Flexible transmission femtosecond laser and laser segmented compression method

Abstract

The invention provides a flexible transmission femtosecond laser. The flexible transmission femtosecond laser comprises a laser light source module, a flexible transmission module and a laser output head module, the laser light source module is used for generating initial femtosecond pulse laser, performing pulse broadening and power amplification processing on the initial femtosecond pulse laser to obtain broadened pulse laser, and performing pulse compression processing on the broadened pulse laser to obtain pulse laser for transmission, and the pulse width T1 of the broadened pulse laser meets the condition that T1 is greater than or equal to 500 ps and smaller than or equal to 1ns, the pulse width T2 of the pulse laser for transmission is greater than or equal to 5ps and less than or equal to 10ps; the flexible transmission module is used for transmitting the pulse laser for transmission to the laser output head module through a flexible transmission optical fiber; and the laser output head module is used for performing pulse compression processing on the received pulse laser for transmission again to obtain femtosecond pulse laser for output. According to the technical scheme, nonlinear accumulation in the flexible optical fiber transmission process can be effectively reduced, the quality of the finally output laser is improved, and the small size of the laser output head module is facilitated.

Description

Technical Field

[0001] The present disclosure relates to the field of laser processing technology, and particularly to a flexible transmission femtosecond laser and a laser segmented compression method. Background Art

[0002] With the rapid development of high-end manufacturing, the demand for processing large-sized complex curved surface parts in fields such as aerospace, automotive manufacturing, and precision optics is increasing day by day. For example, components such as aero-engine blades, satellite reflectors, and automotive body panels usually have geometric features with high curvature and multiple degrees of freedom, and have extremely strict requirements for surface quality, machining accuracy, and material properties. Traditional processing technologies (such as numerical control milling, electrical discharge machining, etc.) are difficult to meet the processing requirements of high precision and low damage due to problems such as tool wear, mechanical stress, and large heat-affected zones.

[0003] Femtosecond laser processing technology, with its ultra-short pulse (in the order of 10 -15 seconds) characteristics, can achieve a "cold processing" effect, that is, ablation is completed within an extremely short time after the material absorbs laser energy, with almost no heat diffusion, thus significantly reducing thermal damage and improving machining accuracy. This characteristic makes it show unique advantages in the processing of high-hardness, brittle materials, and micro-nano structures. However, existing femtosecond laser technologies still face multiple challenges in the processing of large-sized complex curved surfaces. Summary of the Invention

[0004] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a flexible transmission femtosecond laser, including: a laser light source module, a flexible transmission module, and a laser output head module;

[0005] The laser light source module is used to generate an initial femtosecond pulsed laser, perform pulse stretching and power amplification processing on the initial femtosecond pulsed laser to obtain a stretched pulsed laser, and perform pulse compression processing on the stretched pulsed laser to obtain a transmitted pulsed laser. The pulse width T1 of the stretched pulsed laser satisfies: 500 ps ≤ T1 ≤ 1 ns, and the pulse width T2 of the transmitted pulsed laser satisfies: 5 ps ≤ T2 ≤ 10 ps;

[0006] The flexible transmission module is used to transmit the transmitted pulsed laser to the laser output head module through a flexible transmission optical fiber;

[0007] The laser output head module is used to perform secondary pulse compression processing on the received transmitted pulsed laser to obtain an output femtosecond pulsed laser.

[0008] In some embodiments, the laser light source module includes: a seed light source, a circulator, an adjustable pulse stretcher, a power amplification unit, a compressor, and an optical mirror group;

[0009] The seed light source is used to generate the initial femtosecond pulsed laser;

[0010] The circulator is used to receive the initial femtosecond pulsed laser emitted by the seed light source through the first port and emit the initial femtosecond pulsed laser to the tunable pulse stretcher through the second port, and receive the stretched pulsed laser emitted by the tunable pulse stretcher through the second port and emit the stretched pulsed laser to the power amplification unit through the third port;

[0011] The tunable pulse stretcher is used to perform pulse stretching processing on the received initial femtosecond pulsed laser to obtain the stretched pulsed laser;

[0012] The power amplification unit is used to perform power amplification processing on the received stretched pulsed laser;

[0013] The compressor is used to perform pulse compression processing on the stretched pulsed laser after power amplification processing to obtain the pulsed laser for transmission;

[0014] The optical mirror group is used to perform beam expansion processing and collimation processing on the pulsed laser for transmission, and transmit the processed pulsed laser for transmission to the flexible transmission module.

[0015] In some embodiments, the power amplification unit includes: a frequency selection preamplifier and a power amplifier;

[0016] The frequency selection preamplifier is used to perform frequency selection processing and power preamplification processing on the stretched pulsed laser emitted from the circulator;

[0017] The power amplifier is used to perform power reamplification processing on the stretched pulsed laser after power preamplification processing.

