Infrared femtosecond time-resolved multi-wavelength dynamic pump detection system

Abstract

This invention relates to an infrared femtosecond time-resolved multi-wavelength dynamic pump-probe system, comprising: a femtosecond laser; a probe light that, after passing through the sample to be tested, is collimated and passes through a first grating; after passing through the first grating, the dispersed light is incident on a first cylindrical lens via an electrically controlled aperture; the linear spot continues to pass through a second grating for secondary dispersion; each time the time delay line moves one step, the slit on the electrically controlled micrometer aperture is gradually moved from one side of the spot to the other side by a set step size; a photodetector records once for each step of the electrically controlled micrometer aperture; after the set time delay has been completed, full-spectrum time-resolved infrared transient absorption test data is obtained. This invention's infrared femtosecond time-resolved multi-wavelength dynamic pump-probe system utilizes a measurement method of spectral spatial broadening followed by gate shifting to achieve accurate, economical, and rapid full-spectrum transient absorption dynamics testing.

Description

Technical Field

[0001] This invention relates to the field of infrared transient absorption technology, and in particular to an infrared femtosecond time-resolved multi-wavelength dynamic pump detection system. Background Technology

[0002] Time-resolved infrared (TRIR) spectroscopy is an experimental technique used to study materials and molecular dynamics. It measures the change in infrared absorption of a material over time after it has been excited (e.g., photoexcited). TRIR spectroscopy can also provide information on changes in molecular structure, free carrier dynamics, transfer processes between different components in multi-component systems, identification of intermediate products formed in photochemical or photophysical processes, and the study of their properties and reaction pathways.

[0003] Traditional infrared transient absorption testing, especially time-resolved transient infrared spectroscopy in the 1-3 micrometer band, includes the following methods: 1. Using a single-wavelength infrared light generated by an optical parametric amplifier (OPA) or a monochromator as the probe light, and a photodiode as the data detection device, single-wavelength pump-probe dynamics measurements are performed on the sample. Then, the wavelength is changed by the OPA or monochromator, and the measurement is repeated. Finally, the measured data are combined. This method is extremely time-consuming, and the accuracy of the data decreases significantly due to laser drift caused by wavelength changes during repeated testing. 2. Using infrared white light as the probe light and an infrared spectrometer as the data detection device for transient full-spectrum measurements. The problem with this method is that infrared spectrometers rarely perform full-spectrum infrared testing (1-3 micrometers), and even custom-made models are extremely expensive, making them unsuitable for ordinary researchers. Summary of the Invention

[0004] The present invention aims to solve the technical problems in the prior art by providing an infrared femtosecond time-resolved multi-wavelength dynamic pump detection system.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] An infrared femtosecond time-resolved multi-wavelength dynamic pump-detection system includes: a femtosecond laser; the femtosecond laser emitted by the femtosecond laser is split into two beams, one as pump light and the other as detector light, wherein:

[0007] The pump light path first passes through a parametric amplifier for frequency conversion, then through a time delay line, a fourth reflecting mirror, a chopper, and after multiple reflections, is finally focused onto the sample to be tested.

[0008] The probe light beam first passes through a neutral density gradient filter, and then is focused into a sealed air chamber by a first lens. By adjusting the gradient filter, stable infrared white light is obtained. After the infrared white light is generated, it is focused onto the sample to be tested by a second lens, and the beam coincides with the probe light spot on the sample to be tested.

[0009] After the probe light passes through the sample to be tested, it is collimated and passes through the first grating. After passing through the first grating, the dispersed light is incident on the first cylindrical lens through an electrically controlled aperture. The linear spot continues to pass through the second grating for secondary dispersion. After secondary dispersion, the probe light is re-collimated by the second cylindrical lens. Then, the collimated linear light is passed through an electrically controlled micrometer aperture, so that a portion of the wavelength of light passes through the third cylindrical lens and is focused into the photodetector.

[0010] Each time the time delay line moves one step, the slit on the electrically controlled micrometer aperture will gradually move from one side of the light spot to the other side of the light spot according to the step size setting; the photodetector records once for each step of the electrically controlled micrometer aperture; after the set time delay is completed, full-spectrum time-resolved infrared transient absorption test data are obtained.

[0011] In the above technical solution, the electrically controlled optical diaphragm is used to adjust the pre-detection spectral range by adjusting the cut-off positions on both sides.

