System and method for continuous observation of multiple time scales during femtosecond laser processing

Abstract

The present invention discloses a system and method for continuous observation of multiple time scales during femtosecond laser processing. The system comprises a femtosecond laser light source, a laser processing system, a pulse shaping system, and a multi-time scale continuous observation system. The multi-time scale continuous observation system comprises a femtosecond ultrafast continuous imaging system, a picosecond-nanosecond ultrafast pump-probe system, a nanosecond-millisecond ICCD continuous imaging system, and a microsecond-second high-speed camera system. Compared to other ultrafast imaging systems, the present invention enables ultrafast continuous observation of femtosecond laser processing across multiple time scales. Its observation time range extends over 13 orders of magnitude, from hundreds of femtoseconds to seconds, encompassing the entire physical and chemical reaction process. This system plays a crucial role in providing a deeper understanding and understanding of a range of nonequilibrium and nonlinear ultrafast phenomena in femtosecond laser processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrafast imaging, and in particular relates to a system and method for continuous observation of multiple time scales during femtosecond laser processing. Background Art

[0002] Femtosecond laser has an ultrashort pulse duration (10 -15 s) and super high peak power density (>10 14 W / cm 2 The ultra-strong and ultra-fast properties of femtosecond lasers allow them to process any material in the world, and by focusing the beam spot diameter down to the nanometer scale, they also possess exceptional 3D micro- and nano-machining capabilities. These advantages are well-suited for applications in defense equipment, aerospace, information electronics, sensing and detection, biomedicine, and new energy (e.g., cross-scale fabrication of complex 3D structures on difficult-to-process materials), providing crucial manufacturing support for the rapid development of these fields.

[0003] However, femtosecond laser processing is a nonlinear, non-equilibrium, and complex physical and chemical process involving numerous novel mechanisms of laser-material interaction. It is also a continuous reaction process spanning multiple timescales. For example, within femtoseconds, photons in the material often absorb laser energy, leading to the transient ionization of electrons in the material, producing a large number of free electrons. The ionized free electrons, neutral atoms, and large debris form a plasma that erupts into the external environment, a process that occurs on picosecond-nanosecond or even microsecond timescales. On millisecond-second timescales, the material undergoes a melting and recasting process, which involves the mechanism of material forming and property changes.

[0004] In order to deeply understand and reveal the above reaction process and explore the interaction mechanism between femtosecond laser and materials, direct observation is necessary. However, current observation systems only observe a specific reaction process and cannot directly image the entire process of laser-material reaction in femtosecond laser processing continuously across time, or use multiple imaging systems for multiple experiments to observe and image. This determines the time limitation and single function of the system. Therefore, in order to be able to directly observe a series of ultrafast physical and chemical reaction processes in femtosecond laser processing that can be continuous across multiple time scales, a set of systems and methods are needed to continuously observe them at multiple time scales, thereby revealing the interaction mechanism between femtosecond laser and materials and providing observational theoretical support for femtosecond laser processing. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a system and method for continuous observation at multiple time scales during femtosecond laser processing, so as to solve the problem that it is difficult to conduct continuous observation at multiple time scales of the physicochemical processes of a series of ultrafast reactions after the interaction between laser and material.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, a system for continuous observation of multiple time scales during femtosecond laser processing includes a femtosecond laser source; the femtosecond laser source emits a Gaussian femtosecond pulse, which is split into two pulses by a laser processing system; one pulse passes through the laser processing system to a pulse shaping system and is focused on the surface of a sample by a beam combiner I, an objective lens, or a plano-convex lens;

[0008] The other pulse is split into a probe pulse I and a probe pulse II by beam splitter II. The probe pulse I passes through a frequency doubling crystal, a bandpass filter, and a beam combiner I in sequence, then passes through the sample and is captured by the multi-timescale continuous observation system.

