CN113092379B - Spatially resolved transient system - Google Patents
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- CN113092379B CN113092379B CN202110414468.5A CN202110414468A CN113092379B CN 113092379 B CN113092379 B CN 113092379B CN 202110414468 A CN202110414468 A CN 202110414468A CN 113092379 B CN113092379 B CN 113092379B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/3103—Atomic absorption analysis
Abstract
The invention provides a space resolution transient system, which comprises a femtosecond laser source and a light splitting element, wherein femtosecond pulse laser light emitted by the femtosecond laser source is split into pump light and probe light through the light splitting element, the probe light is incident to an achromatic microscope objective after group velocity dispersion compensation is carried out on the probe light through a probe light modulation optical path, the pump light is incident to the achromatic microscope objective after double-grating dispersion compensation is carried out on the pump light modulation optical path, and the probe light and the pump light after dispersion compensation are focused to a common focus of a sample through the achromatic microscope objective. The invention realizes the coincidence of different frequency components of the femtosecond pulse laser on a space domain and a time domain by utilizing a prism and a double-grating dispersion compensation method, can eliminate phase difference, chromatic aberration and time difference, enables the femtosecond pulse laser to still maintain narrower pulse width and higher time resolution after passing through an optical element, has small focusing light spot, high precision and high three-dimensional symmetry characteristic, not only retains the characteristic of the femtosecond pulse laser, but also can realize higher space resolution.
Description
Technical Field
The invention relates to the technical field of optical detection, in particular to a spatial resolution transient system.
Background
The pumping-detection femtosecond transient absorption spectrum enables human beings to really know the dynamic process and the generated dynamic response in the material from molecular and atomic magnitudes, and is an important means for researching the luminous dynamics, the molecular reaction dynamics and the light and substance action process of the material. The method analyzes photochemical and photophysical processes of the substance by detecting absorption changes of a short-life intermediate and an excited state generated by the action of ultrafast laser on the substance to detection light, and has important potential application value in the aspects of researching energy transfer, chemical bond generation and breakage, charge transfer, valence electron ionization, configuration relaxation and the like in the ultrafast process of the substance.
The technical principle of the pump-detection femtosecond transient absorption spectrometer is that one beam of femtosecond pulse light with high energy is used for exciting particles in a material to an excited state, and the other beam of broad-spectrum detection light with low energy is used for detecting an absorption spectrum or a reflection spectrum of an excited sample to obtain a transition process between the number of particles on the energy level of the excited state and other energy levels. And adjusting the delay time of the detection light pulse relative to the pumping light pulse to obtain the condition that the population distribution on each energy level of the excited state of the substance changes along with time, and obtaining the detailed process of the relaxation of the substance molecules from the radiation energy of the excited state to the ground state of other energy levels. By detecting the absorption or reflection spectrum of the sample in the excited state to the detection light, the dynamic process of the action of the substance and the light field is known.
The existing pumping-detection transient absorption spectrum technology with spatial separation mainly combines two beams of femtosecond lasers of pumping light and detection light to be close to coaxial through a scanning reflector group and a focusing objective lens to realize the function of spatial resolution spectrum detection. In the existing space resolution transient absorption microspectrum measuring device, after femtosecond laser output by a femtosecond laser is split by a splitting piece, pump laser and detection laser respectively enter a microspectrum acquisition module after being modulated by a laser performance adjusting module, the detection laser sweeps the pump laser from left to right stagnation points on a microscope objective through the adjustment of a space scanning module, and the time delay of the detection laser and the pump laser is adjusted by a time scanning module at each space point scanned by the detection laser; the signal detection module records differential reflection signals of the detection laser and generates a transient absorption micro spectrum of space-time resolution.
However, when the femtosecond pulse laser passes through an optical element (such as a lens), dispersion is introduced, the femtosecond pulse laser generates great change, pulse broadening is caused, time resolution is reduced, a laser focusing spot cannot present three-dimensional symmetry, axial resolution is low, and the quality of experimental measurement data of a transient absorption spectrum/a transient reflection spectrum is seriously influenced.
