Controllable interval femtosecond laser pulse train generation method and device

Abstract

The application belongs to the technical field of laser pulse shaping, and discloses a controllable-interval femtosecond laser pulse train generation method and device. First, a femtosecond laser is generated by a femtosecond laser device and is incident on a shaping unit, the shaping unit adjusts the femtosecond laser pulse to a horizontal polarization state and amplifies a point pulse to a one-dimensional line pulse; then the one-dimensional line pulse is diffracted into a plurality of monochromatic light waves in two-dimensional distribution by a diffraction unit and is adjusted to parallel light; then the plurality of monochromatic light waves are incident on different regions of a spatial light phase modulator respectively to modulate the phases of the plurality of monochromatic light waves respectively; finally, the plurality of monochromatic light waves are incident on a superposition unit to superimpose all the monochromatic light waves, and a femtosecond laser pulse train composed of a plurality of femtosecond laser pulses with different time delays is obtained. The application can generate a femtosecond laser pulse train with high repetition frequency, and the number of pulses and the time delay are controllable.

Description

Technical Field

[0001] This invention belongs to the field of laser pulse shaping technology, and more specifically, relates to a method and apparatus for generating controllable spacing femtosecond laser pulse trains. Background Technology

[0002] Compared to traditional lasers, femtosecond lasers possess extremely small pulse widths, extremely high instantaneous power, and precise targeted focusing. Achieving high repetition rates with femtosecond laser pulses can effectively improve ablation efficiency while maintaining processing quality in precision micromachining; in precision measurement, the high power and easily distinguishable comb teeth can enhance the beat frequency signal-to-noise ratio and measurement accuracy; and they also have profound implications for information transmission and ultrafast imaging, thus warranting in-depth research.

[0003] The repetition frequency of a typical femtosecond laser pulse is approximately 100 megahertz (10^6 MHz). 8 The time interval between each femtosecond pulse is approximately on the order of 100 microseconds (Hz), meaning it is on the order of 100 microseconds (Hz). -8 The frequency is on the order of s, which is achieved through mode-locking technology. In recent years, repetition frequencies reaching gigahertz (10^6 Hz) have emerged. 9 Femtosecond laser mode-locking techniques on the order of 10 GHz mainly include three techniques: harmonic mode-locking, passive mode-locking based on saturable absorber mirrors (SESAM), and Kerr lens mode-locking (KLM). Harmonic mode-locking is mostly used in fiber lasers. It utilizes soliton splitting to multiply the repetition frequency, achieving mode-locked output of hundreds of harmonics, with repetition frequencies reaching over 10 GHz. However, harmonic mode-locked pulses have poor amplitude uniformity and relatively large timing jitter. SESAM mode-locking technology is suitable for various types of lasers, such as fiber lasers, vertical-cavity surface-emitting semiconductor lasers, and all-solid-state lasers. KLM technology is commonly used in femtosecond oscillators with bulk solid-state gain media, such as Ti:sapphire femtosecond lasers and ytterbium-doped all-solid-state femtosecond oscillators. However, due to the limitations of the mode-locking technology itself, it is difficult to achieve a significant increase in repetition frequency by orders of magnitude.

[0004] Therefore, in the field of femtosecond laser pulse technology, there is a need for a method that can generate femtosecond laser pulses with extremely high repetition rates above gigahertz. This method needs to be simple to operate, have high delay accuracy, and be controllable, so as to further promote the development of femtosecond lasers in various scientific research fields. Summary of the Invention

[0005] This invention provides a method and apparatus for generating controllable-spacing femtosecond laser pulse trains, thereby solving the problem of low repetition frequency of femtosecond laser pulses in the prior art.

[0006] This invention provides a method for generating controllable-gap femtosecond laser pulse trains, comprising the following steps:

[0007] Step 1: A femtosecond laser pulse is generated by a femtosecond laser and incident on a shaping unit. The shaping unit adjusts the femtosecond laser pulse to a horizontal polarization state and amplifies the point pulse into a one-dimensional line pulse.

[0008] Step 2: A one-dimensional line pulse is incident on a diffraction unit, which diffracts the one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and adjusts the multiple monochromatic light waves into parallel light.

