A polarization-resolved fluorescence test system based on a three-dimensional movable optical path

Abstract

The present invention discloses a polarization-resolved fluorescence test system based on a three-dimensional movable optical path, including a laser generating component for generating excitation light; a laser polarization adjusting component for adjusting the polarization state of the excitation light; a filter for reflecting the excitation light and transmitting the fluorescence emitted by the sample; a three-dimensional independent optical path displacement component for three-dimensionally adjusting the optical path to focus the light spot on the sample surface for independent movement in the x, y, and z axes; a microscope system for illuminating and microscopically imaging the sample surface morphology, excitation light, and fluorescence; a fluorescence polarization adjusting component for adjusting the polarization state of fluorescence; and a spectrum detection module for detecting the spectrum and lifespan of the fluorescence. The present invention has the characteristics that the sample does not move but the optical path moves, and is compatible with most non-displaceable cryostats on the market. At the same time, polarization-adjustable components and small-angle incidence are used to realize arbitrary circularly polarized or linearly polarized fluorescence detection.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescence spectrum detection, and more specifically, to a polarization-resolved fluorescence testing system based on a three-dimensional movable optical path. Background Art

[0002] As a type of fermion, electrons naturally have two intrinsic properties: charge and spin. The development of charge-type devices and spin-type devices using the charge and spin of electrons to carry information is the cornerstone of the current information technology industry. With the advent of the information age, many practical needs such as larger capacity, faster transmission and lower power consumption have not only promoted the progress of the industrial technology chain, but also stimulated people's enthusiasm for exploring new electronic degrees of freedom in the field of basic research. In recent years, with the emergence of two-dimensional materials such as graphene and transition metal chalcogenides, people have discovered new electronic degrees of freedom in some material systems - energy valleys, that is, the extreme points of the Bloch electronic energy band. In a single layer of transition metal sulfide, the bottom of the conduction band and the top of the valence band that dominate the excited state luminescence are found to be located at the six K valleys in the first Brillouin zone of the hexagon, and the adjacent valleys are not equivalent, that is, the electrons in the adjacent valleys have equal energy but opposite spins, which can be marked as K and -K valleys respectively.

[0003] Since the energies are equal, ordinary fluorescence spectroscopy without polarization resolution cannot directly distinguish the photons emitted by the K and -K valleys. Studies have shown that the interband transitions of electrons in the K and -K valleys and the related photon emission or absorption behaviors are all related to the circular polarization of light, that is, the K and -K valleys are only coupled with left-handed and right-handed light, respectively. Therefore, using fluorescence spectroscopy with polarization resolution (including linear polarization and circular polarization), the two different valleys can be easily distinguished. However, the actual absorption and luminescence processes are accompanied by phonon scattering, which causes a decrease in circular polarization. The higher the temperature, the more phonons there are, the stronger the phonon scattering, and the smaller the circular polarization, or even indistinguishable. Therefore, in the actual valley fluorescence test measurement process, the sample basically needs to be placed in a liquid nitrogen or even liquid helium environment to reduce the interference of phonon scattering.

[0004] In fact, most cryostats on the market, especially those based on liquid helium circulation, can only move the cryogenic cavity and the samples inside it slightly or even completely fixed on the optical platform in order to reduce sample vibration and ensure that the vibration amplitude is below the order of 100 nanometers. Therefore, how to control the overlap of the excitation spot and the two-dimensional nanomaterial is a core issue of this spectral system.

[0005] In addition, in terms of polarization detection, there are two major problems that need to be solved. First, the excitation light and fluorescence will experience a lot of reflection from optical lenses in the system. How to ensure the polarization degree of the excitation light incident on the sample and the fluorescence reflected at the entrance of the spectral detector? Second, general spectrometers use wire grid gratings for wavelength resolution, which have different polarization response characteristics for fluorescence of different wavelengths. How to reduce the system polarization detection error caused by spectral detection devices.

