A high-power narrow pulse width laser and a method for regulating the same

Abstract

The application provides a high-power narrow-pulse-width laser and a regulation method thereof, the laser comprising a seed source, a first pulse-width regulation grating, a gain fiber, a spectrum shaping system and an amplifier; the first pulse-width regulation grating is arranged behind the seed source and is used for introducing dispersion in initial signal light; the gain fiber is used for amplifying the optical signal to realize spectrum broadening by using the self-phase modulation effect of the optical signal; the spectrum shaping system is arranged behind the gain fiber and is used for performing amplitude modulation and phase modulation on the broadened optical signal; and the amplifier is arranged behind the spectrum shaping system and is used for performing energy amplification on the shaped optical signal to obtain high-power narrow-pulse-width laser. By introducing dispersion in the initial signal light, the self-phase modulation effect of the gain fiber is used to realize spectrum broadening, and the amplitude and phase modulation of the spectrum shaping system on the broadened optical signal effectively compensates the gain narrowing and nonlinear phase accumulation in the amplification process.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a high-power narrow-pulse-width laser and its control method. Background Technology

[0002] Currently, fiber lasers achieve high-power, narrow-pulse-width output mainly by utilizing chirped pulse amplification technology. This involves introducing chirp through a dispersion stretcher to broaden the signal light pulse emitted from the seed source in the time domain. The broadened signal light is then amplified through a gain fiber to reduce its peak power and ensure that the amplification system is not damaged. Finally, pulse width compression is achieved using a device with dispersion characteristics opposite to those of the stretcher, ultimately achieving a high-power, short-pulse effect.

[0003] The amplification media used in femtosecond laser amplifiers mainly include ytterbium-doped fiber and crystal, rubidium glass, and titanium-doped sapphire. Due to the limited spectral width of these media, the gain at the center wavelength of the emission spectrum is typically greater than the gain at the spectral edges. This causes the spectrum of the seed light to narrow after entering the amplification system, a common gain narrowing phenomenon in ultrafast laser amplification systems. Gain narrowing leads to a wider pulse width after passing through the compressor. Furthermore, due to the nonlinear refractive index in the amplification medium, a certain amount of nonlinear phase accumulates in the amplified pulse spectrum. This nonlinear phase causes a noticeable floor in the compressed pulse, and the final compressed pulse width is difficult to approach the Fourier transform limit, resulting in a low-compression-quality pulse in the time domain, which is detrimental to subsequent applications. Eliminating gain narrowing and nonlinear phase accumulation is a major challenge in achieving high-power, narrow-pulse-width pulsed laser amplification.

[0004] Currently, there are several main methods to eliminate gain narrowing: The first method involves pre-shaping the spectrum before amplification using a spectral shaping system to suppress gain narrowing during subsequent amplification. Adjusting the spectral shape using polarization modulation, dielectric layer filters, acousto-optic tunable filters, and liquid crystal spatial light modulators can only passively adjust within the existing spectral width, making it difficult to effectively combat spectral narrowing. The second method utilizes nonlinear pulse amplification technology, rationally using nonlinear effects to broaden the spectrum during pulse amplification to counteract gain narrowing. Currently, mainstream fiber nonlinear amplification technologies can be divided into self-similar parabolic pulse amplification, pre-chirp managed amplification (PCMA), and gain managed nonlinear amplification (GMNA). Self-similar parabolic pulse amplification utilizes the linear characteristics of the nonlinear phase shift accumulated during amplification of a parabolic pulse profile, giving these pulses good compression characteristics. Self-similar parabolic pulse amplification requires several meters of gain fiber to evolve the pulse into a self-similar parabolic shape. Furthermore, it is affected by limited gain bandwidth and harmful stimulated Raman scattering during amplification, thus limiting the maximum pulse energy to the microjoule level. Pre-chirped amplification (PCMA) aims to control the pre-chirp before amplification, achieving microjoule-level pulses with pulse widths in the tens of femtosecond range. However, this requires precise pre-chirp control, increasing system complexity. Gain-managed nonlinear amplification leverages the fact that even if the spectral broadening of the pulse exceeds the gain bandwidth limit, significant nonlinear distortion does not occur. Instead, the pulse spectrum continues to broaden into a smoother shape, ultimately achieving extreme spectral broadening far exceeding the gain bandwidth. However, it is extremely sensitive to the initial pulse parameters entering the amplifier, making it difficult to achieve the desired effect. All three methods limit the achievable energy of the amplified pulse, typically to the microjoule level, and inherently introduce significant nonlinear phase accumulation, severely restricting the temporal quality of the final compressed pulse.