[0009] Step 3: Multiple monochromatic light waves are incident on different regions of a spatial light phase modulator, which modulates the phase of each monochromatic light wave.

[0010] Step 4: Multiple monochromatic light waves after phase modulation are incident on the superposition unit, which superimposes all the monochromatic light waves to obtain a femtosecond laser pulse train consisting of multiple femtosecond laser pulses with different delays.

[0011] Preferably, the grayscale image loaded on the spatial light phase modulator is obtained based on the target delay size of the femtosecond laser pulse train;

[0012] The spatial light phase modulator modulates the phase of multiple monochromatic light waves according to the grayscale image.

[0013] Preferably, the phase modulation amount of the spatial light phase modulator for each monochromatic light wave is linearly related to the gray value corresponding to the region where the monochromatic light wave is incident on the spatial light phase modulator, and the phase modulation amount is in the range of 0 to 2π.

[0014] Preferably, the phase modulation amount of each monochromatic light wave is obtained in the following way:

[0015] The distribution function of a femtosecond laser pulse is simulated, and the target delay of k femtosecond laser pulses is set to t. i Let i = 1, 2, ..., k, and simulate the pulse delay t. i The distribution function of the subsequent femtosecond laser pulse;

[0016] By performing Fourier transforms on the distribution functions before and after the delay, the phase magnitudes of the monochromatic light waves at each frequency of the femtosecond laser pulse can be obtained.

[0017] The phase modulation amount of each monochromatic light wave is obtained by subtracting the phase before and after the delay.

[0018] Preferably, the spatial light phase modulator has a resolution of m×n, and the phase modulation region of the spatial light phase modulator is divided into m×k regions, each region corresponding to a gray value, and the value of k corresponds to the number of femtosecond laser pulses contained in the final femtosecond laser pulse train.

[0019] Preferably, the spatial light phase modulator is a liquid crystal spatial light modulator.

[0020] Preferably, the shaping unit includes a polarizer, a half-wave plate, a first cylindrical mirror, and a second cylindrical mirror arranged sequentially along the optical path; the focal length of the first cylindrical mirror is smaller than the focal length of the second cylindrical mirror, and the two are coaxial; the magnification directions corresponding to the first cylindrical mirror and the second cylindrical mirror are perpendicular to the diffraction direction of the diffraction unit.

[0021] The polarizer and the half-wave plate are used to adjust the femtosecond laser pulse to a horizontal polarization state, and the first cylindrical mirror and the second cylindrical mirror are used to amplify the point pulse into a one-dimensional line pulse.

[0022] Preferably, the diffraction unit includes a first grating and a third cylindrical mirror arranged sequentially along the optical path;

[0023] The first grating is used to diffract a one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and the third cylindrical mirror is used to adjust the multiple monochromatic light waves into parallel light.

[0024] Preferably, the superposition unit includes a second grating, a fourth cylindrical mirror, a fifth cylindrical mirror, and a sixth cylindrical mirror arranged sequentially along the optical path; the second grating and the first grating adopt the same grating structure and are parallel in direction; the focal length of the fifth cylindrical mirror is greater than the focal length of the sixth cylindrical mirror, and the two are coaxial; the shrinkage directions of the fifth cylindrical mirror and the sixth cylindrical mirror are perpendicular to the diffraction direction of the second grating.

[0025] The second grating superimposes all monochromatic light waves, which are then adjusted into parallel light after passing through the fourth cylindrical mirror, and then coaxially passed through the fifth and sixth cylindrical mirrors to finally obtain the femtosecond laser pulse train.

[0026] On the other hand, the present invention provides a controllable spacing femtosecond laser pulse train generation device, comprising: a femtosecond laser, a shaping unit, a diffraction unit, a spatial light phase modulator, and a superposition unit;

[0027] The controllable-spacing femtosecond laser pulse train generation device is used to implement the steps in the controllable-spacing femtosecond laser pulse train generation method.