[0012] In the above technical solution, the time delay line includes: an electrically controlled moving platform and dual reflectors.

[0013] In the above technical solution, the gas content of the sealing gas in the sealed gas chamber meets the following requirements: 95% air, 3% nitrogen, 1% hydrogen, and 1% argon.

[0014] In the above technical solution, the collimated optical path after the probe light passes through the sample to be tested includes, in sequence: a third lens, a first reflecting mirror, a second reflecting mirror, a first collimating aperture, and a second collimating aperture.

[0015] A third mirror is provided between the parametric amplifier and the time delay line;

[0016] A fourth reflector is provided between the time delay line and the chopper;

[0017] The optical path between the chopper and the sample to be tested is provided with the following components in sequence: a fourth lens, a fifth mirror, and a sixth mirror.

[0018] In the above technical solution, the first reflector, the second reflector, the third reflector, the fourth reflector, the fifth reflector, and the sixth reflector are all protective gold-coated reflectors.

[0019] In the above technical solution, the first lens, the second lens, the third lens, and the fourth lens are all calcium fluoride lenses.

[0020] In the above technical solution, a lock-in amplifier and a system synchronization control computer are sequentially arranged in the optical path after the photodetector; the system synchronization control computer is also connected to a time delay line.

[0021] The lock-in amplifier is also connected in sequence to the chopper controller and the chopper;

[0022] A chopper is used to chop a light beam at a specific frequency via a chopper controller, so that a lock-in amplifier can use this fixed frequency as a reference for data acquisition.

[0023] The present invention has the following beneficial effects:

[0024] The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention utilizes a measurement method of spectral spatial broadening followed by gate shifting to achieve accurate, economical, and rapid full-spectrum transient absorption dynamics testing. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a schematic diagram of the infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention.

[0027] Figure 2 This is a schematic diagram of the infrared detection light spectrum of the infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention.

[0028] The reference numerals in the figure are:

[0029] 1-Femtosecond laser; 2-Graded filter; 3-First lens; 4-Sealed gas chamber; 5-Second lens; 6-Sample to be tested; 7-Third lens; 8-First mirror; 9-Second mirror; 10-First collimation aperture; 11-Second collimation aperture; 12-First grating; 13-Electrically controlled aperture gate; 14-First cylindrical lens; 15-Second grating; 16-Second cylindrical lens; 17-Electrically controlled micron aperture; 18-Third cylindrical lens; 19-Photodetector; 20-System synchronization control computer; 21-Parallel amplifier; 22-Third mirror; 23-Time delay line; 24-Fourth mirror; 25-Chopper; 26-Fifth mirror; 27-Sixth mirror; 28-Lock-in amplifier; 29-Chopper controller; 30-Fourth lens. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings.

[0031] like Figure 1As shown, the infrared femtosecond time-resolved multi-wavelength dynamic pump-detection system of the present invention includes: a femtosecond laser 1; the femtosecond laser emitted by the femtosecond laser 1 is split into two beams, one beam serving as pump light and the other as detector light, wherein:

[0032] The pump light path first passes through the parametric amplifier 21 for frequency conversion, then through the time delay line 23, the fourth reflector 24, then through the chopper 25, and after multiple reflections, finally focuses onto the sample 6 to be tested.

[0033] The probe light beam first passes through a neutral density gradient filter 2, and then is focused into the sealed gas chamber 4 by the first lens 3. By adjusting the gradient filter 2, stable infrared white light is obtained. After the infrared white light is generated, it is focused onto the test sample 6 by the second lens 5, and coincides with the probe light spot on the test sample 6. The gas content of the sealed gas in the sealed gas chamber 4 meets the following requirements: 95% air, 3% nitrogen, 1% hydrogen, and 1% argon.

[0034] After the probe light passes through the sample 6 to be tested, it is collimated and passes through the first grating 12. After passing through the first grating 12, the dispersed light is incident on the first cylindrical lens 14 through the electrically controlled aperture 13. The linear spot continues to pass through the second grating 15 for secondary dispersion. After secondary dispersion, the probe light is re-collimated by the second cylindrical lens 16. Then, the collimated linear light is passed through the electrically controlled micrometer aperture 17, so that a portion of the wavelength of light passes through the third cylindrical lens 18 and is focused into the photodetector 19. The electrically controlled aperture 13 is used to adjust the pre-detection spectral range by adjusting the cut-off positions on both sides. The time delay line 23 includes an electrically controlled moving platform and dual reflectors.

