A method and apparatus for modulating the output of a quasi-continuous laser

Abstract

The application discloses a quasi-continuous laser output pulse laser modulation method and device, the method comprises the following steps: obtaining preset pulse laser parameters, the pulse laser parameters comprise a pulse repetition frequency, a pulse width and a pulse peak power; generating a baseband current modulation signal according to the pulse laser parameters; performing pre-distortion compensation processing on the baseband current modulation signal to obtain a pre-compensation modulation signal, the pre-distortion compensation processing is based on dynamic response characteristics of the quasi-continuous laser; the pre-distortion compensation processing further comprises rising edge overshoot suppression compensation and falling edge tail elimination compensation; and applying the pre-compensation modulation signal to a pumping source driving end of the quasi-continuous laser to make the quasi-continuous laser output a shaped pulse laser. The application effectively suppresses the relaxation oscillation overshoot and tail of the quasi-continuous laser pulse output through pre-distortion compensation, and obtains a high-fidelity pulse laser waveform, and is especially suitable for high-repetition-frequency and high-power quasi-continuous lasers.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and specifically to a modulation method and apparatus for output pulsed laser light from a quasi-continuous laser. Background Technology

[0002] Quasi-continuous lasers typically operate in pulsed-driven mode, achieving high-energy laser output by injecting a large current into the pump source within a short time, with the pulse interval used for heat dissipation. This method is widely used in laser processing, lidar, and medical aesthetics. Currently, the most direct way to generate pulsed lasers is by pulse modulation of the pump source's driving current.

[0003] However, due to the population inversion process, stimulated emission relaxation oscillations, and thermal effects within the laser, the laser's response to pulsed current is not ideally linear. Specifically, at the rising edge of the driving current, the laser output exhibits a brief, sharp spike, known as relaxation oscillation overshoot; at the falling edge, because the upper-level particles are not completely depleted, the laser output shows a tail, meaning the light pulse continues for a period after the current is turned off. These waveform distortions reduce the time fidelity of the pulsed laser, leading to decreased processing quality or measurement errors in applications requiring precise pulse shape control, such as laser precision machining and time-resolved spectral measurements. Existing improvement methods include optimizing the laser resonator design, but this method alters the laser's intrinsic structure, resulting in high cost and poor versatility; alternatively, external acousto-optic or electro-optic modulators can be used to chop the continuous laser, but these systems are complex, have high insertion loss, and reduce energy utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a modulation method and apparatus for the output pulsed laser of a quasi-continuous laser, so as to solve the technical problems of pulse leading-edge overshoot and trailing-edge tailing caused by relaxation oscillation and thermal effects during pulse modulation of quasi-continuous lasers in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for modulating pulsed laser output from a quasi-continuous laser includes:

[0007] Step 1: Obtain the preset pulsed laser parameters, which include pulse repetition frequency, pulse width, and pulse peak power;

[0008] Step 2: Generate a baseband current modulation signal based on the pulsed laser parameters;

[0009] Step 3: Perform pre-distortion compensation processing on the baseband current modulation signal to obtain the pre-compensated modulation signal. The pre-distortion compensation processing is based on the dynamic response characteristics of the quasi-continuous laser and includes at least rising edge overshoot suppression compensation and falling edge tail elimination compensation.

[0010] Step 4: Apply the pre-compensated modulation signal to the pump source drive of the quasi-continuous laser so that the quasi-continuous laser outputs shaped pulsed laser.

[0011] By acquiring pulsed laser parameters to generate a baseband current modulation signal, and performing pre-distortion compensation on this signal based on the dynamic response characteristics of the quasi-continuous laser, the compensation includes at least rising edge overshoot suppression and falling edge tailing elimination. The compensated signal is then used to drive the pump source. This scheme suppresses waveform distortion on the rising and falling edges of the pulsed laser output, resulting in a more regular pulse profile and improved pulse shape fidelity.

[0012] As a further aspect of the present invention, the predistortion compensation processing further includes: superimposing a prepulse signal before the rising edge of the baseband current modulation signal. The duration of the prepulse signal is one-hundredth to twenty-hundredth of the set pulse width, and its current amplitude is ten-hundredth to fifty-hundredth of the amplitude of the baseband current modulation signal. The prepulse, added before the rising edge of the baseband current modulation signal, has a shorter duration and a smaller current amplitude relative to the main pulse. The prepulse prematurely excites part of the population inversion, causing the laser gain state to approach saturation when the main pulse arrives, thereby mitigating the spike overshoot phenomenon caused by relaxation oscillations at the rising edge of the main pulse.

