High repetition frequency laser spatiotemporal coupling machining device and method

Abstract

The application provides a high-repetition-frequency laser space-time coupling machining device and method, wherein femtosecond laser pulses are transmitted to a double-pass pulse stretcher through a beam splitter; the double-pass pulse stretcher stretches the high-repetition-frequency femtosecond laser pulses; the stretched laser pulses are returned to the beam splitter through the original path, reflected by the beam splitter to generate laser pulses with group velocity dispersion; the stretched laser pulses pass through a grating compressor to compensate for the group velocity dispersion introduced by the double-pass pulse stretcher and realize spatial dispersion of different frequency components, introduce spatial chirp, and focus the spatially dispersed light through an objective lens, so that the different frequency components of the laser pulses are recombined in time and space at a focal point, and the pulse width is rapidly stretched outside the focal point.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a high repetition rate laser spatiotemporal coupling processing device and method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In recent years, femtosecond laser direct writing (FLDW)-based 3D micromachining technology has attracted widespread attention and has been widely applied in numerous research fields such as microfluidics, micro-optics, microelectronics, photonics, and optofluidics. However, the focal point generated by traditional femtosecond laser direct focusing suffers from asymmetry in lateral and axial resolution, with a significantly reduced axial resolution, limiting the 3D machining capabilities of femtosecond lasers. To balance lateral and axial resolution, several beam shaping techniques have been proposed, such as slit shaping and cross-beam illumination. However, these techniques cannot achieve isotropic 3D fabrication using a single objective lens in a single operation.

[0004] Spatiotemporal focusing technology, as a novel beam shaping technique, can be used to improve axial resolution, but its application in high repetition rate lasers is limited. The main reason is that high repetition rate femtosecond lasers have a narrow spectral width, requiring a larger spatial chirp rate to achieve spatial dispersion. This introduces a large group velocity delay, making it difficult to adjust the pulse width back by the laser itself, thus limiting the application of spatiotemporal focusing technology in high repetition rate lasers. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a high repetition rate laser spatiotemporal coupling processing device and method. A dual-pass pulse stretcher stretches a high repetition rate femtosecond laser pulse, introducing group velocity dispersion. The stretched laser pulse then passes through a grating compressor, where different frequency components are spatially dispersed, introducing spatial chirp. The spatially dispersed light is then focused by an objective lens, causing the different frequency components of the laser pulse to recombine at the focal point, and the pulse width outside the focal point is rapidly stretched.

[0006] To achieve the above objectives, a first aspect of the present invention provides a high repetition rate laser spatiotemporal coupling processing apparatus, comprising:

[0007] A beam splitter is used to transmit femtosecond laser pulses emitted by a high repetition rate femtosecond laser to a dual-pass pulse stretcher and reflect the femtosecond laser pulses that return after passing through the dual-pass pulse stretcher to a grating compressor.

[0008] A dual-pass pulse stretcher is used to stretch the femtosecond laser pulse transmitted through the beam splitter and then return it to the beam splitter via the original path.

[0009] A grating compressor is used to compress the width of the femtosecond laser pulse reflected by the beam splitter and project it onto the objective lens.

[0010] A second aspect of the present invention provides a high repetition rate laser spatiotemporal coupling processing method, comprising:

[0011] Generate femtosecond laser pulses;

[0012] The femtosecond laser pulse is transmitted through a beam splitter to a dual-pass pulse stretcher, and after being stretched by the dual-pass pulse stretcher, it returns to the beam splitter and is then reflected by the beam splitter to the grating compressor.

[0013] The pulse width is compressed by a grating compressor.

[0014] The above one or more technical solutions have the following beneficial effects:

[0015] In this invention, the laser pulse is transmitted through a beam splitter to a dual-pass pulse stretcher, which stretches the high repetition rate femtosecond laser pulse. After returning to the beam splitter via the same path, the pulse is reflected by the beam splitter to generate a laser pulse with group velocity dispersion. The stretched laser pulse then passes through a grating compressor, which compensates for the group velocity dispersion introduced by the dual-pass pulse stretcher while simultaneously achieving spatial dispersion of different frequency components, introducing spatial chirp. The spatially dispersed light is then focused by an objective lens, allowing the different frequency components of the laser pulse to recombine in time and space at the focal point, and the pulse width outside the focal point is rapidly stretched.

[0016] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is Embodiment 1 of the present invention.

[0019] In the figure, 1. High repetition rate femtosecond laser, 2. Beam splitter, 3. First mirror, 4. First grating, 5. First convex lens, 6. Second convex lens, 7. Second grating, 8. Second mirror, 9. Third mirror, 10. Third convex lens, 11. Concave lens, 12. Third grating, 13. Fourth grating, 14. Dichroic mirror, 15. Fourth convex lens, 16. CCD camera, 17. First objective lens, 18. Glass sample, 19. Three-dimensional motion platform, 20. Camera. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0022] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0023] Example 1

[0024] like Figure 1 As shown, this embodiment discloses a high repetition rate laser spatiotemporal coupling processing device, comprising:

[0025] A high repetition rate femtosecond laser 1 is used to emit femtosecond laser pulses;

[0026] Beam splitter 2 is used to transmit femtosecond laser pulses emitted by a high repetition rate femtosecond laser to a dual-pass pulse stretcher and reflect the femtosecond laser pulses that return after passing through the dual-pass pulse stretcher to a grating compressor.

