Time domain stimulated Raman scattering method and system

Abstract

The invention relates to the technical field of spectrum detection and optical imaging, and provides a time domain stimulated Raman scattering method and system.The method comprises the steps that pumping pulses or Stokes pulses are modulated, two stimulated Raman excitation pulse pairs with adjustable relative delay are introduced, a to-be-detected sample is excited to generate transient stimulated Raman scattering, and the time domain stimulated Raman scattering is obtained; transient stimulated Raman scattering signals can be obtained, acquisition of hyperspectral data covering hundreds of wave numbers can be achieved only through single excitation, and the method has the advantage of being high in time resolution. Meanwhile, the spectral resolution of the vibration level life broadening limit can be obtained through the method, and the main technical bottleneck faced by the traditional stimulated Raman scattering spectrum technology can be solved at a time. The method can be applied to the fields of Raman scattering imaging, spectrum detection, related Raman probes and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of spectrum detection and optical imaging, and in particular to a time-domain stimulated Raman scattering method and system. Background Art

[0002] Raman spectroscopy is a powerful tool for analyzing molecular structure. It contains rich information about the sample molecular structure and can be used to analyze the dynamics of sample molecules and their interactions with the solvent environment. It is widely used in the study of molecular reaction processes in biology, chemistry, etc.

[0003] Most of the existing stimulated Raman spectroscopy techniques are based on frequency domain methods, including:

[0004] (1) The method of point-by-point laser tuning using a narrow-band picosecond laser is used. This method often requires minutes of spectrum acquisition time to collect a complete Raman spectrum, and the time resolution is poor.

[0005] (2) The femtosecond laser spectral focusing method is used to obtain the spectrum by adjusting the relative delay of the pulse. The line width of the obtained Raman spectrum is significantly broadened compared to the spontaneous Raman spectrum. When different Raman peaks are relatively close, they are often difficult to distinguish and the spectral resolution is poor. Summary of the invention

[0006] The present invention provides a time-domain stimulated Raman scattering method and system to solve the defects in the prior art.

[0007] The present invention provides a time-domain stimulated Raman scattering method, comprising:

[0008] Generate a pump pulse and a Stokes pulse based on a femtosecond pulse laser, select a first pulse of the pump pulse and the Stokes pulse and modulate it through a modulator to obtain a modulated pulse, align the second pulse of the pump pulse and the Stokes pulse with the modulated pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair;

[0009] Based on the stimulated Raman excitation pulse pair, generating two stimulated Raman excitation pulse pairs with a relative delay and an adjustable relative delay;

[0010] Based on the two stimulated Raman excitation pulse pairs, the relative delay is scanned to excite the sample to be tested to generate transient stimulated Raman scattering, and transient stimulated Raman scattering signals corresponding to each relative delay are obtained. Based on the transient stimulated Raman scattering signals, the Raman spectrum corresponding to the sample to be tested is determined.

[0011] According to a time-domain stimulated Raman scattering method provided by the present invention, if the first pulse is the pump pulse, the transient stimulated Raman scattering signal is a stimulated Raman gain signal;

[0012] If the first pulse is the Stokes pulse, the transient stimulated Raman scattering signal is a stimulated Raman loss signal.

[0013] According to a time-domain stimulated Raman scattering method provided by the present invention, based on two pairs of stimulated Raman excitation pulses, a relative delay is scanned to excite a sample to be tested to generate transient stimulated Raman scattering, a transient stimulated Raman scattering signal corresponding to each relative delay is obtained, and based on the transient stimulated Raman scattering signal, a Raman spectrum corresponding to the sample to be tested is determined, including:

[0014] Based on the two stimulated Raman excitation pulse pairs, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, and obtaining an outgoing excitation pulse pair after interacting with the sample to be tested;

[0015] Performing photoelectric conversion and phase-locked detection on the second pulse in the outgoing excitation pulse pair to obtain the transient stimulated Raman scattering signal;

[0016] The transient stimulated Raman scattering signal is subjected to Fourier transform to obtain the Raman spectrum.

[0017] According to a time-domain stimulated Raman scattering method provided by the present invention, based on the transient stimulated Raman scattering signal, the Raman spectrum corresponding to the sample to be tested is determined, and then the method further includes:

[0018] Based on the Raman spectra corresponding to the excited positions on the sample to be tested, a Raman image corresponding to the sample to be tested is obtained.

[0019] The present invention also provides a time-domain stimulated Raman scattering system, comprising: a femtosecond laser light source, a modulator, an auxiliary alignment component, a time-delay scanning device and a signal acquisition device;

[0020] The femtosecond laser light source is used to generate pump pulses and Stokes pulses based on femtosecond pulse laser;

[0021] The modulator is used to modulate the first pulse of the pump pulse and the Stokes pulse to obtain a modulated pulse;

[0022] The auxiliary alignment component is used to align the modulated pulse with the pump pulse and the second pulse of the Stokes pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair;

[0023] The delayed scanning device is used to generate two pairs of stimulated Raman excitation pulses with relative delay and adjustable relative delay based on the stimulated Raman excitation pulse pair, and the two pairs of stimulated Raman excitation pulses are used to stimulate the sample to be tested to generate transient stimulated Raman scattering;

[0024] The signal acquisition device is used to acquire an outgoing excitation pulse pair obtained after the sample to be tested generates transient stimulated Raman scattering and interacts with the sample to be tested, obtain a transient stimulated Raman scattering signal based on the outgoing excitation pulse pair, and determine the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signal.

[0025] A time-domain stimulated Raman scattering system provided according to the present invention further includes a galvanometer system; the galvanometer system is arranged between the time-delay scanning device and the signal acquisition device.

[0026] According to a time-domain stimulated Raman scattering system provided by the present invention, the signal acquisition device includes a focusing element, a filter element, a photoelectric detection element, a lock-in amplifier and a data acquisition card;

[0027] The focusing element is used to collect the outgoing excitation pulse pair;

[0028] The filter element is used to filter out the first pulse of the outgoing excitation pulse pair;

[0029] The photoelectric detection element is used to detect the light intensity signal of the second pulse in the outgoing excitation pulse pair;

[0030] The lock-in amplifier is used to perform phase-locked detection on the light intensity signal and demodulate the transient stimulated Raman scattering signal from the light intensity signal;

[0031] The data acquisition card is used to acquire the transient stimulated Raman scattering signal and determine the Raman spectrum based on the transient stimulated Raman scattering signal.

[0032] According to a time-domain stimulated Raman scattering system provided by the present invention, the time-delay scanning device comprises an interferometer;

[0033] The moving arm of the interferometer includes a delay control structure, and the delay control structure includes a first reflective element, a second reflective element, and a third reflective element;

[0034] The reflection surfaces of the first reflection element and the second reflection element are parallel and opposite to each other, and the third reflection element is arranged on the reflection light path of the second reflection element;

[0035] The first reflective element and the second reflective element are configured to be able to rotate synchronously in the same direction;

[0036] The third reflecting element is used to offset the light beam on the reflected light path of the second reflecting element and reflect it onto the second reflecting element, and then output it after passing through the second reflecting element and the first reflecting element in sequence.

[0037] According to a time-domain stimulated Raman scattering system provided by the present invention, the third reflecting element includes a first reflecting portion and a second reflecting portion, the reflecting surface of the first reflecting portion is perpendicular to the reflecting surface of the second reflecting portion, and the light beam on the reflecting light path of the second reflecting element is offset by the first reflecting portion and the second reflecting portion in sequence and then reflected to the second reflecting element;

[0038] Alternatively, the third reflecting element includes three mutually perpendicular reflecting surfaces, and the light beam on the reflecting light path of the second reflecting element is deflected by the three reflecting surfaces in sequence and then reflected onto the second reflecting element.

[0039] According to a time-domain stimulated Raman scattering system provided by the present invention, the time delay generated by the delay control structure for incident light is determined based on the rotation angle of the first reflecting element and the second reflecting element, the distance between the first reflecting element and the second reflecting element in the transmission direction of the incident light, the angle between the first reflecting element and the second reflecting element and the transmission direction of the incident light, and the offset of the rotation axis of the first reflecting element relative to the transmission direction of the incident light.

[0040] According to a time-domain stimulated Raman scattering system provided by the present invention, the rotation angle range is -1° to 4°, the distance is 40 mm, the angle is 75°, the offset is 5 mm, and the delay range of the incident light generated by the delay control structure is 0 to 12 ps.

[0041] According to a time-domain stimulated Raman scattering system provided by the present invention, the incident light is an ultrafast pulse laser or any collimated light beam.