[0009] The detection pulse II is split into a detection pulse III and a detection pulse IV by a beam splitter III. The detection pulse III passes through a nonlinear crystal III and a reflector V, passes through the sample, and is captured by a multi-time-scale continuous observation system.

[0010] The detection pulse IV is split into detection pulse V and detection pulse VI by beam splitter IV. The detection pulse V passes through the pulse sequence generator, passes through the sample, and is captured by the multi-time scale continuous observation system.

[0011] The detection pulse VI passes through the reflector VII, the nonlinear crystal IV, the reflector VIII, and the sample, and is captured by the multi-time-scale continuous observation system.

[0012] Furthermore, the parameters of the femtosecond laser light source are set by a computer and transmitted to a pulse signal generator to control the femtosecond laser light source to emit a single pulse.

[0013] Furthermore, the laser processing system includes a beam splitter I, a reflector I, a reflector II, a reflector III, and a reflector IV, which are arranged between the femtosecond laser light source and the pulse shaping system.

[0014] Furthermore, the pulse shaping system includes a pulse time shaping device, a pulse wavelength shaping device and a pulse space shaping device.

[0015] Furthermore, the multi-time-scale continuous observation system includes a femtosecond ultrafast continuous imaging system, a picosecond-nanosecond ultrafast pump-detection system, a nanosecond-millisecond ICCD continuous imaging system, and a microsecond-second high-speed camera system.

[0016] Furthermore, the picosecond-nanosecond ultrafast pump detection system includes an imaging objective lens I for amplifying the detection pulse I and a CCD I for capturing the detection pulse I.

[0017] Furthermore, the microsecond-to-second high-speed imaging system includes an imaging objective lens II for amplifying the detection pulse III and a high-speed camera for capturing the detection pulse III.

[0018] Furthermore, the femtosecond ultrafast continuous imaging system includes a beam splitter V, a beam splitter VI, a beam splitter VII, a reflector VI, a CCD II, a CCD III, a CCD IV and a CCD V; the detection pulse V is separated by the beam splitter V, the beam splitter VI and the beam splitter VII, respectively, and each separated pulse is captured by the corresponding CCD II, CCD III and CCD IV; the detection pulse V passes through the reflector VI and is captured by the CCDV.

[0019] Furthermore, the nanosecond-millisecond ICCD continuous imaging system includes an ICCD for capturing the detection pulse VI and the spectrometer.

[0020] In a second aspect, a method for systematic observation of multi-time scale continuous observation during femtosecond laser processing comprises the following steps:

[0021] The control computer turns on the femtosecond laser light source, which emits a Gaussian femtosecond pulse. The Gaussian femtosecond pulse passes through the beam splitter I and is split into two pulses. One of the pulses serves as a pump pulse and passes through the reflector I, reflector II, reflector III, and reflector IV in sequence to reach the pulse shaping system. The shaped pump pulse passes through the beam combiner I and is then focused on the surface of the sample by an objective lens or a plano-convex lens to perform ablation processing on the sample.

[0022] The other pulse is used as a probe pulse. It first passes through a beam splitter II and is split into a probe pulse I and a probe pulse II. The probe pulse I changes the laser wavelength by passing through the frequency-doubling crystal, and then passes through a bandpass filter to filter out the original wavelength, retaining the frequency-doubled laser wavelength. The probe pulse I then changes its propagation direction by passing through a beam combiner I, and then passes through the sample. The probe pulse I carrying the sample information is amplified by an imaging objective lens I and is finally captured by a CCD I and imaged on a computer. By adjusting the optical path of the probe pulse I relative to the pump pulse in the optical path, a time interval of the order of picoseconds to nanoseconds is achieved.

[0023] The detection pulse II is split into detection pulse III and detection pulse IV by beam splitter III. After passing through nonlinear crystal III, detection pulse III is converted into continuous spectrum white light. After being redirected by reflector V, it passes through the sample. The detection pulse III carrying sample information is amplified by imaging objective II and captured by a high-speed camera. The frame rate of the captured image is millisecond-second intervals.

