A system and method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization.

Abstract

This invention belongs to the field of ultrafast spectroscopy technology, specifically relating to a system and method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization. The system comprises: a femtosecond laser, a first beam splitter, a pump pulse adjustment component, a probe pulse adjustment component, a second beam splitter, a beam combiner, a focusing and imaging device, a third beam splitter, a spectral measurement device, and a polarization measurement device. This system can simultaneously measure transient absorption spectroscopy and magneto-optical polarization.

Description

Technical Field

[0001] This invention belongs to the field of ultrafast spectroscopy technology and relates to a system and method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization. Background Technology

[0002] The combination of traditional optoelectronics with magnetism and spintronics has led to widespread attention and application of novel magnetic optoelectronic devices such as magnetoresistive devices, magneto-optical switches, spin-emitting devices, and spin Hall effect devices. Among these, the exploration of material properties is fundamental to the structural design and performance verification of magnetic optoelectronic devices. Compared to traditional electrical methods, optical detection methods offer advantages such as non-contact, non-destructive, high sensitivity, and high time resolution, enabling the simultaneous acquisition of both photoelectric and magnetic properties within materials. Therefore, they are widely used in the characterization of the state of magnetic materials.

[0003] Ultrafast optical detection technology is a commonly used tool for studying the microscopic dynamics of materials and devices. Transient absorption spectroscopy and transient magneto-optical polarization can respectively reflect the carrier and spin dynamics processes within magnetic materials, facilitating the structural design, mechanism analysis, and performance verification of electromagnetic devices. In recent years, it has been found that in two-dimensional van der Waals magnetic materials such as CrI3 and NiPS3, the spin dynamics processes under photoexcitation are often coupled with the photogenerated carrier dynamics processes. Therefore, the study of the mechanisms of related materials and devices requires simultaneous knowledge of their internal transient absorption and magneto-optical polarization responses. However, in traditional ultrafast optical detection systems, only one of these two signals can be obtained in a single measurement; transient absorption and magneto-optical polarization signals often need to be acquired at different times and in different batches. This not only wastes a significant amount of time but also introduces substantial measurement errors. Furthermore, considering the state changes of materials and devices under long-term femtosecond laser irradiation, inconsistencies may exist between transient signals acquired in different batches.

[0004] Currently, there is a demand for ultrafast optical detection of two-dimensional optoelectronic and magnetic materials, particularly for simultaneously performing transient absorption spectroscopy and transient magneto-optical polarization measurements. Traditional pump-probe techniques can no longer fully meet these measurement requirements. Therefore, researching and developing ultrafast optical detection systems and methods that integrate transient absorption spectroscopy and magneto-optical polarization detection capabilities is of great significance for addressing the testing needs of different materials. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that it is impossible to simultaneously measure transient absorption spectrum and magneto-optical polarization, thereby providing a system and method for parallel measurement of transient absorption spectrum and magneto-optical polarization.

[0006] This invention provides a parallel measurement system for transient absorption spectroscopy and magneto-optical polarization, comprising: a femtosecond laser, a first beam splitter, a pump pulse adjustment component, a probe pulse adjustment component, a second beam splitter, a beam combiner, a focusing and imaging device, a third beam splitter, a spectral measurement device, and a polarization measurement device. The pump pulse adjustment component includes: a pump light parametric amplifier and a pump light coupling and coupling unit; the pump light parametric amplifier is used to adjust the parameters of the pump light; the pump light coupling and coupling unit is used for coupling and coupling the pump light. The probe pulse adjustment component includes a probe light parametric amplifier and a pulse delay device; the probe light parametric amplifier is used to adjust the parameters of the probe light; the pulse delay device is used to adjust the optical path of the probe light. The polarization measurement device includes a third half-wave plate, a polarization beam splitter, and a balanced photodetector sequentially arranged in the optical path reflected from the third beam splitter. The focusing and imaging device includes a microscope objective. The first beam splitter is used to emit the femtosecond laser. The laser beam is split into a probe beam and a pump beam; the pump pulse adjustment component is used to receive the pump beam split from the first beam splitter; the probe pulse adjustment component is used to receive the probe beam split from the first beam splitter; the second beam splitter is used to reflect a portion of the probe beam emitted from the probe pulse adjustment component as a probe reference beam, and the second beam splitter is also used to transmit a portion of the probe beam emitted from the probe pulse adjustment component; the beam combiner is used to collimate and combine the probe beam transmitted from the second beam splitter and the pump beam emitted from the pump pulse adjustment component; the microscope objective is used to confocalize the pump beam and probe beam onto the sample surface, and to image the morphology and spot focusing of the sample surface in a micro-area; the beam combiner is also adapted to transmit the feedback light reflected from the sample surface to the second beam splitter; the second beam splitter is also used to reflect the feedback light to the third beam splitter; the third beam splitter splits the feedback light reflected from the second beam splitter into two paths, which enter the spectral measurement device and the polarization measurement device respectively.

[0007] Optionally, the pump pulse adjustment assembly further includes: a first polarizer, a first half-wave plate, a first reflector, and a chopper and a pump pulse intensity modulator, which are sequentially arranged on the optical path from the pump light parametric amplifier to the pump light coupling and coupling unit; the frequency of the chopper is at least two orders of magnitude higher than the switching frequency of the pump light coupling and coupling unit.

[0008] Optionally, the pump light input and output unit is an optical shutter.

