outputs periodic pulse drive current to the main seed source, driving the main seed source to output broadband pulse seed light; T2. The drive control module synchronously matches the pulse timing of the main seed source with the pulse drive timing of the secondary seed source, aligning the secondary seed pulse to the starting time of the falling edge of the main seed source pulse. T3. At the beginning of the falling edge of the main seed source pulse, the secondary seed source is driven to output a narrow-linewidth pulse seed light. The narrow-linewidth pulse seed light is coupled into the main seed source resonant cavity through an optical beam combiner. The injected narrow-band pulse light matches the target longitudinal mode corresponding energy level of the main seed resonant cavity, preempts the remaining upper energy level carriers in the cavity, and achieves spectral quenching through longitudinal mode competition, thus cutting off the damping tail of the falling edge of the main seed source pulse.

Images