[0042] According to a time-domain stimulated Raman scattering system provided by the present invention, the delay control structure further includes a first driving device and a second driving device;

[0043] The first driving device is used to drive the first reflecting element to rotate;

[0044] The second driving device is used to drive the second reflecting element to rotate.

[0045] A time-domain stimulated Raman scattering system according to the present invention further includes a controller, wherein the controller is connected to the first driving device and the second driving device respectively;

[0046] The controller is configured to control the first driving device and the second driving device to rotate continuously, so as to scan the rotation angles of the first reflecting element and the second reflecting element to achieve delayed scanning.

[0047] According to a time-domain stimulated Raman scattering system provided by the present invention, the interferometer further includes a beam splitter and a reference signal detection device;

[0048] The beam splitter is used to split the target beam of the stimulated Raman excitation pulse pair obtained by the auxiliary alignment component into a first partial beam and a second partial beam, the first partial beam is transmitted along the movable arm of the interferometer, and the second partial beam is transmitted along the fixed arm of the interferometer;

[0049] The beam splitter is also used to combine the light beam output by the movable arm of the interferometer with the light beam output by the fixed arm of the interferometer, and obtain a third partial light beam and a fourth partial light beam respectively, and the third partial light beam is used to stimulate the sample to be tested to generate transient stimulated Raman scattering;

[0050] The reference signal detection device is used to receive the fourth partial light beam and convert the fourth partial light beam into a reference signal with a coherence time greater than a preset threshold, and the reference signal is used to calibrate the position information of the delay control structure.

[0051] According to a time-domain stimulated Raman scattering system provided by the present invention, the reference signal detection device includes a grating, a lens, a slit and a photodiode;

[0052] The fourth partial light beam passes through the grating, the lens and the slit in sequence to obtain the reference signal;

[0053] The photodiode is used to detect the reference signal.

[0054] According to a time-domain stimulated Raman scattering system provided by the present invention, the femtosecond laser light source includes a femtosecond laser, a polarization beam splitter, a first light source branch and a second light source branch;

[0055] The femtosecond laser is used to generate the femtosecond pulse laser; the polarization beam splitter is used to split the femtosecond pulse laser into a fifth partial light beam and a sixth partial light beam;

[0056] The first light source branch includes a dispersion compensation device, and the dispersion compensation device is used to perform dispersion compensation on the fifth partial light beam to obtain the Stokes pulse;

[0057] The second light source branch includes a frequency doubler and an optical parametric oscillator; the frequency doubler is used to double the frequency of the sixth partial light beam to obtain a frequency-doubled laser; the optical parametric oscillator is driven by the frequency-doubled laser to output the pump pulse.

[0058] According to a time-domain stimulated Raman scattering system provided by the present invention, the auxiliary alignment component includes an adjustable optical delay line located on the second light source branch, and a dichroic mirror located on the first light source branch and the second light source branch;

[0059] The optical delay line is used to delay the pump pulse so that the pump pulse is aligned with the Stokes pulse in the time dimension;

[0060] The dichroic mirror is used to align the pump pulse with the Stokes pulse in a spatial dimension.

[0061] The present invention provides a time-domain stimulated Raman scattering method and system. The method first generates a pump pulse and a Stokes pulse based on a femtosecond pulse laser, selects a first pulse of the pump pulse and the Stokes pulse and modulates it through a modulator to obtain a modulated pulse, aligns the second pulse of the pump pulse and the Stokes pulse with the modulated pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair; then, using the stimulated Raman excitation pulse pair, two stimulated Raman excitation pulse pairs with relative delay and adjustable relative delay are generated; finally, using the two stimulated Raman excitation pulse pairs, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, obtaining transient stimulated Raman scattering signals corresponding to each relative delay, and using the transient stimulated Raman scattering signals, determining the Raman spectrum corresponding to the sample to be tested. By modulating the first pulse and introducing two stimulated Raman excitation pulse pairs with adjustable relative delay, the sample to be tested is stimulated to produce transient stimulated Raman scattering, and a transient stimulated Raman scattering signal can be obtained. Only a single excitation is required to achieve high-spectral data acquisition covering hundreds of wave numbers, with the characteristics of high time resolution. At the same time, this method can obtain the spectral resolution of the limit of vibrational energy level lifetime broadening, which can solve the main technical bottlenecks faced by traditional stimulated Raman scattering spectroscopy technology at one time. This method can be used in Raman scattering imaging and spectral detection, related Raman probes and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on the drawings in the following description without paying any creative work.

[0063] Figure 1 This is one of the flow charts of the time-domain stimulated Raman scattering method provided by the present invention;

[0064] Figure 2 It is an excitation energy level diagram of the sample to be tested by the stimulated Raman excitation pulse in the time-domain stimulated Raman scattering method provided by the present invention;

[0065] Figure 3 This is the second flow chart of the time-domain stimulated Raman scattering method provided by the present invention;

[0066] Figure 4 This is the third flow chart of the time-domain stimulated Raman scattering method provided by the present invention;

[0067] Figure 5 This is one of the structural schematic diagrams of the time-domain stimulated Raman scattering system provided by the present invention;

[0068] Figure 6 This is the second structural schematic diagram of the time-domain stimulated Raman scattering system provided by the present invention;

[0069] Figure 7 It is a schematic diagram of a transient stimulated Raman scattering signal obtained in the time-domain stimulated Raman scattering system provided by the present invention, taking the sample to be tested as a DMSO molecule and the first pulse as a Stokes pulse as an example;

[0070] Figure 8 It is a schematic diagram of the Raman spectrum corresponding to the sample to be tested obtained in the time-domain stimulated Raman scattering system provided by the present invention, taking the sample to be tested as a DMSO molecule and the first pulse as a Stokes pulse as an example;

[0071] Fig. 9 It is one of the schematic diagrams of the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention;

[0072] Fig.10 This is the second schematic diagram of the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention;

[0073] Fig.11 This is the third schematic diagram of the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention;

[0074] Fig.12 It is a schematic diagram of the rotation angles of the first reflective element and the second reflective element in the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention;

[0075] Fig.13 It is a schematic diagram of the corresponding relationship between the time delay generated by the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention on the incident light and the rotation angle of the first reflective element and the second reflective element;

[0076] Fig.14 This is the fourth schematic diagram of the delay control structure of the time-domain stimulated Raman scattering system provided by the present invention;

[0077] Fig.15 It is a schematic diagram of imaging results of the time-domain stimulated Raman scattering system provided by the present invention;

[0078] Fig.16 is from Fig.15 Schematic diagram of the spectrum reconstructed from the imaging results. DETAILED DESCRIPTION

[0079] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0080] The term "first" or "second" in the specification and claims of the present invention may include one or more of the features explicitly or implicitly. In the description of the invention, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0081] Figure 1 FIG. 1 is a flow chart of a time-domain stimulated Raman scattering method provided in an embodiment of the present invention, such as Figure 1 As shown, the method includes:

[0082] S1, generating a pump pulse and a Stokes pulse based on a femtosecond pulse laser, and selecting a first pulse of the pump pulse and the Stokes pulse for modulation through a modulator to obtain a modulated pulse, and aligning a second pulse of the pump pulse and the Stokes pulse with the modulated pulse in a time dimension and a space dimension to obtain a stimulated Raman excitation pulse pair;

[0083] S2, based on the stimulated Raman excitation pulse pair, generating two stimulated Raman excitation pulse pairs with a relative delay and an adjustable relative delay;

[0084] S3, based on the two stimulated Raman excitation pulse pairs, scan the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, obtain transient stimulated Raman scattering signals corresponding to each relative delay, and determine the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signals.

[0085] Specifically, the time-domain stimulated Raman scattering method provided in the embodiment of the present invention can be implemented by a time-domain stimulated Raman scattering system.

[0086] First, step S1 is performed to generate a pump pulse and a Stokes pulse using a femtosecond pulse laser. The pump pulse and the Stokes pulse can be generated by a light source, for example, a femtosecond laser light source. The stimulated Raman excitation pulse pair can include a pump pulse and a Stokes pulse aligned in the time dimension and the space dimension generated by the femtosecond pulse laser. The femtosecond laser light source can include a femtosecond laser, which can be used to generate a femtosecond pulse laser.

[0087] In addition, the pump pulse and the Stokes pulse may also be generated by different light sources, which is not specifically limited here.

[0088] The pump pulse may be a femtosecond pulse signal with a wavelength tunable in the range of 800nm-900nm, and the Stokes pulse may be a femtosecond pulse signal with a wavelength tunable in the range of 1020nm-1050nm. Both the pump pulse and the Stokes corresponding light beam may be broadband femtosecond pulse lasers.