[0009] Optionally, the probe pulse adjustment assembly further includes a probe light intensity modulator, a first focusing lens, an optical nonlinear crystal, and a second focusing lens arranged sequentially on the optical path from the probe light parametric amplifier to the pulse delay device, and a second polarizer and a second half-wave plate arranged sequentially on the optical path from the pulse delay device to the second beam splitter; the first focusing lens and the second focusing lens, together with the optical nonlinear crystal, make the probe light emitted from the second focusing lens a supercontinuum white light.

[0010] Optionally, the pulse delay device includes a second reflector, a third reflector, and a one-dimensional displacement stage; the second and third reflectors are located on the one-dimensional displacement stage; the second reflector is used to reflect the probe light emitted from the second focusing lens to the third reflector; the third reflector is used to reflect the probe light reflected from the second reflector to the second polarizer.

[0011] Optionally, the focusing and imaging device further includes a sample stage, and the microscope objective is located in the optical path between the beam combiner and the sample stage.

[0012] Optionally, the focusing and imaging device further includes: a removable beam splitter, a fourth beam splitter, an illumination source, a collimating lens, and a camera; the removable beam splitter is adapted to be located in or removed from the optical path between the beam combiner and the microscope objective; the fourth beam splitter is located in the optical path between the removable beam splitter and the camera; the collimating lens is located in the optical path between the illumination source and the fourth beam splitter; the fourth beam splitter is used to reflect the illumination light emitted by the illumination source to the removable beam splitter; when the removable beam splitter is selected to be located in the optical path between the beam combiner and the microscope objective, the removable beam splitter is adapted to transmit the probe light and pump light to the microscope objective and reflect the illumination light to the microscope objective, the removable beam splitter is also adapted to reflect a portion of the feedback light to the fourth beam splitter and transmit a portion of the feedback light to the beam combiner; the fourth beam splitter is also used to transmit a portion of the feedback light reflected by the removable beam splitter to the camera.

[0013] Optionally, the spectral measurement device includes an optical fiber device and a spectrometer electrically connected to the optical fiber device; the optical fiber device includes a first optical fiber coupler and a first optical fiber, the first optical fiber coupler being used to couple the probe reference light into the first optical fiber; the optical fiber device further includes a second optical fiber coupler and a second optical fiber, the second optical fiber coupler being used to couple the probe light into the second optical fiber; the spectrometer is used to collect the signal of the probe reference light transmitted through the first optical fiber and output the spectrum of the probe reference light; the spectrometer is also used to collect the signal of the reference light transmitted through the second optical fiber and output the spectrum of the probe light.

[0014] Optionally, the polarization measurement device further includes a narrowband filter in the optical path from the third beam splitter to the third half-wave plate, and a lock-in amplifier electrically connected to the balanced photodetector.

[0015] Optionally, it may also include: a measurement and control computer, which is used to control the pulse delay device, the pump light coupling and coupling unit, the spectral measurement device, the polarization measurement device, and the focusing and imaging device.

[0016] This invention also provides a method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization, employing the aforementioned parallel measurement system for transient absorption spectroscopy and magneto-optical polarization, comprising: Step S1: fixing the sample on a sample stage; Step S2: turning on a femtosecond laser, the femtosecond laser beam being split into a probe beam and a pump beam; a pump pulse adjustment component receiving the pump beam split from the first beam splitter; a probe pulse adjustment component receiving the probe beam split from the first beam splitter; a portion of the probe beam emitted by the probe pulse adjustment component being reflected by the second beam splitter as a probe reference beam, and a portion of the probe beam emitted by the probe pulse adjustment component being transmitted by the second beam splitter; Step S3: adjusting the center wavelength and pulse width of the pump beam using a pump beam parametric amplifier, and adjusting the center wavelength and pulse width of the probe beam using a probe beam parametric amplifier, according to the material properties of the sample. Pulse width; Step S4: The pulse delay device adjusts the optical path of the probe light until the pump light and probe light arrive at the sample simultaneously. At this time, the reference position of the pulse delay device is determined, and the spectral measurement device tests the transient absorption spectrum signal of the light transmitted by the third beam splitter to its maximum value; Step S5: The pump light coupling and coupling unit couples the pump light out of the optical path, and the third half-wave plate and polarization beam splitter are adjusted until the output signal of the balanced detector is 0; Step S6: The pulse delay device adjusts the optical path of the probe light until the probe light has a test optical path and the pump light and probe light have a test delay time t; Under the conditions of test delay time t and the pump light coupling and coupling unit coupling the pump light in, the spectral measurement device tests the first light intensity R(t) of the feedback light transmitted by the third reflector, and the spectral measurement device tests the second light intensity R of the probe reference light. f(t), the polarization measurement device outputs differential light intensity ΔI; Step S7: the pump light coupling and coupling unit couples the pump light out and the probe light under the condition that the test optical path is met, the spectral measurement device measures the third light intensity R0(t) of the feedback light transmitted by the third reflector, and the spectral measurement device measures the fourth light intensity R of the probe reference light. f0 (t); Step S8: Based on the first light intensity R(t) and the second light intensity R f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t) Obtain the transient absorption spectrum signal; obtain the transient magneto-optical polarization signal Δθ based on the differential light intensity ΔI.