[0024] The detection pulse IV is divided into a detection pulse V and a detection pulse VI by a beam splitter IV. The detection pulse V is generated by a pulse sequence generator to generate a pulse train with a specific time interval and different laser wavelengths. After passing through the sample, the pulse train carrying the information of the sample at different times is separated by beam splitters V, VI, and VII with specific cutoff wavelengths. Each separated pulse is captured by the corresponding CCD II, CCD III, CCD IV, and CCD V. The time interval between each pulse is on the order of hundreds of femtoseconds.

[0025] The detection pulse VI passes through the reflector VII and the nonlinear crystal IV, and is converted into continuous spectrum white light. After passing through the reflector VIII and the sample, the detection pulse VI carrying the sample information is captured by the ICCD and the spectrometer. The time interval between the image acquisition and the relative pump pulse is controlled by the ICCD's own gate, and the time range is in the nanosecond-millisecond order.

[0026] The system and method for continuous observation of multiple time scales during femtosecond laser processing provided by the present invention have the following beneficial effects:

[0027] The present invention can realize the femtosecond laser processing process, from the material free electron generation, plasma eruption, material phase change, material melting to recasting and the formation of micro-nanostructures and other time scales (10 -13 The panoramic real-time continuous observation of femtosecond lasers (s-1s) plays an important auxiliary role in deeply understanding and revealing the interaction mechanism between femtosecond lasers and materials.

[0028] The present invention has the ability to perform ultrafast continuous observation across multiple time scales during femtosecond laser processing. Its observation time range can reach 13 orders of magnitude between hundreds of femtoseconds and seconds, which can cover the entire physical and chemical reaction process. It plays an important auxiliary role in deeply understanding and revealing a series of non-equilibrium, nonlinear and ultrafast phenomena in femtosecond laser processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the optical path of the system for continuous observation of multiple time scales during femtosecond laser processing according to the present invention.

[0030] Figure 2 Schematic diagram of the system for continuous observation of multiple time scales during femtosecond laser processing of the present invention.

[0031] Among them: 1. Femtosecond laser light source; 2. Laser processing system; 3. Multi-time scale continuous observation system; 4. Pulse shaping system; 5. Pulse time shaping device; 6. Pulse space shaping device; 7. Pulse wavelength shaping device; 8. Femtosecond ultrafast continuous imaging system; 9. Picosecond-nanosecond ultrafast pump detection system; 10. Nanosecond-millisecond ICCD continuous imaging system; 11. Microsecond-second high-speed camera system; 12. Beam splitter I; 13. Reflector I; 14. Reflector II; 15. Reflector III; 16. Reflector IV; 17. Thin film beam splitter; 18. Retroreflector I; 19. Time delay platform I; 20. Nonlinear crystal I; 21. Retroreflector II; 22. Nonlinear crystal II; 23. Sample; 24. Beam splitter II; 25. Frequency doubling crystal; 26. Bandpass filter; 27. Beam combiner I; 28. Imaging objective lens I; 29. CCD I; 30. Beam splitter III; 31. Nonlinear crystal III; 32. Reflector V; 33. Imaging objective II; 34. High-speed camera; 35. Beam splitter IV; 36. Pulse sequence generator; 37. Beam splitter V; 38. Beam splitter VI; 39. Beam splitter VII; 40. Reflector VI; 41. CCD II; 42. CCD III; 43. CCD IV; 44. CCD V; 45. Reflector VII; 46. Nonlinear crystal IV; 47. Reflector VIII; 48. ICCD; 49. Spectrometer; 50. Pulse signal generator; 51. Computer; 52. Time delay platform II. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0033] Example 1, reference Figure 1 and Figure 2 The multi-timescale continuous observation system of the femtosecond laser processing process in this scheme can directly observe a series of continuous ultrafast physical and chemical reaction processes across multiple time scales during femtosecond laser processing, thereby revealing the interaction mechanism between femtosecond laser and materials and providing observational theoretical support for femtosecond laser processing. Specifically, it includes:

[0034] Femtosecond laser light source 1, laser processing system 2, pulse shaping system 4 and multi-timescale continuous observation system 3;

[0035] Each of the above systems will be described in detail below;

[0036] The femtosecond laser light source 1 is a Gaussian femtosecond pulse laser. The parameters can be set by the computer 51 and transmitted to the pulse signal generator 50 to control the femtosecond laser light source 1 to emit a single pulse.