Disclosure of Invention
The invention aims to provide a spatial resolution transient system, which combines an achromatic microscope objective with a prism dispersion compensation principle and a double-grating dispersion compensation technology to realize the coincidence of different frequency components of femtosecond pulse laser on a spatial domain and a time domain, and simultaneously eliminates phase difference, chromatic aberration and time difference, so that the femtosecond pulse laser can still maintain narrower pulse width and higher time resolution after passing through an optical element.
In order to achieve the purpose, the invention adopts the following specific technical scheme:
the invention provides a spatial resolution transient system which comprises a femtosecond laser source, a light splitting element, a detection light modulation light path and a pump light modulation light path, wherein femtosecond pulse laser light emitted by the femtosecond laser source is split into pump light and detection light through the light splitting element, the detection light is incident to an achromatic microscope objective after group velocity dispersion compensation is carried out on the detection light modulation light path, the pump light is incident to the achromatic microscope objective after double-grating dispersion compensation is carried out on the pump light modulation light path, and the detection light and the pump light after dispersion compensation are focused to a common focus of a sample through the achromatic microscope objective.
Preferably, the pump light modulation optical path comprises a first focusing mirror, a frequency doubling crystal, a first collimating mirror, a first dichroic mirror, a second dichroic mirror, a first reflector group, a first grating and a second grating; the first focusing mirror is used for focusing the pump light on the frequency doubling crystal; the frequency doubling crystal is used for frequency doubling the pump light to form two beams of pump light, one beam of pump light is long-wave-band pump light keeping the original wavelength, and the other beam of pump light is short-wave-band pump light smaller than the original wavelength; the first collimating mirror is used for collimating the short-wave-band pump light and the long-wave-band pump light into parallel light; the first dichroic mirror is used for transmitting the long-wave-band pump light to enable the long-wave-band pump light to be reflected to the second dichroic mirror through the reflector of the first reflector group, and reflecting the short-wave-band pump light to enable the short-wave-band pump light to be reflected to the second dichroic mirror through the reflector of the first reflector group; the second dichroic mirror is used for transmitting the long-wave-band pump light and reflecting the short-wave-band pump light, so that the long-wave-band pump light and the short-wave-band pump light are respectively incident to the first grating; the first grating and the second grating are used for modulating long-wave-band pump light and short-wave-band pump light by introducing space chirp, and the modulated long-wave-band pump light and short-wave-band pump light are reflected by a reflector of the first reflector group and vertically incident into the achromatic microscope objective.
Preferably, the pump light modulation optical path further includes a switch disposed in the reflection direction and the transmission direction of the first dichroic mirror and configured to control the long-wavelength band pump light and the short-wavelength band pump light.
Preferably, the pump light modulation optical path further comprises a double-pass mirror disposed in the reflection direction and the transmission direction of the second dichroic mirror for filtering out stray light.
Preferably, the detection light modulation optical path comprises an optical delay line, a half-wave plate, a second focusing mirror, a white light generating medium, a second collimating mirror, a prism group and a second reflecting mirror group; the optical delay line is used for carrying out time delay on the detection light so as to generate time difference between the detection light and the pumping light; the half-wave plate is used for carrying out polarization adjustment on the detection light; the second focusing mirror is used for converging the detection light to the white light generation medium; the white light generating medium is used for generating white light under the excitation of the detection light; the second collimating mirror is used for collimating the white light and reflecting the white light to the prism group through the reflecting mirror of the second reflecting mirror group; the prism group is used for carrying out reverse group velocity dispersion compensation on the collimated white light, and then the collimated white light is reflected to the achromatic microscope objective by the reflector of the second reflector group.
Preferably, the prism group comprises a first prism, a second prism, a third prism and a fourth prism, wherein the apex angles of the first prism, the second prism, the third prism and the fourth prism are respectively 35-60 degrees, the third prism and the fourth prism are symmetrical to the first prism, and the size of the second prism is not less than 1.391-1.651 times of the size of the first prism; after collimated parallel light with the wavelength range of 380nm-780nm enters the first prism, the light angles with different wavelengths are expanded, the light angles are continuously expanded through the second prism, and the light angles are combined into a beam through the third prism and the fourth prism.
Preferably, the detection light modulation optical path further comprises a positioning diaphragm arranged between the optical delay line and the light splitting element for calibrating the position and direction of the detection light.