[0017] Optionally, the probe pulse adjustment assembly further includes a probe light intensity modulator, a first focusing lens, an optical nonlinear crystal, and a second focusing lens arranged sequentially on the optical path from the probe light parametric amplifier to the pulse delay device, and a second polarizer and a second half-wave plate arranged sequentially on the optical path from the pulse delay device to the second beam splitter; the transient absorption spectrum and magneto-optical polarization parallel measurement method further includes: after step S3 and before step S4, adjusting the first focusing lens and the second focusing lens by means of the probe light intensity modulator, so that the first focusing lens and the second focusing lens cooperate with the optical nonlinear crystal to make the probe light emitted by the second focusing lens supercontinuum white light; before step S5, placing a narrowband filter in the optical path between the third beam splitter and the third half-wave plate.

[0018] Optionally, the transient absorption spectral signal ΔR(t) = lg(R(t) × R f0 (t) / R f (t) / R0(t)); the transient magneto-optical polarization signal Δθ is proportional to ΔI.

[0019] Optionally, step S6 can be performed multiple times, with different test optical paths and different test delay times t, to obtain the average value of the first light intensity tested in multiple steps S6. The average value of the second light intensity The average value of the third light intensity and the average value of the fourth light intensity Average value of transient absorption spectral signal Proportional to

[0020] The technical solution of this invention has the following beneficial effects: The transient absorption spectrum and magneto-optical polarization parallel measurement system provided by this invention includes a first beam splitter for splitting the laser beam emitted by a femtosecond laser into a probe beam and a pump beam; a pump pulse adjustment component for receiving the pump beam split by the first beam splitter; a probe pulse adjustment component for receiving the probe beam split by the first beam splitter; and a second beam splitter for reflecting a portion of the probe beam emitted by the probe pulse adjustment component as a probe reference beam. The pump pulse adjustment component can acquire the transient absorption spectrum, and the probe pulse adjustment component can test the magneto-optical polarization effect. Therefore, the transient absorption spectrum and magneto-optical polarization parallel measurement system can achieve parallel polarization and spectral detection with the same time delay, which not only saves measurement time but also avoids the uncertainty caused by repeated measurements in transient optical testing. Thus, the transient absorption spectrum and magneto-optical polarization parallel measurement system can simultaneously measure the transient absorption spectrum and magneto-optical polarization.

[0021] Furthermore, the polarization measurement device also includes a narrowband filter in the optical path from the third beam splitter to the third half-wave plate, and a lock-in amplifier electrically connected to the balanced photodetector. This enables the transient absorption spectroscopy and magneto-optical polarization parallel measurement system to detect the spectral response curve of the polarization rotation angle.

[0022] Furthermore, the spectral measurement device includes an optical fiber device and a spectrometer electrically connected to the optical fiber device. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system uses an optical fiber device to collect the probe light and the probe reference light in the spectral detection, which ensures the stability of the optical path. At the same time, the introduction of the probe reference light can eliminate the measurement error caused by the jitter of the probe light, which greatly improves the signal-to-noise ratio. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0024] Figure 1 This is a schematic diagram of the structure of a parallel measurement system for transient absorption spectroscopy and magneto-optical polarization provided in an embodiment of the present invention;

[0025] Figure 2 (a) is a schematic diagram of the operating frequencies of the pump light coupling input and coupling output units in a transient absorption spectroscopy and magneto-optical polarization parallel measurement system provided in an embodiment of the present invention;

[0026] Figure 2 (b) is a schematic diagram of the signal modulated by the chopper on the pump light in a transient absorption spectroscopy and magneto-optical polarization parallel measurement system provided in an embodiment of the present invention;

[0027] Figure 2 (c) The spectrum of pump light under the modulation of a chopper in a transient absorption spectrum and magneto-optical polarization parallel measurement system provided in an embodiment of the present invention;

[0028] Figure 2 (d) The first light intensity R(t) and the second light intensity R(t) obtained by the transient absorption spectroscopy and magneto-optical polarization parallel measurement system provided in an embodiment of the present invention. f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t) Schematic diagram;

[0029] Figure 2 (e) is a schematic diagram of the differential light intensity ΔI obtained by the transient absorption spectrum and magneto-optical polarization parallel measurement system provided in an embodiment of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] This embodiment provides a system for parallel measurement of transient absorption spectroscopy and magneto-optical polarization, referencing... Figure 1The system includes: a femtosecond laser 1, a first beam splitter 2, a pump pulse adjustment component, a probe pulse adjustment component, a second beam splitter 5, a beam combiner 6, a focusing and imaging device, a third beam splitter 8, a spectral measurement device, and a polarization measurement device. The pump pulse adjustment component includes: a pump light parametric amplifier 31 and a pump light coupling-in and coupling-out unit 32. The pump light parametric amplifier 31 is used to adjust the parameters of the pump light; the pump light coupling-in and coupling-out unit 32 is used for coupling in and out of the pump light. The probe pulse adjustment component includes a probe light parametric amplifier 41 and a pulse delay device 42. The probe light parametric amplifier 41 is used to adjust the parameters of the probe light; the pulse delay device 42 is used to adjust the optical path of the probe light. The polarization measurement device includes a third half-wave plate 101, a polarization beam splitter 102, and a balanced photodetector 103 sequentially arranged in the optical path reflected from the third beam splitter 8. The focusing and imaging device includes a microscope objective 71.

