A high-throughput nanosecond transient absorption spectroscopy measurement system and method

Abstract

The present application relates to the field of sample optical detection, in particular to a high-throughput nanosecond transient absorption spectrum measurement system and method. It comprises a wide-spectrum continuous light source system, a nanosecond pulse laser light source system, a measured sample, a diaphragm, a wedge spectral interferometer, a photomultiplier tube and a digital oscilloscope. The wide-spectrum continuous light source system emits a probe light beam, which intersects with a pump light beam emitted by the nanosecond pulse laser light source system at the measured sample. The probe light beam passes through the measured sample and is sequentially provided with the diaphragm, the wedge spectral interferometer and the photomultiplier tube in its light path. The digital oscilloscope is connected to the nanosecond pulse laser light source system and the photomultiplier tube respectively. The present application uses a frequency domain measurement method combined with a digital oscilloscope to realize the measurement of the nanosecond transient absorption spectrum of the measured sample through Fourier transform.

Description

Technical Field

[0001] This invention relates to the field of sample optical detection, specifically a high-throughput nanosecond transient absorption spectroscopy measurement system and method. Background Technology

[0002] Transient absorption spectroscopy is a pump-probe technique for ultrafast lasers and a powerful tool for studying the relaxation processes of excited states in processes such as luminescence or nonradiative recombination. Nanosecond transient absorption spectroscopy detects these relaxation processes at the nanosecond scale and can effectively record reaction intermediates such as triplet states and free radicals.

[0003] When measuring nanosecond transient absorption spectra using pump-probe technology, high-power lasers with wavelength broadening are typically used as the probe light source, and high-repetition-rate nanosecond lasers are used as the excitation light source. The probe light emitted from the probe light source is transmitted through the sample under test and then subjected to spectral detection by diffraction. This method has high requirements for the light source, and the use of diffraction results in a low intensity of the probe light received by the spectral detection device. The measurement noise caused by light intensity fluctuations has a significant impact on the system measurement results, resulting in a low signal-to-noise ratio for the system's spectral measurement. Summary of the Invention

[0004] The purpose of this invention is to provide a high-throughput nanosecond transient absorption spectroscopy measurement system and method. This system utilizes frequency domain measurement techniques combined with a digital oscilloscope to measure the nanosecond transient absorption spectrum of the sample under test through Fourier transform. To address the problems of high light source requirements and low signal-to-noise ratio in traditional measurement methods, this system uses a digital oscilloscope to acquire the frequency information of the probe light transmitted through the sample under test, and obtains the transient absorption spectrum information through Fourier transform.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A high-throughput nanosecond transient absorption spectroscopy measurement system includes: a broadband continuous light source system, a nanosecond pulsed laser light source system, a sample under test, an aperture, a wedge spectral interferometer, a photomultiplier tube, and a digital oscilloscope, wherein;

[0007] The probe beam emitted by the broadband continuous light source system intersects with the pump beam emitted by the nanosecond pulsed laser light source system at the point where the sample to be tested is placed. After the probe beam passes through the sample to be tested, an aperture, a wedge spectral interferometer, and a photomultiplier tube are sequentially arranged in its optical path. The digital oscilloscope is connected to the nanosecond pulsed laser light source system and the photomultiplier tube respectively.

[0008] The broadband continuous light source system includes a broadband continuous light source and a reflector, a reflector, and a focusing lens, which are disposed on the optical path of the probe beam emitted by the light source. The probe beam is focused onto the sample to be tested by the focusing lens.

[0009] The nanosecond pulsed laser source system includes: a nanosecond pulsed laser source, a beam splitter disposed on the optical path of the pump beam emitted by the source, and a chopper, a third mirror, a fourth mirror, a second focusing mirror, and a photodiode disposed on the optical path of the beam splitter in sequence on the transmission optical path of the beam splitter. The pump beam is focused on the sample under test by the second focusing mirror, and the photodiode is connected to a digital oscilloscope.

[0010] It also includes a chopper controller, through which the digital oscilloscope is connected to the chopper.