[0089] Here, a first pulse can be selected from a pump pulse and a Stokes pulse for pulse modulation to obtain a modulated pulse. The first pulse can be either a pump pulse or a Stokes pulse, and the modulation process can be realized by a modulator. The modulator can be an electro-optic modulator (EOM), which can control the power, phase, polarization and other property information of the first pulse through an electronic control signal. In addition, the modulator can also be an acousto-optic modulator or other types of modulators.

[0090] It can be understood that the pulse that needs to be modulated among the pump pulse and the Stokes pulse is the first pulse, and the other pulse that does not need to be modulated is the second pulse. After the first pulse is modulated by the modulator to obtain the modulated pulse, the first pulse and the second pulse are aligned in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair.

[0091] Among them, alignment means overlapping. Alignment in the time dimension means that the pump pulse and the Stokes pulse are in the same position at a certain moment, that is, the two can meet, which can be achieved by delaying one of the pulses through a delay line. Alignment in the space dimension means that the pump pulse and the Stokes pulse are combined into the same light beam, which can be achieved through components with beam combining function such as dichroic mirrors (DM).

[0092] Then, step S2 is performed to generate two pairs of stimulated Raman excitation pulses with relative delay and adjustable relative delay using the stimulated Raman excitation pulse pair. Here, the two pairs of stimulated Raman excitation pulses can be generated by a delay scanning device, which can be an interferometer or other equipment, which is not specifically limited here.

[0093] Finally, step S3 is performed to use two stimulated Raman excitation pulse pairs to scan the relative delays to excite the sample to be tested to generate transient stimulated Raman scattering, and obtain transient stimulated Raman scattering signals corresponding to each relative delay.

[0094] It can be understood that if the first pulse is a pump pulse, the transient stimulated Raman scattering signal is a stimulated Raman gain signal; if the first pulse is a Stokes pulse, the transient stimulated Raman scattering signal is a stimulated Raman loss signal.

[0095] The excitation energy level diagram of the sample to be tested is shown in Figure 2 If the relative delay between the two stimulated Raman excitation pulse pairs is τ, then the sample to be tested undergoes two stimulated Raman excitations separated by τ, and the vibration quantum state wave packets generated by the two excitations are χ(t) and χ(t) and There is a difference of τ in the propagation time. |e0> is the ground state of the electronic energy level, and |g> is the vibrational ground state.

[0096] For each Raman mode in the vibrational quantum state wave packet |v i >, the final excitation probability P i For the coherent superposition of each excitation, there is a proportional to cos(Ω i τ) of quantum interference beat frequency. Among them, Ω i τ is the phase difference accumulated by the relative delay τ, Ω i is the resonant frequency of the Raman mode.

[0097] The quantum interference beat frequency term can be expressed in the intensity of the transient stimulated Raman scattering signal. Then, the Raman spectrum corresponding to the sample to be tested can be determined using the obtained transient stimulated Raman scattering signal. The sample to be tested can be a spatial proteome, a biological small molecule, and other substances, which are not specifically limited here. For example, by scanning the relative delay τ between two consecutive stimulated Raman excitation pulse pairs, the corresponding stimulated Raman scattering signal time domain sampling is Fourier transformed, and the Raman spectra of all excited Raman modes can be obtained.

[0098] Since the pump pulse and Stokes pulse can be generated by femtosecond pulse laser, the time-domain stimulated Raman scattering method uses ultrafast time-domain spectroscopy technology, namely transient stimulated Raman scattering (T-SRS) spectroscopy technology. T-SRS spectroscopy technology stimulates the sample to be tested to produce transient stimulated Raman scattering by scanning the relative delay between two stimulated Raman excitation pulse pairs including pump pulses and Stokes pulses, and obtains transient stimulated Raman scattering signals corresponding to each relative delay in the time domain. Then, by performing Fourier transform on the transient stimulated Raman scattering signals in the time domain, the corresponding Raman spectrum of the sample to be tested in the frequency domain can be determined.

[0099] The time-domain stimulated Raman scattering method provided in the embodiment of the present invention first generates a pump pulse and a Stokes pulse based on a femtosecond pulse laser, and selects the first pulse of the pump pulse and the Stokes pulse to be modulated by a modulator to obtain a modulated pulse, and aligns the second pulse of the pump pulse and the Stokes pulse with the modulated pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair; then, using the stimulated Raman excitation pulse pair, two stimulated Raman excitation pulse pairs with relative delay and adjustable relative delay are generated; finally, using the two stimulated Raman excitation pulse pairs, the relative delay is scanned to excite the sample to be tested to generate transient stimulated Raman scattering, and the transient stimulated Raman scattering signals corresponding to each relative delay are obtained, and the Raman spectrum corresponding to the sample to be tested is determined by using the transient stimulated Raman scattering signal. By modulating the first pulse and introducing two stimulated Raman excitation pulse pairs with adjustable relative delay, the sample to be tested is stimulated to generate transient stimulated Raman scattering, and a transient stimulated Raman scattering signal can be obtained. Only a single excitation is required to achieve high-spectral data acquisition covering hundreds of wave numbers, and it has the characteristics of high time resolution. At the same time, this method can obtain the spectral resolution of the limit of vibrational energy level lifetime broadening, which can solve the main technical bottleneck faced by traditional stimulated Raman scattering spectroscopy technology at one time. This method can be used in Raman scattering imaging and spectral detection, related Raman probes and other fields.

[0100] On the basis of the above embodiments, the time-domain stimulated Raman scattering method provided in the embodiments of the present invention is based on the two pairs of stimulated Raman excitation pulses, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, obtaining transient stimulated Raman scattering signals corresponding to each relative delay, and determining the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signals, including:

[0101] Based on the two stimulated Raman excitation pulse pairs, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, and obtaining an outgoing excitation pulse pair after interacting with the sample to be tested;

[0102] Performing photoelectric conversion and phase-locked detection on the second pulse in the outgoing excitation pulse pair to obtain the transient stimulated Raman scattering signal;

[0103] The transient stimulated Raman scattering signal is subjected to Fourier transform to obtain the Raman spectrum.

[0104] Specifically, by using two stimulated Raman excitation pulse pairs, scanning the relative delay to stimulate the sample to be tested to produce transient stimulated Raman scattering, the sample to be tested can be stimulated to produce transient stimulated Raman scattering, and an output excitation pulse pair after acting on the sample to be tested is obtained, and the output excitation pulse pair also includes a pump pulse and a Stokes pulse. It can be understood that after the two stimulated Raman excitation pulse pairs act on the sample to be tested, the pump pulse will be partially absorbed, that is, loss will occur; the Stokes pulse will have some gain, that is, gain will occur. Therefore, if the first pulse is a Stokes pulse, the transient stimulated Raman scattering signal demodulated by phase-locked detection is a stimulated Raman loss signal, and if the first pulse is a pump pulse, the transient stimulated Raman scattering signal demodulated by phase-locked detection is a stimulated Raman gain signal.

[0105] Furthermore, when determining the Raman spectrum corresponding to the sample to be tested, the first pulse in the outgoing excitation pulse pair can be first filtered out by a filter to obtain the second pulse in the outgoing excitation pulse pair, and then the second pulse in the outgoing excitation pulse pair can be photoelectrically converted and phase-locked detected to obtain a transient stimulated Raman scattering signal. Here, the second pulse in the outgoing excitation pulse pair can be photoelectrically converted by a photodetector to obtain a light intensity signal of the second pulse. Phase-locked detection can be achieved by inputting the light intensity signal into a phase-locked amplifier (Lock-in), and a transient stimulated Raman scattering signal can be output. Thereafter, by Fourier transforming the transient stimulated Raman scattering signal, the transient stimulated Raman scattering signal in the time domain can be converted into a Raman spectrum in the frequency domain, thereby ensuring the acquisition of the Raman spectrum.

[0106] On the basis of the above embodiments, the time-domain stimulated Raman scattering method provided in the embodiments of the present invention determines the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signal, and then further includes:

[0107] Based on the Raman spectra corresponding to the excited positions on the sample to be tested, a Raman image corresponding to the sample to be tested is obtained.

[0108] Specifically, after determining the Raman spectrum corresponding to the sample to be tested, the Raman spectrum corresponding to each excited position on the sample to be tested can be used to obtain the Raman image corresponding to the sample to be tested. By scanning the sample to be tested, two stimulated Raman excitation pulse pairs can be used to stimulate each excited position on the sample to be tested to produce transient stimulated Raman scattering. Scanning the sample to be tested can be achieved by a two-dimensional galvanometer system or by other devices with scanning functions, which are not specifically limited here.