[0027] The dual-pass pulse stretcher is used to stretch the femtosecond laser pulse transmitted through beam splitter 2 and then return it to the beam splitter via the original path.

[0028] A grating compressor is used to compress the width of a femtosecond laser pulse reflected by a beam splitter before irradiating the material to be processed.

[0029] In this embodiment, the dual-pass pulse stretcher includes a first reflecting mirror 3, a first grating 4, a first convex lens 5, a second convex lens 6, a second grating 7, and a second reflecting mirror 8 arranged sequentially. Specifically, the femtosecond laser pulse emitted by the high repetition rate femtosecond laser 1 is transmitted through the beam splitter 2, then reflected by the first reflecting mirror 3, diffracted by the first grating 4, transmitted through the first convex lens 5 and the second convex lens 6, and diffracted by the second grating 7 towards the second reflecting mirror 8. After being reflected by the second reflecting mirror 8, the laser pulse returns along the original path of the second grating 7, the second convex lens 6, the first convex lens 5, the first grating 4, and the first reflecting mirror 3, and is then reflected by the beam splitter 2 to generate a laser pulse with group velocity dispersion. The pulse duration can reach the tens of picoseconds.

[0030] In this system, the first grating is incident at the Littrow angle, and the distance between the first convex lens and the second convex lens is the sum of their focal lengths. The distance between the first grating and the first convex lens is adjusted according to the amount of dispersion and is less than the focal length of the first convex lens.

[0031] In this embodiment, a third reflecting mirror 9, a third convex lens 10, and a concave lens 11 are also provided along the laser pulse direction.

[0032] Specifically, the laser pulse with group velocity dispersion generated by the beam splitter 2 is reflected by the third mirror 9 and then passed sequentially through the third convex lens 10 and the concave lens 11 to reduce the beam size.

[0033] In this embodiment, the grating compressor includes a third grating 12 and a fourth grating 13.

[0034] Specifically, the laser pulse passing through the concave lens 11 is then passed through the third grating 12 and the fourth grating (13) in sequence to compress the laser pulse width, while different frequency components are spatially dispersed. The spatially dispersed beam is then reflected by the dichroic mirror 14 to the first objective lens 17 and focused into the glass material 18, which is placed on a computer-driven three-dimensional motion platform 19.

[0035] In this embodiment, the entire processing is observed in real time through an imaging system consisting of a first objective lens 17, a fourth convex lens 15, and a CCD camera 16.

[0036] In this embodiment, by setting the output frequency of the high repetition rate femtosecond laser 1, the femtosecond laser pulse emitted from the high repetition rate femtosecond laser 1 passes through the beam splitter 2 and selects the transmitted portion to enter the pulse broadening system composed of the first reflecting mirror 3, the first grating 4, the first convex lens 5, the second convex lens 6, the second grating 7, and the second reflecting mirror 8. According to theoretical calculations, the group velocity delay is adjusted by adjusting the distance between the first grating 4 and the first convex lens 5 or the distance between the second convex lens 6 and the second grating 7. The broadened laser pulse is reflected by the third reflecting mirror 9 and enters the beam shrinking system composed of the third convex lens 10 and the concave lens 11 to reduce the beam size. The beam-shrinking laser pulse enters the single-pass grating compressor composed of the third grating 12 and the fourth grating 13 to achieve spatial dispersion of different spectral components. The distance between the grating pairs of the third grating 12 and the fourth grating 13 determines the amount of time delay introduced. The spatially dispersed light is reflected by the dichroic mirror 14 and enters the focusing objective lens 17 and is focused into the interior of the glass material.

[0037] Example 2

[0038] This embodiment provides a high repetition rate laser spatiotemporal coupling processing method, including:

[0039] Generate femtosecond laser pulses;

[0040] The femtosecond laser pulse is transmitted through a beam splitter to a dual-pass pulse stretcher, and after being stretched by the dual-pass pulse stretcher, it returns to the beam splitter and is then reflected by the beam splitter to the grating compressor.

[0041] The pulse width is compressed by the grating compressor and irradiated onto the material to be processed on the three-dimensional moving stage.

[0042] In this embodiment, the glass material 18 is placed on a three-dimensional electric displacement stage 19, and the output frequency of the high repetition rate femtosecond laser 1 is set. The femtosecond laser pulse emitted by the laser passes through the beam splitter 2 and the selected transmission part enters the pulse broadening system composed of a first reflector 3, a first grating 4, a first convex lens 5, a second convex lens 6, a second grating 7, and a second reflector 8. According to theoretical calculations, the group velocity delay is adjusted by adjusting the spacing between the first grating 4 and the first convex lens 5, as well as the second convex lens 6 and the second grating 7. The broadened laser pulse is reflected by the third reflecting mirror 9 and enters the beam shrinking system composed of the third convex lens 10 and the concave lens 11 to reduce the beam size. The beam-shrinking laser pulse enters the single-pass grating compressor composed of the third grating 12 and the fourth grating 13 to achieve spatial dispersion of different spectral components. The spacing between the grating pairs determines the amount of time delay introduced. The spatially dispersed light is reflected by the dichroic mirror 14 and enters the first objective lens 17 and is focused into the glass material. After the optical path is adjusted, the processing path is set by the computer and the movement of the three-dimensional motion platform 19 is controlled to realize the direct writing processing of the three-dimensional structure inside the glass. The processing process of the laser and the material near the focal point can be observed in real time by the camera 20.