[0011] The external trigger channel of the digital oscilloscope is connected to a photodiode, channel one of the digital oscilloscope is connected to a chopper via a chopper controller, and channel two of the digital oscilloscope is connected to a photomultiplier tube.

[0012] The optical wedge spectral interferometer includes a movable optical wedge one, a movable optical wedge two, and a movable crystal, which are fixed in sequence on an electric translation stage with a degree of freedom of movement. Gaps are left between the movable optical wedge one and the movable optical wedge two, and between the movable optical wedge two and the movable crystal, as air films.

[0013] A high-throughput nanosecond transient absorption spectroscopy measurement method includes the following steps: a probe beam emitted from a broadband continuous light source is reflected and focused onto the sample under test; a pump beam emitted from a nanosecond pulsed laser source is split into a transmission pump beam and a reflection pump beam by a beam splitter; the reflection pump beam is collected by a photodiode and converted into an electrical signal, which is input to the external trigger channel of a digital oscilloscope; the transmission pump beam is frequency-reduced by a chopper and focused onto the sample under test; the focal point of the frequency-reduced transmission pump beam coincides with that of the probe beam, and the focal spot diameter of the probe beam is larger than that of the frequency-reduced transmission pump beam; the chopper controller outputs a square wave signal with the same frequency as the frequency-reduced transmission pump beam to channel one of the digital oscilloscope; the probe beam transmitted through the sample under test is Fourier transformed by an optical wedge spectral interferometer, detected by a photomultiplier tube, and converted into an electrical signal, which is input to channel two of the digital oscilloscope.

[0014] By adjusting reflectors one, two, three, and four, the focal point of the frequency-reduced transmission pump beam and the probe beam on the sample under test is made to coincide.

[0015] The spectral range of the broadband continuous light source can be extended to the ultraviolet band, the visible band, and the near-infrared band.

[0016] The nanosecond pulsed laser source has a pulse frequency range of 20Hz to 20kHz and a pulse wavelength of any one of 266nm, 355nm, 378nm, 400nm, 532nm, 780nm or 800nm.

[0017] The optical wedge spectral interferometer includes a movable optical wedge one, a movable optical wedge two, and a movable crystal, which are fixed in sequence on an electric translation stage with a degree of freedom of movement. By changing the positions of the movable optical wedge one, the movable optical wedge two, and the movable crystal, the Fourier transform frequency can be changed.

[0018] The present invention has the following beneficial effects and advantages:

[0019] This invention utilizes Fourier transform for transient absorption spectrum acquisition in the frequency domain. Halogen lamps or gas light sources can be used as the detection light source. Simultaneously, a light wedge spectral interferometer is used to achieve transient absorption spectrum acquisition in the frequency domain. This method has low light intensity loss, avoiding the low signal-to-noise ratio problem caused by low light intensity in traditional diffraction spectrometry measurement methods. It improves acquisition accuracy and reduces the system's requirements for the light source. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the optical wedge spectral interferometer of the present invention;

[0022] Figure 3 This is a schematic diagram of the timing control of the present invention;

[0023] Figure 4 This is a schematic diagram of the full-spectrum interference signal of the present invention;

[0024] Among them, 1 is a broadband continuous light source, 2 is reflector one, 3 is reflector two, 4 is focusing lens one, 5 is the sample under test, 6 is an aperture, 7 is an optical wedge interferometer, 8 is a photomultiplier tube, 9 is a nanosecond pulsed laser source, 10 is a beam splitter, 11 is a chopper, 12 is reflector three, 13 is reflector four, 14 is focusing lens two, 15 is a chopper controller, 16 is a photodiode, and 17 is a digital oscilloscope;

[0025] 1701 is the external trigger channel, 1702 is channel one, and 1703 is channel two;

[0026] 701 is the first movable optical wedge, 702 is the second movable optical wedge, and 703 is the movable crystal;