[0037] The laser processing system 2 includes a beam splitter I12 , a reflector I13 , a reflector II14 , a reflector III15 , a reflector IV16 , a sample 23 , and a three-dimensional linear translation stage for clamping the sample 23 .

[0038] During specific operation, the femtosecond laser light source 1 emits a Gaussian femtosecond pulse, which passes through the beam splitter I12 and is divided into two pulses; one of them serves as a pump pulse, which passes through the reflector I13, the reflector II14, the reflector III15, and the reflector IV16 in sequence and reaches the pulse shaping system 4. The shaped pump pulse passes through the beam combiner I27 and is then focused on the surface of the sample 23 through an objective lens or a plano-convex lens to perform ablation processing on it.

[0039] The multi-timescale continuous observation system 3 includes a femtosecond ultrafast continuous imaging system 8, a picosecond-nanosecond ultrafast pump-detection system 9, a nanosecond-millisecond ICCD48 continuous imaging system 10, and a microsecond-second high-speed camera system 11. Each subsystem is independent of the others, and its imaging optical paths do not interfere with each other. Each subsystem observes ultrafast reaction phenomena from different angles. A computer 51 controls a pulse signal generator 50 to send a level signal to the femtosecond laser light source 1, the CCDs in the femtosecond ultrafast continuous imaging system 8, the picosecond-nanosecond ultrafast pump-detection system 9, and the microsecond-second high-speed camera system 11, and the ICCD 48 and spectrometer 49 in the nanosecond-millisecond ICCD48 continuous imaging system 10, activating them simultaneously. The optical paths from the detection pulses in each imaging system in the multi-timescale continuous observation system 3 to the sample 23 are equal in optical path length, meaning that the femtosecond laser pulses travel the same distance in each imaging system.

[0040] The femtosecond ultrafast continuous imaging system 8 includes a beam splitter IV35, a pulse sequence generator 36, a beam splitter V37, a beam splitter VI38, a beam splitter VII39, a reflector VI40, a CCD II41, a CCD III42, a CCD IV43 and a CCD V44;

[0041] The femtosecond ultrafast continuous imaging system 8 is used to capture the detection pulse V, specifically:

[0042] The detection pulse V passes through the pulse sequence generator 36 and through the sample 23. The pulse train carrying the information of the sample 23 at different times is separated by the beam splitter V37, beam splitter VI38, and beam splitter VII39 with specific cutoff wavelengths. Each separated pulse is captured by the corresponding CCD II41, CCD III42, CCD IV43 and CCD V44. The time interval between each pulse is on the order of hundreds of femtoseconds.

[0043] The picosecond-nanosecond ultrafast pump detection system 9 includes a beam splitter II12, a frequency doubling crystal 25, a bandpass filter 26, a beam combiner I27, an imaging objective lens I28 and a CCD I29.

[0044] The picosecond-nanosecond ultrafast pump detection system 9 is used to capture the detection pulse I, specifically:

[0045] The detection pulse is divided into detection pulse I and detection pulse II by beam splitter II12; the detection pulse I changes the laser wavelength through the frequency doubling crystal 25, and then filters out the original wavelength through the bandpass filter 26, retaining the laser wavelength after frequency doubling, and then changes the propagation direction through the beam combiner I27, and then passes through the sample 23. The detection pulse I carrying the information of the sample 23 is amplified by the imaging objective lens I28 and finally captured by the CCD I29.