[0109] Then, the Raman spectrum corresponding to each excited position can be obtained. By using each excited position and its corresponding Raman spectrum to perform Raman imaging, a Raman image corresponding to the sample to be tested can be obtained.

[0110] It can be understood that Raman imaging is a technique that generates images using spectral and spatial information, where the spatial information is the excited positions on the sample to be tested. Raman spectra are collected from different excited positions, and then each spectrum is reduced to a corresponding pixel with only one value, and then each Raman spectrum is represented as a value for the corresponding pixel point.

[0111] The most common approach is to use peak intensity for Raman imaging to represent chemical distribution and concentration. Intensities of multiple peaks, peak shifts, peak ratios, peak widths, etc. are also used to generate Raman images in various cases. Pixel values ​​are usually displayed as grayscale or false color.

[0112] The time-domain stimulated Raman scattering method provided in the embodiments of the present invention can be used in the fields of ultra-multicolor microscopic imaging, spatial transcriptome imaging, spatial protein composition imaging, pathological imaging, biological small molecules (such as neurotransmitters, acetylcholine) imaging, efficient disease detection and drug screening.

[0113] like Figure 3 As shown, based on the above embodiment, the time-domain stimulated Raman scattering method provided in the embodiment of the present invention, taking the pump pulse as the first pulse as an example, has the following steps:

[0114] A pump pulse and a Stokes pulse are generated based on a femtosecond pulse laser, and the pump pulse is pulse modulated to obtain a modulated pulse;

[0115] The modulated pulse and the Stokes pulse are aligned in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair, and a time delay scanning device is used to generate two stimulated Raman excitation pulse pairs with a relative time delay and an adjustable relative time delay;

[0116] Using two stimulated Raman excitation pulse pairs, the relative delay is scanned to stimulate the sample to be tested to produce transient stimulated Raman scattering, and the stimulated Raman gain signal obtained under each relative delay is synchronously detected using a phase-locked amplifier;

[0117] The stimulated Raman gain signal is transformed by Fourier transform to obtain the Raman spectrum corresponding to the sample to be tested.

[0118] like Figure 4 As shown, based on the above embodiments, the time-domain stimulated Raman scattering method provided in the embodiments of the present invention, taking the Stokes pulse as the first pulse as an example, has the following steps:

[0119] A pump pulse and a Stokes pulse are generated based on a femtosecond pulse laser, and the Stokes pulse is pulse modulated to obtain a modulated pulse;

[0120] The pump pulse and the modulation pulse are aligned in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair, and a time delay scanning device is used to generate two stimulated Raman excitation pulse pairs with a relative time delay and an adjustable relative time delay;

[0121] Using two stimulated Raman excitation pulse pairs, the relative delay is scanned to stimulate the sample to be tested to produce transient stimulated Raman scattering, and the stimulated Raman loss signals obtained under each relative delay are synchronously detected using a phase-locked amplifier;

[0122] The stimulated Raman loss signal is transformed by Fourier transform to obtain the Raman spectrum corresponding to the sample to be tested.

[0123] like Figure 5 As shown, based on the above embodiment, a time-domain stimulated Raman scattering system is further provided in the embodiment of the present invention, including: a femtosecond laser light source 1, a modulator 2, an auxiliary alignment component 3, a time-delay scanning device 4 and a signal acquisition device 5;

[0124] The femtosecond laser light source 1 is used to generate pump pulses and Stokes pulses based on femtosecond pulse laser;

[0125] The modulator 2 is used for modulating the first pulse of the pump pulse and the Stokes pulse to obtain a modulated pulse;

[0126] The auxiliary alignment component 3 is used to align the modulated pulse with the pump pulse and the second pulse of the Stokes pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair;

[0127] The delayed scanning device 4 is used to generate two pairs of stimulated Raman excitation pulses with relative delay and adjustable relative delay based on the stimulated Raman excitation pulse pair, and the two pairs of stimulated Raman excitation pulses are used to stimulate the sample to be tested 6 to generate transient stimulated Raman scattering;

[0128] The signal acquisition device 5 is used to collect the outgoing excitation pulse pair obtained after the sample to be tested generates transient stimulated Raman scattering and interacts with the sample to be tested, obtain the transient stimulated Raman scattering signal based on the outgoing excitation pulse pair, and determine the Raman spectrum corresponding to the sample to be tested 6 based on the transient stimulated Raman scattering signal.

[0129] Specifically, in the time-domain stimulated Raman scattering system provided by the embodiment of the present invention, the femtosecond laser light source 1 is used to generate pump pulses and Stokes pulses.

[0130] The modulator 2 is used to modulate the pump pulse or the Stokes pulse to obtain a modulated pulse.

[0131] The auxiliary alignment component 3 is used to align the Stokes pulse or pump pulse with the modulated pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair. That is, if the modulator 2 modulates the pump pulse as the first pulse to obtain the modulated pulse, the auxiliary alignment component 3 aligns the Stokes pulse as the second pulse with the modulated pulse in the time dimension and the space dimension; if the modulator 2 modulates the Stokes pulse as the first pulse to obtain the modulated pulse, the auxiliary alignment component 3 aligns the pump pulse as the second pulse with the modulated pulse in the time dimension and the space dimension.

[0132] The auxiliary alignment component 3 may include multiple elements, such as a delay line and a dichroic mirror, etc. The alignment of the time dimension is achieved through the delay line, and the alignment of the space dimension is achieved through the dichroic mirror.

[0133] The stimulated Raman excitation pulse pair obtained by the auxiliary alignment component 3 can be used to pump the molecules of the sample to be tested to a vibration excited state located at the ground state of the electronic energy level.

[0134] The delayed scanning device 4 can use the stimulated Raman excitation pulse pair to generate two stimulated Raman excitation pulse pairs with relative delay and adjustable relative delay, and the two stimulated Raman excitation pulse pairs are used to stimulate the sample to be tested 6 to generate transient stimulated Raman scattering. The delayed scanning device 4 can be an interferometer, and the interferometer can be a Michelson interferometer or a Mach-Zehnder interferometer or other interferometers.

[0135] The interferometer may include two arms, a moving arm and a fixed arm, each of which may obtain a stimulated Raman excitation pulse pair. By making the lengths of the moving arm and the fixed arm different, a relative delay may be provided between the two stimulated Raman excitation pulse pairs, and the relative delay may be adjusted by controlling the length of the moving arm. The length of the moving arm may be adjusted by an optical delay line or by a reflector group, which is not specifically limited here.

[0136] The sample 6 to be tested can be fixed on the stage or placed in a cuvette. The sample 6 to be tested can be set in the transmission optical path of two stimulated Raman excitation pulse pairs, and the two stimulated Raman excitation pulse pairs excite the sample 6 to generate transient stimulated Raman scattering and emit transient stimulated Raman scattering signals.

[0137] In the embodiment of the present invention, the relative delay τ between the two stimulated Raman excitation pulse pairs, i.e., the delay scanning range of the delay scanning device 2, can be set to be greater than 5ps, so as to ensure that the resolution of the subsequently determined Raman spectrum is higher than 8cm -1 The resolution is -1.2 / 5ps under box-car apodization, which is higher than the line width of the general Raman mode. The step length of the time-delay scan can be set to less than 1fs, so that the single-photon and multi-photon transient absorption spectra of the stimulated Raman excitation pulse can be captured simultaneously.

[0138] The time-domain stimulated Raman scattering system also includes a signal acquisition device 5, which can collect the excitation pulse pair emitted after the sample to be tested generates transient stimulated Raman scattering, obtain a transient stimulated Raman scattering signal based on the excitation pulse pair, and use the transient stimulated Raman scattering signal to determine the Raman spectrum corresponding to the sample to be tested 6.

[0139] The signal acquisition device 5 may include a focusing element, a filtering element and a photoelectric detection element arranged in sequence along the optical path, as well as a phase-locked amplifier, a data acquisition card (DAQ) and a spectrum reconstruction device connected to the photoelectric detection element.

[0140] The focusing element may be a focusing mirror, which is used to collect the outgoing excitation pulse pairs.

[0141] The filter element may be a filter for filtering out the first pulse of the outgoing excitation pulse pair.

[0142] The photodetection element may be a photodetector for detecting a light intensity signal of the second pulse in the emitted excitation pulse pair.

[0143] The phase-locked amplifier is used to perform phase-locked detection on the light intensity signal and demodulate the transient stimulated Raman scattering signal from the light intensity signal.

[0144] The data acquisition card is used to collect transient stimulated Raman scattering signals, and can obtain the Raman spectrum corresponding to the sample 6 by Fourier transforming the transient stimulated Raman scattering signals. The data acquisition card can be connected to a display, and the Raman spectrum can be displayed on the display.