[0027] 801 represents a single signal acquisition point. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0029] A high-throughput nanosecond transient absorption spectroscopy measurement system and method includes a continuous broadband light source, a first reflector, a second reflector, a sample under test, an aperture, a wedge interferometer, a photomultiplier tube, a nanosecond pulsed laser source, a beam splitter, a chopper, a third reflector, a fourth reflector, a chopper controller, a photodiode, and a digital oscilloscope. The continuous broadband light source outputs a probe beam, and the nanosecond pulsed laser source outputs a pump beam. During nanosecond transient absorption spectroscopy measurement of the sample under test, the probe beam emitted from the continuous broadband light source is reflected by the first and second reflectors and then focused by the first focusing lens onto the sample area of ​​the sample under test. The probe beam, after passing through the sample under test, passes through the aperture and enters the wedge interferometer. The probe beam transmitted through the wedge interferometer is converted into an electrical signal by the photomultiplier tube and input to channel two of the digital oscilloscope. The pump beam emitted from the nanosecond pulsed laser source is split by the beam splitter into a transmitted excitation beam and a reflected excitation beam. The intensity of the transmitted excitation beam is greater than that of the reflected excitation beam. The intensity of the excitation beam is increased. The transmitted excitation beam is frequency-reduced by a chopper to half the output frequency of the nanosecond pulsed laser source. After being frequency-reduced by the chopper, the transmitted excitation beam is reflected by mirrors three and four and then focused by focusing mirror two onto the sample area of ​​the sample under test, coinciding with the focal point of the detection beam. The transmitted excitation beam that has passed through the sample under test cannot pass through the aperture of the aperture and is thus cut off. The reflected excitation beam is incident on a photodiode, which converts the optical signal into an electrical signal and inputs it to the external trigger channel of the digital oscilloscope. The chopper controller controls the chopping frequency of the chopper through a pulsed square wave signal, which is simultaneously connected to channel one of the digital oscilloscope. This invention obtains the frequency domain information of the detection beam by adjusting the optical wedge spectral interferometer to change the interference of the detection beam. The nanosecond transient absorption intensity information of the detection beam under different interference conditions is obtained using the digital oscilloscope. Finally, the nanosecond transient absorption spectrum of the sample under test is obtained through Fourier transform.

[0030] The optical wedge spectral interferometer includes a movable optical wedge one, a movable optical wedge two, and a movable crystal. The movable optical wedge one, the movable optical wedge two, and the movable crystal are respectively mounted on an electric translation stage with a degree of freedom of movement. The electric translation stage is controlled by software to change the position of the movable optical wedge one, the movable optical wedge two, and the movable crystal, thereby changing the Fourier transform frequency.

[0031] The spectral range of the broadband continuous light source can be extended to the ultraviolet band, visible band, and near-infrared band according to actual needs.

[0032] The pulse frequency of the nanosecond pulsed laser source can vary from 20Hz to 20kHz, and the pulse wavelength can be selected according to actual needs, such as 266nm, 355nm, 378nm, 400nm, 532nm, 780nm or 800nm.