[0035] The first beam splitter 2 is used to split the laser beam emitted by the femtosecond laser into a probe beam and a pump beam; the pump pulse adjustment component is used to receive the pump beam split by the first beam splitter 2; the probe pulse adjustment component is used to receive the probe beam split by the first beam splitter 2; the second beam splitter 5 is used to reflect part of the probe beam emitted by the probe pulse adjustment component as a probe reference beam, and the second beam splitter 5 is also used to transmit part of the probe beam emitted by the probe pulse adjustment component; the beam combiner 6 is used to collimate and combine the probe beam transmitted by the second beam splitter 5 and the pump beam emitted by the pump pulse adjustment component; the microscope objective 71 is used to confocalize the pump beam and probe beam onto the sample surface, and to image the morphology and spot focusing of the sample surface in a micro-area; the beam combiner 6 is also adapted to transmit the feedback light reflected from the sample surface to the second beam splitter 5; the second beam splitter 5 is also used to reflect the feedback light to the third beam splitter 8; the third beam splitter 8 splits the feedback light reflected by the second beam splitter 5 into two paths, which enter the spectral measurement device and the polarization measurement device respectively.

[0036] The transient absorption spectroscopy and magneto-optical polarization parallel measurement system provided in this embodiment includes a first beam splitter for splitting the laser beam emitted by a femtosecond laser into a probe beam and a pump beam; a pump pulse adjustment component for receiving the pump beam split by the first beam splitter; a probe pulse adjustment component for receiving the probe beam split by the first beam splitter; and a second beam splitter for reflecting a portion of the probe beam emitted by the probe pulse adjustment component as a probe reference beam. The pump pulse adjustment component can acquire the transient absorption spectrum, and the probe pulse adjustment component can test the magneto-optical polarization effect. Therefore, the transient absorption spectroscopy and magneto-optical polarization parallel measurement system can achieve parallel polarization and spectral detection with the same time delay, saving measurement time and avoiding the uncertainty caused by repeated measurements in transient optical testing. Thus, the transient absorption spectroscopy and magneto-optical polarization parallel measurement system can simultaneously measure transient absorption spectra and magneto-optical polarization.

[0037] In one embodiment, the microscope objective has the capability of broadband spectral and micro-area measurement. In one embodiment, the femtosecond laser 1 comprises a laser-active material of Yb. 3+ A femtosecond laser of KGd(WO4)2(Yb:KGW) with a fixed output power, pulse width, and repetition frequency, wherein the repetition frequency is 10-1. 5 Hertz level.

[0038] In one embodiment, the first beam splitter 2 is a semi-transparent and semi-reflective mirror, the second beam splitter 5 is a semi-transparent and semi-reflective mirror, and the beam combiner 6 is a dichroic mirror. The beam combiner 6 transmits the probe light in the wavelength band and reflects the pump light in the wavelength band.

[0039] In one embodiment, the first beam splitter 2 projects a portion of the laser emitted by the femtosecond laser onto the pump pulse adjustment component, and the first beam splitter 2 also reflects a portion of the laser emitted by the femtosecond laser onto the probe pulse adjustment component. In another embodiment, the first beam splitter 2 reflects a portion of the laser emitted by the femtosecond laser onto the pump pulse adjustment component, and the first beam splitter 2 also projects a portion of the laser emitted by the femtosecond laser onto the probe pulse adjustment component.

[0040] In one embodiment, the transient absorption spectroscopy and magneto-optical polarization parallel measurement system further includes a measurement and control computer 12, which controls the pulse delay device 42, the pump light coupling and coupling unit 32, the spectral measurement device, the polarization measurement device, and the focusing and imaging device. The measurement and control computer 12 is used for the automatic control of the hardware and software of the transient absorption spectroscopy and magneto-optical polarization parallel measurement system, as well as for signal reception and processing.

[0041] In one embodiment, the pump pulse adjustment assembly further includes: a first polarizer 33, a first half-wave plate 34, a first reflector 35 arranged sequentially on the optical path from the pump light parametric amplifier 31 to the pump light coupling-in and coupling-out unit 32, and a chopper 36 and a pump light intensity modulator 37 arranged sequentially on the optical path from the pump light coupling-in and coupling-out unit 32 to the beam combiner 6.

[0042] In one embodiment, the frequency of the chopper 36 is at least two orders of magnitude higher than the switching frequency of the pump optical input and output unit 32, so that the chopper 36 and the pump optical input and output unit 32 do not interfere with each other in frequency. For example, the frequency of the chopper 36 is at least 100 times higher than the switching frequency of the pump optical input and output unit 32.

[0043] In one embodiment, the pump light input and output unit 32 is an optical shutter.

[0044] The pump light parametric amplifier 31 is used to adjust the center wavelength and pulse width of the pump light; the first polarizer 33 is used to adjust the linear polarization degree of the pump light so that the pump light reaches a high linear polarization degree; the first half-wave plate 34 is used to adjust the polarization direction of the pump light; the first reflector 35 is used to reflect the pump light from the first half-wave plate 34 to the pump light coupling and coupling unit 32; the pump light intensity modulator 37 is used to adjust the light intensity of the pump light; and the chopper 36 is used for secondary modulation of the pump light frequency.

[0045] The measurement and control computer 12 controls the pump light input and output unit 32 and the chopper 36 to realize the switching of the pump light itself. The pump light input and output unit 32, in conjunction with the spectral measurement device, obtains the spectral changes of the probe light with / without pump light.

[0046] In one embodiment, the probe pulse adjustment assembly further includes a probe light intensity modulator 43, a first focusing lens 44, an optical nonlinear crystal 45 and a second focusing lens 46 arranged sequentially on the optical path from the probe light parametric amplifier 41 to the pulse delay device 42, and a second polarizer 47 and a second half-wave plate 48 arranged sequentially on the optical path from the pulse delay device 42 to the second beam splitter 5.

