A femtosecond time resolved pump-probe kerr gate measurement device and method

Abstract

The application discloses a femtosecond time-resolved pump-probe Kerr gate measuring device and method, relates to the technical field of ultrafast measurement, and comprises a femtosecond laser. A beam splitter is arranged on a light emitting path of the femtosecond laser, and the beam splitter divides the light output by the laser into two beams of probe light and pump light. The probe light sequentially passes through an optical delay line and a first shutter, converts the fundamental light into supercontinuum white light, and then sequentially passes through a first reflector and a second reflector and is focused into a sample to be measured by a third convex lens. The pump light sequentially passes through a second shutter, a chopper, a third attenuator and a frequency-doubled light pulse generating module, changes the propagation direction by a fourth reflector, a fifth reflector and a half-wave plate, and is focused into the sample to be measured by a tenth convex lens. The switch between a supercontinuum white light generating module and a photoluminescence signal generating module can be realized by a foldable reflector, so that the switch between the two kinds of measurement technologies can be realized quickly and conveniently.

Description

Technical Field

[0001] This invention relates to the field of ultrafast measurement technology, and in particular to a femtosecond time-resolved pump-probe optical Kerr gate measurement device and method. Background Technology

[0002] The design of optoelectronic devices with excellent performance depends on the ultrafast dynamics of the materials. In traditional femtosecond time-resolved transient absorption spectroscopy measurement devices, the probe light is generally supercontinuous white light and the pump light is monochromatic light, which is an important means to study this ultrafast dynamic process.

[0003] Pump-probe optical Kerr gate gating is an ultrafast time-gating technique based on the optical Kerr effect. It requires no phase matching and boasts switching times on the femtosecond scale, making it widely applicable in ultrafast measurement and imaging. However, in traditional optical Kerr gate photoluminescence gating techniques, the inherent extinction ratio of the two polarizers constituting the pump-probe optical Kerr gate causes significant leakage noise when measuring the photoluminescence signal. Furthermore, the generated photoluminescence signal itself exhibits some jitter, resulting in a low signal-to-noise ratio (SNR) for conventional optical Kerr gate measurement devices, limiting their application in measuring long-lived fluorescence signals. Therefore, developing new techniques to further suppress noise and improve the SNR is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a femtosecond time-resolved pump-probe optical Kerr gate measurement device and method. This invention combines femtosecond laser technology, optical Kerr effect and spectral analysis to achieve high-precision measurement of the transient optical properties of materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a femtosecond time-resolved pump-probe optical Kerr gate measurement device, comprising a femtosecond laser;

[0007] A beam splitter is placed in the emission path of the femtosecond laser to split the laser output light into two beams: a probe beam and a pump beam.

[0008] The probe light sequentially passes through an optical delay line and a first shutter. The probe light emitted from the first shutter is reflected by a first foldable mirror and enters a supercontinuum white light generation module, where the fundamental frequency light is converted into supercontinuum white light. The supercontinuum white light then sequentially passes through a first mirror and a second mirror, and is focused onto the sample under test by a third convex lens. An eleventh convex lens and a spectrometer are sequentially placed behind the sample under test. The probe light emitted from the first shutter is also reflected by the third mirror and enters a photoluminescence signal generation module to generate a photoluminescence signal. The generated photoluminescence signal passes through a second foldable mirror, a second mirror, and a first polarizer, and is focused onto an optical Kerr medium by a third convex lens. An eleventh convex lens, a second polarizer, and a spectrometer are sequentially placed behind the optical Kerr medium, where the polarization directions of the first polarizer and the second polarizer are orthogonal to each other.

[0009] The pump light passes sequentially through the second shutter, chopper, third attenuator, and frequency doubling light pulse generation module, then its propagation direction is changed by the fourth mirror, fifth mirror, and half-wave plate, and finally focused into the sample under test by the tenth convex lens.

[0010] As a further improvement of the present invention, the supercontinuous white light generating module includes: a first attenuator, a first convex lens, a transparent medium, a second convex lens, and a first filter arranged in sequence.

[0011] As a further improvement of the present invention, the photoluminescence generating module includes: a second attenuator, a fourth convex lens, a first frequency doubling crystal, a fifth convex lens, a second filter, a sixth convex lens, a fluorescent sample, a seventh convex lens, and a third filter arranged in sequence.

[0012] As a further improvement of the present invention, the frequency doubling optical pulse generation module includes: an eighth convex lens, a second frequency doubling crystal, a ninth convex lens, and a fourth filter arranged in sequence.

[0013] As a further improvement of the present invention, it also includes a computer, which is connected to the first shutter, the second shutter, the chopper, the optical delay line, and the spectrometer, respectively, and processes the detection data of the spectrometer through the computer's host computer software.

[0014] As a further improvement of the present invention, the femtosecond laser is a femtosecond laser system containing an amplifier;

[0015] The beam splitter has a beam splitting ratio of T:R = 7:3;

[0016] The first attenuator, the second attenuator, and the third attenuator are neutral attenuators, including variable neutral density attenuators or neutral attenuators with fixed optical density.

[0017] The half-wave plate is a zero-order half-wave plate, and its material is quartz or BK glass.

[0018] As a further improvement of the present invention, the optical delay line includes a step displacement platform and two mutually perpendicular mirrors placed on it, the two mutually perpendicular mirrors reflecting the probe light backward.