[0028] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0029] This invention provides a method for generating controllable-spacing femtosecond laser pulse trains based on spatial optical phase modulation. Femtosecond laser pulses generated by a femtosecond laser are spatially diffracted and then irradiated into multiple different regions of a spatial optical phase modulator. Each region modulates the phase of the diffracted light of different wavelengths according to a set delay. The modulated light of different wavelengths is then superimposed to obtain a femtosecond laser pulse train composed of multiple femtosecond laser pulses with different delays. This invention generates femtosecond laser pulse trains with delays ranging from 0 to 100 ps and an accuracy of less than 1 fs using a simple device without affecting pulse quality. The number of pulses and the delay of each pulse are controllable. This method effectively solves the problem of low repetition frequency of femtosecond laser pulses, providing new ideas for the development of information transmission technology, ultrafast imaging, and other technical fields. Attached Figure Description

[0030] Figure 1 A schematic diagram of the frame of a controllable spacing femtosecond laser pulse train generation device provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the waveforms at each stage in a controllable-gap femtosecond laser pulse train generation method provided by an embodiment of the present invention; wherein, Figure 2 (a) in the figure is the waveform after adjustment by the diffraction unit. Figure 2 (b) shows the waveforms after the spatial light modulator performs phase modulation on multiple monochromatic light waves. Figure 2 (c) in the figure shows the waveforms of multiple femtosecond laser pulses obtained after the superposition unit. Figure 2 In the diagram, (d) represents the waveform of the final femtosecond laser pulse train;

[0032] Figure 3 The distribution diagram of the modulation phase on the liquid crystal spatial light modulator in a controllable spacing femtosecond laser pulse train generation method provided in an embodiment of the present invention.

[0033] Among them, 101-femtosecond laser, 102-polarizer, 103-half-wave plate, 104-first cylindrical mirror, 105-second cylindrical mirror, 106-first grating, 107-third cylindrical mirror, 108-liquid crystal spatial light modulator, 109-second grating, 110-fourth cylindrical mirror, 111-fifth cylindrical mirror, and 112-sixth cylindrical mirror. Detailed Implementation

[0034] This invention provides a method for generating controllable-gap femtosecond laser pulse trains, comprising the following steps:

[0035] Step 1: A femtosecond laser pulse is generated by a femtosecond laser and incident on a shaping unit. The shaping unit adjusts the femtosecond laser pulse to a horizontal polarization state and amplifies the point pulse into a one-dimensional line pulse.

[0036] Step 2: A one-dimensional line pulse is incident on a diffraction unit, which diffracts the one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and adjusts the multiple monochromatic light waves into parallel light.

[0037] Step 3: Multiple monochromatic light waves are incident on different regions of a spatial light phase modulator, which modulates the phase of each monochromatic light wave.

[0038] Step 4: Multiple monochromatic light waves after phase modulation are incident on the superposition unit, which superimposes all the monochromatic light waves to obtain a femtosecond laser pulse train consisting of multiple femtosecond laser pulses with different delays.

[0039] Specifically, based on the target delay of the femtosecond laser pulse train, a grayscale image is obtained on the spatial light phase modulator; the spatial light phase modulator performs phase modulation on multiple monochromatic light waves according to the grayscale image.

[0040] The phase modulation amount of each monochromatic light wave by the spatial light phase modulator is linearly related to the gray value corresponding to the region where the monochromatic light wave is incident on the spatial light phase modulator, and the phase modulation amount is in the range of 0 to 2π.

[0041] The phase modulation amount of each monochromatic light wave is obtained in the following way:

[0042] The distribution function of a femtosecond laser pulse is simulated, and the target delay of k femtosecond laser pulses is set to t. i Let i = 1, 2, ..., k, and simulate the pulse delay t. i The distribution function of the subsequent femtosecond laser pulse;

[0043] By performing Fourier transforms on the distribution functions before and after the delay, the phase magnitudes of the monochromatic light waves at each frequency of the femtosecond laser pulse can be obtained.

[0044] The phase modulation amount of each monochromatic light wave is obtained by subtracting the phase before and after the delay.

[0045] For example, the spatial light phase modulator has a resolution of m×n, and the phase modulation region of the spatial light phase modulator is divided into m×k regions, each region corresponding to a gray value, and the value of k corresponds to the number of femtosecond laser pulses contained in the final femtosecond laser pulse train.