[0013] As a further aspect of the present invention, the predistortion compensation processing further includes: superimposing a tail suppression pulse after the falling edge of the baseband current modulation signal. The duration of the tail suppression pulse is 0.5% to 10% of the set pulse width, and its current amplitude is 5% to 30% of the amplitude of the baseband current modulation signal. Furthermore, the current amplitude of the tail suppression pulse is lower than the driving current value corresponding to the laser threshold current of the quasi-continuous laser. Adding a tail suppression pulse after the falling edge of the baseband current modulation signal, where the duration and current amplitude of this pulse are relatively small compared to the main pulse, and its current amplitude is lower than the threshold current required for the laser to generate laser light, causes the pump drive current to rapidly decrease below the threshold, forcibly consuming residual upper-level particles, thereby shortening the tail length of the pulse trailing edge.

[0014] As a preferred embodiment of the present invention, it further includes: real-time monitoring of the output optical pulse waveform of the quasi-continuous laser, and dynamically adjusting the predistortion compensation parameters according to the deviation between the output optical pulse and the target waveform, forming a closed-loop feedback control. The actual output optical pulse waveform of the quasi-continuous laser is monitored in real time, the measured waveform is compared with the target waveform, and the parameters used for predistortion compensation are dynamically adjusted according to the deviation between the two. This closed-loop feedback method can automatically compensate for changes in response characteristics caused by laser aging, temperature drift, or device differences, ensuring that the output waveform remains stable over a long period.

[0015] The present invention also provides a modulation apparatus for outputting pulsed laser light from a quasi-continuous laser to implement the above method, comprising:

[0016] The parameter setting module is used to obtain preset pulse laser parameters;

[0017] A modulation signal generator, connected to a parameter setting module, is used to generate a baseband current modulation signal based on pulsed laser parameters;

[0018] The predistortion compensator, connected to the modulation signal generator, is used to perform predistortion compensation processing on the baseband current modulation signal and output a pre-compensated modulation signal.

[0019] The driving circuit, connected to the predistortion compensator, is used to amplify the power of the pre-compensated modulation signal and apply it to the pump source of the quasi-continuous laser.

[0020] A quasi-continuous laser outputs pulsed laser light when excited by a driving circuit.

[0021] The device provided by this scheme, which implements the above modulation method, loads a shaped current signal onto the pump source of a quasi-continuous laser through the coordinated operation of modules such as parameter setting, modulation signal generation, predistortion compensation, and power driving. The device as a whole can output pulsed lasers with small rise-edge overshoot and short fall-edge tail, and its compact structure makes it easy to integrate into laser systems.

[0022] As a further preferred embodiment of the present invention, the predistortion compensator includes a rising edge compensation unit and a falling edge compensation unit. The rising edge compensation unit is used to superimpose a pre-pulse signal before the rising edge of the baseband current modulation signal, and the falling edge compensation unit is used to superimpose a tail suppression pulse after the falling edge of the baseband current modulation signal. The predistortion compensator has dedicated rising edge compensation unit and falling edge compensation unit, which are responsible for superimposing the pre-pulse and the tail suppression pulse, respectively. This separate structure allows the compensation parameters for the rising and falling edges to be adjusted independently without interference, thereby more accurately suppressing the leading edge spike and trailing edge tail of the pulse.

[0023] As a further preferred embodiment of the present invention, a photoelectric feedback module is also included. The photoelectric feedback module includes a beam splitter and a photodetector. The beam splitter is positioned in the output optical path of the quasi-continuous laser, guiding a portion of the output light to the photodetector. The output of the photodetector is connected to the feedback input of a predistortion compensator. The predistortion compensator adjusts the predistortion compensation parameters in real time based on the difference between the output light pulse waveform collected by the photodetector and the target waveform. The addition of the photoelectric feedback module allows the device to continuously sense changes in the actual output waveform and automatically correct the compensation parameters accordingly, forming a closed control loop and improving the adaptability and accuracy of the compensation.