[0019] As a further improvement of the present invention, the stepping displacement platform adjusts the optical path of the probe light with an adjustment accuracy of 0.15 to 1.5 μm, and the minimum optical path change of the delay platform is 1 to 10 fs.

[0020] As a further improvement of the present invention, the first frequency doubling crystal and the second frequency doubling crystal are both nonlinear crystals of potassium dihydrogen phosphate, potassium dideuterium phosphate or barium β-borate.

[0021] The transparent medium is a nonlinear medium of sapphire, calcium fluoride, or distilled water;

[0022] Both the first and second polarizers are prism polarizers or have an extinction ratio greater than 10. 4 :1 thin-film polarizer;

[0023] The optical Kerr medium is a third-order nonlinear optical material.

[0024] Secondly, the present invention provides a measurement method using the aforementioned femtosecond time-resolved pump-probe optical Kerr gate measurement device, comprising the following steps:

[0025] The horizontally linearly polarized femtosecond pulsed laser output from the femtosecond laser is split into two beams, a probe beam and a pump beam, by a beam splitter.

[0026] Based on the intensity of the supercontinuous white light transmitted through the sample received by the spectrometer, the opening and closing of the first and second shutters are controlled, the optical delay line is moved, and data is acquired in real time to obtain the transient absorption data of the sample. Based on the intensity of the amplified spontaneous emission signal transmitted through the sample received by the spectrometer, the opening and closing of the first and second shutters are controlled, the optical delay line is moved, and data is acquired in real time to obtain the time-resolved amplified spontaneous emission signal under the Kerr gate gating action of the pump-probe light.

[0027] The present invention has the following beneficial effects:

[0028] This invention proposes a femtosecond time-resolved pump-probe optical Kerr measurement device. Its core lies in combining femtosecond laser technology, the optical Kerr effect, and spectral analysis to achieve high-precision measurement of the transient optical properties of materials. It is compatible with both traditional femtosecond time-resolved transient absorption spectroscopy and pump-probe optical Kerr gate measurement techniques. Furthermore, a foldable mirror allows for switching between a supercontinuous white light generation module and a photoluminescence signal generation module. Combined with a detachable half-wave plate and a detachable polarizer, it enables rapid and convenient switching between the two measurement techniques, facilitating a more comprehensive study of the optical properties of materials.

[0029] Furthermore, this device can achieve a higher signal-to-noise ratio. Compared to traditional optical Kerr gate measurement systems, this invention acquires ambient light by controlling the first and second shutters to be closed; acquires pump light stray light by controlling the first shutter to be open and the second shutter to be closed; and acquires leaked probe light by controlling the first shutter to be closed and the second shutter to be open. These methods suppress ambient light and pump light stray noise. Further, this invention uses a chopper to modulate the pump light repetition frequency to 500Hz, dividing two adjacent signal light pulses into a group, one of which interacts with the pump light and is selected, with its intensity denoted as I. pump-on Another pulse, which does not interact with the pump light, serves as a reference pulse, with an intensity denoted as I. pump-off The information provided by the leaked signal light can be obtained by subtracting the two using the written host computer software, yielding ΔI = I. pump-on -I pump-off This can better suppress the effects caused by the jitter of the signal light itself and improve the signal-to-noise ratio of the measurement signal.

[0030] The measurement method provided by this invention is compatible with both traditional transient absorption spectroscopy and pump-probe optical Kerr gate measurement techniques to achieve the following conditions: adjusting the first and second tilting mirrors enables switching between the supercontinuous white light generation module and the photoluminescence generation module, thus achieving a fast and convenient switch between the two measurement techniques; using a computer to detect the first and second shutter switches, and using a spectrometer to absorb noise such as background light, pump light, and leaked signal light, the repetition frequency of the pump light is modulated to 500Hz using a chopper, and the influence caused by the jitter of the signal light itself is further suppressed by introducing a reference pulse, thereby giving the pump-probe optical Kerr gate measurement device a higher signal-to-noise ratio compared to the traditional optical Kerr measurement device. Attached Figure Description

[0031] Figure 1 A schematic diagram of a femtosecond time-resolved pump-probe optical Kerr gate measurement device provided by the present invention;

[0032] Among them, 1. Femtosecond laser; 2. Beam splitter; 3. Optical delay line; 4. First shutter; 5. First flip-flop mirror; 6. First attenuator; 7. First convex lens; 8. Transparent medium; 9. Second convex lens; 10. First filter; 11. First mirror; 12. Third mirror; 13. Second attenuator; 14. Fourth convex lens; 15. First frequency doubling crystal; 16. Fifth convex lens; 17. Second filter; 18. Sixth convex lens; 19. Fluorescent sample; 20. Seventh convex lens; 21. Third... 21. Filter; 22. Second flip-up mirror; 23. Second mirror; 24. First polarizer; 25. Third convex lens; 26. Optical material; 27. Second shutter; 28. Chopper; 29. ​​Third attenuator; 30. Eighth convex lens; 31. Second frequency doubling crystal; 32. Ninth convex lens; 33. Fourth filter; 34. Fourth mirror; 35. Fifth mirror; 36. Half-wave plate; 37. Tenth convex lens; 38. Eleventh convex lens; 39. Second polarizer; 40. Spectrometer; 41. Computer.

[0033] Figure 2 An optical photograph of the methylamine lead bromide perovskite microsheet used in Example 1;

[0034] Figure 3 The transient absorption (TA) spectra of the methylamine lead bromide perovskite microsheets measured in Example 1 are shown in (a) as a two-dimensional pseudo-color image and (b) as transient absorption spectra at several different delay times.