[0046] Specifically, the spatial light phase modulator can be a liquid crystal spatial light modulator (LC-SLM).

[0047] The shaping unit includes a polarizer, a half-wave plate, a first cylindrical mirror, and a second cylindrical mirror arranged sequentially along the optical path; the focal length of the first cylindrical mirror is smaller than the focal length of the second cylindrical mirror, and the two are coaxial; the magnification directions corresponding to the first cylindrical mirror and the second cylindrical mirror are perpendicular to the diffraction direction of the diffraction unit; the polarizer and the half-wave plate are used to adjust the femtosecond laser pulse to a horizontal polarization state, and the first cylindrical mirror and the second cylindrical mirror are used to amplify the point pulse into a one-dimensional line pulse.

[0048] The diffraction unit includes a first grating and a third cylindrical mirror arranged sequentially along the optical path; the first grating is used to diffract a one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and the third cylindrical mirror is used to adjust the multiple monochromatic light waves into parallel light.

[0049] The superposition unit includes a second grating, a fourth cylindrical mirror, a fifth cylindrical mirror, and a sixth cylindrical mirror arranged sequentially along the optical path. The second grating and the first grating adopt the same grating structure and are parallel in direction. The focal length of the fifth cylindrical mirror is greater than that of the sixth cylindrical mirror, and the two are coaxial. The shrinkage directions of the fifth and sixth cylindrical mirrors are perpendicular to the diffraction direction of the second grating. The second grating superimposes all monochromatic light waves, which are then adjusted into parallel light after passing through the fourth cylindrical mirror, and then coaxially passed through the fifth and sixth cylindrical mirrors to finally obtain the femtosecond laser pulse train.

[0050] Corresponding to the above method, the present invention also provides a controllable-pitch femtosecond laser pulse train generation device, comprising: a femtosecond laser, a shaping unit, a diffraction unit, a spatial light phase modulator, and a superposition unit. The controllable-pitch femtosecond laser pulse train generation device is used to implement the steps in the controllable-pitch femtosecond laser pulse train generation method described above.

[0051] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0052] The controllable-spacing femtosecond laser pulse train generation device provided in this embodiment of the invention is as follows: Figure 1 As shown, it includes: a femtosecond laser 101, a polarizer 102, a half-wave plate 103, a first cylindrical mirror 104, a second cylindrical mirror 105, a first grating 106, a third cylindrical mirror 107, a liquid crystal spatial light modulator 108, a second grating 109, a fourth cylindrical mirror 110, a fifth cylindrical mirror 111, and a sixth cylindrical mirror 112.

[0053] See Figures 1 to 3 The present invention provides a method for generating controllable-spacing femtosecond laser pulse trains, comprising the following steps:

[0054] Step 1: The femtosecond laser 101 generates femtosecond laser pulses and incident them onto the polarizer 102. The femtosecond laser 101 is preferably a Coherent Vitara-T-HP femtosecond laser, with a center wavelength of 800 nm, a spectral width of 40 nm, a pulse width of 40 fs, and a repetition frequency of 80 MHz. The polarizer 102 and the half-wave plate 103 adjust the femtosecond laser pulses to a horizontal polarization state. Then, the first cylindrical mirror 104 and the second cylindrical mirror 105 convert the point pulses into one-dimensionally distributed line pulses.

[0055] Step 2: A one-dimensional line pulse is incident on the first grating 106. The line pulse is diffracted on the first grating 106 to obtain multiple monochromatic light waves distributed in two dimensions. After passing through the third cylindrical mirror 107, parallel light is obtained, and its distribution is as follows: Figure 2 As shown in (a) in the figure.

[0056] Step 3: Multiple monochromatic light waves are incident on different regions of the liquid crystal spatial light modulator 108, completely covering the phase modulation region of the liquid crystal spatial light modulator 108. The liquid crystal spatial light modulator 108 is a UPOLabs liquid crystal spatial light modulator, model HDSLM80R-Plus, with a resolution of 1920×1200, a single pixel size of 8μm, a data bit depth of 10bit, and a frame rate of 60Hz. The liquid crystal spatial light modulator 108 is divided into 1920×10 regions, and the monochromatic light waves are phase modulated from 0 to 2π. The phase modulation amount (0~2π) of the monochromatic light waves in each region corresponds linearly to the grayscale value (0~1023) loaded on the liquid crystal spatial light modulator.