[0006] There is a huge demand for research on low-temperature polarization fluorescence spectroscopy detection of low-dimensional semiconductor materials, and traditional fluorescence spectroscopy test systems cannot meet the measurement needs. It is of great significance to study fluorescence spectroscopy measurement technology that can integrate polarization resolution, micro-area detection and wide-spectrum detection to meet the special needs of nanomaterials and ensure that the sample is immobile. Summary of the invention

[0007] The object of the present invention is to provide a polarization-resolved fluorescence testing system based on a three-dimensional movable optical path to overcome the defects of the prior art.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A polarization-resolved fluorescence testing system based on a three-dimensional movable optical path, comprising:

[0010] A laser generating component, used for generating excitation light;

[0011] A laser polarization adjustment component, used to adjust the polarization state of the excitation light;

[0012] A filter, used for reflecting the excitation light and transmitting the fluorescence emitted by the sample;

[0013] A three-dimensional independent optical path displacement component is used to three-dimensionally adjust the optical path so that the focused light spot can be independently moved in three axes of x, y and z on the surface of the sample;

[0014] A microscope system, used for illuminating and microscopically imaging the surface morphology, excitation light and fluorescence of the sample;

[0015] A fluorescence polarization adjustment component, used for adjusting the polarization state of fluorescence;

[0016] and a spectrum detection module, used for detecting the spectrum and lifetime of the fluorescence.

[0017] Furthermore, the laser generating component includes a laser, an optical parametric amplifier, an optical wavelength selector and a light intensity regulator which are sequentially arranged on the optical path, the laser is used to generate excitation light, the optical parametric amplifier is used to adjust the wavelength of the excitation light, the optical wavelength selector is used to select the wavelength of the excitation light, and the light intensity regulator is used to adjust the light intensity of the excitation light.

[0018] Furthermore, the incident angle of the incident light of the filter is less than 5 degrees.

[0019] Furthermore, the laser polarization adjustment component includes a first polarizer and a first wave plate arranged in sequence, the first polarizer is used to adjust the polarization state of the excitation light, and the first wave plate is used to change the polarization state of the excitation light.

[0020] Furthermore, the three-dimensional independent optical path displacement assembly includes an x-axis displacement stage, a y-axis displacement stage, a z-axis displacement stage, a second reflector placed on the x-axis displacement stage, and a third reflector placed on the y-axis displacement stage. The y-axis displacement stage is arranged on the x-axis displacement stage, and the z-axis displacement stage is arranged on the y-axis displacement stage. The x-axis displacement stage is used to realize the x-axis movement of the light spot focused on the sample surface, the y-axis displacement stage is used to realize the y-axis movement of the light spot focused on the sample surface, and the z-axis displacement stage is used to realize the z-axis movement of the light spot focused on the sample surface. The second reflector is used to vertically reflect the excitation light from the x-axis displacement stage to the y-axis displacement stage, and the third reflector is used to vertically reflect the excitation light from the y-axis displacement stage to the z-axis displacement stage.

[0021] Furthermore, the laser beam of the excitation light reflected by the filter to the second reflector is parallel to the displacement direction of the x-axis translation stage.

[0022] Furthermore, the laser beam of the excitation light reflected from the second reflector to the third reflector is parallel to the displacement direction of the y-axis translation stage.

[0023] Furthermore, it also includes a microscope system placed on a z-axis translation stage, the microscope system is used to perform microscopic imaging of the sample to be tested, the microscope system includes a first thin film beam splitter, a microscope objective lens, a second thin film beam splitter, an imaging camera, a fourth reflector and an illumination light source, the first thin film beam splitter and the microscope objective lens are sequentially arranged between the third reflector and the sample surface, the second thin film beam splitter and the fourth reflector are sequentially arranged on one side of the first thin film beam splitter, the imaging camera is arranged on one side of the second thin film beam splitter, and the illumination light source is arranged on one side of the fourth reflector.

[0024] Furthermore, the fluorescence polarization adjustment component includes a second wave plate and a second polarizer, the second wave plate is used to adjust the polarization state of the fluorescence emitted by the sample, and the second polarizer is used to detect the polarization state of the fluorescence emitted by the sample.

[0025] Furthermore, it also includes a computer, which is connected to the laser generating component, the laser polarization adjusting component, the filter, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module; and is used to control the laser generating component, the laser polarization adjusting component, the filter, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module, and receive the measurement result of the spectrum detection module and the imaging image of the microscope system.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] 1. The precise coupling between the laser spot and the sample in the present invention does not require a sample displacement stage. By using the idea that sample displacement and laser spot displacement are equivalent, the motion trajectory generated by conventional sample displacement is decomposed along three orthogonal directions of x / y / z. By using a three-dimensional independent optical path displacement component, the three-dimensional parallel movement of the laser beam in space is directly controlled, and precise coupling between the sample to be tested and the laser spot can be achieved. In specific environments such as low temperature and strong magnetism, when the sample or sample cavity is inconvenient to move, this method can be used to achieve coupling with micron-level accuracy.