[0033] like Figure 1 As shown, this invention includes: 1. a broadband continuous light source; 2. a first reflector; 3. a second reflector; 4. a first focusing lens; 5. a sample under test; 6. an aperture; 7. a wedge interferometer; 8. a photomultiplier tube; 9. a nanosecond pulsed laser source; 10. a beam splitter; 11. a chopper; 12. a third reflector; 13. a fourth reflector; 14. a second focusing lens; 15. a chopper controller; 16. a photodiode; and 17. a digital oscilloscope. The broadband continuous light source 1 outputs a probe beam, and the nanosecond pulsed laser source 9 outputs a pump beam. This invention obtains the sample under test... In the nanosecond transient absorption spectrum analysis of sample 5, a signal acquisition step is performed first, followed by a data processing step. In the signal acquisition step, the probe beam output from the broadband continuous light source is reflected by reflectors 2 and 3 and focused by focusing lens 4 onto the sample region of the sample 5. The probe beam transmitted through the sample 5 passes through the aperture of aperture 6 and enters the optical wedge interferometer 7. The optical wedge interferometer 7 performs a Fourier transform on the probe beam. The probe beam transmitted through the optical wedge interferometer is converted into an electrical signal by photomultiplier tube 8. The electrical signal is transmitted through the data connection line. The signal is input to channel 1703 of the digital oscilloscope 17. Simultaneously, the pump beam emitted from the nanosecond pulse laser source 9 is split into a transmitted pump beam and a reflected pump beam by the beam splitter 10. The intensity of the transmitted pump beam is greater than that of the reflected pump beam. The reflected pump beam is converted into an electrical signal by the photodiode 16 and input to the external trigger channel 1701 of the digital oscilloscope. The transmitted pump beam is frequency-reduced by the chopper 11, and the frequency of the frequency-reduced transmitted pump beam is half of the original frequency. The frequency-reduced transmitted pump beam is then reflected by the third reflector 12 and the reflector... After reflection by the fourth projection mirror 13, the beam is focused onto the sample 5 under test by the second focusing mirror 14. The focal position of the frequency-reduced transmission pump beam coincides with the focal position of the detection beam, and the focal spot diameter of the detection beam is larger than the focal spot diameter of the frequency-reduced transmission pump beam. After the frequency-reduced transmission pump beam passes through the sample 5 under test, it is intercepted by the aperture 6. The chopper 11 is controlled by the chopper controller 15 to reduce the frequency of the transmission pump beam. At the same time, the chopper controller 15 provides a square wave signal with the same frequency as the frequency-reduced beam to channel 1702 of the digital oscilloscope.

[0034] like Figure 2As shown, the optical wedge spectral interferometer 7 includes a movable optical wedge 701, a movable optical wedge 702, and a movable crystal 703. The movable optical wedge 701, the movable optical wedge 702, and the movable crystal 703 are respectively fixed on an electric translation stage with a degree of freedom of movement. The electric translation stage can perform continuous scanning or step displacement according to the control program.

[0035] like Figure 3 As shown, photodiode 16 receives and detects the light beam output by nanosecond pulse laser source 9, and converts the optical signal of the detected light beam into an electrical signal. The electrical signal is transmitted to the external trigger channel 1701 of digital oscilloscope 17 via a data transmission line. Digital oscilloscope 17 receives the electrical signal and is triggered by the electrical signal to perform data acquisition. Chopper controller 15 controls the rotation speed of chopper 11. Chopper 11 down-frequencys the transmission pump beam. The frequency of the down-frequency transmission pump beam is half of the transmission pump beam frequency. Chopper controller 15 has an output terminal. The output terminal outputs a square wave signal with a frequency equal to that of the down-frequency transmission pump beam. The pump beams have the same frequency. The output terminal is connected to channel 1702 of the digital oscilloscope 17 via a data transmission line. The square wave signal output from the output terminal is first input to channel 1702 of the digital oscilloscope 17 via the data transmission line. Channel 1702 of the digital oscilloscope 17 is used to distinguish between the pump-on and pump-off processes during the acquisition process. During the signal period of channel 1702 of the digital oscilloscope 17, the photomultiplier tube 8 acquires the probe light signal transmitted through the sample under test 5 and converts the probe light signal transmitted through the sample under test 5 into an electrical signal, which is then input to channel 1703 of the digital oscilloscope 17.

[0036] like Figure 4 As shown, 801 is the signal point acquired in a single sampling, and the signal is... Figure 3 The photomultiplier tube 8 receives signals at fixed time points within a collection cycle provided by the chopper controller 15. The motorized translation stage in the optical wedge interferometer 7 is controlled by software, which controls the movement direction and step size of the motorized translation stage. During each movement of the optical wedge interferometer 7, the photomultiplier tube 8 can perform one or more repeated acquisitions. The average signal of the one or more repeated acquisitions is the interference signal corresponding to the optical wedge interferometer in that movement. The movement of the optical wedge interferometer 7 allows the photomultiplier tube 8 to acquire interference signals at different movement positions. The interference signals at different movement positions are extracted and stitched together to obtain a full-spectrum interference signal map.