[0057] The determination of the phase modulation amount for each monochromatic light wave needs to be accomplished using a computer algorithm. First, the distribution function of the femtosecond laser pulse is simulated, typically using a Gaussian function as the envelope function, with the delay of 10 femtosecond laser pulses set to t. i (i = 1, 2, ..., 10), and simulate the pulse delay t. i The distribution function of the femtosecond laser pulse is then obtained. Subsequently, Fourier transforms are performed on the distribution functions before and after the delay to obtain the phase magnitudes of the monochromatic light at each frequency of the femtosecond laser pulse. The difference between these two values ​​yields the phase modulation amount of each monochromatic light beam. Furthermore, since the liquid crystal spatial light modulator can only perform phase modulation in the range of 0–2π, phase modulation amounts outside this range also need to be converted to the 0–2π range.

[0058] The following explanation uses the formula as an example.

[0059] Let the i-th monochromatic light wave be y i The amplitude is A i The frequency is w iThe initial phase is Its wave function is shown in equation (5).

[0060]

[0061] When the i-th monochromatic light wave y i Perform θ i When the phase is modulated, it is equivalent to modulating the i-th monochromatic light wave y i Delay t i As shown in equation (6).

[0062] t i =w i θ i (6)

[0063] Since monochromatic light has a period of T i The sine function, therefore for any delay t, i0 It is equivalent to t i As shown in equation (7).

[0064] t i0 =t i +2kT i (k is a positive integer) 7)

[0065] Therefore, for any desired delay t i0 For monochromatic light waves, only a delay of t is needed. i That is, the phase modulation θ of the i-th monochromatic light wave i As shown in equation (8).

[0066]

[0067] According to the phase modulation amount θ of each monochromatic light wave i The correspondence between the grayscale values ​​loaded on the liquid crystal spatial light modulator 108 and the grayscale values ​​of each pixel on the liquid crystal spatial light modulator 108 is established, and the grayscale image loaded on the liquid crystal spatial light modulator 108 is finally formed, such as... Figure 3 As shown. The femtosecond laser pulse delay size t is set. i Taking 0ps, 0.4ps, 0.9ps, 1.5ps, 2ps, 2.6ps, 3.5ps, 4.2ps, 6ps, and 8ps as examples, the modulation results after modulation by the liquid crystal spatial light modulator 108 are shown in the schematic diagram below. Figure 2 As shown in (b) of the diagram.

[0068] Step 4: Multiple monochromatic light waves after phase modulation are incident on the second grating 109. The delayed monochromatic light is superimposed by the second grating 109 to obtain 10 femtosecond laser pulses, which are then parallelized by the fourth cylindrical mirror 110, as shown below. Figure 2 As shown in (c) in the diagram. Afterwards, the 10 femtosecond laser pulses pass coaxially through the fifth cylindrical mirror 111 and the sixth cylindrical mirror 112, transforming into a pulse train composed of 10 femtosecond laser pulses, as shown in the diagram. Figure 2 As shown in (d) in the figure.

[0069] In summary, when generating femtosecond laser pulse trains using the method provided by this invention, the experimenter can calculate and set the phase modulation amount of each region (specifically, each pixel) on the spatial light modulator according to the required femtosecond laser pulse delay size in the experimental environment. The femtosecond laser emits a single femtosecond laser pulse as needed, and then sequentially passes through a shaping unit, a diffraction unit, a spatial light phase modulator, and a superposition unit for controllable delay. This allows a single femtosecond laser pulse to be transformed into a femtosecond laser pulse train, and each femtosecond laser pulse in the femtosecond laser pulse train can achieve the set delay effect.