[0035] Figure 4 (a) shows the transient amplified spontaneous emission (ASE) kinetics curves of the methylamine lead bromide perovskite microsheets measured in Example 1. The inset shows the data fitting for the portion within the dashed box (delay time in the range of 20–48 ps). Figure 4 (b) for Figure 3 The results of comparing the residual values ​​obtained from fitting the inset in (a) are shown. Detailed Implementation

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Comprehensive research on the optical properties of optoelectronic materials typically requires the use of multiple measurement devices, including femtosecond time-resolved transient absorption spectroscopy measurement devices and pump-probe optical Kerr gate measurement devices. However, setting up multiple measurement devices simultaneously is time-consuming, consumes a lot of optical components, and is cumbersome to use. Therefore, designing a measurement device that is compatible with transient absorption spectroscopy measurement technology and pump-probe optical Kerr gate gating measurement technology, can quickly switch between the two measurement technologies, and has a higher signal-to-noise ratio than traditional optical Kerr gate measurement devices is of great significance.

[0038] like Figure 1 As shown, a schematic diagram of a femtosecond time-resolved pump-probe photokere measurement device of the present invention is presented. The device includes a femtosecond laser 1, an optical delay line 3, a first shutter 4, a second shutter 27, a supercontinuum white light generation module I, a photoluminescence signal generation module II, a chopper 28, a frequency doubling light pulse generation module III, a polarizer 24, 39, a half-wave plate 36, a spectrometer 40, and a computer 41.

[0039] A beam splitter 2 is installed in the emission optical path of the femtosecond laser 1. The beam splitter 2 splits the optical path into a probe beam and a pump beam. The probe beam passes sequentially through an optical delay line 3 and a first shutter 4. The probe beam emitted from the first shutter 4 can be reflected by a first reversible mirror 5 and enter the supercontinuum white light generation module I, where the fundamental frequency light is converted into supercontinuum white light. The supercontinuum white light then passes sequentially through a first mirror 11 and a second mirror 23, and is focused into an optical material 26 by a third convex lens 25. An eleventh convex lens is then sequentially installed after the optical material 26. 38. Spectrometer 40; The probe light emitted through the first shutter 4 can also be reflected by the third reflector 12 into the photoluminescence signal generation module II to generate a photoluminescence signal. The generated photoluminescence signal passes through the second flip-flop reflector 22, the second reflector 23, the first polarizer 24, and is focused into the optical material 26 by the third convex lens 25. The eleventh convex lens 38, the second polarizer 39, and the spectrometer 40 are sequentially arranged after the optical material 26. The polarization directions of the first polarizer 24 and the second polarizer 39 are orthogonal to each other.

[0040] Traditional femtosecond time-resolved transient absorption spectroscopy measurement technology: Supercontinuous white light emitted from the first shutter 4 illuminates the front of the first flip-out mirror 5 and enters the supercontinuous white light generation module I.

[0041] The pump light passes through the second shutter 27, chopper 28, and third attenuator 29. The pump light emitted from the third attenuator 29 passes through the fourth mirror 34 and the fifth mirror 35 in sequence, and is focused into the sample 26 under test by the tenth convex lens 37. The pump light emitted from the third attenuator 29 can also enter the frequency doubling light pulse generation module III to convert the 800nm ​​fundamental frequency light into 400nm frequency doubling light. The pump light is used to excite the sample and spatially coincides with the supercontinuum white light in the sample under test. The optical delay line 3 is adjusted so that the optical path of the supercontinuum white light and the pump light are the same. The supercontinuum white light passing through the sample is focused by the eleventh convex lens 38 and enters the spectrometer for detection.

[0042] Based on the intensity of the supercontinuous white light transmitted through the sample 26 to be tested received by the spectrometer 40, the computer 41 controls the opening and closing of the shutters 4 and 27, the computer 41 controls the chopper 28 to modulate the repetition frequency of the pump light to 500Hz, the computer 41 controls the movement of the optical delay line 3 by a precision stepping platform, and the computer collects data in real time to obtain the transient absorption data of the methylamine lead bromide perovskite microsheet.

[0043] Pump-probe optical Kerr gate measurement technology: The probe light emitted from the first shutter 4 passes through the third reflector 12 and enters the photoluminescence generation module II to generate a photoluminescence signal. The generated photoluminescence signal illuminates the front of the second tilting reflector 22, and then passes through the second reflector 23. The second tilting reflector 22 and the reflector 23 are adjusted so that the propagation direction of the photoluminescence signal is consistent with the propagation direction of the supercontinuum white light. The generated photoluminescence signal then passes through the first polarizing polarizer 24 and the third convex lens 25 and is focused into the optical Kerr medium 26. After the pump light passes through the third attenuator 29, it passes sequentially through the fourth reflector 34, the fifth reflector 35, the half-wave plate 36, and the tenth convex lens 37 and is focused into the optical Kerr medium 26. In medium 26, an eleventh convex lens 38 and a second polarizer 39 are sequentially arranged after the photoker medium 26. The polarization directions of the two polarizers are orthogonal to each other. After passing through the third attenuator 29, the pump light passes through the fourth reflector 34, the fifth reflector 35, and the 800nm ​​half-wave plate 36 in sequence. The half-wave plate 36 is used to change the polarization direction of the pump light so that it forms a 45° angle with the polarization direction of the photoluminescence signal. The pump light is then focused in the photoker medium 26 by the tenth convex lens 37 and spatially coincides with the signal light in the photoker medium 26. By adjusting the optical delay line 3, the optical path of the photoluminescence signal is made the same as that of the pump light. The signal light can enter the spectrometer 40 through the second polarizer 39 and be detected.