[0046] The nanosecond-millisecond ICCD 48 continuous imaging system 10 includes a reflector VII 45 , a nonlinear crystal IV 46 , a reflector VIII 47 , an ICCD 48 and a spectrometer 49 ;

[0047] The nanosecond-millisecond ICCD48 continuous imaging system 10 is used to capture the detection pulse VI, specifically:

[0048] The detection pulse VI passes through the reflector VII45 and the nonlinear crystal IV46, and is converted into continuous spectrum white light. After passing through the reflector VIII47 and the sample 23, the detection pulse VI carrying the information of the sample 23 is captured by the ICCD48 and the spectrometer 49.

[0049] The microsecond-to-second high-speed imaging system 11 includes a beam splitter III30, a nonlinear crystal III31, a reflector V32, an imaging objective II33 and a high-speed camera 34;

[0050] The microsecond-second high-speed camera system 11 is used to capture the detection pulse III, specifically:

[0051] After passing through the nonlinear crystal III31, the detection pulse III is converted into continuous spectrum white light, which is then changed in direction by the reflector V32 and passes through the sample 23. The detection pulse III carrying the information of the sample 23 is amplified by the imaging objective lens II33 and captured by the high-speed camera 34.

[0052] The pulse shaping system 4 includes a pulse time shaping device 5, a pulse wavelength shaping device 7, and a pulse space shaping device 6. The shaping of the laser wavelength / spatial shape of the pulse shaping system 4 is achieved by nonlinear elements I and II placed in the optical path. The time shaping of the pulse shaping system 4 is achieved by a time delay platform I19 placed in the optical path.

[0053] The pulse shaping system 4 of this embodiment is a shaping system based on an improved Michelson interferometer, which realizes the time / space / frequency trinity shaping requirements of femtosecond laser pulses by adding nonlinear optical elements and a time delay platform I19 in the optical path system.

[0054] Example 2, reference Figure 1 and Figure 2 The present invention provides a systematic observation method for continuous observation of multiple time scales during femtosecond laser processing, which includes:

[0055] The computer 51 turns on the femtosecond laser light source 1 and sets it to an external trigger mode, and then controls the pulse signal generator 50 to emit a rising edge level signal, which is synchronously transmitted to the femtosecond laser light source 1 and the multi-time-scale continuous observation system 3. The femtosecond laser light source 1 emits a Gaussian femtosecond pulse, which passes through the beam splitter I12 and is split into two pulses; one of the pulses is used as a pump pulse and passes through the reflector I13, reflector II14, reflector III15, and reflector IV16 in sequence to reach the pulse shaping system 4. The shaped pump pulse passes through the beam combiner I27 and is then focused on the surface of the sample 23 by an objective lens or a plano-convex lens to perform ablation processing on it.

[0056] The other pulse is used as a detection pulse. It first passes through the beam splitter II12 and is divided into a detection pulse I and a detection pulse II. The detection pulse I changes the laser wavelength through the frequency doubling crystal 25, and then passes through the bandpass filter 26 to filter out the original wavelength, retaining the laser wavelength after frequency doubling. It then changes the propagation direction through the beam combiner I27 and then passes through the sample 23. The detection pulse I carrying the information of the sample 23 is amplified by the imaging objective lens I28 and is finally captured by the CCD I29 and imaged on the computer 51. By adjusting the optical path of the detection pulse I relative to the pump pulse in the optical path, a time interval of the order of picoseconds to nanoseconds is achieved.

[0057] The detection pulse II is split into detection pulse III and detection pulse IV by beam splitter III30. After passing through nonlinear crystal III31, detection pulse III is converted into continuous spectrum white light. After being redirected by reflector V32, it passes through sample 23. The detection pulse III carrying information about sample 23 is amplified by imaging objective II33 and captured by high-speed camera 34. The frame rate of the captured image is millisecond-second intervals.