[0018] In some embodiments, the mode field diameter of the gain medium of the power amplifier is: 80um to 100um.

[0019] In some embodiments, the optical mirror group includes: a first reflector, a second reflector, a first lens, and a second lens arranged in sequence along the optical path;

[0020] The first reflector and the second reflector are used to collimate the pulsed laser for transmission emitted from the compressor through their reflecting surfaces;

[0021] The first lens is used to expand the collimated pulsed laser for transmission emitted from the second reflector;

[0022] The second lens is configured to expand and collimate the transmission pulsed laser beam that has been expanded by the first lens and emitted therefrom.

[0023] In some embodiments, the flexible transmission module includes: a third lens, a flexible transmission optical fiber, and a fourth lens;

[0024] The third lens is configured to focus the transmission pulsed laser beam emitted from the laser light source module and transmit it to the flexible transmission optical fiber;

[0025] The flexible transmission optical fiber is configured to transmit the incident transmission pulsed laser beam to the fourth lens;

[0026] The fourth lens is configured to collimate the transmission pulsed laser beam emitted from the flexible transmission optical fiber and transmit it to the laser output head module.

[0027] In some embodiments, the laser output head module includes: a half-wave plate, a polarization beam splitter prism, a quarter-wave plate, a pair of gratings, a third mirror, and a fourth mirror, and the optical path is configured as follows: the laser pulse passes through the half-wave plate and then reaches the polarization beam splitter prism and undergoes transmission at the polarization beam splitter prism. The pulsed laser beam transmitted through the polarization beam splitter prism passes through the quarter-wave plate and the pair of gratings and then reaches the third mirror and undergoes reflection at the third mirror. The pulsed laser beam reflected by the third mirror passes through the pair of gratings and the quarter-wave plate again and then reaches the polarization beam splitter prism and undergoes reflection. The pulsed laser beam reflected by the polarization beam splitter prism reaches the fourth mirror and undergoes reflection at the fourth mirror, and is reflected to the light output port of the laser output head module;

[0028] The half-wave plate is configured to convert the polarization direction of the received pulsed laser beam into a first polarization direction;

[0029] The polarization beam splitter prism is configured to transmit the pulsed laser beam with the first polarization direction and reflect the pulsed laser beam with the second polarization direction;

[0030] The quarter-wave plate and the third mirror are configured to convert the polarization direction of the pulsed laser beam with the first polarization direction transmitted from the polarization beam splitter prism into a second polarization direction;

[0031] The pair of gratings is disposed on the optical path between the quarter-wave plate and the third mirror and is configured to perform pulse compression processing on the passing pulsed laser beam, wherein the pulsed laser beam emitted from the pair of gratings to the quarter-wave plate is the output femtosecond pulsed laser beam.

[0032] In some embodiments, the length of a single grating in the grating pair is a and the width is b, where 20 mm ≤ a ≤ 40 mm and 5 mm ≤ b ≤ 18 mm;

[0033] The spacing l between the two gratings in the grating pair is such that 40 mm ≤ l ≤ 60 mm.

[0034] In some embodiments, the power P0 of the initial femtosecond pulsed laser satisfies: P0 ≤ 10 mW, and the pulse width T0 of the initial femtosecond pulsed laser satisfies 200 fs ≤ T0 ≤ 300 fs;

[0035] The power P3 of the output femtosecond pulsed laser satisfies: P3 ≥ 50 W, and the pulse width T3 of the output femtosecond pulsed laser satisfies: 200 fs ≤ T3 ≤ 300 fs.

[0036] In a second aspect, the embodiments of the present disclosure provide a laser segmented compression method. Based on the flexible transmission femtosecond laser provided in the first aspect, the laser segmented compression method includes:

[0037] The laser light source module generates an initial femtosecond pulsed laser, performs pulse broadening and power amplification processing on the initial femtosecond pulsed laser to obtain a broadened pulsed laser, and performs pulse compression processing on the broadened pulsed laser to obtain a transmitted pulsed laser. The pulse width T1 of the broadened pulsed laser satisfies: 500 ps ≤ T1 ≤ 1 ns, and the pulse width T2 of the transmitted pulsed laser satisfies: 5 ps ≤ T2 ≤ 10 ps;

[0038] The flexible transmission module transmits the transmitted pulsed laser to the laser output head module through a flexible transmission optical fiber;

[0039] The laser output head module performs secondary pulse compression processing on the received transmitted pulsed laser to obtain an output femtosecond pulsed laser.