[0047] In one embodiment, the pulse delay device 42 includes a second reflector 421, a third reflector 422, and a one-dimensional displacement stage 423. The second reflector 421 and the third reflector 422 are located on the one-dimensional displacement stage 423. The second reflector 421 is used to reflect the probe light emitted from the second focusing lens 46 to the third reflector 422; the third reflector 422 is used to reflect the probe light reflected by the second reflector 421 to the second polarizer 47.

[0048] In one embodiment, the optical nonlinear crystal 45 comprises sapphire and calcium fluoride; in other embodiments, the optical nonlinear crystal may also comprise other crystals.

[0049] The probe light parametric amplifier 41 is used to adjust the center wavelength and pulse width of the probe light; the first focusing lens 44 and the second focusing lens 46, in conjunction with the optical nonlinear crystal 45, make the probe light emitted from the second focusing lens 46 a supercontinuum white light; the probe light intensity modulator 43 is used to adjust the intensity of the probe light. The spectrum of the supercontinuum white light output by the first focusing lens 44, the optical nonlinear crystal 45, and the second focusing lens 46 is adjusted by the probe light parametric amplifier 41. The first focusing lens 44 and the second focusing lens 46 are used to increase the power density of the probe light and collimate the supercontinuum white light; the pulse delay device 42 is used to adjust the optical path of the probe light so that the interval between the time the probe light arrives at the sample surface and the time the pump light arrives at the sample surface is equal. Specifically, when the pump light and the probe light are of the same source and frequency, the position of the one-dimensional displacement stage is precisely adjusted by the measurement and control computer to change the optical path of the probe light, where "same frequency" refers to the same pulse frequency. The second polarizer 47 is used to make the probe light a highly linearly polarized light; the second half-wave plate 48 is used to adjust the polarization direction of the probe light.

[0050] In one embodiment, the focusing and imaging device further includes a sample stage 72, and the microscope objective 71 is located in the optical path between the beam combiner 6 and the sample stage 72.

[0051] In one embodiment, the focusing and imaging device further includes: a removable beam splitter 73, a fourth beam splitter 74, an illumination source 75, a collimating lens 76, and a camera 77; the removable beam splitter 73 is adapted to be located in or removed from the optical path between the beam combiner 6 and the microscope objective 71; the fourth beam splitter 74 is located in the optical path between the removable beam splitter 73 and the camera 77; the collimating lens 76 is located in the optical path between the illumination source 75 and the fourth beam splitter 74.

[0052] The fourth beam splitter 74 is used to reflect the illumination light emitted by the illumination source 75 to the removable beam splitter 73; when the removable beam splitter is selected to be located in the optical path between the beam combiner and the microscope objective, the removable beam splitter 73 is adapted to transmit the probe light and pump light to the microscope objective 71 and reflect the illumination light to the microscope objective 71, the removable beam splitter 73 is also adapted to reflect part of the feedback light to the fourth beam splitter 74 and transmit part of the feedback light to the beam combiner; the fourth beam splitter 74 is also used to transmit part of the feedback light reflected by the removable beam splitter 73 to the camera 77.

[0053] In one embodiment, the microscope objective 71 includes a reflective objective. The microscope objective 71 can focus the probe light, pump light, and illumination light, and can also collect feedback light. The microscope objective can avoid chirp broadening, self-phase modulation, and other effects on broadband probe light, pump light, and illumination light.

[0054] In one embodiment, the removable beam splitter 73 is a semi-transparent and semi-reflective mirror.

[0055] In one embodiment, the sample stage 72 is used to carry the sample and adjust its position. In another embodiment, the sample stage 72 consists of a three-axis adjustable displacement stage and a fixing device, with the fixing device located on the three-axis adjustable displacement stage. The fixing device carries the sample, and the three-axis adjustable displacement stage adjusts its position. The measurement and control computer controls the three-axis adjustable displacement stage to achieve high-precision limiting and positioning of the sample stage 72.

[0056] In one embodiment, the illumination source 75 is used to provide an illumination source, the collimating lens 76 is used to collimate the illumination source, and the camera 77 is used to receive part of the feedback light transmitted by the fourth beam splitter 74 and to receive an image formed by the confocal state of the pump light and the probe light and the surface morphology of the sample under test.

[0057] In one embodiment, the spectral measurement device includes an optical fiber device and a spectrometer electrically connected to the optical fiber device; the optical fiber device includes a first optical fiber coupler 911 and a first optical fiber 912, the first optical fiber coupler 911 being used to couple the probe reference light to the first optical fiber 912; the optical fiber device further includes a second optical fiber coupler 921 and a second optical fiber 922, the second optical fiber coupler 921 being used to couple the probe light to the second optical fiber 922; the spectrometer 91 is used to collect the signal of the probe reference light transmitted through the first optical fiber 912 and output the spectrum of the probe reference light; the spectrometer 91 is also used to collect the signal of the probe light transmitted through the second optical fiber 922 and output the spectrum of the probe light.

[0058] The transient absorption spectroscopy and magneto-optical polarization parallel measurement system uses an optical fiber device to collect the probe light and the probe reference light in the spectral detection, which ensures the stability of the optical path. At the same time, the introduction of the probe reference light can eliminate the measurement error caused by probe light jitter and greatly improve the signal-to-noise ratio.

[0059] In one embodiment, the detector of the spectrometer 91 includes an array of charge-coupled devices or an array of complementary metal-oxide-semiconductor devices.