[0044] Light source and beam splitting:

[0045] A femtosecond laser is used as the light source, and a beam splitter separates the laser into two paths: a pump beam and a probe beam. An optical delay line is placed on the probe beam path to adjust the time delay between the probe beam and the pump beam.

[0046] Multi-mode applications of probe light:

[0047] The probe light can be selectively directed to the supercontinuous white light generation module or the photoluminescence signal generation module by controlling the first shutter.

[0048] Supercontinuous white light mode: used for traditional transient absorption spectroscopy measurements, the probe light is converted into supercontinuous white light and focused into the sample, and the changes in transmitted light intensity are analyzed by a spectrometer.

[0049] Photoluminescence signal mode: used for photokergating measurements, the probe light is first converted into a photoluminescence signal, then focused into the photokergating medium, and interacts with the pump light through a polarizer.

[0050] Pump light processing:

[0051] Pump light passes through components such as shutter, chopper, and attenuator to control its intensity, frequency, and polarization state.

[0052] It can selectively enter the frequency doubling light pulse generation module to convert the fundamental frequency light into frequency doubling light for specific excitation needs.

[0053] Focused onto the sample or photoker medium, it coincides with the probe light supercontinuous white light or photoluminescence signal in time and space.

[0054] Measurement of the optical Kerr effect:

[0055] In the optical Kerr measurement mode, the pump light and the photoluminescence signal interact in the optical Kerr medium. By changing the polarization direction of the pump light using a half-wave plate, the polarization direction of the pump light is made to form a certain angle with the polarization direction of the signal light, such as 45°.

[0056] After the interaction, the polarization state of the signal light changes. After passing through the orthogonal polarizer, only light with a specific polarization state can pass through and enter the spectrometer for detection.

[0057] By adjusting the optical delay line, the pump light and signal light can have the same optical path, thus achieving time-resolved measurement.

[0058] Data acquisition and analysis: Automated measurement is achieved by using computer-controlled components such as the shutter, chopper, and stepper platform. Spectrometer data is acquired in real time and processed by the computer to obtain the transient absorption spectrum or photoKerr effect data of the sample.

[0059] This device achieves high-precision, multi-mode measurement of the transient optical properties of materials by flexibly configuring the optical paths of the probe light and pump light, and combining supercontinuous white light generation, photoluminescence signal generation and photoKerr effect measurement techniques.

[0060] This invention integrates traditional femtosecond time-resolved transient absorption spectroscopy and pump-probe optical Kerr gate measurement techniques. A flip-flop mirror enables switching between the supercontinuous white light generation module and the photoluminescence signal generation module, allowing for rapid and convenient switching between the two measurement techniques. This facilitates a more comprehensive study of the optical properties of materials. Furthermore, the introduction of a reference pulse further suppresses the effects of signal light jitter, resulting in a higher signal-to-noise ratio for the pump-probe optical Kerr gate measurement device compared to traditional optical Kerr gate measurement devices.

[0061] As a specific embodiment, the supercontinuous white light generating module I includes: a first attenuator 6, a first convex lens 7, a transparent medium 8, a second convex lens 9, and a first filter 10 arranged sequentially; the supercontinuous white light generating module I comprises:

[0062] First attenuator 6: Used to adjust the intensity of incident light to prevent subsequent components from being damaged by excessive light intensity.

[0063] First convex lens 7: Focuses the incident light, enabling it to be better coupled into the transparent medium.

[0064] Transparent medium 8: Typically a nonlinear optical medium, such as optical fiber or certain crystals. When a high-intensity laser pulse passes through, it produces nonlinear effects, such as self-phase modulation and four-wave mixing, thereby broadening the spectrum and producing supercontinuous white light.

[0065] Second convex lens 9: Collects and focuses supercontinuous white light emitted from the transparent medium.

[0066] First filter 10: Used to filter out unwanted wavelength components and further purify the supercontinuous white light.

[0067] This module utilizes the nonlinear effect of high-intensity laser pulses in a nonlinear medium to generate broadband supercontinuous white light. This type of white light source has wide applications in spectroscopy, optical measurement, and other fields.

[0068] The photoluminescence generating module II includes: a second attenuator 13, a fourth convex lens 14, a first frequency doubling crystal 15, a fifth convex lens 16, a second filter 17, a sixth convex lens 18, a fluorescent sample 19, a seventh convex lens 20, and a third filter 21 arranged sequentially; the photoluminescence generating module II is composed of:

[0069] Second attenuator 13: Also used to adjust the intensity of incident light.

[0070] Fourth convex lens 14: focuses the incident light onto the first frequency doubling crystal.

[0071] First frequency doubling crystal 15: Doubles the frequency of incident light to produce frequency-doubled light.

[0072] Fifth convex lens 16: Collects and focuses frequency-doubled light.

[0073] Second filter 17: Filters out stray light in the frequency-doubled light.

[0074] The sixth convex lens 18 focuses the frequency-doubled light onto the fluorescent sample 19, exciting it to emit light.

[0075] Fluorescent sample 19: emits fluorescence at a specific wavelength when excited by frequency-doubled light.

[0076] Seventh convex lens 20: collects and focuses fluorescence.

[0077] Third filter 21: Filters out stray light in fluorescence and purifies the fluorescence signal.