[0040] In the present invention, in the laser light source module, the initial femtosecond pulsed laser is first subjected to pulse broadening processing to obtain a broadened pulsed laser with a pulse width T1 in the range of [500 ps, 1 ns]. Then, the broadened pulsed laser is subjected to primary compression processing to obtain a pulsed laser for transmission with a pulse width T2 in the range of [5 ps, 10 ps] (picosecond level or close to picosecond level). Then, the pulsed laser for transmission is emitted into the flexible transmission module for transmission. Compared with shorter pulses such as femtosecond pulses, the pulse width of the pulsed laser for transmission in the present disclosure is relatively long. At the same average power, the peak power of the pulsed laser for transmission is relatively low, which can effectively reduce the non-linear accumulation during the flexible optical fiber transmission process. In addition, since the duration of the pulsed laser for transmission is very short and the peak power is low, the probability of the laser damaging the flexible optical fiber can be effectively reduced. Thereafter, the pulsed laser for transmission output from the flexible transmission module is incident on the laser output head module. The laser output head module performs secondary compression processing and dispersion compensation on the received pulsed laser for transmission. At this time, the amount of dispersion to be compensated is also relatively small. Therefore, the size of the grating pair used for compression and dispersion compensation can also be set relatively small, which is beneficial to the miniaturization of the laser output head module. Description of the Drawings

[0041] Figure 1 FIG. is a schematic structural diagram of a flexible transmission femtosecond laser provided by an embodiment of the present disclosure.

[0042] Figure 2 Based on Figure 1 FIG. is a specific schematic structural diagram of the flexible transmission femtosecond laser shown.

[0043] Figure 3 FIG. is a schematic curve diagram of the corresponding transmission efficiency when pulsed lasers with different pulse widths are transmitted in the flexible transmission module.

[0044] Figure 4A FIG. is a pulse diagram of inputting a femtosecond pulsed laser into the flexible transmission module in the prior art.

[0045] Figure 4B In the prior art, when inputting Figure 4A FIG. is a pulse diagram of the pulsed laser finally output by the flexible transmission module after inputting the shown pulsed laser.

[0046] Figure 5A FIG. is a pulse diagram of inputting a pulsed laser for transmission into the flexible transmission module in the present disclosure.

[0047] Figure 5B In the present disclosure, when inputting Figure 5A FIG. is a pulse diagram of the pulsed laser finally output by the laser after inputting the shown pulsed laser into the flexible transmission module.

[0048] Figure 6 Flowchart of a laser segmented compression method provided by an embodiment of the present disclosure. Specific implementation manners

[0049] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0050] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should have the ordinary meanings understood by those of ordinary skill in the art to which the present disclosure pertains. The "first", "second" and similar terms used in the present disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, the terms such as "a", "an" or "the" do not denote a quantity limitation, but mean that there is at least one. The terms such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships, and when the absolute position of the described target changes, the relative positional relationship may also change accordingly.

[0051] In the respective drawings, the same elements are denoted by similar reference numerals. For the sake of clarity, not all parts in the drawings are drawn to scale. In addition, some well-known parts may not be shown in the figures.

[0052] In the following, many specific details of the present disclosure are described, such as the structure, materials, dimensions, processing techniques and technologies of components, in order to understand the present disclosure more clearly. However, as those skilled in the art can understand, the present disclosure may be implemented without these specific details.

[0053] Most existing femtosecond laser processing systems use a rigid optical path for transmission and rely on a high-precision mechanical motion platform to adjust the processing position. When dealing with large-sized curved surfaces (such as several-meter-sized aviation structural components), complex motion coordination between the laser and the sample stage is required, posing extremely high requirements on the processing system. The flexible transmission of femtosecond lasers just solves this problem. By simply moving the output head, large-sized complex curved surface processing can be achieved. However, due to the extremely high peak power of femtosecond pulses, the nonlinearity during transmission in the optical fiber is extremely high. If femtosecond pulsed lasers are directly transmitted, both the transmission efficiency and the pulse quality will decrease due to high nonlinearity, and the optical fiber may even be damaged. Moreover, a vacuum system is required for assistance, making the entire system complex and costly, which is not conducive to large-scale applications. For the technical solution of frequency selection, broadening, amplification, transmission, and then compression, the amount of dispersion to be compensated is very large, resulting in a high optical path complexity and large volume of the laser output head, making it difficult to deeply integrate with flexible transmission systems such as large-sized robotic arms and multi-axis linkage platforms. As a result, problems such as high equipment cost and poor stability of the processing system will occur.

[0054] The present disclosure aims to solve at least one of the technical problems existing in the flexible femtosecond lasers in the above-mentioned prior art, such as high nonlinearity, the need for a vacuum system for assistance, low transmission efficiency, poor pulse quality, and large size of the laser output head, and provides a novel flexible transmission femtosecond laser.

[0055] Figure 1 FIG. is a schematic structural diagram of a flexible transmission femtosecond laser provided by an embodiment of the present disclosure. Figure 2 Based on Figure 1 A specific schematic structural diagram of the flexible transmission femtosecond laser shown. As Figure 1 and Figure 2 shown, the flexible transmission femtosecond laser includes: a laser light source module 1, a flexible transmission module 2, and a laser output head module 3.