[0035] Each time the time delay line 23 moves one step, the slit on the electrically controlled micrometer aperture 17 will gradually move from one side of the light spot to the other side of the light spot according to the step size setting; each time the electrically controlled micrometer aperture 17 moves one step, the photodetector 19 records once; after the set time delay is completed, the full-spectrum time-resolved infrared transient absorption test data is obtained.

[0036] The collimated optical path after the probe light passes through the test sample 6 includes, in sequence: a third lens 7, a first reflector 8, a second reflector 9, a first collimating pinhole 10, and a second collimating pinhole 11; a third reflector 22 is provided between the parametric amplifier 21 and the time delay line 23; a fourth reflector 24 is provided between the time delay line 23 and the chopper 25; the optical path between the chopper 25 and the test sample 6 includes, in sequence: a fourth lens 30, a fifth reflector 26, and a sixth reflector 27. A lock-in amplifier 28 and a system synchronization control computer 20 are also provided in sequence on the optical path after the photodetector 19; the system synchronization control computer 20 is also connected to the time delay line 23; the lock-in amplifier 28 is also connected in sequence to the chopper controller 29 and the chopper 25; the chopper 25 is used to chop the beam at a specific frequency through the chopper controller 29, so that the lock-in amplifier 28 uses this fixed frequency as a reference for data acquisition.

[0037] The first reflecting mirror 8, the second reflecting mirror 9, the third reflecting mirror 22, the fourth reflecting mirror 24, the fifth reflecting mirror 26, and the sixth reflecting mirror 27 are all gold-coated reflectors. The first lens 3, the second lens 5, the third lens 7, and the fourth lens 30 are all calcium fluoride lenses.

[0038] Specifically:

[0039] The femtosecond laser 1 serves to provide an ultrashort pulse source with sufficient energy for the entire optical detection system.

[0040] The graded filter 2 is used to control and determine the optimal pump source energy for generating infrared white light in the probe light path by means of energy regulation.

[0041] The system comprises a first lens 3, a second lens 5, a third lens 7, and a fourth lens 30. The first lens 3 focuses the light beam into the sealed gas chamber of the infrared white light generating chamber 4 to produce infrared white light. The second lens 5 focuses the generated white light as a probe beam onto the sample 6 to be tested. The third lens 7 collimates the diverging probe light passing through the sample. The fourth lens 30 focuses the pump light onto the sample. The first lens 3, second lens 5, third lens 7, and fourth lens 30 are all calcium fluoride lenses.

[0042] The sealed gas chamber 4, used for generating infrared white light, serves to produce white light. Since the primary purpose of this system is time-resolved pump detection in the infrared spectrum, especially in the 1-3 micrometer band, the detection light must cover a range of 1-3 micrometers or even wider. Therefore, traditional media such as glass, sapphire, and water cannot be used to generate white light. The sealed gas within the infrared white light generating chamber 4 has the following composition: 95% air, 3% nitrogen, 1% hydrogen, and 1% argon. This ensures the generation of more stable 1-3 micrometer infrared detection light. Its spectrum is as follows: Figure 2 As shown.

[0043] Sample 6 to be tested; This system can be applied to solution and thin film samples, but not to infrared total reflection materials.

[0044] The first reflector 8, the second reflector 9, the third reflector 22, the fourth reflector 24, the fifth reflector 26, and the sixth reflector 27 are protective gold-plated reflectors (gold reflectors). Since the detection light is broadband infrared light, gold reflectors are used to increase the reflection efficiency.

[0045] The first collimation pinhole 10 and the second collimation pinhole 11 serve the following functions: when the probe light experiences optical drift, the probe light path is reset by adjusting the first reflecting mirror 8 and the second reflecting mirror 9, using the first collimation pinhole 10 and the second collimation pinhole 11 as references.

[0046] The first grating 12 and the second grating 15. The function of the first grating 12 is that when the probe light propagates to the first grating 12, the beam undergoes reflective dispersion to obtain a horizontally broadened long light spot with different wavelengths. The function of the second grating 15 is to further broaden the broadened long light spot to obtain an ultra-long light spot with higher spatial resolution.