[0024] As a further preferred embodiment of the present invention, the driving circuit is a programmable constant current source driving circuit, with an output current range of 0.1 amperes to 100 amperes, an output current rise time of less than one microsecond, and an output current fall time of less than one microsecond. The driving circuit adopts a programmable constant current source form, with an output current range covering from a few tenths of an ampere to hundreds of amperes, and both the current rise and fall response times are very short. This driving capability ensures that the pre-compensated current waveform can be quickly and accurately applied to the pump source, without weakening the compensation effect due to the bandwidth limitation of the driving circuit.

[0025] As a further preferred embodiment of the present invention, the quasi-continuous laser is a diode-pumped solid-state laser or a fiber laser, with a laser diode bar array as the pump source. The driving current of the pump source adopts a quasi-continuous mode, the pulse repetition frequency ranges from 1 Hz to 50 kHz, the pulse width ranges from 10 microseconds to 10 milliseconds, and the duty cycle ranges from 1% to 50%. The quasi-continuous laser is limited to a diode-pumped solid-state laser or a fiber laser, the pump source is a laser diode bar array, and the applicable ranges for the repetition frequency, pulse width, and duty cycle of the driving current are given. Within these operating parameter ranges, the device can perform pulse waveform shaping, meeting the needs of most quasi-continuous laser application scenarios.

[0026] As a further preferred embodiment of the invention, the modulation signal generator includes a direct digital frequency synthesizer or a field-programmable gate array (FPGA) for generating baseband current modulation signals of arbitrary waveforms, including rectangular waves, trapezoidal waves, half-sine waves, or triangular waves. The modulation signal generator, employing a direct digital frequency synthesizer or FPGA, is capable of generating baseband current waveforms of various shapes, including rectangular, trapezoidal, half-sine, and triangular waves. This function allows users to select or customize the profile of the drive current according to the needs of different applications, such as for applications requiring gradual light intensity output or electromagnetic interference reduction.

[0027] As a further preferred embodiment of the present invention, the predistortion compensator also includes a temperature compensation unit. The temperature compensation unit is connected to a temperature sensor, which is disposed on the heat sink of the quasi-continuous laser. The temperature compensation unit corrects the predistortion compensation parameters based on the real-time temperature. The predistortion compensator includes a temperature compensation unit that acquires temperature information in real time through a temperature sensor disposed on the laser heat sink and adjusts the predistortion compensation parameters accordingly. Temperature compensation can counteract the effects of temperature changes on the laser threshold current and relaxation oscillation frequency, ensuring that the compensation effect remains stable under different temperature conditions.

[0028] As a further preferred embodiment of the present invention, the device also includes a pulse synchronization output interface for outputting a level signal synchronized with the pulsed laser for triggering by external devices. The device is equipped with a pulse synchronization output interface for outputting a level signal that is time-aligned with the pulsed laser. External devices such as oscilloscopes, data acquisition cards, or subsequent processing equipment can receive this synchronization signal to achieve timing synchronization with the laser pulse, facilitating system integration and signal measurement.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Using the modulation method and apparatus provided by this invention, the pulsed laser output from a quasi-continuous laser exhibits significantly suppressed peak overshoot at the rising edge, resulting in a flattened pulse top and a noticeably shortened or even eliminated tailing after the falling edge. The pulse waveform more closely matches the preset target shape, improving time fidelity. By establishing a suitable gain state in advance through a pre-pulse, the rise response speed of the main pulse is accelerated, while avoiding energy waste and the risk of impact on subsequent components due to overshoot. The tail-suppression pulse ensures rapid cutoff of the optical pulse after current cutoff, preventing temporal dispersion of pulse energy and improving pulse contrast and energy concentration. Closed-loop feedback control allows compensation parameters to automatically adapt to laser aging drift and environmental temperature changes, ensuring waveform stability during long-term operation. Temperature compensation further eliminates differences in compensation effects under different operating temperatures. The high-speed performance of the drive circuit ensures precise application of the compensation waveform without introducing additional distortion. The synchronous output interface facilitates system integration. In summary, this invention improves the pulse output quality of a quasi-continuous laser through electrical pre-compensation without altering the intrinsic structure of the laser or adding external modulation devices. It is applicable to a wide range of repetition frequencies, pulse widths, and duty cycles, and can flexibly adapt to the needs of different waveforms. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only examples of embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart of a modulation method for output pulsed laser light from a quasi-continuous laser provided in an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0034] See Figure 1 As shown, the specific implementation method provides the following embodiments.