[0056] Among them, the laser light source module 1 is used to generate an initial femtosecond pulsed laser, perform pulse broadening and power amplification processing on the initial femtosecond pulsed laser to obtain a broadened pulsed laser, and perform pulse compression processing on the broadened pulsed laser to obtain a pulsed laser for transmission. The pulse width T1 of the broadened pulsed laser satisfies: 500 ps ≤ T1 ≤ 1 ns, and the pulse width T2 of the pulsed laser for transmission satisfies: 5 ps ≤ T2 ≤ 10 ps. That is to say, the pulsed laser for transmission is actually a picosecond-level (several picoseconds) pulsed laser.

[0057] The flexible transmission module 2 is used to transmit the pulsed laser for transmission to the laser output head module 3 through a flexible transmission optical fiber 202.

[0058] The laser output head module 3 is used to perform secondary pulse compression processing on the received pulsed laser for transmission to obtain an output femtosecond pulsed laser.

[0059] In some embodiments, the power P0 of the initial femtosecond pulsed laser satisfies: P0 ≤ 10 mW, and the pulse width T0 of the initial femtosecond pulsed laser satisfies 200 fs ≤ T0 ≤ 300 fs;

[0060] The power P3 of the output femtosecond pulsed laser satisfies: P3 ≥ 50 W, and the pulse width T3 of the output femtosecond pulsed laser satisfies: 200 fs ≤ T3 ≤ 300 fs.

[0061] In the embodiments of the present disclosure, in the laser light source module 1, the initial femtosecond pulsed laser is first subjected to pulse broadening processing to obtain a broadened pulsed laser with a pulse width T1 in the range of [500 ps, 1 ns]. Then, the broadened pulsed laser is subjected to primary compression processing to obtain a pulsed laser for transmission (picosecond level) with a pulse width T2 in the range of [5 ps, 10 ps]. Then, the pulsed laser for transmission is emitted into the flexible transmission module 2 for transmission. Compared with femtosecond pulses and shorter pulses, the pulse width of the pulsed laser for transmission in the present disclosure is relatively long. At the same average power, the peak power of the pulsed laser for transmission is relatively low, which can effectively reduce the non-linear accumulation during the flexible optical fiber transmission process. In addition, since the duration of the pulsed laser for transmission is very short and the peak power is low, the probability of the laser damaging the flexible optical fiber can be effectively reduced. Thereafter, the pulsed laser for transmission output via the flexible transmission module 2 is incident on the laser output head module 3. The laser output head module 3 performs secondary compression processing and dispersion compensation on the received pulsed laser for transmission. At this time, the amount of dispersion to be compensated is also relatively small, so the size of the grating pair 304 used for compression and dispersion compensation can also be set relatively small, which is beneficial to the miniaturization of the laser output head module 3.

[0062] Figure 3 It is a schematic diagram of the curve of the transmission efficiency corresponding to pulsed lasers with different pulse widths during transmission in the flexible transmission module. As Figure 3 shown, when the pulse width of the pulsed laser input to the flexible transmission module is greater than 250 fs, the laser transmission efficiency is greater than 80%, and as the pulse width increases, the laser transmission efficiency increases accordingly. Among them, when the pulse width is equal to 5 ps, the laser transmission efficiency is greater than 90%. Therefore, the pulse width T2 of the pulsed laser for transmission input to the flexible transmission module in the present disclosure is set to 5 ps ≤ T2 ≤ 10 ps to ensure better laser transmission efficiency.

[0063] Based on the above content, it can be seen that the flexible transmission femtosecond laser provided by the present disclosure can provide high-energy femtosecond pulses with high transmission efficiency and high pulse quality. Compared with the prior art, the technical solution of the present disclosure can effectively improve the laser transmission efficiency and pulse quality, and reduce the size of the laser output head module 3.

[0064] See Figure 2As shown, in some embodiments, the laser light source module 1 includes: a seed light source 101, a circulator 102, a tunable pulse stretcher 103, a power amplification unit, a compressor 106, and an optical mirror group.

[0065] Among them, the seed light source 101 is used to generate an initial femtosecond pulsed laser.

[0066] Optionally, the seed light source 101 is a femtosecond milliwatt-level fiber oscillator. This femtosecond milliwatt-level fiber oscillator can emit femtosecond pulsed laser with a fixed repetition frequency of 45 MHz, a stable output power of 8 mW to 10 mW, and a pulse width in the range of 200 fs to 300 fs.

[0067] The circulator 102 is used to receive the initial femtosecond pulsed laser emitted by the seed light source 101 through the first port and emit the initial femtosecond pulsed laser to the tunable pulse stretcher 103 through the second port, and receive the broadened pulsed laser emitted by the tunable pulse stretcher 103 through the second port and emit the broadened pulsed laser to the power amplification unit through the third port.