[0005] Methods to eliminate nonlinear phase accumulation mainly involve spectral phase shaping using spatial light modulators, which offer flexible adjustment; or designing appropriate phase compensation compression devices. These methods are more suitable for systems with fixed parameters. However, simple phase modulation cannot solve the spectral narrowing problem during amplification. Summary of the Invention

[0006] The purpose of this invention is to provide a high-power, narrow-pulse-width laser and its control method, which effectively suppresses gain narrowing and reduces nonlinear phase accumulation, thereby achieving high-power laser output while maintaining narrow pulse-width characteristics and improving laser temporal quality.

[0007] The first aspect of this invention provides a high-power, narrow-pulse-width laser, comprising a seed source, a first pulse-width modulation grating, a gain fiber, a spectral shaping system, and an amplifier; the first pulse-width modulation grating is disposed after the seed source and is used to introduce dispersion in the initial signal light; the gain fiber is used to amplify the optical signal to achieve spectral broadening by utilizing the self-phase modulation effect of the optical signal; the spectral shaping system is disposed after the gain fiber and is used to perform amplitude modulation and phase modulation on the broadened optical signal; the amplifier is disposed after the spectral shaping system and is used to amplify the energy of the shaped optical signal to obtain a high-power, narrow-pulse-width laser.

[0008] Furthermore, the first pulse width modulation grating is a chirped fiber Bragg grating or a chirped volume Bragg grating.

[0009] Furthermore, the laser also includes a pump source and a wavelength division multiplexing device; the input end of the wavelength division multiplexing device is connected to the output end of the pump source and the output end of the pulse width adjustment grating, respectively, or the input end of the wavelength division multiplexing device is connected to the output end of the pump source and the output end of the gain fiber, respectively, for coupling pump light and signal light.

[0010] Furthermore, the laser also includes an isolator located between the output end of the gain fiber and the input end of the spectral shaping system to ensure unidirectional optical transmission.

[0011] Furthermore, the laser also includes a second pulse width modulation grating, which is disposed between the output end of the gain fiber and the input end of the isolator, for widening the signal light.

[0012] Furthermore, the spectral shaping system includes a liquid crystal spatial light modulator, an acousto-optic tunable filter, or a digital micromirror device.

[0013] Furthermore, the laser also includes an acousto-optic modulator for reducing the pulse repetition frequency, and the acousto-optic modulator is located before or after the amplifier.

[0014] Furthermore, the laser also includes a compressor, which is located after the amplifier and is used to compress the amplified optical signal.

[0015] A second aspect of the present invention provides a high-power narrow pulse width modulation method, comprising: The initial laser is emitted from a seed source; The initial laser is introduced into the dispersion to control the pulse width of the output optical signal; The output optical signal is amplified by entering the gain fiber, and the pulse spectrum is broadened by utilizing the self-phase modulation effect. The pulse spectrum of the signal light is modulated in both amplitude and phase using spectral shaping techniques. The shaped optical signal is amplified at high power to obtain a high-power, narrow-pulse laser.

[0016] The beneficial effects of this plan are as follows: This application combines nonlinear spectral pre-broadening with spectral shaping. First, a first pulse width modulation grating is introduced after the seed source. By adjusting the amount of dispersion introduced by the first pulse width modulation grating, the output pulse width can be precisely controlled, thereby changing the initial peak power of the pulse when it enters the gain fiber. Subsequently, the pulse enters the gain fiber and is amplified. At the same time, the pulse spectrum is broadened by utilizing the self-phase modulation effect. The self-phase modulation is related to the accumulated nonlinear phase shift, which is proportional to the effective fiber length, the pulse peak power, and the fiber nonlinear coefficient. Therefore, reasonable control of the pulse width can regulate the spectral broadening within the gain fiber. Subsequently, the pulse spectrum is amplitude-modulated and phase-modulated using a spectral shaping system. Finally, while using a high-power amplifier for amplification, a high-quality femtosecond laser with a wider spectrum and narrower pulse width than the seed source can be output. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the optical path architecture of an embodiment of the high-power, narrow-pulse-width laser of this scheme; Figure 2 This is a schematic diagram of the optical path structure of another embodiment of the high-power narrow-pulse laser of this scheme; Figure 3 This is a schematic diagram of the optical path architecture of another embodiment of the high-power, narrow-pulse-width laser of this scheme; Figure 4 This is a flowchart illustrating the high-power, narrow-pulse-width control method of this scheme.