[0078] This module generates frequency-doubled light using a frequency-doubled crystal, and then uses the frequency-doubled light to excite the fluorescent sample to emit light. This method is commonly used in fields such as fluorescence spectroscopy analysis and biolabeling.

[0079] The frequency-doubled optical pulse generating module III includes: an eighth convex lens 30, a second frequency-doubled crystal 31, a ninth convex lens 32, and a fourth filter 33 arranged sequentially; the frequency-doubled optical pulse generating module III is composed of:

[0080] Eighth convex lens 30: focuses the incident light onto the second frequency-doubled crystal.

[0081] Second frequency doubling crystal 31: doubles the frequency of the incident light again to generate a higher frequency light pulse.

[0082] Ninth convex lens 32: collects and focuses the frequency-doubled light pulse.

[0083] Fourth filter 33: Filters out stray light in the frequency-doubled light pulse.

[0084] This module uses a frequency-doubling crystal to double the frequency of incident light, generating higher-frequency light pulses. These high-frequency light pulses have important applications in fields such as nonlinear optics and ultrafast optics.

[0085] Based on the time-resolved amplified spontaneous emission signal received by the spectrometer 40, the computer 41 controls the opening and closing of shutters 4 and 27, the computer 41 controls the chopper 28 to modulate the repetition frequency of the pump light to 500Hz, the computer 41 controls the movement of the optical delay line 3 by a precision stepping platform, and data is collected in real time to obtain the time-resolved amplified spontaneous emission signal under the Kerr gate gating of the pump-probe light.

[0086] Optionally, the femtosecond laser is a femtosecond laser system containing an amplifier. As a preferred embodiment, the beam splitter has a splitting ratio of T:R = 7:3.

[0087] The first, second, and third attenuators are neutral attenuators, including variable neutral density attenuators or fixed optical density neutral attenuators. The 800nm ​​half-wave plate 36 is a zero-order half-wave plate, made of quartz or BK glass.

[0088] The computer 41 is connected to the first shutter 4, the second shutter 27, the chopper 28, the optical delay line 3, and the spectrometer 40, respectively, and is used to control the first shutter 4, the second shutter 27, the chopper 28, and the optical delay line 3, and to process the detection data of the spectrometer 40 through the upper computer software written by the computer.

[0089] Optionally, the time delay platform consists of a computer-controlled precision stepping displacement platform and two mutually perpendicular reflectors placed on it. The two mutually perpendicular reflectors reflect the probe light backward. The precision stepping displacement platform adjusts the optical path of the probe light with an adjustment accuracy of 0.15 to 1.5 μm, and the minimum optical path change of the delay platform is 1 to 10 fs.

[0090] Optionally, the supercontinuous white light generating module I includes: a first attenuator, a first convex lens, a transparent medium, a second convex lens, and a first filter arranged sequentially; wherein the transparent medium is a nonlinear medium of sapphire Al2O3, calcium fluoride CaF2, or distilled water H2O.

[0091] Optionally, the photoluminescence generating module II includes: a second attenuator, a fourth convex lens, a first frequency doubling crystal, a fifth convex lens, a second filter, a sixth convex lens, a fluorescent sample, a seventh convex lens, and a third filter arranged sequentially; wherein the fluorescent sample includes perovskite microsheet material or fluorescent quantum dot material.

[0092] Further optionally, the frequency doubling optical pulse generation module III includes: an eighth convex lens, a second frequency doubling crystal, a ninth convex lens, and a fourth filter arranged sequentially; wherein the frequency doubling crystal is a nonlinear crystal such as potassium dihydrogen phosphate (KDP), potassium dideuterium phosphate (DKDP), or barium β-borate (BBO).

[0093] Alternatively, the half-wave plate is a zero-order half-wave plate, and its material is fused silica or BK glass.

[0094] Further optionally, the polarizer is a prism polarizer or a micron-plate polarizer, wherein the prism polarizer is a Glan-Taylor prism polarizer, a Glan-Thompson prism, or a Nicol prism polarizer.

[0095] The optical material is either a photoker medium or the sample to be tested. The photoker medium is a third-order nonlinear optical material, including non-fully electronically responsive photoker media such as carbon disulfide, nitrobenzene, carbon tetrachloride, or benzene. The sample to be tested is a solid or solution, including semiconductor samples such as photovoltaic materials, organic optoelectronic materials, two-dimensional materials and their heterojunctions, and photocatalytic materials.

[0096] The computer is connected to the first shutter, the second shutter, the chopper, the optical delay line, and the spectrometer, respectively, and is used to control the first and second shutters, the chopper, and the optical delay line, and to process the detection results of the spectrometer through upper computer software written by the computer.

[0097] The preferred parameters of the femtosecond time-resolved pump-probe optical Kerr gate measurement device of the present invention are as follows:

[0098] The femtosecond laser output has a single-pulse energy of 3 mJ, a center wavelength of 800 nm, a pulse width of 60 fs, and a repetition frequency of 1 kHz. The beam splitter has a splitting ratio of T:R = 7:3, and the intensity of each beam is adjusted by three attenuators. The focal lengths of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, and eleventh convex lenses are 2.5 cm, 5 cm, 10 cm, 10 cm, 10 cm, 10 cm, 10 cm, 10 cm, 10 cm, 15 cm, and 5 cm, respectively. The two frequency doubling crystals used are 1 mm thick BBO crystals. The two polarizers are Glan-Taylor prisms. The transparent medium used is a 5 mm thick sapphire sheet. The fluorescent sample used is a methylamine lead bromide perovskite microsheet. The photoker medium used is carbon disulfide, and the sample to be tested is a methylamine lead bromide perovskite microsheet.