[0037] The working principle of this invention is as follows:

[0038] like Figure 1As shown, this invention includes a probe beam and a pump beam. The probe beam is emitted from a broadband continuous light source 1, and the pump beam is emitted from a nanosecond pulsed laser source 9. The probe beam is reflected and focused onto the sample under test 5. The pump beam is split into a transmission pump beam and a reflection pump beam by a beam splitter 10. The reflection pump beam is collected by a photodiode 16 and converted into an electrical signal, which is input to the external trigger channel 1701 of a digital oscilloscope 17. The transmission pump beam is frequency-reduced by a chopper 11 and then focused onto the sample under test 5. The pump beam and the probe beam have their focal points aligned, and the diameter of the probe beam's focal spot is larger than the diameter of the down-frequency transmitted pump beam's spot. The rotation speed of the chopper 11 is controlled by the chopper controller 15. The chopper controller 15 outputs a square wave signal with the same frequency as the down-frequency transmitted pump beam to channel 1702 of the digital oscilloscope 17. The probe beam, after passing through the sample under test, is Fourier transformed by the optical wedge interferometer 7, detected by the photomultiplier tube 8, and converted into an electrical signal input to channel 1703 of the digital oscilloscope 17.

[0039] The overlap between the probe beam and the down-frequency pump beam at the position of the sample 5 under test is achieved by adjusting reflector 2, reflector 3, reflector 12 and reflector 13.

[0040] like Figure 3 As shown, the optical wedge spectral interferometer 7 consists of a movable optical wedge 701, a movable optical wedge 702, and a movable crystal 703. The movable optical wedges 701, 702, and 703 are all mounted on a translation stage with a degree of freedom of movement. By changing the positions of the movable optical wedges 701, 702, and 703, the thickness of the air film between them is changed, thereby achieving interference of light of different frequencies in the probe beam, and thus realizing the Fourier transform of the probe beam.

[0041] like Figure 1 As shown, a single acquisition process involves time-resolved acquisition of the optical signal after Fourier transform of a single frequency of the probe beam. Channel 2 1703 of the digital oscilloscope 17 can acquire a single signal or multiple repetitions of the Fourier transform of a single frequency of the transmitted probe beam within one cycle of channel 1702 during the single acquisition process, thereby obtaining the time delay information of the transmitted probe beam after passing through the sample 5 and undergoing Fourier transform of the optical wedge spectral interferometer 7.

[0042] like Figure 4As shown, during data processing, the information obtained by the transmission probe beam passing through the sample 5 and undergoing Fourier transform by the optical wedge spectral interferometer 7 at the same time delay position in each single acquisition process is extracted. The information from each single acquisition process is then stitched together to obtain the Fourier spectrum information of the probe beam passing through the sample 5 and undergoing Fourier transform by the optical wedge spectral interferometer 7 at the time delay position. By performing an inverse Fourier transform on this information, the corresponding transient absorption spectrum information can be obtained. By selecting different time delay positions and repeating the above operation, transient absorption spectrum information at different time delay positions can be obtained.

Claims

1. A high-throughput nanosecond transient absorption spectroscopy measurement system, characterized in that, include: A broadband continuous light source system, a nanosecond pulsed laser light source system, a sample under test (5), an aperture (6), an optical wedge interferometer (7), a photomultiplier tube (8), and a digital oscilloscope (17), among which; The probe beam emitted by the broadband continuous light source system and the pump beam emitted by the nanosecond pulse laser light source system are intersected at the point where the sample to be tested (5) is placed. After the probe beam passes through the sample to be tested (5), an aperture (6), a wedge spectral interferometer (7), and a photomultiplier tube (8) are arranged in sequence on its optical path. The digital oscilloscope (17) is connected to the nanosecond pulse laser light source system and the photomultiplier tube (8) respectively. The optical wedge spectral interferometer (7) includes a movable optical wedge one (701), a movable optical wedge two (702), and a movable crystal (703) that are fixed in sequence on an electric translation stage with a degree of freedom of movement. There are gaps between the movable optical wedge one (701) and the movable optical wedge two (702) and between the movable optical wedge two (702) and the movable crystal (703) to serve as air films, thereby changing the Fourier transform frequency.