[0145] like Figure 6As shown, taking the adjustment of the arm length of the moving arm of the interferometer through an optical delay line (DL) as an example, the pump pulse generated in the time-domain stimulated Raman scattering system is delayed by an optical delay line (DL) and aligned in the time dimension with the modulated pulse generated by the Stokes pulse modulator.

[0146] The delayed pump pulse is reflected by the reflector and reaches the dichroic mirror 7. The modulated pulse generated by the Stokes pulse being modulated by the modulator 2 reaches the dichroic mirror 7, where it is aligned with the pump pulse in the spatial dimension, thereby obtaining a stimulated Raman excitation pulse pair.

[0147] After passing through the interferometer, the stimulated Raman excitation pulse generates two stimulated Raman excitation pulse pairs with a relative delay τ and adjustable relative delay. The interferometer includes a beam splitter (BS) 41, an optical delay line (DL) and two reflectors. The arm length of the moving arm of the interferometer is adjusted by the optical delay line.

[0148] The pulse sequence including two stimulated Raman excitation pulse pairs is focused to the sample 6 to be tested through the objective lens (Obj) 8 to achieve the excitation of the sample 6 to be tested. Thereafter, the outgoing excitation pulse pair is collected by the condenser (Condenser) 51, the Stokes pulse is filtered out by the filter (Filter) 52, and the stimulated Raman loss signal is detected by the photodiode (PD) 53. The collected stimulated Raman loss signal is detected by the phase-locked amplifier (Lock-in) 54, and then collected by the data acquisition card (DAQ) and the spectrum is reconstructed.

[0149] Taking the sample 6 to be tested as DMSO molecule as an example, if the first pulse is a Stokes pulse, the transient stimulated Raman scattering signal obtained is a stimulated Raman loss signal. Figure 7 As shown, Figure 7 The horizontal axis is the relative delay τ (ps) between two stimulated Raman excitation pulse pairs, and the vertical axis is the relative intensity ΔI / I of the stimulated Raman loss signal, which is on the order of 10 -4 .

[0150] Then, the Raman spectrum corresponding to the sample 6 to be tested is obtained as follows: Figure 8 As shown, Figure 8 The horizontal axis is the wave number (cm -1 ), the vertical axis is the signal strength of the amplified signal.

[0151] The time-domain stimulated Raman scattering system provided in the embodiment of the present invention includes: a femtosecond laser light source, a modulator, an auxiliary alignment component, a time delay scanning device and a signal acquisition device, wherein a pump pulse and a Stokes pulse are generated by the femtosecond laser light source; a first pulse is modulated by the modulator to obtain a modulated pulse; the modulated pulse is aligned with the second pulse in the time dimension and the space dimension by the auxiliary alignment component to obtain a stimulated Raman excitation pulse pair; two stimulated Raman excitation pulse pairs with relative delay and adjustable relative delay are generated by the time delay scanning device; a transient stimulated Raman scattering signal obtained by transient stimulated Raman scattering generated by the sample to be tested after being stimulated is collected by the signal acquisition device, and the Raman spectrum corresponding to the sample to be tested is determined by using the transient stimulated Raman scattering signal. The system uses a modulator to modulate the first pulse, and introduces a delayed scanning device to generate two stimulated Raman excitation pulse pairs with adjustable relative delays, which stimulate the sample to be tested to produce transient stimulated Raman scattering, and can obtain transient stimulated Raman scattering signals. Only a single excitation is required to achieve high-spectral data acquisition covering hundreds of wave numbers, with the characteristics of high time resolution. At the same time, the spectral resolution of the vibration energy level lifetime limit can be obtained through this system, which can solve the main technical bottlenecks faced by traditional stimulated Raman scattering spectroscopy technology at one time. This method can be used in Raman scattering imaging and spectral detection, related Raman probes and other fields.

[0152] On the basis of the above-mentioned embodiment, the time-domain stimulated Raman scattering system provided in the embodiment of the present invention further includes a two-dimensional galvanometer system; the two-dimensional galvanometer system can be arranged between the time-delay scanning device 4 and the signal acquisition device 5, so that the two-dimensional galvanometer system can be used to scan the sample to be tested, and then two stimulated Raman excitation pulse pairs are used to stimulate each excited position on the sample to be tested to produce transient stimulated Raman scattering, and obtain the Raman spectrum corresponding to each excited position.

[0153] Thereafter, Raman imaging is performed using each excited position and its corresponding Raman spectrum to obtain a Raman image corresponding to the sample to be tested.

[0154] On the basis of the above-mentioned embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the delayed scanning device includes an interferometer.

[0155] The moving arm of the interferometer includes a delay control structure, Fig. 9 is a top view of the delay control structure 42 in the moving arm of the interferometer, Fig.10 for Fig. 9 Side view of.

[0156] The delay control structure 42 includes: a first reflective element 421, a second reflective element 422 and a third reflective element 423;

[0157] The reflection surfaces of the first reflection element 421 and the second reflection element 422 are parallel and opposite to each other, and the third reflection element 423 is disposed on the reflection light path of the second reflection element 422;

[0158] The first reflective element 421 and the second reflective element 422 are configured to be able to rotate synchronously in the same direction;

[0159] The third reflecting element 423 is used to deflect the light beam on the reflected light path of the second reflecting element 422 and reflect it onto the second reflecting element 422 , and then output after passing through the second reflecting element 422 and the first reflecting element 421 in sequence.

[0160] The reflection surfaces of the first reflection element 421 and the second reflection element 422 are parallel and opposite, and the two are configured to rotate synchronously in the same direction to ensure that the reflection surfaces of the two remain parallel during the synchronous rotation. Here, the first reflection element 421 and the second reflection element 422 can be driven by electrical signals and can rotate to a specific angle.

[0161] The first reflective element 421 and the second reflective element 422 can be a scanning galvanometer, or other forms of high-speed scanning devices such as a resonant mirror. Since the linearity of the scanning galvanometer can reach 99.9% and the repeated positioning accuracy is high, the delay control structure can have extremely high stability and accuracy. At the same time, the scanning galvanometer has a very fast swing speed, which can improve the response speed of the delay control structure, which is conducive to the practical application of the delay control structure.

[0162] The third reflecting element 423 is disposed on the reflecting light path of the second reflecting element 422 to offset the light beam on the reflecting light path of the second reflecting element 422 and reflect it onto the second reflecting element 422 and output it after passing through the second reflecting element 422 and the first reflecting element 421 in sequence.

[0163] The incident light is reflected by the first reflecting element 421 to the second reflecting element 422. The light beam obtained after reflection by the second reflecting element 422, that is, the light beam on the reflected light path of the second reflecting element 422, is parallel to the incident light and has the same transmission direction. The light beam on the reflected light path of the second reflecting element 422 continues to be transmitted to the third reflecting element 423 and is reflected by the third reflecting element 423.

[0164] The third reflecting element 423 can deflect the light beam on the reflected light path of the second reflecting element 422 and then reflect it, so that the adjusted transmission direction is opposite to the original transmission direction.

[0165] Fig. 9 and Fig.10Only the light beam on the reflected light path of the second reflecting element 422 is shown, and the transmission direction after adjustment by the third reflecting element 423 is opposite to the original transmission direction.

[0166] Due to the existence of the first reflecting element 421 and the second reflecting element 422 , the delay control structure 42 can generate a time delay for the incident light, and the phase and optical path of the incident light also change.

[0167] Moreover, since the first reflecting element 421 and the second reflecting element 422 can rotate synchronously in the same direction, the time delay generated by the delay control structure 42 for the incident light can be adjusted according to the rotation angle of the first reflecting element 421 and the second reflecting element 422 and the placement of the first reflecting element 421 and the second reflecting element 422.

[0168] Furthermore, by scanning the rotation angles of the first reflecting element 421 and the second reflecting element 422, the time delay generated by the incident light can be scanned. The transmission direction of the light beam on the reflected light path of the second reflecting element 422 is adjusted by the third reflecting element 423 to achieve spatial descanning, so that the propagation direction of the incident light does not change with the rotation of the first reflecting element 421 or the second reflecting element 422, but the time delay (optical path, phase) will change with the rotation angles of the first reflecting element 421 and the second reflecting element 422.

[0169] The delay control structure is simple, the optical path is easy to adjust, and high-speed delay scanning can be achieved by only synchronous rotation of the first reflecting element and the second reflecting element. It has the advantages of fast scanning speed and wide applicability.