[0018] Explanation of reference numerals in the attached figures: 1. Seed source; 2. First pulse width modulation grating; 3. Pump source; 4. Wavelength division multiplexing device; 5. Gain fiber; 6. Isolator; 7. Second pulse width modulation grating; 8. Spectral shaping system; 9. Acousto-optic modulator; 10. Amplifier; 11. Compressor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "joined" should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal communication of two components. For those skilled in the art, the specific meaning of the terms in this invention can be understood according to the specific circumstances.

[0021] The high-power narrow-pulse-width laser disclosed in this embodiment includes a seed source 1, a first pulse width modulation grating 2, a gain fiber 5, a spectral shaping system 8, and an amplifier 10. The first pulse width modulation grating 2 is disposed after the seed source 1 and is used to introduce dispersion in the initial signal light. The gain fiber 5 is used to amplify the optical signal to achieve spectral broadening by utilizing the self-phase modulation effect of the optical signal. The spectral shaping system 8 is disposed after the gain fiber 5 and is used to perform amplitude modulation and phase modulation on the broadened optical signal. The amplifier 10 is disposed after the spectral shaping system 8 and is used to amplify the energy of the shaped optical signal to obtain a high-power narrow-pulse-width laser.

[0022] Seed source 1 refers to the device that generates the initial laser pulse. It is usually a low-power, narrow-pulse laser source that can be used to emit the initial pulse laser. The pulse width is on the order of ps or femtoseconds.

[0023] The first pulse width adjustment grating 2 is a device used to introduce dispersion into the optical signal. By changing the transmission speed of the optical signal at different wavelengths, the optical pulse can be broadened or compressed in the time domain. By introducing dispersion, the seed source 1 pulse can be adjusted in the time domain to 1ps to 2ps.

[0024] The first pulse width modulation grating 2 is a chirped fiber Bragg grating (CFBG) and a circulator, or a chirped volume Bragg grating (CVBG) and a circulator.

[0025] A chirped fiber Bragg grating is a periodic refractive index modulation structure formed in the core of an optical fiber using ultraviolet laser writing technology. The grating period or refractive index modulation depth is gradually distributed along the fiber axis. This gradual distribution causes different wavelengths of light to experience different propagation delays when passing through the grating, thus introducing controllable dispersion. Through precise design and manufacturing, chirped fiber Bragg gratings can provide high-precision, low-loss dispersion compensation or introduction, and have good compatibility with fiber optic systems, making them easy to integrate.

[0026] A chirped volume Bragg grating is a diffraction grating with a gradually changing period or tilt angle, formed in a bulk material (such as photosensitive glass or crystal) using holographic exposure techniques. Similar to fiber Bragg gratings, its gradually changing structural characteristics allow it to produce different diffraction delays for different wavelength components of incident light, thus achieving precise dispersion management. Chirped volume Bragg gratings typically have a high damage threshold and large dispersion, making them particularly suitable for processing high-power laser pulses and capable of stable operation at high energy densities.

[0027] A circulator is a multi-port fiber optic device used to force unidirectional sequential transmission of optical signals. While a CFBG (Continuous Beam Array) handles the timing shape of the pulse, the circulator provides a clear, unidirectional optical path for this process, ensuring stable and efficient system operation. By configuring the circulator and CFBG, pulse broadening and output coupling can be achieved simultaneously within the laser cavity, preventing harmful nonlinear effects from accumulating before amplification.

[0028] Gain fiber 5 refers to an optical fiber with optical gain characteristics, where the energy of an optical signal is amplified when it passes through. Under certain conditions, the optical signal in gain fiber 5 undergoes self-phase modulation, resulting in spectral broadening. Gain fiber 5 is ytterbium-doped (Yb). 3+ Active optical fiber. Small-diameter single-mode fiber is selected, and its length has been optimized.

[0029] The spectral shaping system 8 performs spectral intensity and phase shaping on the input light, pre-compensates for nonlinear effects generated by the amplifier 10 during amplification, and optimizes spectral narrowing.

