A device for realizing in-situ measurement of time-domain waveform of ultrahigh intensity laser pulse

Abstract

The application discloses a device for realizing in-situ measurement of time-domain waveforms of ultrahigh-intensity laser pulses, which comprises a component to be measured, wherein the component to be measured comprises a femtosecond laser source, a beam splitter arranged on one side of the femtosecond laser source, a mirror component arranged on one side of the beam splitter, a first focusing lens arranged on one side of the mirror component, a vacuum component arranged on one side of the first focusing lens, a dual-color mirror arranged on one side of the vacuum component, a narrow-band filter arranged on one side of the dual-color mirror, a 10cm focusing lens arranged on one side of the narrow-band filter and a spectrometer; and a detection component, wherein the detection component comprises a mirror, a second focusing lens arranged on one side of the mirror and a time-delay device mounted on an electrically-controlled displacement table. According to the application, the limitation of traditional equipment in terms of damage threshold can be broken, only a common spectrometer is needed to record optical frequency domain information, the method is simple, the cost is low and the applicability is wide.

Description

Technical Field

[0001] This invention relates to the technical field of measuring femtosecond laser pulses, and particularly to a device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses. Background Technology

[0002] Measuring the temporal width and structure of femtosecond laser pulses is fundamental and crucial for the development of ultrafast optics and the research on the nonlinear interaction between ultrafast laser pulses and media. To date, various techniques based on different principles have been proposed. Commonly used techniques include autocorrelators, frequency-resolved optical switches (FROG), and the spectral phase coherence direct electric field reconstruction method (SPIDER). However, all measurement devices have optical damage thresholds for their internal optical components, limiting all methods to directly measuring the temporal shape of pulses with energies in the nanojoule to microjoule range. However, for common femtosecond laser systems, the output pulse energy is in the millijoule to joule range, and the focused laser intensity easily exceeds 10¹⁴ W / cm², causing ionization of any material, including gases. Since strong laser pulses easily damage traditional detectors or equipment, conventional detection devices cannot measure the temporal shape and evolution of laser pulses near the focal point when strong lasers interact with gases in situ. Recently, researchers have proposed the photoelectron suprathreshold ionization (ATI) measurement method for measuring the temporal information of high-intensity, few-period (10 fs) pulses near the focal point. This scheme enables the measurement of pulse length at the laser-gas interaction point. This method is based on the ATI spectrum of inert gases (such as Xe), which depends on the carrier envelope phase (CEP), and this dependence weakens with increasing pulse length. Therefore, this method is only applicable to few-period pulses and requires sophisticated detection instruments to measure free electrons. Consequently, under normal circumstances, the temporal information of the pulse near the focal point in cases of strong laser pulses and nonlinear interactions between matter can only be estimated through numerical simulations.

[0003] Existing measurement techniques, due to the damage threshold of optical components, are limited to measuring the temporal shape of laser pulses at low energies. Traditional equipment and methods cannot measure the ultra-high intensity photoelectric fields within laser plasmas. The recently proposed ATI method is only applicable to pulses with few cycles, not to commonly used femtosecond pulses, and requires large, complex, and high-precision detectors to measure free electrons, resulting in high measurement costs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses. This device overcomes the limitations of traditional equipment in terms of damage threshold, requiring only a common spectrometer to record optical frequency domain information. The method is simple, low-cost, and widely applicable. To achieve the above-mentioned objectives and other advantages of the present invention, a device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses is provided, comprising:

[0005] The component under test includes a femtosecond laser source, a beam splitter disposed on one side of the femtosecond laser source, a mirror component disposed on one side of the beam splitter, a first focusing lens disposed on one side of the mirror component, a vacuum component disposed on one side of the first focusing lens, a dichroic mirror disposed on one side of the vacuum component, a narrowband filter disposed on one side of the dichroic mirror, a 10cm focusing lens disposed on one side of the narrowband filter, and a spectrometer; the detection component includes a mirror, a second focusing lens disposed on one side of the mirror, and a delay device mounted on an electrically controlled displacement stage.