[0068] Optionally, the circulator 102 is a polarization-maintaining fiber circulator 102. It generally includes three ports: an input port, an output port, and a specific function port. In the present disclosure, the first port is the input port, the second port is the specific function port, and the third port is the output port. The polarization-maintaining fiber circulator 102 can ensure that the polarization state of the optical signal does not change during transmission, avoid polarization-related losses and distortions, improve the stability and transmission quality of the optical signal, and is beneficial to improving the quality of the laser output by the flexible transmission femtosecond laser.

[0069] The tunable pulse stretcher 103 (abbreviated as TPSR) is used to perform pulse broadening processing on the received initial femtosecond pulsed laser to obtain broadened pulsed laser. In the present disclosure, the tunable pulse stretcher 103 can specifically be used to broaden the femtosecond pulsed laser and selectively output pulsed laser with a pulse width in the range of 250 fs to 10 ps.

[0070] The power amplification unit is used to perform power amplification processing on the received broadened pulsed laser.

[0071] In some embodiments, the power amplification unit includes: a frequency selection preamplifier 104 and a power amplifier 105. The frequency selection preamplifier 104 is used to perform frequency selection processing and power preamplification processing on the broadened pulsed laser emitted from the circulator 102; the power amplifier 105 is used to perform power reamplification processing on the broadened pulsed laser after the power preamplification processing is completed.

[0072] In some embodiments, the mode field diameter of the gain medium of the power amplifier 105 is: 80 um to 100 um; in the present disclosure, by designing a larger module area, on the one hand, it can disperse the heat load and avoid performance degradation of the gain medium due to local high temperature, and on the other hand, the larger mode field area can accommodate higher optical power, reduce the optical power density, and reduce the limitation of nonlinear effects, which is beneficial to improving the output power of the power amplifier 105.

[0073] Optionally, the gain medium of the power amplifier 105 is an inflexible rod-shaped optical fiber or a bulk crystal.

[0074] The compressor 106 is used to perform pulse compression processing on the broadened pulsed laser after power amplification processing to obtain the pulsed laser for transmission.

[0075] The optical lens group is used to perform beam expansion processing and collimation processing on the pulsed laser for transmission, and transmit the processed pulsed laser for transmission to the flexible transmission module 2.

[0076] See Figure 2 As shown, in some embodiments, the optical lens group includes: a first reflector 107, a second reflector 108, a first lens 109, and a second lens 110 arranged in sequence along the optical path. Among them, the first reflector 107 and the second reflector 108 are used to collimate the pulsed laser for transmission emitted from the compressor 106 through their reflecting surfaces; the first lens 109 is used to expand the collimated pulsed laser for transmission emitted from the second reflector 108; the second lens 110 is used to collimate the expanded pulsed laser for transmission emitted from the first lens 109.

[0077] Optionally, the first lens 109 is a concave lens (the first lens 109 is exemplarily drawn as a plano-concave lens in the drawings), and the second lens 110 is a convex lens (the second lens 110 is exemplarily drawn as a plano-convex lens in the drawings).

[0078] In some embodiments, the flexible transmission module 2 includes: a third lens 201, a flexible transmission optical fiber 202, and a fourth lens 203; the third lens 201 is used to focus the pulsed laser for transmission emitted from the laser light source module 1 and transmit it to the flexible transmission optical fiber 202; the flexible transmission optical fiber 202 is used to transmit the incident pulsed laser for transmission to the fourth lens 203; the fourth lens 203 is used to collimate the pulsed laser for transmission emitted from the flexible transmission optical fiber 202 and transmit it to the laser output head module 3.

[0079] In practical applications, the spot diameter of the collimated optical fiber emitted by the second lens 110 is several millimeters (for example, 3 mm), while the diameter of the light incident port of the flexible transmission optical fiber 202 is only dozens of micrometers (for example, 45 μm). Therefore, it is necessary to use the third lens 201 to focus the laser emitted by the second lens 110 to ensure that all of it can be incident on the flexible transmission optical fiber 202. In addition, the laser emitted by the flexible transmission optical fiber 202 is scattered light. For the convenience of subsequent processing, it is necessary to set up the fourth lens 203 to collimate the laser emitted by the flexible transmission optical fiber 202.

[0080] Optionally, both the third lens 201 and the fourth lens 203 are convex lenses (in the attached drawings, the third lens 201 and the fourth lens 203 are both plano-convex lenses as an example).