[0035] Example 1:

[0036] A quasi-continuous fiber laser with a pulse repetition frequency of 1 Hz, a pulse width of 10 ms, and a peak power of 100 W was used. The laser threshold current of this laser corresponds to a pump drive current of 5 amps. The baseband current modulation signal is a rectangular wave with an amplitude corresponding to a pump current of 10 amps.

[0037] Technical Solution: The pre-pulse width is set to 100 microseconds, which is 1% of the set pulse width, and the pre-pulse amplitude is 1 ampere, which is 10% of the baseband current modulation signal amplitude. The tail suppression pulse width is set to 50 microseconds, which is 0.5% of the set pulse width, and the tail suppression pulse amplitude is 0.5 amperes, which is 5% of the baseband current modulation signal amplitude. This amplitude is lower than the laser threshold current of 5 amperes. The pre-pulse is superimposed before the rising edge of the baseband current modulation signal, and the tail suppression pulse is superimposed after the falling edge to form a pre-compensated modulation signal. This signal is amplified by the drive circuit and then applied to the pump source.

[0038] Working principle: Under low repetition frequency and long pulse width conditions, the laser has sufficient time to recover to thermal equilibrium during the pulse interval. However, relaxation oscillations on the rising edge still exist, and the tailing on the falling edge is also significant due to the longer lifetime of particles in the upper energy level. The pre-pulse injects energy in advance with extremely low amplitude and extremely short duration, allowing a small number of inverted particles to accumulate in the gain medium. When the main pulse arrives, the laser quickly enters steady-state gain, avoiding severe relaxation spikes. The tailing suppression pulse reduces the driving current below the threshold after the pump current main pulse ends, forcing the remaining inverted particles to be rapidly consumed through stimulated emission or spontaneous emission, shortening the tail length of the optical pulse.

[0039] Technical Effects: After the above modulation, the amplitude of the rising edge spike of the output laser pulse is significantly reduced, the flatness of the pulse top is improved, the trailing edge tail is significantly shortened, and the pulse waveform is closer to the ideal rectangular profile. Compared with direct current modulation without pre-distortion compensation, the pulse leading edge overshoot amplitude is reduced, the trailing edge tail duration is shortened, and the pulse energy concentration is improved.

[0040] Experimental data: Under the settings of a repetition frequency of 1 Hz, a pulse width of 10 ms, and a peak power of 100 W, the uncompensated direct current modulation output laser pulse exhibits overshoot on the rising edge, with its peak power exceeding the set value by approximately 40%, and a tail lasting for approximately 1.2 ms. After adopting the scheme of this embodiment, the rising edge overshoot amplitude is reduced to less than 5% of the set value, the tail duration is shortened to less than 0.1 ms, and the power fluctuation at the pulse top is less than 3% within 90% of the pulse width.

[0041] Example 2:

[0042] A quasi-continuous-wave solid-state laser (Nd:YAG) with a pulse repetition frequency of 1 kHz, a pulse width of 500 microseconds, and a peak power of 500 W was used. The laser threshold current of this laser corresponds to a pump drive current of 20 A. The baseband current modulation signal is a trapezoidal wave with adjustable rise and fall slopes, and the amplitude corresponds to a pump current of 50 A.

[0043] Technical Solution: The pre-pulse width is set to 75 microseconds, which is 15% of the set pulse width, and the pre-pulse amplitude is 15 amperes, which is 30% of the baseband current modulation signal amplitude. The tail suppression pulse width is set to 25 microseconds, which is 5% of the set pulse width, and the tail suppression pulse amplitude is 7.5 amperes, which is 15% of the baseband current modulation signal amplitude. This amplitude is lower than the laser threshold current of 20 amperes. The pre-pulse and tail suppression pulses are superimposed on the baseband trapezoidal wave modulation signal, amplified by a high-speed drive circuit, and then applied to the laser diode bar array pump source. Simultaneously, the photoelectric feedback module in the device extracts 5% of the output laser through a beam splitter, which is converted into an electrical signal by a photodetector and sent to the pre-distortion compensator. The pre-distortion compensator compares the measured waveform with the preset trapezoidal target waveform and dynamically adjusts the parameters of the pre-pulse and tail suppression pulses using a proportional-integral-derivative control algorithm, updating the compensation value every 100 pulses. The temperature sensor is placed on the laser heat sink, and the temperature compensation unit corrects the predistortion parameters according to the real-time temperature. The correction coefficients are stored in a lookup table.