[0030] Amplifier 10 refers to a device used to increase the energy of optical signals. It typically consists of a gain medium and a pump source 3, converting low-energy optical signals into high-energy optical signals. It can amplify the energy of shaped pulses.

[0031] Self-phase modulation effect: refers to the nonlinear optical effect that occurs when an optical signal is transmitted in a nonlinear medium. Due to the change in refractive index caused by the light intensity, the phase of the optical signal is modulated, which in turn causes spectral broadening.

[0032] Amplitude modulation: refers to the process of transmitting information or adjusting the shape of the spectrum by changing the intensity of the light signal.

[0033] Phase modulation: refers to the process of transmitting information or adjusting the shape of a spectrum by changing the phase of an optical signal.

[0034] Specifically, a chirped fiber Bragg grating is introduced after seed source 1. By adjusting the dispersion introduced by the chirped fiber Bragg grating, the output pulse width can be precisely controlled, thereby changing the initial peak power of the pulse when it enters gain fiber 5. Subsequently, the pulse is amplified upon entering gain fiber 5, and the pulse spectrum is broadened using the self-phase modulation effect. Self-phase modulation is related to the accumulated nonlinear phase shift, which is proportional to the effective fiber length, pulse peak power, and fiber nonlinear coefficient. Therefore, reasonable control of the pulse width can regulate the spectral broadening within gain fiber 5. Subsequently, the pulse spectrum is amplitude-modulated and phase-modulated using spectral shaping technology. In the liquid crystal spatial light modulator, the anisotropy of liquid crystal molecules and the electrically controlled birefringence effect are utilized. By applying a controlled voltage to the pixel array, the deflection angle of the liquid crystal molecules is controlled, thereby achieving phase modulation. At the same time, the liquid crystal spatial light modulator can freely adjust the voltage on each pixel to simulate the corresponding phase blazed grating. By controlling the maximum modulation depth of the blazed grating loaded on each column of pixels, the diffraction efficiency of the emitted first-order diffracted light is changed, thereby achieving amplitude modulation of the spectrum. It effectively overcomes the gain narrowing effect caused by high gain in subsequent chirped pulse amplification (CPA) systems; ultimately, while achieving high power amplification, it can output high-quality femtosecond laser with a wider spectrum and narrower pulse width than seed source 1.

[0035] This embodiment introduces dispersion into the initial signal light and utilizes the self-phase modulation effect of the gain fiber 5 to achieve spectral broadening. The broadened optical signal is then modulated in amplitude and phase by a spectral shaping system 8, effectively compensating for gain narrowing and nonlinear phase accumulation during amplification. As a result, this laser can output high-power laser light with narrow pulse width characteristics, while simultaneously improving the temporal quality of the pulse, overcoming the limitations of traditional schemes in terms of energy, pulse width, and pulse quality.

[0036] In one embodiment, the laser further includes a pump source 3 and a wavelength division multiplexing device 4; the pump source 3 emits pump light, which is absorbed by the subsequent gain fiber 5. The wavelength division multiplexing device 4 is used to wavelength-couple the pump light generated by the pump source 3 with the signal light processed by the first pulse width adjustment grating 2.

[0037] Pump source 3 is a key component providing the energy required for the laser gain medium. It typically employs a high-power semiconductor laser, whose emitted pump light wavelength matches the absorption spectrum of the gain fiber 5 to achieve efficient energy conversion. For example, for ytterbium-doped fiber, pump source 3 can be a laser diode with a wavelength of 915 nm or 976 nm. Wavelength division multiplexing device 4 is an optical device used to combine or split optical signals of different wavelengths. In this embodiment, its core function is to efficiently couple the pump light emitted from pump source 3 with the signal light, ensuring that pump energy can be smoothly introduced into the gain fiber 5.

[0038] In one embodiment, the laser further includes an isolator 6, which is located between the output end of the gain fiber 5 and the input end of the spectral shaping system 8, to prevent back-reflected light from damaging the front-end devices and to ensure unidirectional optical transmission.