Preferably, the white light generating medium is a sapphire crystal, a calcium fluoride crystal, or a water tank.
Preferably, the spatial resolution transient system further comprises a data acquisition device, wherein the data acquisition device comprises a chopper, a chopper controller, a fiber coupling spectrophotometer and a PC, and is used for acquiring two-dimensional imaging of the sample on the detection light absorption signal or the reflection signal after the pumping light and the detection light act on the sample together.
Preferably, the spatially resolved transient system further comprises a motorized displacement stage for moving the sample in a horizontal direction.
The invention can obtain the following technical effects:
1. the method has the advantages that the prism dispersion compensation principle and the double-grating dispersion compensation technology are combined with an achromatic microobjective, so that different frequency components of pump light and probe light are superposed on a space domain and a time domain, the shortest pulse width of a Fourier transform limit is achieved, and phase difference, chromatic aberration and time difference are eliminated, so that the pump light and the probe light can still maintain the narrower pulse width and the higher time resolution after passing through an optical element, the laser focusing device has the advantages of small laser focusing light spot, high precision and three-dimensional symmetry, and the characteristics of femtosecond pulse laser are kept, and the higher space resolution can be achieved.
2. Because different frequency components of light outside the optical focal plane are not superposed on a time domain and a space domain, the pulse width is widened, and the time resolution is reduced, so that the invention achieves the effect of simultaneously focusing the different frequency components of the pump light and the detection light in the time domain and the space domain only at the geometric focusing point of the achromatic microscope objective, and the obtained focusing light spot is small, high in precision and highly three-dimensionally symmetrical.
3. The double-optical-path control can effectively inhibit errors caused by laser fluctuation, and a double-grating and prism dispersion compensation method can effectively realize high signal-to-noise ratio, stability, wide band and multiple control parameters.
Drawings
Fig. 1 is a schematic structural diagram of a spatially resolved transient system according to an embodiment of the invention.
Wherein the reference numerals include: the femtosecond laser source 1, the light splitting element 2, the first focusing mirror 31, the frequency doubling crystal 32, the first collimating mirror 33, the first dichroic mirror 341, the second dichroic mirror 342, the first reflecting mirror 351, the second reflecting mirror 352, the third reflecting mirror 353, the fourth reflecting mirror 354, the fifth reflecting mirror 355, the dual-passing mirror 36, the first grating 371, the second grating 372, the switch 38, the optical delay line 41, the half-wave plate 42, the second focusing mirror 43, the white light generating medium 44, the second collimating mirror 45, the sixth reflecting mirror 461, the seventh reflecting mirror 462, the eighth reflecting mirror 463, the ninth reflecting mirror 464, the first prism 471, the second prism 472, the third prism 473, the fourth prism 474, the positioning diaphragm 48, the achromatic microscope objective 5, the sample chopper 6, the electric displacement stage 7, the chopper 81, the chopper controller 82, the fiber-coupled spectrometer 83, and the PC 84.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
The integral thought of the invention is that different frequency components of the femtosecond pulse laser are spread in space by utilizing a prism dispersion compensation principle and a double-grating dispersion compensation technology, certain space chirp is introduced, and two beams of the femtosecond pulse laser modulated by chirp are focused at a confocal point of a detected object through an achromatic microscope objective. Different frequency components of the pulse coincide in space and time at the geometric focus of the focusing objective lens, and the shortest pulse width of the Fourier transform limit is achieved. And the simultaneous focusing effect of a time domain and a space domain is realized on different frequency components of the pulse only at the geometric focusing point of the achromatic microscope objective, the broadening effect of the optical system on the pulse is counteracted, and the obtained focusing light spot is small, high in precision and highly three-dimensionally symmetrical. The double-optical-path control can effectively inhibit errors caused by laser fluctuation, and a double-grating and prism dispersion compensation method can effectively realize high signal-to-noise ratio, stability, wide band and multiple control parameters. By combining the X-Y two-dimensional high-precision electric displacement table, a scanning area and spatial resolution can be set according to the specification of a semiconductor laser chip, a spatial resolution transient detection system with high spatial resolution is realized, and the precision of measured data is high.
Fig. 1 shows the structure of a spatially resolved transient system according to one embodiment of the invention.