[0047] The electrically controlled optical shutter 13 is used to obtain a tunable spectral detection range by controlling the optical shutter to cut off the spectrum on both sides of the broadened light spot.

[0048] The first cylindrical lens 14, the second cylindrical lens 16, and the third cylindrical lens 18; the functions of the first cylindrical lens 14 and the second cylindrical lens 16 are respectively to receive the transverse light spot with the axial plane of the cylindrical lens, and to longitudinally focus the dispersed probe light into a thin line and laterally collimate it. The function of the third cylindrical lens 18 is to receive the transverse light spot with the transverse curved surface of the cylindrical lens, thereby focusing the linear light spot into the photodetector 19.

[0049] The electrically controlled micrometer aperture 17 consists of an electrically controlled translation stage and a single-slit light-receiving plate fixed on it. The single-slit light-receiving plate receives the linear light spot and transmits a single-wavelength beam through the single slit, and the wavelength is selected by moving the electrically controlled translation stage.

[0050] Photodetector 19 is a Thorlabs InAsSb amplified detector, model PDA10PT-EC. This detector can detect light in the 1-5 micrometer range, meeting the detection requirements.

[0051] The system synchronous control computer 20; in the infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention, all electrical control equipment is programmed to complete the synchronous detection of the entire system and the program is executed by the system synchronous control computer 20.

[0052] Parametric amplifier (OPA) 21; Since different materials require different pump light spectra, the pump light is sourced from a 1 femtosecond laser and frequency conversion is achieved through the OPA. Continuously tunable spectrum from 450 to 2000 nanometers can be realized.

[0053] The time delay line 23, composed of the electrically controlled moving platform and the dual mirrors, is used to adjust the optical path and complete the time-resolved test. The time resolution depends on the step size of the electrically controlled moving platform based on the femtosecond laser pulse width. The shorter the step size, the smaller the time resolution of the data.

[0054] Chopper 25 is used to chop the beam at a specific frequency by chopper controller 29, so that lock-in amplifier 28 can use this fixed frequency as a reference to perform data acquisition.

[0055] Lock-in amplifier 28, used in conjunction with chopper 25, is used to collect light of a specific frequency and perform digital-to-analog conversion to acquire data.

[0056] Chopper controller 29 is used to control chopper 25 to chop at a set frequency.

[0057] The detection process of the infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention is as follows:

[0058] The femtosecond laser emitted by femtosecond laser 1 is split into two beams: one as the pump light and the other as the probe light. Wherein:

[0059] The pump light first passes through the parametric amplifier 21 for frequency conversion, converting it into the wavelength required for the experiment. Then it passes through the time delay line 23, then through the chopper 25, and finally through multiple reflections to be focused onto the sample 6 to be tested.

[0060] The probe light first passes through the neutral density gradient filter 2, and then is focused into the sealed air chamber 4 by the first lens 3. By adjusting the gradient filter 2, a stable infrared white light is obtained. After the infrared white light is generated, it is focused on the sample 6 to be tested, and the probe light spot coincides with the sample 6 to be tested.

[0061] After the probe light passes through the sample 6 to be tested, it is collimated and passes through the first grating 12. Since the light spot is dispersed after passing through the first grating 12 and becomes laterally longer with increasing distance, the dispersed light needs to be incident on the first cylindrical lens 14. This not only focuses the dispersed probe light longitudinally into a thin line but also collimates it laterally. Furthermore, because the white light range is not limited to only 1-3 micrometers, an electrically controlled aperture 13 needs to be inserted in the optical path between the first grating 12 and the first cylindrical lens 14. The pre-detection spectral range is adjusted by adjusting the cut-off positions on both sides of the electrically controlled aperture 13. After selecting the spectral range, the linear light spot continues to pass through the second grating 15 for secondary dispersion. The purpose of this secondary dispersion is to expand different spectral spaces, laying the foundation for subsequent spectral selection. After secondary dispersion, the probe light is re-collimated by the second cylindrical lens 16. Then, the collimated linear light passes through the electrically controlled micrometer aperture 17, causing a segment of wavelength to pass through the third cylindrical lens 18 and be focused into the photodetector 19.