[0070] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for generating controllable-gap femtosecond laser pulse trains, characterized in that, Includes the following steps: Step 1: A femtosecond laser pulse is generated by a femtosecond laser and incident on a shaping unit. The shaping unit adjusts the femtosecond laser pulse to a horizontal polarization state and amplifies the point pulse into a one-dimensional line pulse. The shaping unit includes a polarizer, a half-wave plate, a first cylindrical mirror, and a second cylindrical mirror arranged sequentially along the optical path. The focal length of the first cylindrical mirror is smaller than that of the second cylindrical mirror, and the two are coaxial. The magnification directions of the first and second cylindrical mirrors are perpendicular to the diffraction direction of the diffraction unit. The polarizer and the half-wave plate are used to adjust the femtosecond laser pulse to a horizontal polarization state, and the first and second cylindrical mirrors are used to amplify the point pulse into a one-dimensional line pulse. Step 2: A one-dimensional line pulse is incident on a diffraction unit, which diffracts the one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and adjusts the multiple monochromatic light waves into parallel light. The diffraction unit includes a first grating and a third cylindrical mirror arranged sequentially along the optical path; the first grating is used to diffract a one-dimensional line pulse into multiple monochromatic light waves distributed in two dimensions, and the third cylindrical mirror is used to adjust the multiple monochromatic light waves into parallel light. Step 3: Multiple monochromatic light waves are incident on different regions of a spatial light phase modulator, which modulates the phase of each monochromatic light wave. Step 4: Multiple monochromatic light waves after phase modulation are incident on the superposition unit, which superimposes all the monochromatic light waves to obtain a femtosecond laser pulse train consisting of multiple femtosecond laser pulses with different delays.

2. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 1, characterized in that, Based on the target delay magnitude of the femtosecond laser pulse train, the grayscale image loaded on the spatial light phase modulator is obtained; The spatial light phase modulator modulates the phase of multiple monochromatic light waves according to the grayscale image.

3. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 2, characterized in that, The phase modulation amount of each monochromatic light wave by the spatial light phase modulator is linearly related to the gray value corresponding to the region where the monochromatic light wave is incident on the spatial light phase modulator, and the phase modulation amount is in the range of 0~2π.

4. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 3, characterized in that, The phase modulation amount of each monochromatic light wave is obtained in the following way: The distribution function of a femtosecond laser pulse is simulated, and the target delay of k femtosecond laser pulses is set to t. i Let i = 1, 2, ..., k, and simulate the pulse delay t. i The distribution function of the subsequent femtosecond laser pulse; By performing Fourier transforms on the distribution functions before and after the delay, the phase magnitudes of the monochromatic light waves at each frequency of the femtosecond laser pulse can be obtained. The phase modulation amount of each monochromatic light wave is obtained by subtracting the phase before and after the delay.

5. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 4, characterized in that, The spatial light phase modulator has a resolution of m×n, and its phase modulation region is divided into m×k regions, each region corresponding to a gray value. The value of k corresponds to the number of femtosecond laser pulses contained in the final femtosecond laser pulse train.

6. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 1, characterized in that, The spatial light phase modulator is a liquid crystal spatial light modulator.

7. The method for generating controllable-spacing femtosecond laser pulse trains according to claim 1, characterized in that, The superposition unit includes a second grating, a fourth cylindrical mirror, a fifth cylindrical mirror, and a sixth cylindrical mirror arranged sequentially along the optical path; the second grating and the first grating adopt the same grating structure and are parallel in direction; the focal length of the fifth cylindrical mirror is greater than the focal length of the sixth cylindrical mirror, and the two are coaxial; the shrinkage directions of the fifth cylindrical mirror and the sixth cylindrical mirror are perpendicular to the diffraction direction of the second grating. The second grating superimposes all monochromatic light waves, which are then adjusted into parallel light after passing through the fourth cylindrical mirror, and then coaxially passed through the fifth and sixth cylindrical mirrors to finally obtain the femtosecond laser pulse train.

8. A controllable-spacing femtosecond laser pulse train generation device, characterized in that, include: Femtosecond laser, shaping unit, diffraction unit, spatial light phase modulator, and superposition unit; The controllable-spacing femtosecond laser pulse train generation device is used to implement the steps in the controllable-spacing femtosecond laser pulse train generation method as described in any one of claims 1-7.

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