[0170] On the basis of the above embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the third reflecting element includes a first reflecting portion and a second reflecting portion, the reflecting surface of the first reflecting portion is perpendicular to the reflecting surface of the second reflecting portion, and the light beam on the reflected light path of the second reflecting element is offset by the first reflecting portion and the second reflecting portion in sequence and then reflected onto the second reflecting element;

[0171] Alternatively, the third reflecting element includes three mutually perpendicular reflecting surfaces, and the light beam on the reflecting light path of the second reflecting element is deflected by the three reflecting surfaces in sequence and then reflected onto the second reflecting element.

[0172] Specifically, Fig.11 As shown, the third reflective element 423 may be a roof mirror, including a first reflective portion 4231 and a second reflective portion 4232 arranged in a vertical direction, and the reflective surface of the first reflective portion 4231 is perpendicular to the reflective surface of the second reflective portion 4232. The first reflective portion 4231 may be above the second reflective portion 4232 or below the second reflective portion 4232. Fig.11 Only the case where the first reflecting portion 4231 is above the second reflecting portion 4232 is shown.

[0173] The light beam on the reflection light path of the second reflection element 422 is reflected by the first reflection part 4231 and the second reflection part 4232 in sequence, and then is offset in the vertical direction and reflected to the second reflection element 422, and then is output after being reflected by the second reflection element 422 and the first reflection element 421 in sequence. In particular, due to the different setting positions and setting directions of the second reflection element 422, the light beam on the reflection light path of the second reflection element 422 is reflected by the first reflection part 4231 and the second reflection part 4232 in sequence, and then can be offset in any direction and reflected to the second reflection element 422, and then is output after being reflected by the second reflection element 422 and the first reflection element 421 in sequence. Fig.11 Only the case where the arbitrary direction is the vertical direction is given.

[0174] When the first reflecting portion 4231 is above the second reflecting portion 4232, the light beam on the reflection light path of the second reflecting element 422 is sequentially reflected by the first reflecting portion 4231 and the second reflecting portion 4232, and the obtained light beam can be above the light beam on the reflection light path of the second reflecting element 422. When the first reflecting portion 4231 is below the second reflecting portion 4232, the light beam on the reflection light path of the second reflecting element 422 is sequentially reflected by the first reflecting portion 4231 and the second reflecting portion 4232, and the obtained light beam can be below the light beam on the reflection light path of the second reflecting element 422.

[0175] In addition, the third reflective element 423 can also be a retroreflector, including three mutually perpendicular reflective surfaces, and the light beam on the reflected light path of the second reflective element 422 is deflected in any direction by the three reflective surfaces in sequence and then reflected onto the second reflective element 422 .

[0176] In the embodiment of the present invention, the transmission direction of the light beam can be quickly adjusted by a third reflecting element having a first reflecting portion and a second reflecting portion or a third reflecting element having three mutually perpendicular reflecting surfaces, and the structure is simple and easy to implement.

[0177] On the basis of the above embodiments, in the time-domain stimulated Raman scattering system provided in the embodiments of the present invention, the time delay generated by the delay control structure for the incident light is determined based on the rotation angle of the first reflecting element and the second reflecting element, the distance between the first reflecting element and the second reflecting element in the transmission direction of the incident light, the angle between the first reflecting element and the second reflecting element and the transmission direction of the incident light, and the offset of the rotation axis of the first reflecting element relative to the transmission direction of the incident light.

[0178] Specifically, the delay generated by the delay control structure 42 for the incident light is mainly generated by the first reflecting element 421 and the second reflecting element 422. The delay size can be determined according to the rotation angle of the first reflecting element 421 and the second reflecting element 422, given the distance between the first reflecting element 421 and the second reflecting element 422 in the transmission direction of the incident light, the angle between the first reflecting element 421 and the second reflecting element 422 and the transmission direction of the incident light, and the offset of the rotation axis of the first reflecting element 421 relative to the transmission direction of the incident light.

[0179] like Fig.12 As shown, a y0z coordinate system is constructed on a horizontal plane, the rotation axis of the first reflective element 421 is A, and the rotation axis of the second reflective element 422 is C. The initial positions of the first reflective element 421 and the second reflective element 422 can be represented by the angle between the first reflective element 421 and the second reflective element 422 and the transmission direction of the incident light, Fig.12 The transmission direction of the incident light is the y direction, and the complementary angle of the angle between the first reflective element 421 and the second reflective element 422 and the transmission direction of the incident light is the angle α between the reflection surfaces of the first reflective element 421 and the second reflective element 422 and the z direction. Fig.12 In the figure, the projection of A on the y-axis is A′, and the angle between the line AA′ and the reflective surface of the first reflective element 421 is α.

[0180] The distance between the first reflective element 421 and the second reflective element 422 in the transmission direction of the incident light is the distance between the projection C" of C on the y-axis and A' That is y A -y C .

[0181] The offset of the rotation axis of the first reflective element 421 relative to the transmission direction of the incident light, that is, the distance between A and B

[0182] The incident point of the incident light on the first reflecting element 421 is B, the incident point of the reflected light of the first reflecting element 421 on the second reflecting element 422 is C, and the incident point of the reflected light of the second reflecting element 422 on the third reflecting element 423 is D.

[0183] On this basis, when the rotation axis A of the first reflecting element 421 rotates clockwise by an angle θ and the rotation axis C of the second reflecting element 422 rotates clockwise by an angle θ, the incident point of the incident light on the first reflecting element 421 is B', the incident point of the reflected light of the first reflecting element 421 on the second reflecting element 422 is C', and the incident point of the reflected light of the second reflecting element 422 on the third reflecting element 423 is D'.

[0184] Therefore, the time delay of the incident light caused by the rotation angle θ can be calculated by the length difference between the path B'C'D'C'B' and the path B'BCDCBB', and the phase or optical path difference can also be calculated by the length difference.

[0185] In the embodiment of the present invention, the time delay caused by the delay control structure to the incident light is determined by means of the rotation angles of the first reflective element and the second reflective element, so that the time delay can be quickly determined and controlled.

[0186] Based on the above embodiment, the rotation angle ranges from -1° to 4°, the distance is 40 mm, the angle is 75°, the offset is 5 mm, and the delay range of the incident light generated by the delay control structure is 0 to 12 ps.

[0187] Specifically, in Fig.12 If the offset is The distance between the first reflecting element 421 and the second reflecting element 422 in the transmission direction of the incident light is y A -y C =40mm, i.e. length The angle between the first reflective element 421 and the second reflective element 422 and the transmission direction of the incident light is 75°, that is, α=15°. The time delay τ generated on the incident light is obtained by calculating the length difference between the path B'C'D'C'B' and the path B'BCDCBB' by rotating the angle θ.

[0188] In the embodiment of the present invention, the corresponding relationship between the time delay τ and the rotation angle θ is as follows: Fig.13 As shown, when the rotation angle ranges from -1° to 4°, the time delay τ can range from 0 to 12 ps, which can easily achieve the order of 10 picoseconds, meeting the delay control requirements of most ultrafast pulses and achieving a wide range of optical delay control of the incident light.

[0189] On the basis of the above embodiments, in the time-domain stimulated Raman scattering system provided in the embodiments of the present invention, the incident light is an ultrafast pulse laser or any collimated light beam.

[0190] Specifically, the delay control structure in the time-domain stimulated Raman scattering system can not only perform delay control and delay scanning on the incident light of any collimated light beam, but also perform delay control and delay scanning on the incident light of ultrafast pulse laser, thus having a wide range of applications.

[0191] On the basis of the above-mentioned embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the delay control structure further includes a first driving device and a second driving device;

[0192] The first driving device is used to drive the first reflecting element to rotate;

[0193] The second driving device is used to drive the second reflecting element to rotate.

[0194] Specifically, in the embodiment of the present invention, the delay control structure may further include a first driving device for driving the first reflective element 421 to rotate and a second driving device for driving the second reflective element 422 to rotate. The first driving device and the second driving device may be devices such as motors that can be used to drive the elements to rotate.

[0195] In the embodiment of the present invention, two driving devices are used to drive the rotation of the first reflecting element and the second reflecting element respectively, so that the driving processes of the first reflecting element and the second reflecting element can be related and independent, thereby simplifying the driving process.

[0196] On the basis of the above embodiment, the time-domain stimulated Raman scattering system provided in the embodiment of the present invention further includes a controller, wherein the controller is connected to the first driving device and the second driving device respectively;

[0197] The controller is configured to control the first driving device and the second driving device to rotate continuously, so as to scan the rotation angles of the first reflecting element and the second reflecting element to achieve delayed scanning.