[0099] The optical delay line 3 is composed of a precision stepping displacement platform controlled by the computer 41 and two mutually perpendicular reflectors placed on it. The two mutually perpendicular reflectors reflect the probe light backward. The precision stepping displacement platform adjusts the optical path of the probe light with an adjustment accuracy of 0.15 to 1.5 μm. The minimum optical path change of the delay platform is 1 to 10 fs.

[0100] The first frequency doubling crystal 15 and the second frequency doubling crystal 31 are nonlinear crystals of potassium dihydrogen phosphate (KDP), potassium dideuterium phosphate (DKDP), or barium β-borate (BBO). The transparent medium 8 is a nonlinear medium of sapphire (Al2O3), calcium fluoride (CaF2), or distilled water (H2O).

[0101] Both the first polarizer 24 and the second polarizer 39 are prism polarizers or have an extinction ratio greater than 10. 4Thin-film polarizers of type 1; wherein the prism polarizers include Glan-Taylor prism polarizers, Glan-Thompson prisms, or Nicol prism polarizers.

[0102] The photoker medium 26 used is a third-order nonlinear optical material. The photoker medium includes non-fully electronically responsive photoker media such as carbon disulfide, nitrobenzene, carbon tetrachloride, or benzene.

[0103] The present invention also provides a measurement method for a femtosecond time-resolved pump-probe optical Kerr gate measurement device, comprising the following steps:

[0104] S1 splits the horizontally linearly polarized femtosecond pulsed laser output from femtosecond laser 1 into two beams, probe and pump, via beam splitter 2.

[0105] The S2 probe light passes through the optical delay line 3 and the first shutter 4. The probe light emitted from the first shutter 4 can be reflected by the first flip-flop mirror 5 and enter the supercontinuous white light generation module I, converting the fundamental frequency light into supercontinuous white light. The supercontinuous white light then passes through the first mirror 11 and the second mirror 23 in sequence, and is focused into the sample 26 under test by the third convex lens 25. After the sample 26 under test, the eleventh convex lens 38 and the spectrometer 40 are arranged in sequence. The probe light emitted from the first shutter 4 can also be reflected by the third mirror 12 and enter the photoluminescence signal generation module II to generate a photoluminescence signal. The generated photoluminescence signal passes through the second flip-flop mirror 22, the second mirror 23, the first polarizer 24, and is focused into the photoker medium 26 by the third convex lens 25. After the photoker medium 26, the eleventh convex lens 38, the second polarizer 39, and the spectrometer 40 are arranged in sequence, wherein the polarization directions of the first polarizer 24 and the second polarizer 39 are orthogonal to each other.

[0106] S3's traditional femtosecond time-resolved transient absorption spectroscopy measurement technology: Supercontinuum white light emitted from the first shutter 4 illuminates the front of the first flip-flop mirror 5 and enters the supercontinuum white light generation module I; the pump light passes through the second shutter 27, chopper 28, and third attenuator 29, and the pump light emitted from the third attenuator 29 passes sequentially through the fourth mirror 34 and the fifth mirror 35, and is focused by the tenth convex lens 37 into the sample 26 to be tested; the pump light emitted from the third attenuator 29 can also enter the frequency doubling light pulse generation module III to convert the 800nm ​​fundamental frequency light into 400nm frequency doubling light. The pump light is used to excite the sample and spatially coincides with the supercontinuum white light in the sample. The optical delay line 3 is adjusted so that the optical path of the supercontinuum white light and the pump light are the same. The supercontinuum white light passing through the sample is focused by the eleventh convex lens 38 and enters the spectrometer for detection.

[0107] S4 uses the intensity of the supercontinuous white light transmitted through the sample 26 to be tested, received by the spectrometer 40, and uses the computer 41 to control the opening and closing of the first shutter 4 and the second shutter 27. The computer 41 controls the chopper 28 to modulate the repetition frequency of the pump light to 500Hz. The computer 41 controls the movement of the optical delay line 3 by a precision stepping platform, and collects data in real time to obtain the transient absorption data of the sample to be tested.

[0108] S5 Pump-Probe Kerr Gate Measurement Technology: The probe light emitted from the first shutter 4 enters the photoluminescence signal production module II via the third reflector 12; the pump light emitted from the third attenuator 29 passes sequentially through the fourth reflector 34, the fifth reflector 35, and the half-wave plate 36, and is focused by the tenth convex lens 37 into the photokel medium 26, where it spatially coincides with the photoluminescence signal. The optical delay line 3 is adjusted so that the optical path of the photoluminescence signal is the same as that of the pump light, and then the photoluminescence signal enters the spectrometer for detection via the second polarizer 39.

[0109] S6 receives the time-resolved amplified spontaneous emission signal from the spectrometer 40, controls the opening and closing of the first shutter 4 and the second shutter 27 using the computer 41, modulates the repetition frequency of the pump light to 500Hz using the chopper 28 using the computer 41, controls the movement of the optical delay line 3 using a precision stepping platform controlled by the computer 41, and collects data in real time to obtain the time-resolved amplified spontaneous emission signal under the Kerr gate gating of the pump-probe light.

[0110] To make the above-mentioned objectives and advantages of the present invention more apparent and understandable, the following examples illustrate the method of a femtosecond time-resolved pump-probe optical Kerr gate measurement device according to the present invention.