[0006] Preferably, the reflector component includes a first reflector, a second reflector disposed directly below the first reflector, a third reflector disposed on the other side of the second reflector, and a fourth reflector disposed below the third reflector, with a first focusing lens disposed on one side of the fourth reflector.

[0007] Preferably, the vacuum component includes a vacuum chamber filled with nitrogen gas and plasma disposed within the vacuum chamber.

[0008] Preferably, a light-blocking plate is provided directly above the dichroic mirror.

[0009] Preferably, the pulsed beam emitted from the femtosecond laser source is split into reflected light and transmitted light at an energy ratio of 8:2 by a beam splitter.

[0010] A method for realizing in-situ measurement of the time-domain waveform of an ultra-high intensity laser pulse, comprising the following steps:

[0011] S1. The pulsed beam emitted by femtosecond laser 1 is split into reflected light and transmitted light by beam splitter 2;

[0012] S2. The transmitted light is reflected by the first, second, third, and fourth reflecting mirrors.

[0013] S3. Simultaneously, the reflected light is reflected by the mirror.

[0014] S4. The transmitted light in step S2 and the reflected light in step S3 both enter the nitrogen-filled vacuum cavity 10 after reflection, and both coincide with the 800nm ​​pulse in space to form plasma and generate an enhanced 400nm second harmonic.

[0015] S5. The residual probe light is reflected off the optical baffle 13 by the dichroic mirror, and the background light signal of stray light is filtered out by the narrow-band filter.

[0016] S6. The second harmonic signal generated at the plasma is focused and coupled into the fiber optic spectrometer through a 10cm focusing lens, and then measured using the spectrometer.

[0017] Compared with existing technologies, the advantages of this invention are as follows: by utilizing the enhanced second harmonic effect generated by the probe pulse and the test pulse in the gas plasma, in-situ characterization of the time-domain waveform of ultra-high intensity laser pulses in the plasma can be achieved; by using an electrically controlled displacement platform, the time delay of the coincidence of the test light and the probe light can be precisely controlled, thereby using a spectrometer to accurately measure the change of enhanced second harmonic intensity with time delay, and realizing the cross-correlation measurement of pulse width; this method is based on the interaction between laser and matter and can be applied to the time-domain waveform measurement of ultra-high intensity laser pulses in various gases and isotropic solids. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses according to the present invention;

[0019] Figure 2 The second harmonic spectrum of the probe light generated in air is obtained by the apparatus for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses according to the present invention.

[0020] Figure 3 The graph shows the evolution of the second harmonic signal of the test pulse at different positions in the plasma as a function of delay, as presented in the device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Reference Figure 1-3A device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses includes: a component under test, which includes a femtosecond laser source 1, a beam splitter 2 disposed on one side of the femtosecond laser source 1, a reflector component disposed on one side of the beam splitter 2, a first focusing lens 9 disposed on one side of the reflector component, a vacuum component disposed on one side of the first focusing lens 9, a dichroic mirror 14 disposed on one side of the vacuum component, a narrowband filter 15 disposed on one side of the dichroic mirror 14, a 10cm focusing lens 16 disposed on one side of the narrowband filter 15, and a spectrometer 17. Figure 1 The focal length of the lens used in the optical path under test and the optical path under test is not necessary. It can be replaced by a lens with a suitable focal length, as long as it can generate plasma.

[0023] For the gas inside the vacuum cavity, other gases can be used, as long as they can generate second harmonics with the high-intensity laser pulse. Furthermore, this method can also be applied to in-situ time-domain waveform measurement of ultra-high intensity laser pulses in isotropic solids.

[0024] The laser wavelength can also be replaced with other different wavelengths of laser light;

[0025] The detection components include a reflector 7, a second focusing lens 8 disposed on one side of the reflector 7, and a time delay device mounted on an electrically controlled displacement stage.