As shown in fig. 1, a spatially resolved transient system provided by an embodiment of the present invention includes: the device comprises a femtosecond laser source 1, a light splitting element 2, an achromatic microscope objective 5, a detection light modulation light path, a pump light modulation light path and a data acquisition device.
The femtosecond laser source 1 emits femtosecond pulse laser light with the central wavelength of 800nm, the femtosecond pulse laser light is divided into two beams by the light splitting element 2, one beam with higher energy is used as pump light, one beam with lower energy is used as detection light, the detection light is reflected to enter a detection light modulation light path, and the pump light is transmitted to enter a pump light modulation light path. The light splitting element 2 may be a beam splitting sheet or a dichroic mirror.
The pumping light modulation optical path comprises a first focusing mirror 31, a frequency doubling crystal 32, a first collimating mirror 33, a first dichroic mirror 341, a second dichroic mirror 342, a first mirror group, a double-pass mirror 36, a first grating 371 and a second grating 372.
The first mirror group includes a first mirror 351, a second mirror 352, a third mirror 353, a fourth mirror 354 and a fifth mirror 355.
The pumping light is incident on the frequency doubling crystal 32 after being converged by the first focusing mirror 31, so that the optical density on the frequency doubling crystal 32 is improved. The converged pump light is frequency-doubled by the frequency doubling crystal 32 to form two pump lights, one of which is a long-wavelength-band pump light maintaining the original wavelength, the other of which is a short-wavelength-band pump light smaller than the original wavelength, and the short-wavelength-band pump light and the long-wavelength-band pump light are changed into parallel light through the first collimating mirror 33 and then incident on the first dichroic mirror 341.
Since the short-wavelength-band pump light and the long-wavelength-band pump light are parallel light, the switches 38 may be respectively disposed in the transmission direction and the reflection direction of the first dichroic mirror 341, and the short-wavelength-band pump light and the long-wavelength-band pump light are controlled by the two switches 38.
The long-wave-band pump light is transmitted by the first dichroic mirror 341, reflected by the first reflecting mirror 351, reflected by the second reflecting mirror 352, transmitted by the second dichroic mirror 342 and incident to the dual-pass mirror 36, the short-wave-band pump light is reflected by the first dichroic mirror 341, reflected by the third reflecting mirror 353, reflected by the fourth reflecting mirror 354, reflected by the second dichroic mirror 342 and incident to the dual-pass mirror 36, and the short-wave-band pump light and the long-wave-band pump light are incident to the first grating 371 after stray light is filtered by the dual-pass mirror 36.
The first grating 371 and the second grating 372 are placed in parallel, the short-wavelength-band pump light and the long-wavelength-band pump light are firstly diffracted on the first grating 371, each diffracted light is diffracted again on the second grating 372, and the positive chirp can be compensated by adjusting the distance between the first grating 371 and the second grating 372. The first grating 371 and the second grating 372 arranged in parallel can spatially spread different frequency components of the short-wavelength-band pump light and the long-wavelength-band pump light, introduce a certain spatial chirp, and vertically inject the chirp-modulated short-wavelength-band pump light and the chirp-modulated long-wavelength-band pump light into the achromatic microscope objective 5 through the fifth reflector 355 to be focused at a confocal point of the sample 6.
The sample 6 is mounted on a motorized stage 7, and the two-dimensional movement of the sample 6 in the horizontal direction is realized by the motorized stage 7.
Spatial chirp is the effect of spreading out light of different wavelengths spatially. Specifically, the short pulse spectral band is wide, the optical refractive indexes of the light with different wavelengths are different, and the short wavelength component (high frequency component) in the incident light pulse is influenced by the group velocity dispersion effect, the group velocity of the short wavelength component (high frequency component) is high, and the short wavelength component (high frequency component) is located at the front edge of the pulse after being transmitted by the optical fiber, the long wavelength component (low frequency component) is located at the rear edge of the pulse, and the effect that the light with different wavelengths spreads in space is the spatial chirp.
The detection light modulation optical path comprises an optical delay line 41, a half-wave plate 42, a second focusing mirror 43, a white light generating medium 44, a second collimating mirror 45, a second mirror group and a prism group.