[0111] Combination Figure 1 In this embodiment, lead methylamine bromide perovskite microsheets are used as the fluorescent sample, carbon disulfide as the photoker medium, and lead methylamine bromide perovskite microsheets as the test sample. An optical photograph of the lead methylamine bromide perovskite microsheets is shown below. Figure 2 As shown. The specific implementation steps are as follows:

[0112] 1) The femtosecond pulsed laser output by the laser has a single pulse energy of 3mJ, a pulse width of 60fs, a repetition frequency of 1kHz, and a horizontal polarization direction. It is split into two beams by a beam splitter with a splitting ratio of T:R = 7:3. One beam is the probe beam and the other is the pump beam.

[0113] 2) The probe light passes sequentially through the optical delay line 3 and the first shutter 4. The probe light emitted from the first shutter 4 can be reflected by the first flip-flop mirror 5 and enter the supercontinuum white light generation module I, converting the fundamental frequency light into supercontinuum white light. The supercontinuum white light then passes sequentially through the first mirror 11 and the second mirror 23, and is focused into the optical material 26 by the third convex lens 25. After the optical material 26, the eleventh convex lens 38 and the spectrometer 40 are sequentially arranged. The probe light emitted from the first shutter 4 can also be reflected by the third mirror 12 and enter the photoluminescence signal generation module II to generate an amplified spontaneous emission (ASE) signal. The generated photoluminescence signal passes through the second flip-flop mirror 22, the second mirror 23, the first polarizer 24, and is focused into the optical material 26 by the third convex lens 25. After the optical material 26, the eleventh convex lens 38, the second polarizer 39, and the spectrometer 40 are sequentially arranged. The polarization directions of the first polarizer 24 and the second polarizer 39 are orthogonal to each other.

[0114] 3) Traditional femtosecond time-resolved transient absorption spectroscopy measurement technology: The supercontinuum white light emitted from the first shutter 4 illuminates the front of the first flip-flop mirror 5 and enters the supercontinuum white light generation module I; the pump light passes through the second shutter 27, chopper 28, and third attenuator 29, and the pump light emitted from the third attenuator 29 enters the frequency doubling light pulse generation module III to convert the 800nm ​​fundamental frequency light into 400nm frequency doubling light, which is used to excite the methylamine lead bromide perovskite microsheet and spatially coincides with the supercontinuum white light in the sample. The optical delay line 3 is adjusted so that the optical path of the supercontinuum white light and the pump light are the same. The supercontinuum white light passing through the sample is focused by the eleventh convex lens 38 and enters the spectrometer for detection.

[0115] 4) Based on the intensity of the supercontinuous white light received by the spectrometer 40 through the sample 26, the computer 41 controls the opening and closing of the shutters 4 and 27, the computer 41 controls the chopper 28 to modulate the repetition frequency of the pump light to 500Hz, the computer 41 controls the movement of the optical delay line 3 by the precision stepping platform, and the computer collects data in real time to obtain the transient absorption data of the methylamine lead bromide perovskite microsheet.

[0116] 5) Pump-probe optical Kerr gate measurement technology: The probe light emitted from the first shutter 4 enters the photoluminescence signal production module II via the third reflector 12; the pump light emitted from the third attenuator 29 passes sequentially through the fourth reflector 34, the fifth reflector 35, and the half-wave plate 36, and is focused into the optical Kerr medium 26 by the tenth convex lens 37, and spatially coincides with the photoluminescence signal in the optical Kerr medium 26. The 800nm ​​half-wave plate is adjusted so that the polarization direction of the pump light is at a 45° angle with the polarization direction of the photoluminescence signal. The optical delay line 3 is adjusted so that the optical path of the photoluminescence signal is the same as that of the pump light. Then the photoluminescence signal enters the spectrometer for detection through the second polarizer 39.

[0117] 6) Based on the time-resolved amplified spontaneous emission signal received by the spectrometer 40, the computer 41 controls the opening and closing of shutters 4 and 27, the computer 41 controls the chopper 28 to modulate the repetition frequency of the pump light to 500Hz, the computer 41 controls the movement of the optical delay line 3 by a precision stepping platform, and data is collected in real time to obtain the time-resolved amplified spontaneous emission signal under the Kerr gate gating of the pump-probe light.

[0118] Figure 3 a is a two-dimensional pseudo-color image of the transient absorption spectrum of methylamine lead bromide perovskite microsheets, measured using the conventional femtosecond time-resolved transient absorption spectroscopy measurement technique of this invention. Figure 3 b represents the transient absorption spectra at several different delay times, which are typical transient absorption spectra of methylamine lead bromide perovskite microsheets.

[0119] Figure 4 Figure a shows the dynamic results of the time-resolved spontaneous emission signal of a methylamine lead bromide perovskite microsheet measured using the pump-probe Kerr gate measurement technique of this invention. It can be seen that the signal-to-noise ratio (SNR) of the signal measured by introducing a reference pulse is significantly higher than that measured without a reference pulse. Data fitting was performed on the particularly significant delay times in the 20–48 ps range, and the results are shown in the inset of the figure. Figure 4 b is correct. Figure 4 The results of comparing the residual values ​​obtained from the fitting in the illustration in Figure a are as follows. The residual value is the error between the fitted value and the true value, reflecting the magnitude of the fitting error. The data fitting residual value of the signal measured with the reference pulse is approximately 10 times that of the data measured without the reference pulse.