[0039] Isolator 6 is an optical device whose main function is to allow light signals to pass in one direction while blocking or significantly attenuating light signals propagating in the opposite direction. Its working principle is typically based on the Faraday effect, achieved through a combination of a Faraday rotator and a polarizer. When the light signal passes in the forward direction, its polarization state is rotated by a specific angle by the Faraday rotator and then passes through a polarizer; when the light signal passes in the reverse direction, its polarization state is rotated again, and the total rotation angle causes it to be blocked by the polarizer, thus achieving unidirectional transmission. Placing isolator 6 between the output end of gain fiber 5 and the input end of spectral shaping system 8 effectively intercepts light signals reflected from spectral shaping system 8 or subsequent optical paths, preventing their reverse propagation. This avoids interference from reflected light on the amplification process in gain fiber 5, prevents damage to upstream optical components such as gain fiber 5 or seed source 1 due to reverse light, thereby ensuring the stability and reliability of the laser operation and guaranteeing the output quality of high-power narrow-pulse lasers.

[0040] In one embodiment, the laser further includes a second pulse width modulation grating 7, which is disposed between the output end of the gain fiber 5 and the input end of the isolator 6, and can time-domain broaden the pulse to nanoseconds or hundreds of picoseconds. The second pulse width modulation grating 7 can be a chirped fiber Bragg grating, which achieves dispersion through periodic refractive index modulation within the fiber; it can also be a chirped bulk Bragg grating, which introduces dispersion through periodic changes in the refractive index of the bulk material; or it can be a dispersion compensator based on prism pairs or grating pairs, which introduces the desired dispersion by adjusting the optical path geometry. In this embodiment, the second pulse width modulation grating 7 is strategically disposed between the output end of the gain fiber 5 and the input end of the isolator 6, and its core function is to further pulse broaden the signal light that has been amplified and broadened by the gain fiber 5.

[0041] Introducing a second pulse width modulation grating 7 to broaden the signal light effectively reduces its instantaneous peak power. This reduction in peak power significantly reduces the risk of nonlinear effects when the signal light passes through isolator 6, thereby protecting isolator 6 from potential damage caused by high-power pulses and ensuring the stability of unidirectional optical transmission and the long-term reliability of the device.

[0042] In one embodiment, the spectral shaping system 8 includes programmable components such as a liquid crystal spatial light modulator (LC-SLM), an acousto-optic tunable filter (AOTF), or a digital micromirror device (DMD).

[0043] By employing a liquid crystal spatial light modulator, arbitrary phase and amplitude shaping of the spectrum can be achieved, thereby precisely compensating for dispersion, compressing pulses, and customizing pulse shapes to obtain ultrashort, high peak power laser pulses. Using an acousto-optic tunable filter enables rapid, programmable amplitude modulation of the spectrum, suitable for scenarios requiring dynamic adjustment of spectral characteristics. Digital micromirror devices provide high-resolution, high-speed spectral amplitude shaping capabilities. These specific implementation methods allow for fine-grained control of the laser pulse's spectral and temporal characteristics according to different application requirements, significantly improving the performance and application range of high-power, narrow-pulse-width lasers, ensuring that the output laser pulse has the required high peak power and narrow pulse width.

[0044] Specifically, the input of wavelength division multiplexing device 4 is connected to the output of pump source 3 and the output of pulse width modulation grating, respectively, for forward pumping. See also Figure 1 The input of the wavelength division multiplexing device 4 can be connected to the output of the pump source 3 and the output of the pulse width modulation grating, respectively. This means that the pump light is combined with the signal light before the signal light enters the gain fiber 5, i.e., after the signal light is processed by the first pulse width modulation grating 2. This forward pumping method enables the pump light and the signal light to propagate in the same direction, which is beneficial for achieving higher gain efficiency.

[0045] Alternatively, reverse pumping can be used. The input of wavelength division multiplexing device 4 is connected to the output of pump source 3 and the output of gain fiber 5, respectively, for coupling pump light and signal light. See also Figure 2The input of the wavelength division multiplexing device 4 can be connected to the output of the pump source 3 and the output of the gain fiber 5, respectively. In this configuration, the pump light is injected from the output of the gain fiber 5 and propagates in the opposite direction to the signal light within the gain fiber 5. This backward pumping method helps improve the temperature distribution inside the gain fiber 5, reduces nonlinear effects, and may provide better noise performance in some applications.

[0046] In one embodiment, the laser further includes a compressor 11, located after the amplifier 10, for compressing the amplified optical signal. The amplified pulse can be compressed so that its pulse width does not exceed 200 fs (Gaussian fitting or hyperbolic secant fitting).