The second mirror group includes a sixth mirror 461, a seventh mirror 462, an eighth mirror 463, and a ninth mirror 464.
The detection light sequentially passes through the optical delay line 41, the half-wave plate 42, the second focusing mirror 43, the white light generating medium 44, the second collimating mirror 45, the sixth reflecting mirror 461, the prism group, the seventh reflecting mirror 462, the eighth reflecting mirror 463 and the ninth reflecting mirror 464 to enter the achromatic microscope objective 5, and is focused by a diaphragm at the front end of the achromatic microscope objective 5, so that the detection light is vertically incident on the sample 6.
The detection light is time delayed by an optical delay line 41, so that a time difference is generated between the detection light and the pump light. The optical delay line 41 includes a horizontal displacement stage and a polygon mirror, which may be replaced with a mirror group. The horizontal displacement stage must ensure that the position and orientation of the lower beam is unchanged and the beam shape remains unchanged while moving. The detecting light is required to be parallel light or quasi-parallel light, the incident direction is consistent with the optical delay displacement direction, and a positioning diaphragm 48 is arranged between the optical delay line 41 and the light splitting element 2 to calibrate the position and the direction of the detecting light.
After the polarization adjustment of the optically delayed detection light is realized by the half-wave plate 42, the detection light is converged by the second focusing lens 43 and then enters the white light generating medium 44, so that the light density on the white light generating medium 44 is improved.
The white light generating medium 44 is generally a sapphire crystal, a calcium fluoride crystal, a water tank, etc., wherein the sapphire crystal can generate a stable and smooth spectrum of femtosecond pulse white light with a wavelength starting from about 400nm under the excitation of a fundamental frequency light of 800 nm; calcium fluoride can generate femtosecond pulse white light from 360nm to about 1 μm; the water box can generate femtosecond pulse white light with the wavelength of 450nm to 1.0 μm. The generated wide white light is changed into parallel light by the second collimating mirror 45.
The white light generated by the white light generating medium 44 has a wavelength range of 380nm to 780nm, the wavelength range is wide, the laser beam spot can be widened into a strip after optical delay, and the generated wide white light is changed into parallel light through the second collimating mirror 45 and has a certain geometric space, so that the grating can not be used for group velocity dispersion compensation, and only the prism group can be used for dispersion compensation.
The prism group is added on the detection light modulation optical path to introduce negative group velocity dispersion compensation, and the prism group can compensate positive chirp and negative chirp to offset the pulse broadening effect of the optical system. The distance between the prisms introduces negative group velocity dispersion, while the optical path within the prisms introduces positive group velocity dispersion. Negative group velocity dispersion is caused by the optical path difference of different wavelengths and is only affected by the spacing between prisms. For positive group velocity dispersion, the optical path inside the prism plays a decisive role, and moving the prism in the right direction can change the different wavelengths through the thickness in the prism material to the same extent. Thus, by moving the prism, the value of the positive dispersion can be changed, and the total dispersion result depends on the sum of the positive dispersion and the negative dispersion at different positions of the prism.
The prism group includes a first prism 471, a second prism 472, a third prism 473, and a fourth prism 474, and the wide white light is reflected to the first prism 471 by the sixth reflector 461, and then the light angles of different wavelengths are expanded, and the light angles are expanded continuously after passing through the second prism 472. The third prism 473 is disposed symmetrically to the second prism 472, the fourth prism 474 is disposed symmetrically to the first prism 471, and after passing through the third prism 473 and the fourth prism 474, the split direction of the spectrum is opposite to that before, and thus, the light is converged into one light. And the light is reflected by the seventh reflector 462, the eighth reflector 463 and the ninth reflector 464 in sequence and then enters the achromatic microscope 5 for focusing, so that the effect of simultaneously focusing different frequency components of the detection light in a time domain and a space domain only at the geometric focusing point of the objective lens can be achieved, and the obtained focused light spot is small, high in precision and highly three-dimensionally symmetrical.
In the existing prism group velocity dispersion compensation technology, the four prisms are designed completely the same, however, it is not suitable to perform group velocity dispersion compensation on white light with a wide wavelength range. The prisms change the propagation direction of light and simultaneously change the beam width and the opening angle of the light beam in the incident plane, so that the relative positions and the relative sizes of the four prisms need to be reasonably designed.