[0120] The specific embodiments described above are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes, alterations, improvements, etc., made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A femtosecond time-resolved pump-probe Kerr gate measurement apparatus, characterized by, Including femtosecond laser (1); The beam splitter (2) is arranged on the light path of the femtosecond laser (1), and the beam splitter (2) divides the light output by the laser (1) into two beams of light, namely probe light and pump light; The probe light passes through the optical delay line (3) and the first shutter (4) in sequence, the probe light emitted from the first shutter (4) is reflected by the first foldable mirror (5) into the supercontinuum white light generation module (I), the fundamental light is converted into supercontinuum white light, the supercontinuum white light passes through the first mirror (11) and the second mirror (23) in sequence, and is focused into the optical Kerr medium (26) by the third convex lens (25), and the optical Kerr medium (26) is provided with the eleventh convex lens (38) and the spectrometer (40) in sequence; the probe light emitted from the first shutter (4) is also reflected into the photoluminescence signal generation module (II) by the third mirror (12) to generate a photoluminescence signal, the generated photoluminescence signal passes through the second foldable mirror (22), the second mirror (23) and the first polarizer (24), and is focused into the optical Kerr medium (26) by the third convex lens (25), and the optical Kerr medium (26) is provided with the eleventh convex lens (38), the second polarizer (39) and the spectrometer (40) in sequence, wherein the polarization directions of the first polarizer (24) and the second polarizer (39) are orthogonal to each other; The pump light passes through the second shutter (27), the chopper (28) and the third attenuator (29) in sequence, and then changes the propagation direction by the fourth mirror (34), the fifth mirror (35) and the half-wave plate (36), and is focused into the optical Kerr medium (26) by the tenth convex lens (37).

2. The apparatus according to claim 1, wherein the apparatus is characterized by: The supercontinuum white light generation module (I) comprises a first attenuator (6), a first convex lens (7), a transparent medium (8), a second convex lens (9) and a first filter (10) arranged in sequence.

3. The femtosecond time resolved pump-probe Kerr gate measurement device according to claim 2, wherein, The photoluminescence signal generation module (II) comprises a second attenuator (13), a fourth convex lens (14), a first frequency doubling crystal (15), a fifth convex lens (16), a second filter (17), a sixth convex lens (18), a fluorescent sample (19), a seventh convex lens (20) and a third filter (21) arranged in sequence.

4. The femtosecond time resolved pump-probe Kerr gate measurement device according to claim 3, wherein, The frequency-doubled light pulse generation module (III) comprises an eighth convex lens (30), a second frequency doubling crystal (31), a ninth convex lens (32) and a fourth filter (33) arranged in sequence.

5. The femtosecond time-resolved pump-probe Kerr gate measurement device according to any one of claims 1 to 4, characterized in that: Further comprising a computer (41), the computer (41) is connected with the first shutter (4), the second shutter (27), the chopper (28), the optical delay line (3) and the spectrometer (40) respectively, and the detection data of the spectrometer (40) is processed by the upper computer software of the computer (41).

6. The apparatus of claim 3, wherein the apparatus is a femtosecond time resolved pump-probe Kerr gate measurement apparatus. The femtosecond laser (1) is a femtosecond laser system containing an amplifier; The splitting ratio of the beam splitter (2) is T:R=7:3; The first attenuator (6), the second attenuator (13) and the third attenuator (29) are neutral attenuators, including variable neutral density attenuators or fixed optical density neutral attenuators. The half-wave plate (36) is a zero-order half-wave plate, and the material is quartz or BK glass.

7. The apparatus of claim 1, wherein the apparatus is a femtosecond time resolved pump-probe Kerr gate measurement apparatus. The optical delay line (3) comprises a step displacement platform and two mutually perpendicular mirrors placed thereon, and the two mutually perpendicular mirrors perform backward reflection on the probe light.

8. The apparatus of claim 7, wherein the apparatus is configured to measure a femtosecond time resolved pump-probe Kerr gate. The step displacement platform adjusts the optical path of the probe light, and the adjustment precision is 0.15-1.5 μm, and the minimum optical path change of the delay platform is 1-10 fs.

9. The apparatus of claim 4, wherein the apparatus is a femtosecond time resolved pump-probe Kerr gate measurement apparatus. The first frequency-doubling crystal (15) and the second frequency-doubling crystal (31) are both nonlinear crystals of potassium dihydrogen phosphate, potassium di-deuterium phosphate or beta-barium borate. The transparent medium (8) is a nonlinear medium of white sapphire, calcium fluoride or distilled water. The first polarizer (24) and the second polarizer (39) are each a prismatic polarizer or a thin film polarizer having an extinction ratio greater than 10 4 :

1. The optical Kerr medium (26) is a third-order nonlinear optical material. 10.A measurement method, using the femtosecond time-resolved pump-probe Kerr gate measurement device according to any one of claims 1 to 9, comprising the following steps: The horizontally polarized femtosecond pulse laser output by the femtosecond laser (1) is divided into probe light and pump light by the beam splitter (2); According to the intensity of the supercontinuum white light received by the spectrometer (40) and transmitted through the optical Kerr medium (26), the opening and closing of the first shutter (4) and the second shutter (27) are controlled, the movement of the optical delay line (3) is controlled, and the data is collected in real time, so that the transient absorption data of the optical Kerr medium (26) are obtained, and then the time-resolved amplified spontaneous emission signal under the pump-probe Kerr gate gating is obtained.

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