[0047] After the optical signal receives high-energy output from amplifier 10, compressor 11 is introduced to compress the amplified optical signal. Because the optical signal accumulates dispersion during transmission through optical components such as gain fiber 5, causing pulse width broadening, compressor 11 effectively compensates for this dispersion, recompressing the broadened pulse to a narrow pulse width close to its Fourier transform limit. This allows the laser to maintain an extremely narrow pulse width while outputting high power, thus significantly improving the laser's peak power. High-peak-power narrow-pulse lasers have wide applications in precision materials processing, nonlinear optics, ultrafast spectroscopy, and biomedical imaging, enabling finer processing effects, stronger nonlinear effects, or higher spatial / temporal resolution. Therefore, this scheme effectively solves the problem of pulse width broadening after high-power amplification, ensuring that the laser outputs high power and narrow pulse width characteristics can be achieved simultaneously, improving the overall performance and application potential of the laser.

[0048] In one embodiment, the laser further includes an acousto-optic modulator 9, which is used to reduce the pulse repetition frequency and select the desired pulse repetition frequency. The acousto-optic modulator 9 is a device that uses the acousto-optic effect to control a laser beam. Its working principle is that a piezoelectric transducer converts a radio frequency electrical signal into ultrasonic waves. When the ultrasonic waves propagate in the acousto-optic crystal, they cause periodic changes in the crystal's refractive index, forming a dynamic diffraction grating. When the laser beam passes through this diffraction grating, part of the beam is diffracted. By precisely controlling the on and off of the radio frequency signal, the laser pulse can be selected or blocked, thereby effectively reducing the laser pulse repetition frequency. For example, if the pulse repetition frequency output by the seed source 1 is high, the acousto-optic modulator 9 can periodically select pulses at a preset lower frequency, allowing only a portion of the pulses to pass, thereby reducing the pulse repetition frequency. The position of the acousto-optic modulator 9 is flexible.

[0049] The acousto-optic modulator 9 is located before the amplifier 10, see [link / reference]. Figure 1When the acousto-optic modulator 9 is placed before the amplifier 10, its function is to regulate the pulse repetition frequency during the low-power stage. This means that only the selected pulses will be amplified by the subsequent amplifier 10, thereby avoiding unnecessary amplification of unwanted pulses, which helps to improve the efficiency of the amplifier 10 and reduce the thermal load.

[0050] In another embodiment, the acousto-optic modulator 9 is located after the amplifier 10, see [reference needed]. Figure 3 When the acousto-optic modulator 9 is placed after the amplifier 10, its function is to regulate the pulse repetition frequency during the high-power output stage. This setting ensures that the amplifier 10 always amplifies continuously in its optimal operating state and performs precise frequency selection of the high-power pulse at the final output, making it suitable for scenarios where high frequency control accuracy of the final output pulse is required.

[0051] See Figure 4 The high-power narrow pulse width modulation method disclosed in this invention includes: S1. The initial laser is emitted through seed source 1; seed source 1 is typically a low-power, short-pulse oscillator, such as a femtosecond fiber optic oscillator.

[0052] S2. Introducing dispersion into the initial laser beam controls the pulse width of the output optical signal; controlled dispersion is introduced into the initial signal light, thereby broadening the laser pulse in the time domain. This pre-broadening operation can significantly reduce the peak power of the pulse, effectively protect the optical components in the subsequent amplification stage from damage, and lay the foundation for achieving high-energy amplification.

[0053] S3. The output optical signal enters the gain fiber 5 for amplification, and simultaneously utilizes the self-phase modulation effect to broaden the pulse spectrum; within the gain fiber 5, the signal light receives energy amplification. More importantly, this system utilizes the self-phase modulation effect of the optical signal to achieve spectral broadening. During amplification, due to the nonlinear effects of the fiber, the pulse spectrum broadens. This active spectral broadening mechanism effectively counteracts the gain narrowing phenomenon commonly present during amplification.

[0054] S4. Combine spectral shaping technology to perform amplitude and phase modulation on the pulse spectrum of the signal light; In terms of amplitude modulation, the spectral shaping system 8 can finely adjust the shape of the spectrum to further compensate for any residual gain narrowing effect, or shape a more ideal spectral profile as needed. In terms of phase modulation, the spectral shaping system 8 can accurately compensate for the nonlinear phase accumulated in the gain fiber 5. This scheme, through the active and flexible correction of the nonlinear phase by the spectral shaping system 8, significantly improves the temporal quality of the final compressed pulse, enabling it to obtain a cleaner, closer-to-ideal narrow pulse. This ability to perform both amplitude and phase modulation simultaneously makes this scheme more advantageous and flexible than existing methods that only perform pre-shaping or simple phase modulation in eliminating gain narrowing and nonlinear phase accumulation.