Assuming that the white light is composed of a series of parallel monochromatic lights (380nm-780nm), each monochromatic light ray is incident on the first working surface of the first prism 471 at an incident angle of 60 °, the exit surface of the first prism 471 is parallel to the incident surface of the second prism 472, and the distance between the first prism 471 and the second prism 472 is 1 cm. Each monochromatic light with different wavelengths needs to be emitted from the emitting surface of the first prism 471.
Assuming that the prism material is BK7 glass, the refractive index is 1.5337 when the wavelength of monochromatic light is 380 nm; the refractive index was 1.5112 at a wavelength of 780 nm. Monochromatic light with wavelengths within the two extreme ranges is incident in parallel to a BK7 glass triangular prism, and the vertex angle of the prism is usually between 35 ° and 60 °. The incident angle of the incident surface is alpha160 degrees, according to the refractive index law and the beam expansion ratio calculation formula:
n1·sinα1＝n2·sinα2
m and M' represent the ratio of the expanded beam, i.e., the beam width ratio, of the monochromatic light with wavelengths of 380nm and 780nm, respectively, entering the second prism 472 through the first prism 471. Alpha1、ɑ2Respectively representing an incident angle and a refraction angle, a, of monochromatic light with a wavelength of 380nm on a first working surface (i.e., an incident surface) of the first prism 4713、ɑ4Respectively representing the incident angle and the exit angle of monochromatic light with a wavelength of 380nm on the second working surface (i.e., the exit surface) of the first prism 471. Alpha1、ɑ`2Respectively representing the incident angle and the refraction angle, a ″, of a monochromatic light with a wavelength of 780nm on the first working surface of the first prism 4713，ɑ`4Respectively representing the incident angle and the exit angle of monochromatic light with a wavelength of 780nm on the second working surface of the first prism 471.
When the apex angle of the first prism 471 and the second prism 472 is 35 °, M and M' are 1.651 and 1.639, respectively; when the vertex angle of the first prism 471 and the second prism 472 is 60 °, M and M' are 1.370 and 1.391, respectively; when the vertex angle of the first prism 471 and the second prism 472 is 35 degrees, the size of the second prism 472 should be not less than 1.651 times of the size of the first prism 471; when the vertex angle of the first prism 471 and the second prism 472 is 60 °, the size of the second prism 472 should be not less than 1.391 times the size of the first prism 471.
When the vertex angles of the first prism 471 and the second prism 472 are 35 degrees, the side length of the first prism 471 is designed to be 1cm, and the primary side length size of the second prism 472 ranges from 1.651 cm to 3.5 cm; when the vertex angle of the first prism 471 and the vertex angle of the second prism 472 are 60 °, the side length of the first prism 471 is designed to be 1cm, and the primary side length of the second prism 472 is in the range of 1.391-3 cm. The third prism 473 and the second prism 472 have the same size, and the fourth prism 474 and the first prism 471 have the same size.
The invention carries out group velocity dispersion compensation on the wide white light on the detection light path through the prisms with different sizes, thereby not only avoiding the waste of material cost and space, but also achieving the purpose of group velocity dispersion compensation.
The double-optical-path control can effectively inhibit errors caused by laser fluctuation, and a double-grating and prism dispersion compensation method can effectively realize high signal-to-noise ratio, stability, wide band and multiple control parameters.
The data acquisition device comprises a chopper 81, a chopper controller 82, a fiber coupling spectrophotometer 83 and a PC 84, and is used for acquiring two-dimensional imaging of the sample 6 to a detection light absorption signal or a reflection signal after the pumping light and the detection light act on the sample 6 together.
In the description herein, references to the description of "one embodiment," "an example," "another example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A space resolution transient system comprises a femtosecond laser source and a light splitting element, wherein femtosecond pulse laser light emitted by the femtosecond laser source is split into pump light and probe light through the light splitting element, the probe light is incident to an achromatic microscope objective after group velocity dispersion compensation is carried out on the probe light through a prism group in a probe light modulation light path, the prism group comprises a first prism, a second prism, a third prism and a fourth prism, the apex angle of the first prism is 35-60 degrees, the third prism is symmetrical to the second prism, the fourth prism is symmetrical to the first prism, and the size of the second prism is not less than 1.391-1.651 times of the size of the first prism; and the pump light enters the achromatic microobjective after being subjected to double-grating dispersion compensation through the pump light modulation optical path, and the probe light and the pump light after dispersion compensation are focused to a confocal point of a sample through the achromatic microobjective.