[0058] The detection pulse IV is divided into a detection pulse V and a detection pulse VI by a beam splitter IV35. The detection pulse V is generated by a pulse sequence generator 36 to generate a pulse train with a specific time interval and different laser wavelengths. After passing through the sample 23, the pulse train carrying the information of the sample 23 at different times is separated by beam splitters V37, VI38, and VII39 with specific cutoff wavelengths. Each separated pulse is captured by the corresponding CCD II41, CCD III42, CCD IV43, and CCD V44. The time interval between each pulse is on the order of hundreds of femtoseconds.

[0059] The detection pulse VI passes through the reflector VII45 and the nonlinear crystal IV46, and is converted into continuous spectrum white light. After passing through the reflector VIII47 and the sample 23, the detection pulse VI carrying the information of the sample 23 is captured by the ICCD48 and the spectrometer 49. The time interval between the image acquisition and the relative pump pulse is controlled by the ICCD48's own gate, and the time range is in the nanosecond-millisecond order.

[0060] Finally, through the coordinated and complementary acquisition of images among the subsystems of the above-mentioned multi-time-scale continuous observation system 3, ultrafast continuous images covering the time scale from hundreds of femtoseconds to 13 seconds after the pump pulse ablates the sample 23 are acquired and saved in the computer 51.

[0061] Example 3: This example is a specific case of Example 2, which specifically includes:

[0062] The femtosecond laser light source 1 is turned on by the computer 51, and the mode is changed to the gated mode. Then, the computer 51 controls the pulse signal generator 50 to emit a rising edge level signal with a voltage of 5V, which is input to the femtosecond laser light source 1 and the multi-time scale continuous observation system 3 at the same time. At this time, the femtosecond laser light source 1 emits a Gaussian femtosecond laser pulse with a wavelength of 800nm and a pulse width of 35fs. After passing through the beam splitter I12, it is divided into a pump pulse and a detection pulse. The pump pulse passes through the reflector I13, the reflector II14 located on the time delay platform II52, the reflector III15 and the reflector IV16 in sequence, enters the pulse shaping system 4, and passes through the thin film beam splitter 17 to be equally divided into two pump pulses I and pump pulse II. The pump pulse I returns in the same direction through the retroreflective mirror II21, and then passes through the nonlinear crystal II22, and is spatially transformed from the original Gaussian pulse to a flat-top light pulse. The pump pulse II is also transformed into a flat-top light pulse after passing through the retroreflective mirror I18 and the nonlinear crystal I20. The difference is that the retroreflective mirror I18 is placed on the time delay platform I19, and the position of the retroreflective mirror I18 can be moved by controlling the time delay platform I19. In this way, the two shaped pump pulses will be delayed when they reach the thin film beam splitter 17. Compared to the single Gaussian pulse before entering the pulse shaping system 4, the emitted pulse laser achieves dual shaping in time and space. After shaping, the pulse laser passes through the beam combiner I27, is focused by the objective lens, reaches the surface of the sample 23, and ablates it.

[0063] While the pump pulse is propagating, the detection pulse is first divided into a detection pulse I and a detection pulse II by the beam splitter II12. The detection pulse I passes through the frequency doubling crystal 25 (BBO crystal) to generate a femtosecond laser pulse with a wavelength of 400nm, and then passes through the 400nm bandpass filter 26 to filter out the 800nm wavelength laser. The propagation direction is then changed by the beam combiner I27, and the pulse passes through the sample 23. The image carrying the information of the sample 23 is magnified by the 20x imaging objective lens I28 and is finally captured by the CCD I29. In the propagation light path of the detection pulse I, the optical path difference between the detection pulse I and the pump pulse is precisely controlled to be 150mm by the position of the reflector and the placement of the time delay platform, thereby achieving 500ps time-lapse photography, that is, capturing the reaction phenomenon after the pump pulse ablates the sample 23500ps.