[0026] A method for realizing in-situ measurement of the time-domain waveform of an ultra-high intensity laser pulse, comprising the following steps:

[0027] S1. The pulsed beam emitted by femtosecond laser 1 is split into reflected light and transmitted light by beam splitter 2;

[0028] S2. The transmitted light is reflected by the first reflecting mirror 3, the second reflecting mirror 4, the third reflecting mirror 5, and the fourth reflecting mirror 6.

[0029] S3. Simultaneously, the reflected light is reflected by mirror 7.

[0030] S4. The transmitted light in step S2 and the reflected light in step S3 both enter the nitrogen-filled vacuum cavity 10 after reflection, and both coincide with the 800nm ​​pulse in space to form plasma and generate an enhanced 400nm second harmonic.

[0031] S5. The residual probe light is reflected off the optical baffle 13 by the dichroic mirror 14, and the background light signal of stray light is filtered out by the narrowband filter 15.

[0032] S6. The second harmonic signal generated at the plasma is focused and coupled into the fiber optic spectrometer via a 10cm focusing lens 16, and measured using the spectrometer 17. The experimenter can measure the pulse time-domain waveform by observing the change of the second harmonic signal collected by the spectrometer with time delay.

[0033] Furthermore, the reflector component includes a first reflector 3, a second reflector 4 disposed directly below the first reflector 3, a third reflector 5 disposed on the other side of the second reflector 4, and a fourth reflector 6 disposed below the third reflector 5. A first focusing lens 9 is disposed on one side of the fourth reflector 6.

[0034] Furthermore, the vacuum component includes a vacuum chamber 10 filled with nitrogen gas 11, and a plasma 12 disposed within the vacuum chamber 10.

[0035] Furthermore, a light-blocking plate 13 is provided directly above the dichroic mirror 14.

[0036] Furthermore, the pulsed beam emitted from the femtosecond laser source 1 is split into reflected and transmitted light at an energy ratio of 8:2 by the beam splitter 2. The transmitted light, serving as the probe light, is reflected by the first reflecting mirror 3, the second reflecting mirror 4, the third reflecting mirror 5, and the fourth reflecting mirror 6, and then focused by the first focusing lens 9 into a nitrogen-filled vacuum cavity 10. Another reflected 800nm ​​test light beam is reflected by the reflecting mirror 7 and then focused by the second focusing lens 8 into the nitrogen-filled vacuum cavity 10, where it overlaps with the 800nm ​​probe light to form plasma and generate an enhanced 400nm second harmonic. A dichroic mirror 14 reflects the residual probe light onto an optical baffle 13, and a filter 15 filters out stray light and other background light signals. The second harmonic signal generated in the plasma is focused and coupled into a fiber optic spectrometer by a 10cm focusing lens 16, and measured using the spectrometer 17. The experimenter can measure the pulse time-domain waveform by observing the change in the second harmonic signal collected by the spectrometer over time.