[0044] Operating Principle: At a repetition frequency of 1 kHz and a pulse width of 500 microseconds, with a duty cycle of 50%, the laser operates in typical quasi-continuous mode, where thermal accumulation effects begin to appear. A trapezoidal baseband signal is used to obtain a smoother pulse top, avoiding transient oscillations that may be caused by rectangular waves. A prepulse excites population inversion with a moderate amplitude, ensuring a smooth transition of the main pulse's rising edge. A tail suppression pulse pulls the pump current below the threshold, eliminating tailing. A closed-loop feedback module continuously monitors the output waveform. When the laser's threshold drifts due to temperature increases or aging, it automatically increases or decreases the prepulse amplitude and tail suppression pulse amplitude to maintain a stable output waveform. The temperature compensation unit further anticipates changes in dynamic response caused by temperature variations, adjusting compensation parameters in advance to reduce feedback lag.

[0045] Technical Results: At a repetition frequency of 1 kHz, the waveform stability of the laser output pulse is significantly improved. The slopes of the leading and trailing edges of the trapezoidal wave are maintained, and no fluctuations caused by relaxation oscillations appear at the pulse top. Closed-loop feedback control ensures waveform consistency over long-term operation, and the influence of temperature changes on pulse shape is effectively suppressed. The rise and fall times of the output laser match well with the set trapezoidal wave parameters, and pulse energy fluctuations are small.

[0046] Experimental data: After 30 minutes of continuous operation, the laser without feedback and temperature compensation experienced a 12-degree Celsius increase in heat sink temperature, resulting in an approximately 8% decrease in output pulse peak power, a recurrence of rise-edge overshoot reaching 15% of the set value, and a tail lengthening to 30 microseconds. With the solution described in this embodiment, after the same 30-minute operation, the output pulse peak power fluctuation was less than 2%, the rise-edge overshoot remained consistently below 3% of the set value, and the tail length remained stable within 5 microseconds. The closed-loop feedback system automatically adjusted the pre-pulse amplitude from the initial 15 amps to 16.5 amps and the tail suppression pulse amplitude from 7.5 amps to 8.2 amps during temperature changes, compensating for threshold drift.

[0047] Example 3:

[0048] A quasi-continuous fiber laser with a pulse repetition frequency of 50 kHz, a pulse width of 10 microseconds, and a peak power of 1000 W was used. The laser threshold current of this laser corresponds to a pump drive current of 30 A. The baseband current modulation signal is a rectangular wave with an amplitude corresponding to a pump current of 100 A.

[0049] Technical Solution: The pre-pulse width is set to 2 microseconds, which is 20% of the set pulse width, and the pre-pulse amplitude is 50 amperes, which is 50% of the baseband current modulation signal amplitude. The tail suppression pulse width is set to 1 microsecond, which is 10% of the set pulse width, and the tail suppression pulse amplitude is 25 amperes, which is 25% of the baseband current modulation signal amplitude. This amplitude is lower than the laser threshold current of 30 amperes. The pre-pulse and tail suppression pulses are superimposed to form a pre-compensated modulation signal, which is amplified by a high-speed drive circuit based on silicon carbide metal-oxide-semiconductor field-effect transistors. The rise and fall times of the output current of this drive circuit are both 0.3 microseconds. The pulse synchronization output interface in the device outputs a transistor-to-transistor logic level signal aligned with the leading edge of the laser pulse, which is used to trigger an oscilloscope or subsequent processing equipment.

[0050] Working Principle: Under conditions of high repetition frequency and short pulse width, the pulse interval is only 20 microseconds, resulting in significant thermal effects, and the response speed of the drive circuit becomes a key limiting factor. The pre-pulse rapidly establishes population inversion with a relatively large width and amplitude. Due to the short pulse width, the pre-pulse itself produces almost no laser output, but it ensures that the main pulse is in a high-gain state at the start of its rising edge, thus achieving stable output in a very short time. The tail suppression pulse amplitude is set below the threshold current level, which effectively depletes residual upper-level particles and avoids the need for the pump diode to re-establish electrical steady state before the next pulse arrives due to excessively low current. The high-speed performance of the drive circuit ensures that the pre-compensated waveform is faithfully transmitted. The synchronous output interface provides a precise time reference for external devices, facilitating timing control in pulsed laser applications.