[0064] The 800nm probe pulse II continues to pass through the beam splitter III30 and is split into a probe pulse III and a probe pulse IV. After passing through the nonlinear crystal III31 (calcium fluoride crystal), the probe pulse III is converted from the original monochromatic light with a wavelength of 800nm to white light with a continuous spectrum (wavelength of 400nm-900nm). After being redirected by the reflector V32, it passes through the sample 23 and is magnified by the 20x imaging objective lens II33. Finally, it is captured by the high-speed camera 34. The frame rate of the high-speed camera 34 is set to 100ms by the computer 51. In this way, the reaction phenomenon with an interval of 100ms after the pump pulse ablates the sample 23 can be continuously captured. The 800nm detection pulse IV continues to propagate and is divided into an 800nm detection pulse V and an 800nm detection pulse VI through a beam splitter IV35. The 800nm detection pulse V generates multiple sub-pulses with a time interval of 200fs through a pulse sequence generator 36, and each sub-pulse has a different wavelength (covering 340nm-960nm). After passing through the sample 23, the pulse train carrying the information of the sample 23 at different times is separated by the beam splitter V37 (490nm), beam splitter VI38 (560nm), and beam splitter VII39 (780nm) with a specific cutoff wavelength. Finally, each separated pulse is captured by the corresponding CCD II41, CCD III42, CCD IV43 and CCD V44. In this way, the reaction phenomenon within hundreds of femtoseconds after the pump pulse ablates the sample 23 is photographed and imaged on the computer 51.

[0065] The 800nm detection pulse VI passes through the reflector VII45 and the nonlinear crystal IV46 (calcium fluoride crystal), and is converted from the original monochromatic light with a wavelength of 800nm to white light with a continuous spectrum (wavelength 400nm-900nm). After passing through the reflector VIII47 and the sample 23, the 800nm detection pulse VI carrying the sample information is captured by the ICCD48 and the spectrometer 49. The gate time of the ICCD48 is set to 20ns. In this way, the reaction phenomenon 20ns after the pump pulse ablates the sample 23 and several times 20ns later is captured.

[0066] In summary, through the coordinated and complementary acquisition of images among the subsystems of the above-mentioned multi-time-scale continuous observation system 3, ultrafast continuous images covering the time scale from hundreds of femtoseconds to 13 seconds after the pump pulse ablates the sample 23 are acquired and saved in the computer 51.

[0067] Although the specific embodiments of the invention are described in detail in conjunction with the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A system for continuous observation of multiple time scales during femtosecond laser processing, characterized by: It includes a femtosecond laser light source; the femtosecond laser light source emits a Gaussian femtosecond pulse, which is divided into two pulses by a laser processing system; one pulse passes through the laser processing system to reach a pulse shaping system, and is focused on the surface of the sample by a beam combiner I, an objective lens or a plano-convex lens; The other pulse is split into detection pulse I and detection pulse II by beam splitter II; The detection pulse I passes through the frequency doubling crystal, the bandpass filter, and the beam combiner I in sequence, passes through the sample, and is captured by the multi-time scale continuous observation system; The detection pulse II is divided into detection pulse III and detection pulse IV by beam splitter III; The detection pulse III passes through the nonlinear crystal III and the reflector V, passes through the sample, and is captured by the multi-time scale continuous observation system; The detection pulse IV is divided into a detection pulse V and a detection pulse VI by a beam splitter IV; The detection pulse V passes through the pulse sequence generator, penetrates the sample, and is captured by the multi-time scale continuous observation system; The detection pulse VI passes through the reflector VII, the nonlinear crystal IV, the reflector VIII, and the sample, and is captured by the multi-time-scale continuous observation system; The femtosecond laser light source is configured with parameters by a computer and transmitted to a pulse signal generator to control the femtosecond laser light source to emit a single pulse; The laser processing system includes a beam splitter I, a reflector I, a reflector II, a reflector III and a reflector IV, which are arranged between the femtosecond laser light source and the pulse shaping system; The pulse shaping system includes a pulse time shaping device, a pulse wavelength shaping device and a pulse space shaping device; The multi-timescale continuous observation system includes a femtosecond ultrafast continuous imaging system, a picosecond-nanosecond ultrafast pump-detection system, a nanosecond-millisecond ICCD continuous imaging system, and a microsecond-second high-speed camera system; The picosecond-nanosecond ultrafast pump detection system includes an imaging objective lens 1 for amplifying the detection pulse 1 and a CCD 1 for capturing the detection pulse 1; The microsecond-second high-speed imaging system includes an imaging objective lens II for amplifying the detection pulse III and a high-speed camera for capturing the detection pulse III; The femtosecond ultrafast continuous imaging system includes a beam splitter V, a beam splitter VI, a beam splitter VII, a reflector VI, a CCD II, a CCD III, a CCD IV, and a CCD V; the detection pulse V is separated by the beam splitter V, the beam splitter VI, and the beam splitter VII, and each separated pulse is captured by the corresponding CCD II, CCD III, and CCD IV; the detection pulse V passes through the reflector VI and is captured by the CCD V; The nanosecond-millisecond ICCD continuous imaging system includes an ICCD for capturing a detection pulse VI and a spectrometer.