[0060] In one embodiment, the polarization measurement device includes a third half-wave plate 101, a polarization beam splitter 102, and a balanced photodetector 103 sequentially arranged in the optical path reflected from the third beam splitter 8. The polarization measurement device also includes a narrowband filter 104 in the optical path from the third beam splitter 8 to the third half-wave plate 101, and a lock-in amplifier 105 electrically connected to the balanced photodetector 103. This enables the transient absorption spectroscopy and magneto-optical polarization parallel measurement system to detect the spectral response curve of the polarization rotation angle.

[0061] In one embodiment, the chopper 36, in conjunction with a spectral measurement device and a lock-in amplifier 105, obtains the polarization change of the probe light with / without pump light.

[0062] The narrowband filter 104 is used to filter out excess broadband components of the feedback light outside the selected wavelength and to separate quasi-monochromatic light in the spectrum of the feedback light for polarization detection; the polarization beam splitter 102 is used to separate orthogonally linearly polarized components in space; the third half-wave plate 101 is used to adjust the polarization direction of the feedback light before pump-probe zero delay and for initial zeroing of the balanced detector; the balanced photodetector 103 is used to detect the light intensity of different polarization components. The balanced photodetector 103 and the lock-in amplifier 105 are used to detect the feedback light signal and regenerate it.

[0063] In one embodiment, the polarization beam splitter 102 includes a Wollaston prism, and the two orthogonally polarized lights separated by the polarization beam splitter 102 have equal intensities.

[0064] In one embodiment, the measurement and control computer is connected to the lock-in amplifier 105, and the measurement and control computer controls the integration time and averaging number of the lock-in amplifier 105, and controls the lock-in amplifier 105 to process the electrical signal of the returned feedback light.

[0065] In one embodiment, the measurement and control computer also controls the spectrometer in the spectral measurement device, the balanced photodetector 103 in the polarization measurement device, and the camera and sample stage in the focusing and imaging device. The measurement and control computer receives and displays optical information of a portion of the feedback light received by the camera and an image of the surface morphology of the sample under test. The measurement and control computer can also achieve high-precision control of the limiting and positioning of the sample stage.

[0066] Another embodiment of the present invention provides a method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization, employing the above-described parallel measurement system for transient absorption spectroscopy and magneto-optical polarization, and including the following steps:

[0067] Step S1: Fix the sample on the sample stage;

[0068] Step S2: Turn on the femtosecond laser. The laser beam emitted by the femtosecond laser is split into a probe beam and a pump beam. The pump pulse adjustment component receives the pump beam split from the first beam splitter. The probe pulse adjustment component receives the probe beam split from the first beam splitter. The second beam splitter reflects a portion of the probe beam emitted from the probe pulse adjustment component as a probe reference beam. The second beam splitter transmits a portion of the probe beam emitted from the probe pulse adjustment component.

[0069] Step S3: Based on the material properties of the sample, adjust the center wavelength and pulse width of the pump light parametric amplifier, and adjust the center wavelength and pulse width of the probe light parametric amplifier.

[0070] Step S4: The pulse delay device adjusts the optical path of the probe light until the pump light and the probe light arrive at the sample simultaneously. At this time, the reference position of the pulse delay device is determined, and the spectral measurement device measures the transient absorption spectrum signal of the light transmitted by the third spectrometer to its maximum value.

[0071] Step S5: The pump light input and output unit couples the pump light out of the optical path, and adjusts the third half-wave plate and polarization beam splitter until the output signal of the balanced detector is 0.

[0072] Step S6: The pulse delay device adjusts the optical path of the probe light until the probe light has a test optical path and the pump light and probe light have a test delay time t; under the conditions of test delay time t and the pump light being coupled in by the pump light coupling unit, the spectral measurement device tests the first light intensity R(t) of the feedback light transmitted by the third reflector, and the spectral measurement device tests the second light intensity R of the probe reference light. f (t), the polarization measurement device outputs differential light intensity ΔI;

[0073] Step S7: Under the condition that the pump light and probe light have the test optical path length, the pump light coupling unit couples the pump light and probe light into the input and output units. The spectral measurement device then measures the third intensity R0(t) of the feedback light transmitted by the third reflector, and measures the fourth intensity R of the probe reference light. f0 (t);

[0074] Step S8: Based on the first light intensity R(t) and the second light intensity R f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t) Obtain the transient absorption spectrum signal; obtain the transient magneto-optical polarization signal Δθ based on the differential light intensity ΔI.

[0075] In one embodiment, the probe pulse adjustment assembly further includes a probe light intensity modulator, a first focusing lens, an optical nonlinear crystal and a second focusing lens arranged sequentially on the optical path from the probe light parametric amplifier to the pulse delay device, and a second polarizer and a second half-wave plate arranged sequentially on the optical path from the pulse delay device to the second beam splitter.

[0076] The method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization further includes: after step S3 and before step S4, adjusting the first focusing lens and the second focusing lens by means of a probe light intensity modulator, so that the first focusing lens and the second focusing lens, together with the optical nonlinear crystal, make the probe light emitted by the second focusing lens supercontinuum white light; before step S5, placing a narrowband filter in the optical path between the third beam splitter and the third half-wave plate.

[0077] Transient absorption spectral signal ΔR(t)=lg(R(t)×R f0 (t) / R f (t) / R0(t)); the transient magneto-optical polarization signal Δθ is proportional to ΔI.

[0078] In one embodiment, step S6 is performed multiple times, with different test optical paths and different test delay times t in each step S6, to obtain the average value of the first light intensity tested in multiple steps S6. The average value of the second light intensity The average value of the third light intensity and the average value of the fourth light intensity Average value of transient absorption spectral signal Proportional to

[0079] The balanced detector directly obtains the differential light intensity ΔI, which is linearly related to the change in the polarization direction of the probe light, under the synchronous action of the chopper and the lock-in amplifier.