[0081] In some embodiments, the laser output head module 3 includes: a half-wave plate 301, a polarization beam splitter prism 302, a quarter-wave plate 303, a grating pair 304, a third mirror 305, and a fourth mirror 306, and the optical path is configured as follows: the laser pulse passes through the half-wave plate 301 and then reaches the polarization beam splitter prism 302 and undergoes transmission at the polarization beam splitter prism 302. The pulsed laser transmitted through the polarization beam splitter prism 302 passes through the quarter-wave plate 303 and the grating pair 304 and then reaches the third mirror 305 and undergoes reflection at the third mirror 305. The pulsed laser reflected by the third mirror reaches the grating pair 304 and the quarter-wave plate 303 again and then reaches the polarization beam splitter prism and undergoes reflection. The pulsed laser reflected by the polarization beam splitter prism 302 reaches the fourth mirror 306 and undergoes reflection at the fourth mirror 306, and is reflected to the light output port of the laser output head module 3.

[0082] The half-wave plate 301 is used to convert the polarization direction of the received pulsed laser into the first polarization direction. At this time, the pulsed laser with the first polarization direction is parallel polarized light, that is, p light.

[0083] The polarization beam splitter prism 302 is used to transmit the pulsed laser with the first polarization direction and reflect the pulsed laser with the second polarization direction.

[0084] The quarter-wave plate 303 and the third mirror 305 (optionally, a zero-degree mirror can be selected to improve the reflection efficiency) are used to convert the polarization direction of the pulsed laser with the first polarization direction transmitted from the polarization beam splitter prism 302 into the second polarization direction; the first polarization direction is perpendicular to the second polarization direction. At this time, the pulsed laser with the first polarization direction is vertically polarized light, that is, s light.

[0085] The grating pair 304 is disposed between the optical paths of the quarter-wave plate 303 and the third mirror 305, and is used for pulse compression processing of the passing pulsed laser. The pulsed laser emitted from the grating pair 304 to the quarter-wave plate 303 is the output femtosecond pulsed laser.

[0086] In the present disclosure, the grating pair 304 has functions of pulse compression and dispersion compensation. Optionally, the grating pair 304 is a small-sized and polarization-insensitive grating, and is configured to only compensate for the dispersion amount at the picosecond level of the pulse width.

[0087] In the present disclosure, since the dispersion amount that needs to be compensated by the grating pair 304 is relatively small, the size of the grating pair 304 can also be set relatively small. Optionally, the length of a single grating in the grating pair 304 is a, and the width is b, where 20 mm ≤ a ≤ 40 mm, 5 mm ≤ b ≤ 18 mm; as an example, the size of a single grating is 31 mm × 12 mm, and the specific size can be designed and adjusted accordingly according to actual needs. The distance l between the two gratings in the grating pair 304, where 40 mm ≤ l ≤ 60 mm; as an example, the distance between the two gratings is 52 mm.

[0088] Compared with the situation in the prior art where the length, width, and distance of the grating pair 304 to be set are all dozens of centimeters, the technical solution of the present disclosure can greatly reduce the size of the grating pair 304, which is beneficial to the miniaturization of the laser output head module 3.

[0089] In practical applications, the dispersion can be finely adjusted by the adjustable pulse stretcher 103 to achieve the optimal dispersion matching, and finally output femtosecond pulsed laser with high pulse energy, high transmission efficiency, and high pulse quality.

[0090] As a specific example in the present disclosure, the seed light source 101 emits pulsed laser with a repetition frequency of 45 MHz, a power of 8 mW to 10 mW, and a pulse width of 200 fs to 300 fs. After passing through the adjustable pulse stretcher 103, it is stretched to 500 ps to 1 ns, and the power is less than 1 mW, and the repetition frequency is 500 KHz. Then, after being processed by the frequency selection pre-amplifier 104, pulsed laser with a repetition frequency of 500 kHz and a power of 30 mW to 40 mW can be obtained as the input light beam of the power amplifier 105. Then, through the power amplification process of the power amplifier 105, the power of the pulsed laser can be amplified to more than 50 W. Then, through the compression process of the compressor 106, the pulse width of the pulsed laser can be compressed to 5 ps to 10 ps (as a specific example, by adjusting the adjustable pulse stretcher 103, the pulse width of the pulsed laser for transmission finally output by the compressor 106 can be 6.11 ps, and at this time the laser transmission efficiency can reach 90%), and the pulsed laser for transmission is obtained. The pulsed laser for transmission is transmitted to the laser output head module 3 through the flexible transmission module 2. In the laser output head module 3, after the re-compression and scattering compensation process of the grating pair 304, the laser output head module 3 can output femtosecond pulsed laser with a single pulse energy greater than 80 uJ (for example, 100 uJ) and a pulse width range of 200 fs to 300 fs.