[0198] On the basis of the above-mentioned embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the interferometer further includes a beam splitter and a reference signal detection device;

[0199] The beam splitter is used to split the target beam of the stimulated Raman excitation pulse pair obtained by the auxiliary alignment component into a first partial beam and a second partial beam, the first partial beam is transmitted along the movable arm of the interferometer, and the second partial beam is transmitted along the fixed arm of the interferometer;

[0200] The beam splitter is also used to combine the light beam output by the movable arm of the interferometer with the light beam output by the fixed arm of the interferometer, and obtain a third partial light beam and a fourth partial light beam respectively, and the third partial light beam is used to stimulate the sample to be tested to generate transient stimulated Raman scattering;

[0201] The reference signal detection device is used to receive the fourth partial light beam and convert the fourth partial light beam into a reference signal with a coherence time greater than a preset threshold, and the reference signal is used to calibrate the position information of the delay control structure.

[0202] Specifically, Fig.14 As shown, the interferometer 40 includes not only a beam splitter 41 and a delay control structure 42, but also a reference signal detection device. The beam splitter 41 can be a semi-transparent and semi-reflective beam splitter, and the transmittance can be about 50%.

[0203] The stimulated Raman excitation pulse pair generated by the femtosecond laser light source is incident on the beam splitter 41 through the space above the first reflector 43, and the beam splitter 41 splits the target beam of the stimulated Raman excitation pulse pair generated by the femtosecond laser light source into a first partial beam and a second partial beam. The first partial beam is transmitted along the movable arm of the interferometer 40, and the second partial beam is transmitted along the fixed arm of the interferometer 40.

[0204] The beam splitter 41 is also used to combine the light beam output by the movable arm with the light beam output by the fixed arm, and obtain the third partial light beam and the fourth partial light beam respectively. The third partial light beam can be reflected to the second reflector by the first reflector 43 in sequence, reflected to the two-dimensional galvanometer system 9 by the second reflector, and incident to the third reflector after being expanded by two convex lenses with different focal lengths in sequence, reflected to the objective lens 8 by the third reflector, and focused to the sample to be tested 6 on the stage by the objective lens 8, so as to achieve the excitation of the sample to be tested 6. Thereafter, the outgoing excitation pulse pair is collected by the condenser (Condenser) 51, and the Stokes pulse is filtered out by the filter (Filter) 52, and the light intensity signal of the pump pulse is detected by the photodiode (PD) 53. The collected light intensity signal of the pump laser is demodulated by the phase-locked amplifier (Lock-in) 54 to obtain the stimulated Raman loss signal, which is collected by the data acquisition card (DAQ) and the spectrum is reconstructed.

[0205] The reference signal detection device can receive the sixth partial light beam and can convert the sixth partial light beam into a reference signal whose coherence time is greater than a preset threshold. The preset threshold here can be set as needed, for example, it can be set to 10ps. The reference signal is a narrowband high-coherence light. The interference fringes of the reference signal can be used to calibrate the position information of the delay control structure.

[0206] In the embodiment of the present invention, the reference signal detection device is introduced to avoid the deviation of the control of the relative delay caused by the non-uniform movement of the translation stage where the delay control structure is located, and the accurate collection of the transient stimulated Raman scattering signal can be achieved, thereby improving the accuracy of the Raman spectrum.

[0207] On the basis of the above-mentioned embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the reference signal detection device comprises a grating 44, a lens 45, a slit 46 and a photodiode 47;

[0208] The fourth partial light beam passes through the grating 44, the lens 45 and the slit 46 in sequence to achieve spectral filtering, and obtains a reference signal. The reference signal can be detected by the photodiode 47. That is, the photodiode 47 is used to detect the reference signal.

[0209] On the basis of the above embodiments, in the time-domain stimulated Raman scattering system provided in the embodiments of the present invention, the femtosecond laser light source 1 includes a femtosecond laser 11, a polarization beam splitter 12, a first light source branch and a second light source branch;

[0210] The femtosecond laser 11 is used to generate the femtosecond pulse laser; the polarization beam splitter 12 is used to split the femtosecond pulse laser into a fifth partial beam and a sixth partial beam;

[0211] The first light source branch includes a dispersion compensation device 13, and the dispersion compensation device 13 is used to perform dispersion compensation on the fifth partial light beam to obtain the Stokes pulse;

[0212] The second light source branch includes a frequency doubler 14 and an optical parametric oscillator 15; the frequency doubler 14 is used to double the frequency of the sixth partial light beam to obtain a frequency-doubled laser; the optical parametric oscillator 15 is driven by the frequency-doubled laser to output the pump pulse.

[0213] Specifically, the parameters of the femtosecond laser 11 may include: a central wavelength of 1030 nm, a repetition rate of 100 MHz, and a pulse width of 80 fs. The femtosecond laser 11 is used to generate femtosecond pulse laser light. The polarization beam splitter 12 may split the femtosecond pulse laser light into a fifth partial beam having a first polarization state and a sixth partial beam having a second polarization state.

[0214] The dispersion compensation device 13 can perform dispersion compensation on the fifth partial light beam, so that the pulse width of the fifth partial light beam is close to the Fourier transform limit, thereby obtaining a Stokes pulse.

[0215] In order to shorten the optical path length and reduce the size of the time-domain stimulated Raman scattering system, a fourth reflector 16 can be introduced into the first light source branch. The height of the fourth reflector 16 can be lower than the transmission optical path of the fifth partial light beam, so that the fifth partial light beam can be transmitted above the fourth reflector to the dispersion compensation device 13. A quarter wave plate (QWP) and a convex lens are also arranged in sequence between the fourth reflector 16 and the modulator 2.

[0216] The dispersion compensation device 13 may include two prisms and a reflector. The fifth partial light beam passes through the two prisms in sequence and then is reflected by the reflector. The reflected light beam passes through the two prisms in sequence and then is reflected by the fourth reflector 16 to obtain a Stokes pulse light beam.

[0217] The frequency doubler 14 doubles the frequency of the sixth part of the light beam, that is, increases the frequency of the sixth part of the light beam to twice the original frequency, and obtains a frequency-doubled laser. The optical parametric oscillator 15 is driven by the frequency-doubled laser and outputs a pump pulse. The optical parametric oscillator 15 includes an LBO crystal, a temperature-controlled oven (Oven), a Piezo and a Lyot filter. The LBO crystal and the temperature-controlled oven (Oven) are used for laser wavelength tuning, the Piezo is used for laser wavelength locking, and the Lyot filter is used for mode control and filtering.

[0218] On the basis of the above embodiment, in the time-domain stimulated Raman scattering system provided in the embodiment of the present invention, the auxiliary alignment component includes an adjustable optical delay line located on the second light source branch, and a dichroic mirror 7 located on the first light source branch and the second light source branch;

[0219] The optical delay line is used to delay the pump pulse so that the pump pulse is aligned with the Stokes pulse in the time dimension;

[0220] The dichroic mirror is used to align the pump pulse with the Stokes pulse in a spatial dimension.

[0221] Specifically, Fig.14 As shown, a reflector and a half-wave plate (HWP) are sequentially arranged on the second light source branch between the optical delay line and the dichroic mirror 7. A convex lens, a polarization beam splitter and a half-wave plate are sequentially arranged on the first light source branch between the modulator 2 and the dichroic mirror 7. A polarization beam splitter is also arranged between the dichroic mirror 7 and the first reflector 43.

[0222] Fig.15 Demonstrated the use of Fig.14 The time-domain stimulated Raman scattering system shown in Fig.13 The imaging results of polystyrene and polymethyl methacrylate (PMMA) mixed microspheres collected under the parameter setting conditions of the time-lapse control structure shown in FIG. Fig.15 There are two kinds of microspheres, namely microsphere 1 and microsphere 2, and the scale length is 10 μm.

[0223] Fig.16 Shows from Fig.15 The high spectral information reconstructed from microsphere 1 and microsphere 2 in the obtained imaging results. The spectral information can be used to distinguish the two microspheres. Fig.16 The horizontal axis is the wave number (cm -1 ), the ordinate is the normalized signal intensity.

[0224] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0225] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0226] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A time-domain stimulated Raman scattering method, characterized in that: include: Generate a pump pulse and a Stokes pulse based on a femtosecond pulse laser, select a first pulse of the pump pulse and the Stokes pulse and modulate it through a modulator to obtain a modulated pulse, align the second pulse of the pump pulse and the Stokes pulse with the modulated pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair; Based on the stimulated Raman excitation pulse pair, two stimulated Raman excitation pulse pairs are generated with a relative delay and an adjustable relative delay; Based on the two stimulated Raman excitation pulse pairs, the relative delay is scanned to excite the sample to be tested to generate transient stimulated Raman scattering, and transient stimulated Raman scattering signals corresponding to each relative delay are obtained. Based on the transient stimulated Raman scattering signals, the Raman spectrum corresponding to the sample to be tested is determined.