[0043] First, a high-repetition-rate femtosecond laser pulse is broadened using a dual-pass pulse stretcher, introducing group velocity dispersion. The broadened laser pulse is then passed through a single-pass grating compressor. At this point, different frequency components are spatially dispersed, introducing spatial chirp. The spatially dispersed light is then focused by an objective lens, causing the different frequency components of the laser pulse to recombine at the focal point, resulting in a rapid broadening of the pulse width outside the focal point. This method differs from ordinary femtosecond laser processing in that the femtosecond laser pulse is pre-broadened using a stretcher and then compressed back using a single-pass compressor, achieving spatial and temporal recombination at the focal point. This feature effectively improves the longitudinal resolution of laser processing, thereby achieving three-dimensional isotropic processing. Furthermore, the use of high-repetition-rate femtosecond lasers greatly improves processing speed and efficiency, and the resolution of three-dimensional isotropic processing can be continuously adjusted by changing the energy. According to the threshold effect, high energy results in larger processing sizes, while low energy results in smaller processing sizes. This method enables femtosecond laser processing to achieve higher efficiency, more symmetrical processing resolution, and more flexible adjustment of processing resolution. It provides a favorable technical means for the development of femtosecond laser three-dimensional isotropic processing and is of great significance for high-efficiency and high-precision three-dimensional laser processing.

[0044] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A high repetition rate laser spatiotemporal coupling processing device, characterized in that, include: A beam splitter is used to transmit femtosecond laser pulses emitted by a high repetition rate femtosecond laser to a dual-pass pulse stretcher and reflect the femtosecond laser pulses that return after passing through the dual-pass pulse stretcher to a grating compressor. A dual-pass pulse stretcher is used to stretch the femtosecond laser pulse transmitted through the beam splitter and then return it to the beam splitter via the original path. The dual-pass pulse stretcher is provided with a first reflector, a first grating, a first convex lens, a second convex lens, a second grating, and a second reflector along the incident direction of the femtosecond laser pulse. The femtosecond laser pulse reflected by the second reflector returns to the beam splitter via the second grating, the second convex lens, the first convex lens, the first grating, and the first reflector in sequence. The group velocity delay is adjusted by adjusting the spacing between the first grating and the first convex lens, and between the second convex lens and the second grating. A grating compressor is used to compress the width of the femtosecond laser pulse reflected by the beam splitter and project it onto the objective lens.

2. The high repetition rate laser spatiotemporal coupling processing device as described in claim 1, characterized in that, Also includes: The femtosecond laser pulses reflected by the beam splitter are converged to the grating compressor by passing through the third reflecting mirror, the third convex lens, and the concave lens in sequence.

3. The high repetition rate laser spatiotemporal coupling processing device as described in claim 1, characterized in that, The grating compressor consists of a third grating and a fourth grating arranged sequentially along the incident direction of the femtosecond laser pulse.

4. The high repetition rate laser spatiotemporal coupling processing device as described in claim 1, characterized in that, Also includes: The femtosecond laser pulse compressed by the grating compressor is reflected by a dichroic mirror onto the first objective lens, and then focused by the first objective lens.

5. The high repetition rate laser spatiotemporal coupling processing device as described in claim 1, characterized in that, The distance between the first grating and the first convex lens is adjusted according to the amount of dispersion and is less than the focal length of the first convex lens.

6. The high repetition rate laser spatiotemporal coupling processing device as described in claim 1, characterized in that, It also includes an imaging system consisting of a first objective lens, a fourth convex lens, and a camera arranged in sequence.

7. The high repetition rate laser spatiotemporal coupling processing device as described in claim 3, characterized in that, The introduced time delay is adjusted by adjusting the spacing between the third and fourth gratings.

8. A high-repetition-rate laser spatiotemporal coupling processing method, characterized in that, include: Generate femtosecond laser pulses; The femtosecond laser pulse is transmitted through a beam splitter to a dual-pass pulse stretcher, and after being stretched by the dual-pass pulse stretcher, it returns to the beam splitter and is then reflected by the beam splitter to the grating compressor. The dual-pass pulse stretcher is provided with a first reflector, a first grating, a first convex lens, a second convex lens, a second grating, and a second reflector along the incident direction of the femtosecond laser pulse. The femtosecond laser pulse reflected by the second reflector returns to the beam splitter via the second grating, the second convex lens, the first convex lens, the first grating, and the first reflector in sequence. The group velocity delay is adjusted by adjusting the spacing between the first grating and the first convex lens, and between the second convex lens and the second grating. The pulse width is compressed using a grating compressor.

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