2. The spatially resolved transient system of claim 1, wherein the pump light modulation optical path comprises a first focusing mirror, a frequency doubling crystal, a first collimating mirror, a first dichroic mirror, a second dichroic mirror, a first mirror group, a first grating, and a second grating; wherein the content of the first and second substances,
the first focusing mirror is used for focusing the pump light onto the frequency doubling crystal;
the frequency doubling crystal is used for doubling the frequency of the pump light to form two beams of pump light, one beam of pump light is long-wave-band pump light with the original wavelength kept, and the other beam of pump light is short-wave-band pump light with the wavelength smaller than the original wavelength;
the first collimating mirror is used for collimating the short-wavelength-band pump light and the long-wavelength-band pump light into parallel light;
the first dichroic mirror is used for transmitting the long-wavelength-band pump light to enable the long-wavelength-band pump light to be reflected to the second dichroic mirror through the reflector of the first reflector group, and reflecting the short-wavelength-band pump light to enable the short-wavelength-band pump light to be reflected to the second dichroic mirror through the reflector of the first reflector group;
the second dichroic mirror is used for transmitting the long-wave-band pump light and reflecting the short-wave-band pump light, so that the long-wave-band pump light and the short-wave-band pump light are respectively incident to the first grating;
the first grating and the second grating are used for modulating the long-wave-band pump light and the short-wave-band pump light by introducing space chirp, and the modulated long-wave-band pump light and the modulated short-wave-band pump light are reflected by the reflector of the first reflector group and vertically incident into the achromatic microscope objective.
3. The spatially resolved transient system of claim 2, wherein the pump light modulation optical path further comprises a switch disposed in the reflection direction and the transmission direction of the first dichroic mirror for controlling the long-wavelength band pump light and the short-wavelength band pump light.
4. The spatially resolved transient system of claim 2, wherein the pump light modulation optical path further comprises a double pass mirror disposed in the reflection direction and the transmission direction of the second dichroic mirror for filtering out stray light.
5. The spatially resolved transient system of claim 1, wherein the probing light modulation optical path comprises an optical delay line, a half-wave plate, a second focusing mirror, a white light generating medium, a second collimating mirror, and a second mirror set; wherein the content of the first and second substances,
the optical delay line is used for carrying out time delay on the detection light so as to generate a time difference between the detection light and the pumping light;
the half-wave plate is used for carrying out polarization adjustment on the detection light;
the second focusing mirror is used for converging the detection light to the white light generation medium;
the white light generating medium is used for generating white light under the excitation of the detection light;
the second collimating mirror is used for collimating the white light and reflecting the white light to the prism group through the reflecting mirror of the second reflecting mirror group;
the prism group is used for carrying out reverse group velocity dispersion compensation on the collimated white light, and then the collimated white light is reflected to the achromatic microscope objective through the reflector of the second reflector group.
6. The spatially resolved transient system of claim 5, wherein after collimated parallel light with a wavelength range of 380nm to 780nm is incident on the first prism, the light with different wavelengths is spread out in angle, continues to spread out through the second prism, and is combined into a beam through the third prism and the fourth prism.
7. The spatially resolved transient system of claim 5, wherein the probe light modulation optical path further comprises a positioning diaphragm disposed between the optical delay line and the beam splitting element for calibrating the position and direction of the probe light.
8. The spatially-resolved transient system of claim 5, wherein the white light generating medium is a sapphire crystal, a calcium fluoride crystal, or a water box.
9. The spatially resolved transient system of claim 1, further comprising a data acquisition device, wherein the data acquisition device comprises a chopper, a chopper controller, a fiber-coupled spectrophotometer and a PC, and is configured to obtain a two-dimensional image of the probe light absorption signal or the reflection signal of the sample after the pump light and the probe light act on the sample together.
10. The spatially-resolved transient system of claim 8, further comprising a motorized stage that moves the sample in a horizontal direction.
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