[0051] Technical Results: Under conditions of a high repetition frequency of 50 kHz and a narrow pulse width of 10 microseconds, the output laser pulse exhibits a steep rising edge without overshoot, a flat pulse top, and a rapid falling edge with no tailing. The high-speed response of the drive circuit ensures that the actual waveforms of the pre-pulse and tail-suppression pulses are highly consistent with the preset waveforms. The jitter between the level signal output from the synchronization interface and the optical pulse is minimal, meeting the requirements for precise triggering. Compared to uncompensated direct modulation, the pulse waveform quality remains excellent even under extreme parameters.

[0052] Experimental data: Without compensation, the leading edge of the output laser pulse modulated by a direct rectangular wave at a repetition frequency of 50 kHz exhibits a spike of approximately 80 amperes of equivalent optical power, with the trailing edge extending into the next pulse cycle, resulting in inter-pulse crosstalk and a pulse contrast ratio below 10:1. Using the scheme in this embodiment, the leading edge spike is suppressed, the peak power stabilizes around 1000 watts, the trailing edge completely stops within 1 microsecond, and the pulse contrast ratio is improved to over 50:1. The time delay jitter between the synchronous output signal and the midpoint of the rising edge of the optical pulse is less than 10 nanoseconds, suitable for triggering measurement equipment with picosecond-level precision. The actual output pre-pulse rise time of the drive circuit is 0.28 microseconds, and the trailing-suppression pulse fall time is 0.31 microseconds, both meeting the design requirements.

[0053] Working principle:

[0054] This invention, based on the dynamic response characteristics of quasi-continuous lasers, performs pre-distortion compensation on the drive current waveform. Quasi-continuous lasers exhibit relaxation oscillation overshoot at the pulse rising edge because when population inversion is established from zero, stimulated emission increases sharply after the gain exceeds the threshold, subsequently falling back due to the consumption of excessive inverted particles, forming a spike. To address this phenomenon, a short, low-amplitude pre-pulse is injected before the rising edge of the drive current. This pre-pulse allows a small amount of inverted particles to accumulate in the gain medium beforehand, so that the gain state is close to the saturation region when the main pulse arrives, avoiding the drastic jump from zero to overshoot and thus suppressing the relaxation oscillation spike. Regarding the tailing phenomenon at the falling edge, this is because inverted particles still exist after the main pulse ends, continuing to generate stimulated emission until depletion. A tailing suppression pulse is superimposed after the falling edge of the drive current, with the current amplitude of this pulse set below the laser's threshold current. At this point, the pump power is insufficient to maintain laser oscillation, but the remaining inverted particles are consumed more rapidly, thus shortening the tail length of the optical pulse. Furthermore, by monitoring the output optical pulse waveform in real time and comparing it with the target waveform, and using closed-loop feedback to dynamically adjust the parameters of the pre-pulse and tail suppression pulse, changes in response characteristics caused by long-term variations such as laser aging and temperature drift can be compensated. The temperature compensation unit further corrects the compensation parameters according to the laser heat sink temperature, ensuring that the compensation effect remains stable at different temperatures.

[0055] How to use:

[0056] When using this invention, the pulse repetition frequency, pulse width, and peak pulse power required by the quasi-continuous laser are first set according to application requirements. These parameters determine the basic shape of the baseband current modulation signal. Subsequently, based on the dynamic response characteristics of the laser itself, mainly the amplitude and frequency of relaxation oscillation and the tailing duration, the pre-distortion compensation parameters are determined, including the duration and current amplitude of the pre-pulse, and the duration and current amplitude of the tailing suppression pulse. The amplitude of the tailing suppression pulse must be lower than the laser's threshold current. The pre-pulse is superimposed before the rising edge of the baseband current modulation signal, and the tailing suppression pulse is superimposed after the falling edge, forming the pre-compensated modulation signal. This signal, after power amplification, is applied to the pump source drive of the quasi-continuous laser to obtain the shaped pulsed laser output. If the device is equipped with a photoelectric feedback module, the user can also set the target waveform, and the system will automatically monitor the output waveform and adjust the compensation parameters without manual intervention. When collaboration with external devices is required, a level signal synchronized with the laser pulse can be obtained using the pulse synchronization output interface.