[0062] All electronic and optoelectronic devices are controlled via LabVIEW programming. When the program runs, each time the time delay line 23 formed by the electronically controlled moving platform and the dual reflectors moves one step, the slit on the electronically controlled micrometer aperture 17 gradually moves from one side of the light spot to the other, according to the set step size. Each step size of the electronically controlled micrometer aperture 17 is the spectral resolution of the system. With each step of the electronically controlled micrometer aperture 17, the photodetector 19 records data once, i.e., different single-wavelength data under the same time delay. In this way, after the set time delay is completed, full-spectrum time-resolved infrared transient absorption test data can be obtained.

[0063] In summary, the system of this invention can measure the full spectrum on the same delay line and complete the test in an accurate and economical manner.

[0064] The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system of the present invention utilizes a measurement method of spectral spatial broadening followed by gate shifting to achieve accurate, economical, and rapid full-spectrum transient absorption dynamics testing.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An infrared femtosecond time-resolved multi-wavelength dynamic pump detection system, characterized in that, include: Femtosecond laser (1); the femtosecond laser emitted by the femtosecond laser (1) is split into two beams, one as pump light and the other as probe light, wherein: The pump light path first passes through the parametric amplifier (21) for frequency conversion, then through the time delay line (23), the fourth reflector (24), then through the chopper (25), and after multiple reflections, finally focuses on the sample to be tested (6). The probe light beam first passes through a neutral density gradient filter (2), and then is focused into a sealed air chamber (4) by a first lens (3). By adjusting the gradient filter (2), a stable infrared white light is obtained. After the infrared white light is generated, it is focused onto the sample to be tested (6) by a second lens (5), and coincides with the probe light spot on the sample to be tested (6). After the probe light passes through the sample to be tested (6), it is collimated and passes through the first grating (12). After passing through the first grating (12), the dispersed light is incident on the first cylindrical lens (14) through the electronically controlled aperture gate (13). The linear spot continues to pass through the second grating (15) for secondary dispersion. After secondary dispersion, the probe light is re-collimated through the second cylindrical lens (16). Then, the collimated linear light is passed through the electronically controlled micrometer aperture (17) so that a portion of the wavelength of light is focused into the photodetector (19) through the third cylindrical lens (18). Each time the time delay line (23) moves one step, the slit on the electrically controlled micrometer aperture (17) will gradually move from one side of the light spot to the other side of the light spot by setting the step size; each time the electrically controlled micrometer aperture (17) moves one step, the photodetector (19) records once; after the set time delay is completed, full-spectrum time-resolved infrared transient absorption test data are obtained.

2. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 1, characterized in that, The electrically controlled aperture (13) is used to adjust the pre-detection spectral range by adjusting the cut-off position on both sides.

3. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 1, characterized in that, The time delay line (23) includes: an electrically controlled moving platform and two reflectors.

4. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 1, characterized in that, The gas content of the sealed gas in the sealed gas chamber (4) meets the following requirements: 95% air, 3% nitrogen, 1% hydrogen, and 1% argon.

5. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 1, characterized in that, The collimated optical path after the probe light passes through the sample to be tested (6) includes, in sequence: a third lens (7), a first reflecting mirror (8), a second reflecting mirror (9), a first collimation aperture (10), and a second collimation aperture (11). A third reflector (22) is provided between the parametric amplifier (21) and the time delay line (23); A fourth reflector (24) is provided between the time delay line (23) and the chopper (25); The optical path between the chopper (25) and the sample to be tested (6) is provided with the following components in sequence: a fourth lens (30), a fifth mirror (26), and a sixth mirror (27).

6. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 5, characterized in that, The first reflector (8), the second reflector (9), the third reflector (22), the fourth reflector (24), the fifth reflector (26), and the sixth reflector (27) are protective gold-coated reflectors.

7. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 5, characterized in that, The first lens (3), the second lens (5), the third lens (7), and the fourth lens (30) are calcium fluoride lenses.

8. The infrared femtosecond time-resolved multi-wavelength dynamic pump detection system according to claim 1, characterized in that, A lock-in amplifier (28) and a system synchronization control computer (20) are sequentially installed in the optical path after the photodetector (19); the system synchronization control computer (20) is also connected to the time delay line (23); The lock-in amplifier (28) is also connected in sequence to the chopper controller (29) and the chopper (25); The chopper (25) is used to chop the beam at a specific frequency through the chopper controller (29), so that the lock-in amplifier (28) can use this fixed frequency as a reference to acquire data.

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