[0080] In one embodiment, in the parallel measurement method of transient absorption spectroscopy and magneto-optical polarization, during the measurement process, the pump light coupling-in and coupling-out units operate at a switching frequency on the order of 1 Hz, periodically blocking the pump light, and the reference... Figure 2 (a), Figure 2 (a) is the operating frequency of the pump optical input and output units, with the chopper operating at 10... 2 It operates at frequencies on the order of Hertz and modulates the pump light when the pump light coupling-in and coupling-out units are open. (Reference) Figure 2 (b), Figure 2 (b) is a schematic diagram of the signal modulated by the chopper on the pump light. The repetition rate of the femtosecond laser source is around 10. 5 The magnitude is around 10, and the repetition rate is around 10. 5 Light sources of this magnitude can be approximated as continuous light relative to low-frequency modulation, reference... Figure 2 (c), Figure 2 (c) is the spectrum of the pump light under the modulation of the chopper; during the spectral measurement, with the pump light coupled in and out by the coupling and coupling units, the first light intensity R(t) and the second light intensity R are obtained respectively. f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t), reference Figure 2 (d), Figure 2 (d) represents the first light intensity R(t) and the second light intensity R f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t) Schematic diagram; For polarization measurement, with the pump light coupled into the pump light via the pump light coupling unit, ΔI is obtained by locking the chopper frequency through a lock-in amplifier, referencing... Figure 2 (e), Figure 2 (e) is a schematic diagram of the differential light intensity ΔI.

[0081] 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. A system for parallel measurement of transient absorption spectroscopy and magneto-optical polarization, characterized in that, include: Femtosecond laser, first beam splitter, pump pulse adjustment component, probe pulse adjustment component, second beam splitter, beam combiner, focusing and imaging device, third beam splitter, spectral measurement device and polarization measurement device; The pump pulse adjustment assembly includes: a pump light parametric amplifier and a pump light coupling and coupling unit, wherein the pump light parametric amplifier is used to adjust the parameters of the pump light; the pump light coupling and coupling unit is used for coupling and coupling the pump light; the probe pulse adjustment assembly includes a probe light parametric amplifier and a pulse delay device, wherein the probe light parametric amplifier is used to adjust the parameters of the probe light; the pulse delay device is used to adjust the optical path of the probe light; the polarization measurement device includes a third half-wave plate, a polarization beam splitter, and a balanced photodetector sequentially arranged in the optical path reflected from the third beam splitter; the focusing and imaging device includes a microscope objective. The first beam splitter is used to split the laser beam emitted by the femtosecond laser into a probe beam and a pump beam; the pump pulse adjustment component is used to receive the pump beam split by the first beam splitter; the probe pulse adjustment component is used to receive the probe beam split by the first beam splitter; the second beam splitter is used to reflect a portion of the probe beam emitted by the probe pulse adjustment component as a probe reference beam, and the second beam splitter is also used to transmit a portion of the probe beam emitted by the probe pulse adjustment component; the beam combiner is used to collimate and combine the probe beam transmitted by the second beam splitter and the pump beam emitted by the pump pulse adjustment component; the microscope objective is used to confocalize the pump beam and probe beam onto the sample surface, and to image the morphology and spot focusing of the sample surface in a micro-area; the beam combiner is also adapted to transmit the feedback light reflected from the sample surface to the second beam splitter; the second beam splitter is also used to reflect the feedback light to a third beam splitter; the third beam splitter splits the feedback light reflected by the second beam splitter into two paths, which enter the spectral measurement device and the polarization measurement device respectively.

2. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 1, characterized in that, The pump pulse adjustment assembly further includes: a first polarizer, a first half-wave plate, a first reflector, and a chopper and a pump pulse modulator, which are sequentially arranged on the optical path from the pump light parametric amplifier to the pump light coupling and coupling unit, and on the optical path from the pump light coupling and coupling unit to the beam combiner. The frequency of the chopper is at least two orders of magnitude higher than the switching frequency of the pump optical input and output units.

3. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 1, characterized in that, The pump light input and output unit is an optical shutter.

4. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 1, characterized in that, The probe pulse adjustment assembly further includes a probe light intensity modulator, a first focusing lens, an optical nonlinear crystal and a second focusing lens arranged sequentially on the optical path from the probe light parametric amplifier to the pulse delay device, and a second polarizer and a second half-wave plate arranged sequentially on the optical path from the pulse delay device to the second beam splitter; The first focusing lens and the second focusing lens, together with the optical nonlinear crystal, make the probe light emitted from the second focusing lens a supercontinuum white light.

5. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 4, characterized in that, The pulse delay device includes a second reflector, a third reflector, and a one-dimensional displacement stage; the second and third reflectors are located on the one-dimensional displacement stage. The second reflector is used to reflect the probe light emitted from the second focusing lens to the third reflector; The third reflector is used to reflect the probe light reflected by the second reflector to the second polarizer.

6. The system for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 1, characterized in that, The focusing and imaging device also includes a sample stage, and the microscope objective is located in the optical path between the beam combiner and the sample stage.

7. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 6, characterized in that, The focusing and imaging device further includes: a removable beam splitter, a fourth beam splitter, an illumination source, a collimating lens, and a camera; the removable beam splitter is adapted to be located in or removed from the optical path between the beam combiner and the microscope objective; the fourth beam splitter is located in the optical path between the removable beam splitter and the camera; the collimating lens is located in the optical path between the illumination source and the fourth beam splitter; The fourth beam splitter is used to reflect the illumination light emitted by the illumination source to the removable beam splitter; when the removable beam splitter is selected to be located in the optical path between the beam combiner and the microscope objective, the removable beam splitter is adapted to transmit the probe light and pump light to the microscope objective and reflect the illumination light to the microscope objective, the removable beam splitter is also adapted to reflect a portion of the feedback light to the fourth beam splitter and transmit a portion of the feedback light to the beam combiner; the fourth beam splitter is also used to transmit a portion of the feedback light reflected by the removable beam splitter to the camera.

8. The system for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 1, characterized in that, The spectral measurement device includes an optical fiber device and a spectrometer electrically connected to the optical fiber device; The optical fiber device includes a first optical fiber coupler and a first optical fiber, wherein the first optical fiber coupler is used to couple the probe reference light into the first optical fiber; The optical fiber device further includes a second optical fiber coupler and a second optical fiber, wherein the second optical fiber coupler is used to couple the probe light into the second optical fiber; The spectrometer is used to collect the signal of the probe reference light transmitted through the first optical fiber and output the spectrum of the probe reference light; The spectrometer is also used to collect the signal of the reference light transmitted through the second optical fiber and output the spectrum of the probe light.

9. The system for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 1, characterized in that, The polarization measurement device also includes a narrowband filter in the optical path from the third beam splitter to the third half-wave plate, and a lock-in amplifier electrically connected to the balanced photodetector.

10. The transient absorption spectroscopy and magneto-optical polarization parallel measurement system according to claim 1, characterized in that, Also includes: The measurement and control computer is used to control the pulse delay device, the pump light coupling and coupling unit, the spectral measurement device, the polarization measurement device, and the focusing and imaging device.

11. A method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization, employing the parallel measurement system for transient absorption spectroscopy and magneto-optical polarization as described in any one of claims 1 to 10, characterized in that, include: Step S1: Fix the sample on the sample stage; Step S2: Turn on the femtosecond laser. The laser beam emitted by the femtosecond laser is split into probe light and pump light. The pump pulse adjustment component receives the pump light split by the first beam splitter; the probe pulse adjustment component receives the probe light split by the first beam splitter; The second beam splitter reflects a portion of the probe light emitted from the probe pulse adjustment component as a probe reference light, and the second beam splitter transmits a portion of the probe light emitted from the probe pulse adjustment component. Step S3: Based on the material properties of the sample, adjust the center wavelength and pulse width of the pump light parametric amplifier, and adjust the center wavelength and pulse width of the probe light parametric amplifier. Step S4: The pulse delay device adjusts the optical path of the probe light until the pump light and the probe light arrive at the sample simultaneously. At this time, the reference position of the pulse delay device is determined, and the spectral measurement device measures the transient absorption spectrum signal of the light transmitted by the third spectrometer to its maximum value. Step S5: The pump light input and output unit couples the pump light out of the optical path, and adjusts the third half-wave plate and polarization beam splitter until the output signal of the balanced detector is 0. Step S6: The pulse delay device adjusts the optical path of the probe light until the probe light has a test optical path and the pump light and probe light have a test delay time t; under the conditions of test delay time t and the pump light being coupled in by the pump light coupling unit, the spectral measurement device tests the first light intensity R(t) of the feedback light transmitted by the third reflector, and the spectral measurement device tests the second light intensity R of the probe reference light. f (t), the polarization measurement device outputs differential light intensity ΔI; Step S7: Under the condition that the pump light and probe light have the test optical path length, the pump light coupling unit couples the pump light and probe light into the input and output units. The spectral measurement device then measures the third intensity R0(t) of the feedback light transmitted by the third reflector, and measures the fourth intensity R of the probe reference light. f0 (t); Step S8: Based on the first light intensity R(t) and the second light intensity R f (t), the third light intensity R0(t) and the fourth light intensity R f0 (t) Obtain the transient absorption spectrum signal; obtain the transient magneto-optical polarization signal Δθ based on the differential light intensity ΔI.

12. The method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 11, characterized in that, The probe pulse adjustment assembly further includes a probe light intensity modulator, a first focusing lens, an optical nonlinear crystal and a second focusing lens arranged sequentially on the optical path from the probe light parametric amplifier to the pulse delay device, and a second polarizer and a second half-wave plate arranged sequentially on the optical path from the pulse delay device to the second beam splitter; The method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization further includes: after step S3 and before step S4, adjusting the first focusing lens and the second focusing lens by a probe light intensity modulator, so that the first focusing lens and the second focusing lens, together with the optical nonlinear crystal, make the probe light emitted from the second focusing lens supercontinuum white light; Before step S5, a narrowband filter is placed in the optical path between the third beam splitter and the third half-wave plate.

13. The method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 11, characterized in that, Transient absorption spectral signal ΔR(t) = lg(R(t) × R f0 (t) / R f (t) / R0(t)); the transient magneto-optical polarization signal Δθ is proportional to ΔI.

14. The method for parallel measurement of transient absorption spectroscopy and magneto-optical polarization according to claim 11, characterized in that, Perform step S6 multiple times, with different test optical paths and test delay times t in each step S6, and obtain the average value of the first light intensity from the multiple tests in step S6. The average value of the second light intensity The average value of the third light intensity and the average value of the fourth light intensity The average value of the transient absorption spectral signal =lg( × / / ), Proportional to .

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