[0055] S5. The shaped optical signal is amplified at high power to obtain a high-power, narrow-pulse laser.

[0056] The proposed solution employs a first pulse width adjustment grating 2 for pre-broadening, utilizes the self-phase modulation effect of the gain fiber 5 to actively broaden the spectrum to counteract gain narrowing, and uses a spectral shaping system 8 to perform amplitude and phase modulation of the spectrum, thereby simultaneously addressing the two major challenges of gain narrowing and nonlinear phase accumulation. This synergistic approach enables the laser to output high-power, narrow-pulse-width lasers with excellent temporal quality, overcoming the limitations of existing technologies where single methods cannot simultaneously address multiple issues, and significantly improving the performance of ultrafast lasers.

[0057] The positive dispersion pre-chirp of the CFBG-modulated pulse allows the new frequency components generated by self-phase modulation to appropriately broaden the spectrum, thus avoiding light wave splitting to some extent. Based on the combination of nonlinear broadening and spectral shaping, the unavoidable gain narrowing and nonlinear phase accumulation problems in high-power amplification are solved, enabling high-power, narrow-pulse-width output.

[0058] By combining the methods of "active spectral broadening through self-phase modulation" and "passive compensation through spectral shaping", the new frequency generated by the self-phase modulation effect is used to broaden the spectral width, and the intensity and phase are pre-shaped using a spectral shaping device to overcome the problems of gain narrowing effect and low pulse compression quality in the subsequent amplification optical path.

[0059] High-power, narrow-pulse ultrafast lasers have been widely used in fields such as industrial ultrafast micro-nano fabrication, biomedical imaging, scientific research, and cutting-edge exploration due to their excellent performance.

[0060] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A high-power, narrow-pulse-width laser, characterized in that, It includes a seed source, a first pulse width modulation grating, a gain fiber, a spectral shaping system, and an amplifier; the first pulse width modulation grating is disposed after the seed source and is used to introduce dispersion in the initial signal light; The gain fiber is used to amplify the optical signal to achieve spectral broadening by utilizing the self-phase modulation effect of the optical signal; the spectral shaping system is located after the gain fiber and is used to perform amplitude modulation and phase modulation on the broadened optical signal; the amplifier is located after the spectral shaping system and is used to amplify the energy of the shaped optical signal to obtain a high-power, narrow-pulse-width laser.

2. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The first pulse width modulation grating is a chirped fiber Bragg grating or a chirped volume Bragg grating.

3. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The laser also includes a pump source and a wavelength division multiplexing device.

4. The high-power narrow-pulse-width laser according to claim 3, characterized in that, The input terminals of the wavelength division multiplexing device are respectively connected to the output terminals of the pump source and the output terminals of the pulse width adjustment grating, or the input terminals of the wavelength division multiplexing device are respectively connected to the output terminals of the pump source and the output terminals of the gain fiber, for coupling pump light and signal light.

5. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The laser also includes an isolator, which is located between the output end of the gain fiber and the input end of the spectral shaping system to ensure unidirectional optical transmission.

6. The high-power narrow-pulse-width laser according to claim 5, characterized in that, The laser also includes a second pulse width modulation grating, which is located between the output end of the gain fiber and the input end of the isolator to broaden the signal light.

7. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The spectral shaping system includes systems based on liquid crystal spatial light modulators, acousto-optic tunable filters, or digital micromirror devices.

8. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The laser also includes an acousto-optic modulator for reducing the pulse repetition frequency, and the acousto-optic modulator is located before or after the amplifier.

9. The high-power narrow-pulse-width laser according to claim 1, characterized in that, The laser also includes a compressor, which is located after the amplifier and is used to compress the amplified optical signal.

10. A high-power, narrow-pulse-width modulation method, characterized in that, include: The initial laser is emitted from a seed source; The initial laser is introduced into the dispersion to control the pulse width of the output optical signal; The output optical signal is amplified by entering the gain fiber, and the pulse spectrum is broadened by utilizing the self-phase modulation effect. The pulse spectrum of the signal light is modulated in both amplitude and phase using spectral shaping techniques. The shaped optical signal is amplified at high power to obtain a high-power, narrow-pulse laser.

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