2. The time-domain stimulated Raman scattering method according to claim 1, characterized in that: If the first pulse is the pump pulse, the transient stimulated Raman scattering signal is a stimulated Raman gain signal; If the first pulse is the Stokes pulse, the transient stimulated Raman scattering signal is a stimulated Raman loss signal.

3. The time-domain stimulated Raman scattering method according to claim 1, characterized in that: Based on the two stimulated Raman excitation pulse pairs, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, obtaining transient stimulated Raman scattering signals corresponding to each relative delay, and determining the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signals, including: Based on the two stimulated Raman excitation pulse pairs, scanning the relative delay to excite the sample to be tested to generate transient stimulated Raman scattering, and obtaining an outgoing excitation pulse pair after interacting with the sample to be tested; Performing photoelectric conversion and phase-locked detection on the second pulse in the outgoing excitation pulse pair to obtain the transient stimulated Raman scattering signal; The transient stimulated Raman scattering signal is subjected to Fourier transform to obtain the Raman spectrum.

4. The time-domain stimulated Raman scattering method according to any one of claims 1 to 3, characterized in that: Based on the transient stimulated Raman scattering signal, determining the Raman spectrum corresponding to the sample to be tested, and then further comprising: Based on the Raman spectra corresponding to the excited positions on the sample to be tested, a Raman image corresponding to the sample to be tested is obtained.

5. A time-domain stimulated Raman scattering system, characterized in that: include: Femtosecond laser light source, modulator, auxiliary alignment component, time-delay scanning device and signal acquisition device; The femtosecond laser light source is used to generate pump pulses and Stokes pulses based on femtosecond pulse laser; The modulator is used to modulate the first pulse of the pump pulse and the Stokes pulse to obtain a modulated pulse; The auxiliary alignment component is used to align the modulated pulse with the pump pulse and the second pulse of the Stokes pulse in the time dimension and the space dimension to obtain a stimulated Raman excitation pulse pair; The delayed scanning device is used to generate two pairs of stimulated Raman excitation pulses with relative delay and adjustable relative delay based on the stimulated Raman excitation pulse pair, and the two pairs of stimulated Raman excitation pulses are used to stimulate the sample to be tested to generate transient stimulated Raman scattering; The signal acquisition device is used to acquire an outgoing excitation pulse pair obtained after the sample to be tested generates transient stimulated Raman scattering and interacts with the sample to be tested, obtain a transient stimulated Raman scattering signal based on the outgoing excitation pulse pair, and determine the Raman spectrum corresponding to the sample to be tested based on the transient stimulated Raman scattering signal.

6. The time-domain stimulated Raman scattering system according to claim 5, characterized in that: It also includes a galvanometer system; the galvanometer system is arranged between the time-delay scanning device and the signal acquisition device.

7. The time-domain stimulated Raman scattering system according to claim 5, characterized in that: The signal acquisition device includes a focusing element, a filtering element, a photoelectric detection element, a lock-in amplifier and a data acquisition card; The focusing element is used to collect the outgoing excitation pulse pair; The filter element is used to filter out the first pulse of the outgoing excitation pulse pair; The photoelectric detection element is used to detect the light intensity signal of the second pulse in the outgoing excitation pulse pair; The lock-in amplifier is used to perform phase-locked detection on the light intensity signal and demodulate the transient stimulated Raman scattering signal from the light intensity signal; The data acquisition card is used to acquire the transient stimulated Raman scattering signal and determine the Raman spectrum based on the transient stimulated Raman scattering signal.

8. The time-domain stimulated Raman scattering system according to claim 5, characterized in that: The delayed scanning device includes an interferometer; The moving arm of the interferometer includes a delay control structure, and the delay control structure includes a first reflective element, a second reflective element, and a third reflective element; The reflection surfaces of the first reflection element and the second reflection element are parallel and opposite to each other, and the third reflection element is arranged on the reflection light path of the second reflection element; The first reflective element and the second reflective element are configured to be able to rotate synchronously in the same direction; The third reflecting element is used to offset the light beam on the reflected light path of the second reflecting element and reflect it onto the second reflecting element, and then output it after passing through the second reflecting element and the first reflecting element in sequence.

9. The time-domain stimulated Raman scattering system according to claim 8, characterized in that: The third reflecting element comprises a first reflecting portion and a second reflecting portion, the reflecting surface of the first reflecting portion is perpendicular to the reflecting surface of the second reflecting portion, and the light beam on the reflecting light path of the second reflecting element is offset by the first reflecting portion and the second reflecting portion in sequence and then reflected to the second reflecting element; Alternatively, the third reflecting element includes three mutually perpendicular reflecting surfaces, and the light beam on the reflecting light path of the second reflecting element is deflected by the three reflecting surfaces in sequence and then reflected onto the second reflecting element.

10. The time-domain stimulated Raman scattering system according to claim 8, characterized in that: The time delay generated by the delay control structure for the incident light is determined based on the rotation angle of the first reflecting element and the second reflecting element, the distance between the first reflecting element and the second reflecting element in the transmission direction of the incident light, the angle between the first reflecting element and the second reflecting element and the transmission direction of the incident light, and the offset of the rotation axis of the first reflecting element relative to the transmission direction of the incident light.

11. The time-domain stimulated Raman scattering system according to claim 10, characterized in that: The rotation angle ranges from -1° to 4°, the distance is 40 mm, the included angle is 75°, the offset is 5 mm, and the delay range of the incident light generated by the delay control structure is 0 to 12 ps.

12. The time-domain stimulated Raman scattering system according to claim 10, characterized in that: The incident light is an ultrafast pulse laser or any collimated light beam.

13. The time-domain stimulated Raman scattering system according to claim 8, characterized in that: The delay control structure also includes a first driving device and a second driving device; The first driving device is used to drive the first reflecting element to rotate; The second driving device is used to drive the second reflecting element to rotate.

14. The time-domain stimulated Raman scattering system according to claim 13, characterized in that: Also includes a controller, the controller is connected to the first driving device and the second driving device respectively; The controller is configured to control the first driving device and the second driving device to rotate continuously, so as to scan the rotation angles of the first reflecting element and the second reflecting element to achieve delayed scanning.

15. The time-domain stimulated Raman scattering system according to claim 8, characterized in that: The interferometer also includes a beam splitter and a reference signal detection device; The beam splitter is used to split the target beam of the stimulated Raman excitation pulse pair obtained by the auxiliary alignment component into a first partial beam and a second partial beam, the first partial beam is transmitted along the movable arm of the interferometer, and the second partial beam is transmitted along the fixed arm of the interferometer; The beam splitter is also used to combine the light beam output by the movable arm of the interferometer with the light beam output by the fixed arm of the interferometer, and obtain a third partial light beam and a fourth partial light beam respectively, and the third partial light beam is used to stimulate the sample to be tested to generate transient stimulated Raman scattering; The reference signal detection device is used to receive the fourth partial light beam and convert the fourth partial light beam into a reference signal with a coherence time greater than a preset threshold, and the reference signal is used to calibrate the position information of the delay control structure.

16. The time-domain stimulated Raman scattering system according to claim 15, characterized in that: The reference signal detection device includes a grating, a lens, a slit and a photodiode; The fourth partial light beam passes through the grating, the lens and the slit in sequence to obtain the reference signal; The photodiode is used to detect the reference signal.

17. The time-domain stimulated Raman scattering system according to any one of claims 5 to 16, characterized in that: The femtosecond laser light source comprises a femtosecond laser, a polarization beam splitter, a first light source branch and a second light source branch; The femtosecond laser is used to generate the femtosecond pulse laser; the polarization beam splitter is used to split the femtosecond pulse laser into a fifth partial light beam and a sixth partial light beam; The first light source branch includes a dispersion compensation device, and the dispersion compensation device is used to perform dispersion compensation on the fifth partial light beam to obtain the Stokes pulse; The second light source branch includes a frequency multiplier and an optical parametric oscillator; The frequency doubler is used to double the frequency of the sixth partial light beam to obtain a frequency-doubled laser; the optical parametric oscillator is driven by the frequency-doubled laser to output the pump pulse.

18. The time-domain stimulated Raman scattering system according to claim 17, characterized in that: The auxiliary alignment assembly includes an adjustable optical delay line located on the second light source branch, and a dichroic mirror located on the first light source branch and the second light source branch; The optical delay line is used to delay the pump pulse so that the pump pulse is aligned with the Stokes pulse in the time dimension; The dichroic mirror is used to align the pump pulse with the Stokes pulse in a spatial dimension.

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