[0091] Figure 4A FIG. is a pulse schematic diagram of inputting femtosecond pulsed laser into the flexible transmission module in the prior art. Figure 4B is for inputting into the flexible transmission module in the prior art Figure 4A FIG. is a pulse schematic diagram of the pulsed laser finally output by the flexible transmission module after inputting the pulsed laser shown. Figure 5A FIG. is a pulse schematic diagram of inputting the pulsed laser for transmission into the flexible transmission module in the present disclosure. Figure 5B is for inputting into the flexible transmission module in the present disclosure Figure 5A FIG. is a pulse schematic diagram of the pulsed laser finally output by the laser after inputting the pulsed laser shown. As Figures 4A to 5B shown, in order to more clearly reflect the advantages of the technical solution of the present disclosure, the prior art and the technical solution of the present disclosure are respectively simulated and tested. Among them, taking the hyperbolic secant fitting as an example, the corresponding coefficient is 1.54 (the deconvolution factor in the fitting).

[0092] See Figure 4A and Figure 4B shown, in the prior art, when directly inputting femtosecond pulsed laser into the flexible transmission module (simulated and tested with a pulse width of 274 fs), the pulse width of the pulsed laser output by the flexible transmission module (the output of the flexible transmission module in the prior art is directly used as the output of the laser) is about 6.11 ps. Through analysis, this is because femtosecond laser has high nonlinearity in the flexible transmission module, and the pulse width will increase during the transmission process. See Figure 5Aand Figure 5B As shown, in the present disclosure, when picosecond pulsed laser is directly input into the flexible transmission module (simulated and tested with a pulse width of 7.377 ps), the pulse width of the pulsed laser finally output by the laser output head module (the output of the laser output head module in the present disclosure is used as the output of the laser) is 253 fs. Based on the above comparison, it can be seen that the quality of the pulsed laser output by the flexible transmission femtosecond laser provided by the present disclosure is significantly better than that of the prior art.

[0093] Based on the same inventive concept, an embodiment of the present disclosure also provides a laser segmented compression method. Figure 6 It is a flowchart of a laser segmented compression method provided by an embodiment of the present disclosure. As Figure 6 shown, the laser segmented compression method includes:

[0094] Step S1: The laser light source module generates an initial femtosecond pulsed laser, performs pulse broadening and power amplification on the initial femtosecond pulsed laser to obtain a broadened pulsed laser, and performs pulse compression on the broadened pulsed laser to obtain a transmitted pulsed laser.

[0095] Among them, the pulse width T1 of the broadened pulsed laser satisfies: 500 ps ≤ T1 ≤ 1 ns, and the pulse width T2 of the transmitted pulsed laser satisfies: 5 ps ≤ T2 ≤ 10 ps.

[0096] Step S2: The flexible transmission module transmits the transmitted pulsed laser to the laser output head module through a flexible transmission optical fiber.

[0097] Step S3: The laser output head module performs secondary pulse compression on the received transmitted pulsed laser to obtain an output femtosecond pulsed laser.

[0098] In practical applications, the adjustable pulse stretcher in the laser light source module can also be used for fine dispersion adjustment to achieve the optimal dispersion matching, so as to finally output femtosecond pulsed laser with high pulse energy, high transmission efficiency and high pulse quality.

[0099] For the specific descriptions of the above steps, reference can be made to the content in the previous embodiments, and details are not described here.

[0100] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

1. A flexible transmission femtosecond laser, characterized in that: include: Laser light source module, flexible transmission module and laser output head module; The laser light source module is used to generate an initial femtosecond pulse laser, and perform pulse stretching and power amplification processing on the initial femtosecond pulse laser to obtain a stretched pulse laser, and perform pulse compression processing on the stretched pulse laser to obtain a transmission pulse laser, wherein the pulse width T1 of the stretched pulse laser satisfies: 500ps≤T1≤1ns, and the pulse width T2 of the transmission pulse laser satisfies: 5ps≤T2≤10ps; The flexible transmission module is used to transmit the transmission pulse laser to the laser output head module through a flexible transmission optical fiber; The laser output head module is used to perform pulse compression processing on the received transmission pulse laser to obtain output femtosecond pulse laser.

2. The flexible transmission femtosecond laser according to claim 1, characterized in that: The laser light source module includes: a seed light source, a circulator, an adjustable pulse stretcher, a power amplifier unit, a compressor, and an optical lens group; The seed light source is used to generate the initial femtosecond pulse laser; The circulator is used to receive the initial femtosecond pulse laser emitted by the seed light source through the first port and emit the initial femtosecond pulse laser to the adjustable pulse stretcher through the second port, and to receive the stretched pulse laser emitted by the adjustable pulse stretcher through the second port and emit the stretched pulse laser to the power amplification unit through the third port; The adjustable pulse stretcher is used to perform pulse stretching processing on the received initial femtosecond pulse laser to obtain the stretched pulse laser; The power amplification unit is used to perform power amplification processing on the received stretched pulse laser; The compressor is used to perform pulse compression processing on the stretched pulse laser after power amplification processing to obtain the transmission pulse laser; The optical lens group is used to perform beam expansion and collimation processing on the transmission pulse laser, and transmit the processed transmission pulse laser to the flexible transmission module.