[0037] Example 1

[0038] This embodiment uses a commercial Ti:sapphire laser source with a center wavelength of 796 nm. The laser pulse output from the Ti:sapphire laser 1 has a center wavelength of 796 nm, a pulse width of 35 fs, an energy of 12 mJ, a repetition rate of 1 kHz, and is a horizontally polarized femtosecond laser pulse. It is incident on a beam splitter 2 with a reflectivity of 80% and a transmittance of 20%, splitting into two paths: a test beam and a probe beam. In the test beam path, the test beam, after being reflected by the beam splitter 2, is reflected by the reflector 7 and then focused by the second focusing lens 8, forming a plasma filament of approximately 10 mm in length in the gas. The ultra-high intensity laser field inside the filament serves as the object under test. In the probe beam path, the third reflector 5 and the fourth reflector 6 are mounted on an electrically controlled displacement platform. By controlling the electrically controlled displacement platform, the timing of the test beam pulse and the probe beam pulse can be controlled. In the detection optical path, the detection light is reflected by the first reflecting mirror 3, the second reflecting mirror 4, the third reflecting mirror 5, and the fourth reflecting mirror 6, and then focused by the first focusing lens 9 into a sealed gas chamber 10 filled with pure nitrogen, thus forming a thin, relatively weak plasma filament 12. A dichroic mirror 14 (reflecting 800nm ​​and transmitting 400nm) incident at a 45° angle reflects the remaining 800nm ​​detection pulse to a light-blocking plate to prevent it from disrupting the subsequent signal acquisition system. An interference filter 15 with a center wavelength of 400nm and a bandwidth of 10nm is used to filter out the influence of background light on the target signal detection. Then, a quartz lens 16 with a focal length of 10cm couples the generated 400nm second harmonic signal into a fiber optic spectrometer (Avantes, Avaspec-3648) 17 to measure the signal spectrum. Experimental results are shown in […]. Figure 2 By changing the time delay between the probe light and the test light, the intensity change of the second harmonic signal over time is detected. Furthermore, the first focusing lens 9 is mounted on a three-dimensional translation stage, thereby allowing the probe position to be changed and the pulse time-domain shape of the test pulse at different positions within the plasma filament to be measured. Figure 3 As shown.

[0039] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0040] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses, characterized in that, include: The component under test includes a femtosecond laser source (1), a beam splitter (2) disposed on one side of the femtosecond laser source (1), a mirror component disposed on one side of the beam splitter (2), a first focusing lens (9) disposed on one side of the mirror component, a vacuum component disposed on one side of the first focusing lens (9), a dichroic mirror (14) disposed on one side of the vacuum component, a narrowband filter (15) disposed on one side of the dichroic mirror (14), a 10cm focusing lens (16) disposed on one side of the narrowband filter (15), and a spectrometer (17). A combination of a dichroic mirror and a narrowband filter is used to filter out stray light. The vacuum component includes a vacuum chamber (10) filled with nitrogen gas (11) and a plasma (12) disposed therein. The electronically controlled displacement platform can precisely control the time delay of the overlap between the light to be measured and the probe light, thereby using a spectrometer to accurately measure the change of the enhanced second harmonic intensity with the delay, and realize the cross-correlation measurement of the pulse width. The detection components include a reflector (7), a second focusing lens (8) disposed on one side of the reflector (7), and a time delay device mounted on an electrically controlled displacement stage.

2. The device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses as described in claim 1, characterized in that, The reflector component includes a first reflector (3), a second reflector (4) located directly below the first reflector (3), a third reflector (5) located on the other side of the second reflector (4), and a fourth reflector (6) located below the third reflector (5). A first focusing lens (9) is provided on one side of the fourth reflector (6).

3. The device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses as described in claim 1, characterized in that, A light-blocking plate (13) is provided directly above the dichroic mirror (14).

4. The device for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses as described in claim 1, characterized in that, The pulsed beam emitted from the femtosecond laser source (1) is split into reflected light and transmitted light at an energy ratio of 8:2 after passing through the beam splitter (2).

5. A method for implementing the apparatus for in-situ measurement of the time-domain waveform of ultra-high intensity laser pulses as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. The pulsed beam emitted by the femtosecond laser (1) is split into reflected light and transmitted light by the beam splitter (2); S2. The transmitted light is reflected by the first reflecting mirror (3), the second reflecting mirror (4), the third reflecting mirror (5) and the fourth reflecting mirror (6); S3, Simultaneously, the reflected light is reflected by the mirror (7); S4. The transmitted light in step S2 and the reflected light in step S3 both enter the nitrogen-filled vacuum cavity (10) after reflection, and both coincide with the 800nm ​​pulse in space to form plasma and generate an enhanced 400nm second harmonic. S5. The residual probe light is reflected off the optical baffle (13) by the dichroic mirror (14), and the background light signal of stray light is filtered out by the narrow-band filter (15). S6. The second harmonic signal generated at the plasma is focused and coupled into the fiber optic spectrometer through a 10cm focusing lens (16), and measured using the spectrometer (17).

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