2. The high-throughput nanosecond transient absorption spectroscopy measurement system according to claim 1, characterized in that, The broadband continuous light source system includes a broadband continuous light source (1) and a reflector (2), a reflector (3), and a focusing mirror (4) disposed on the optical path of the probe beam emitted by the light source. The probe beam is focused onto the sample (5) being tested by the focusing mirror (4).

3. The high-throughput nanosecond transient absorption spectroscopy measurement system according to claim 1, characterized in that, The nanosecond pulse laser source system includes: a nanosecond pulse laser source (9), a beam splitter (10) disposed on the pump beam path emitted by the source, and a chopper (11), a third mirror (12), a fourth mirror (13), a second focusing mirror (14), and a photodiode (16) disposed on the transmission path of the beam splitter (10). The pump beam is focused on the sample (5) under test by the second focusing mirror (14), and the photodiode (16) is connected to a digital oscilloscope (17). It also includes a chopper controller (15), through which the digital oscilloscope (17) is connected to the chopper (11).

4. The high-throughput nanosecond transient absorption spectroscopy measurement system according to claim 1, characterized in that, The external trigger channel (1701) of the digital oscilloscope (17) is connected to the photodiode (16), the first channel (1702) of the digital oscilloscope (17) is connected to the chopper (11) through the chopper controller (15), and the second channel (1703) of the digital oscilloscope (17) is connected to the photomultiplier tube (8).

5. A high-throughput nanosecond transient absorption spectroscopy measurement method, characterized in that, Includes the following steps: The probe beam emitted by the broadband continuous light source (1) is reflected and focused onto the sample under test (5). The pump beam emitted by the nanosecond pulse laser source (9) is split into a transmission pump beam and a reflection pump beam by the beam splitter (10). The reflection pump beam is collected by the photodiode (16) and converted into an electrical signal input to the external trigger channel (1701) of the digital oscilloscope (17). The transmission pump beam is reduced in frequency by the chopper (11) and focused onto the sample under test (5). The focal position of the reduced transmission pump beam coincides with that of the probe beam, and the focal spot diameter of the probe beam is larger than that of the reduced transmission pump beam. The chopper controller (15) outputs a square wave signal with the same frequency as the reduced transmission pump beam to channel one (1702) of the digital oscilloscope (17). The probe beam that has passed through the sample under test is Fourier transformed by the optical wedge spectral interferometer (7) and detected by the photomultiplier tube (8) and converted into an electrical signal input to channel two (1703) of the digital oscilloscope (17). The optical wedge spectral interferometer (7) includes a movable optical wedge one (701), a movable optical wedge two (702) and a movable crystal (703) fixed in sequence on an electric translation stage with a degree of freedom of movement. The Fourier transform frequency can be changed by changing the position of the movable optical wedge one (701), the movable optical wedge two (702) and the movable crystal (703).

6. The high-throughput nanosecond transient absorption spectroscopy measurement method according to claim 5, characterized in that, By adjusting reflector one (2), reflector two (3), reflector three (12), and reflector four (13), the focal positions of the frequency-reduced transmission pump beam and the probe beam on the sample (5) are made to coincide.

7. The high-throughput nanosecond transient absorption spectroscopy measurement method according to claim 5, characterized in that, The spectral range of the broadband continuous light source (1) can be extended to the ultraviolet band, the visible band and the near-infrared band.

8. The high-throughput nanosecond transient absorption spectroscopy measurement method according to claim 5, characterized in that, The nanosecond pulsed laser source (9) has a pulse frequency range of 20Hz to 20kHz and a pulse wavelength of any one of 266nm, 355nm, 378nm, 400nm, 532nm, 780nm or 800nm.

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