[0057] The above description illustrates the basic principles of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The above embodiments and descriptions in the specification are only for illustrating the principles of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the present invention without departing from the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A modulation method for pulsed laser output from a quasi-continuous laser, characterized in that... include: Step 1: Obtain preset pulsed laser parameters, including pulse repetition frequency, pulse width, and pulse peak power; Step 2: Generate a baseband current modulation signal based on the pulsed laser parameters; Step 3: Perform pre-distortion compensation processing on the baseband current modulation signal to obtain a pre-compensated modulation signal. The pre-distortion compensation processing is based on the dynamic response characteristics of the quasi-continuous laser and includes at least rising edge overshoot suppression compensation and falling edge tail elimination compensation. Step 4: Apply the pre-compensated modulation signal to the pump source drive end of the quasi-continuous laser so that the quasi-continuous laser outputs shaped pulsed laser.

2. The modulation method for output pulsed laser from a quasi-continuous laser according to claim 1, characterized in that: The pre-distortion compensation process further includes superimposing a pre-pulse signal before the rising edge of the baseband current modulation signal. The duration of the pre-pulse signal is one to twenty percent of the set pulse width, and its current amplitude is ten to fifty percent of the amplitude of the baseband current modulation signal.

3. The modulation method for output pulsed laser from a quasi-continuous laser according to claim 2, characterized in that: The pre-distortion compensation process further includes: superimposing a tail suppression pulse after the falling edge of the baseband current modulation signal. The duration of the tail suppression pulse is 0.5% to 10% of the set pulse width, and its current amplitude is 5% to 30% of the amplitude of the baseband current modulation signal. The current amplitude of the tail suppression pulse is lower than the driving current value corresponding to the laser threshold current of the quasi-continuous laser.

4. The modulation method for output pulsed laser from a quasi-continuous laser according to claim 1, characterized in that: It also includes real-time monitoring of the output optical pulse waveform of the quasi-continuous laser, and dynamic adjustment of the predistortion compensation parameters based on the deviation between the output optical pulse and the target waveform to form a closed-loop feedback control.

5. A modulation apparatus for outputting pulsed laser light from a quasi-continuous laser, implementing the method of any one of claims 1 to 4, characterized in that... include: The parameter setting module is used to obtain preset pulse laser parameters; A modulation signal generator, connected to a parameter setting module, is used to generate a baseband current modulation signal based on pulsed laser parameters; The predistortion compensator, connected to the modulation signal generator, is used to perform predistortion compensation processing on the baseband current modulation signal and output a pre-compensated modulation signal. The driving circuit, connected to the predistortion compensator, is used to amplify the power of the pre-compensated modulation signal and apply it to the pump source of the quasi-continuous laser. A quasi-continuous laser outputs pulsed laser light when excited by a driving circuit.

6. The modulation device for outputting pulsed laser from a quasi-continuous laser according to claim 5, characterized in that: The predistortion compensator includes a rising edge compensation unit and a falling edge compensation unit. The rising edge compensation unit is used to superimpose a prepulse signal before the rising edge of the baseband current modulation signal, and the falling edge compensation unit is used to superimpose a tail suppression pulse after the falling edge of the baseband current modulation signal.

7. The modulation device for outputting pulsed laser light from a quasi-continuous laser according to claim 5, characterized in that: It also includes a photoelectric feedback module, which includes a beam splitter and a photodetector. The beam splitter is set in the output optical path of the quasi-continuous laser and guides part of the output light to the photodetector. The output end of the photodetector is connected to the feedback input end of the predistortion compensator. The predistortion compensator adjusts the predistortion compensation parameters in real time according to the difference between the output light pulse waveform collected by the photodetector and the target waveform.

8. The modulation device for outputting pulsed laser from a quasi-continuous laser according to claim 5, characterized in that: The driving circuit is a programmable constant current source driving circuit, with an output current range of 0.1 ampere to 100 amperes, an output current rise time of less than 1 microsecond, and an output current fall time of less than 1 microsecond.

9. The modulation device for outputting pulsed laser light from a quasi-continuous laser according to claim 5, characterized in that: The quasi-continuous laser is a diode-pumped solid-state laser or a fiber laser, and its pump source is a laser diode bar array. The driving current of the pump source adopts a quasi-continuous mode, the pulse repetition frequency ranges from 1 Hz to 50 kHz, the pulse width ranges from 10 microseconds to 10 milliseconds, and the duty cycle ranges from 1% to 50%.

10. The modulation device for outputting pulsed laser light from a quasi-continuous laser according to claim 5, characterized in that: The modulation signal generator includes a direct digital frequency synthesizer or a field-programmable gate array (FPGA) for generating baseband current modulation signals of arbitrary waveforms, including rectangular waves, trapezoidal waves, sine half-waves, or triangular waves.

Images