2. An observation method using the system for continuous observation of multiple time scales during femtosecond laser processing according to claim 1, characterized in that: The following steps are involved: Controlling the computer to turn on the femtosecond laser light source, the femtosecond laser light source emits a Gaussian femtosecond pulse, which passes through the beam splitter I and is split into two pulses; one of the pulses serves as a pump pulse, which passes through the reflector I, reflector II, reflector III, and reflector IV in sequence and reaches the pulse shaping system; the shaped pump pulse passes through the beam combiner I and is then focused on the surface of the sample through an objective lens or a plano-convex lens to perform ablation processing on the sample; The other pulse is used as a probe pulse, which is first split into a probe pulse I and a probe pulse II by a beam splitter II. The probe pulse I changes the laser wavelength by passing through the frequency-doubling crystal, and then filters out the original wavelength by the bandpass filter, retaining the frequency-doubled laser wavelength. The probe pulse I then changes its propagation direction by passing through a beam combiner I, and then passes through the sample. The probe pulse I carrying the sample information is amplified by the imaging objective lens I and is finally captured by the CCD I and imaged on the computer. By adjusting the optical path of the probe pulse I relative to the pump pulse in the optical path, a time interval of the order of picoseconds to nanoseconds is achieved. The detection pulse II is divided into a detection pulse III and a detection pulse IV by the beam splitter III, wherein the detection pulse III is converted into a continuous spectrum of white light after passing through the nonlinear crystal III, and then passes through the sample after changing direction by the reflector V. The detection pulse III carrying the sample information is amplified by the imaging objective lens II and captured by the high-speed camera, and the frame rate of the captured photo is millisecond-second interval; The detection pulse IV is divided into a detection pulse V and a detection pulse VI by the beam splitter IV, wherein the detection pulse V is generated by the pulse sequence generator to generate a pulse train with a specific time interval and different laser wavelengths. After passing through the sample, the pulse train carrying the information of the sample at different times is separated by the beam splitter V, beam splitter VI, and beam splitter VII with specific cutoff wavelengths. Each separated pulse is captured by the corresponding CCD II, CCD III, CCD IV, and CCD V, and the time interval between each pulse is on the order of hundreds of femtoseconds. The detection pulse VI passes through the reflector VII and the nonlinear crystal IV, and is converted into continuous spectrum white light. After passing through the reflector VIII and the sample, the detection pulse VI carrying the sample information is captured by the ICCD and the spectrometer. The image acquisition and the time interval relative to the pump pulse are controlled by the ICCD's own gate, and the time range is in the nanosecond-millisecond order.

Images