3. The flexible transmission femtosecond laser according to claim 2, characterized in that: The power amplification unit comprises: a frequency-selective preamplifier and a power amplifier; The frequency-selective preamplifier is used to perform frequency-selective processing and power pre-amplification processing on the stretched pulse laser emitted from the circulator; The power amplifier is used to re-amplify the power of the stretched pulse laser after the power pre-amplification process is completed.

4. The flexible transmission femtosecond laser according to claim 3, characterized in that: The mode field diameter of the gain medium of the power amplifier is 80um to 100um.

5. The flexible transmission femtosecond laser according to claim 2, characterized in that: The optical lens assembly comprises: a first reflector, a second reflector, a first lens and a second lens arranged in sequence along the optical path; The first reflector and the second reflector are used to collimate the transmission pulse laser emitted from the compressor through their reflection surfaces; The first lens is used to expand the transmission pulse laser that has been collimated and emitted from the second reflector; The second lens is used to expand and collimate the transmission pulse laser that has been expanded and emitted from the first lens.

6. The flexible transmission femtosecond laser according to claim 1, characterized in that: The flexible transmission module comprises: a third lens, a flexible transmission optical fiber and a fourth lens; The third lens is used to focus the transmission pulse laser emitted from the laser light source module and transmit it to the flexible transmission optical fiber; The flexible transmission optical fiber is used to transmit the incident transmission pulse laser to the fourth lens; The fourth lens is used to collimate the transmission pulse laser emitted from the flexible transmission optical fiber and transmit it to the laser output head module.

7. The flexible transmission femtosecond laser according to claim 1, characterized in that: The laser output head module comprises: a half wave plate, a polarization beam splitter prism, a quarter wave plate, a grating pair, a third reflector and a fourth reflector, and the optical path configuration is as follows: the laser pulse reaches the polarization beam splitter prism after passing through the half wave plate and is transmitted at the polarization beam splitter prism, the pulsed laser transmitted through the polarization beam splitter prism reaches the third reflector after passing through the quarter wave plate and the grating pair and is reflected at the third reflector, the pulsed laser reflected by the third transmitting mirror reaches the polarization beam splitter prism after passing through the grating pair and the quarter wave plate again and is reflected, the pulsed laser reflected by the polarization beam splitter prism reaches the fourth reflector and is reflected at the fourth reflector, and is reflected to the light outlet of the laser output head module; The half-wave plate is used to convert the polarization direction of the received pulsed laser into the first polarization direction; The polarization beam splitter prism is used to transmit the pulse laser with a first polarization direction and reflect the pulse laser with a second polarization direction; The quarter wave plate and the third reflector are used to convert the polarization direction of the pulsed laser with a first polarization direction transmitted from the polarization beam splitter prism into a second polarization direction; The grating pair is arranged between the optical path of the quarter wave plate and the third reflector, and is used to perform pulse compression processing on the pulse laser passing therethrough, wherein the pulse laser emitted from the grating pair to the quarter wave plate is the output femtosecond pulse laser.

8. The flexible transmission femtosecond laser according to claim 7, characterized in that: The length of a single grating in the grating pair is a, and the width is b, wherein 20 mm ≤ a ≤ 40 mm, and 5 mm ≤ b ≤ 18 mm; The distance l between two gratings in the grating pair is 40 mm ≤ l ≤ 60 mm.

9. The flexible transmission femtosecond laser according to any one of claims 1 to 8, characterized in that: The power P0 of the initial femtosecond pulse laser satisfies: P0≤10mW, and the pulse width T0 of the initial femtosecond pulse laser satisfies 200fs≤T0≤300fs; The power P3 of the output femtosecond pulse laser satisfies: P3 ≥ 50 W, and the pulse width T3 of the output femtosecond pulse laser satisfies: 200 fs ≤ T3 ≤ 300 fs.

10. A laser segmented compression method, characterized in that: Based on the flexible transmission femtosecond laser according to any one of claims 1 to 9, the laser segmented compression method comprises: The laser light source module generates an initial femtosecond pulse laser, performs pulse stretching and power amplification processing on the initial femtosecond pulse laser to obtain a stretched pulse laser, and performs pulse compression processing on the stretched pulse laser to obtain a transmission pulse laser, wherein the pulse width T1 of the stretched pulse laser satisfies: 500ps≤T1≤1ns, and the pulse width T2 of the transmission pulse laser satisfies: 5ps≤T2≤10ps; The flexible transmission module transmits the transmission pulse laser to the laser output head module through a flexible transmission optical fiber; The laser output head module performs pulse compression processing on the received transmission pulse laser to obtain output femtosecond pulse laser.

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