[0028] 2. In the present invention, the filter is placed in the light path with a small angle of incidence, and the incident light is incident at an angle of incidence less than 5°, which ensures that the polarization state of the excitation light remains unchanged; at the same time, the fluorescence emitted by the sample transmits the filter at an angle of incidence less than 5°, which ensures that the polarization state of the fluorescence remains unchanged before reaching the second wave plate, and can realize the excitation and detection of any linear polarized light and circular polarized light.

[0029] 3. The wave plates and polarizers used in the laser polarization adjustment component and the fluorescence polarization adjustment component of the present invention are of exactly the same model, thereby eliminating the polarization detection error caused by the performance difference of optical components to the greatest extent.

[0030] 4. The laser polarization adjustment component and the fluorescence polarization adjustment component in the present invention adopt a solution of fixing the polarizer angle and rotating the wave plate angle when adjusting the polarization state of the light beam. Firstly, it avoids the movement of the focusing spot and the fluorescence spot when adjusting the polarizer angle, greatly reducing the polarization detection error of the rear-end spectral detection module; secondly, it ensures that the polarization angle of the fluorescence incident to the rear-end spectral detection module remains unchanged, eliminating the polarization measurement error caused by the polarization response characteristics of the spectral detection module. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic diagram of the principle of the xyz three-dimensional independent optical path displacement component in the present invention.

[0033] Figure 2 It is a schematic diagram of the structure of a specific embodiment of the present invention.

[0034] In the figure: 1. laser; 2. optical parametric amplifier; 3. optical wavelength selector; 4. light intensity regulator; 5. first reflector; 6. first polarizer; 7. first wave plate; 8. filter; 9. second reflector; 10. x-axis translation stage; 11. third reflector; 12. y-axis translation stage; 13. z-axis translation stage; 14. first thin film beam splitter; 15. microscope objective; 16. sample to be measured; 17. second thin film beam splitter; 18. imaging camera; 19. fourth reflector; 20. illumination light source; 21. second wave plate; 22. second polarizer; 23. spectrum detection module; 24. computer. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0036] See also Figure 1 and Figure 2 As shown, this embodiment discloses a polarization-resolved fluorescence testing system based on a three-dimensional movable optical path, including: a laser generating component for generating excitation light; a laser polarization adjusting component for adjusting the polarization state of the excitation light; a filter 8 for reflecting the excitation light and transmitting the fluorescence emitted through the sample; a three-dimensional independent optical path displacement component for three-dimensionally adjusting the optical path to focus the light spot on the sample surface for independent movement of the three axes of x, y, and z; a microscope system for illuminating and microscopically imaging the sample surface morphology, excitation light, and fluorescence; a fluorescence polarization adjusting component for adjusting the polarization state of fluorescence; and a spectral detection module 23 for detecting the spectrum and lifetime of the fluorescence.

[0037] Three-dimensional independent optical path displacement components such as Figure 1As shown, it includes a filter 8, an x-displacement stage 10, a y-displacement stage 12, a z-displacement stage 13, a second reflecting mirror 9, a third reflecting mirror 11, and a microscope objective lens 15. The horizontally incident excitation light is horizontally reflected into the three-dimensional displacement stage through the filter. The x-axis displacement stage 10 is a one-dimensional linear displacement stage. The second reflector 9 is placed on the x-axis displacement stage 10. The second reflector is driven to move forward and backward by the x-axis displacement stage to adjust the movement of the horizontal reflection light path in the x direction. The y-axis displacement stage 12 is a one-dimensional linear displacement stage, which is superimposed on the x-axis displacement stage 10. The third reflector 11 is placed on the y-axis displacement stage 12 to reflect the horizontal excitation light to the vertical direction. The third reflector 11 is driven to move left and right by the y-axis displacement stage 12 to adjust the movement of the reflection light path in the y direction. The z-axis displacement stage 13 is further superimposed on the y-axis displacement stage 12. A microscope objective lens 15 is further placed on the z-axis displacement stage 13. The microscope objective lens is driven to move up and down by the z-axis displacement stage 13 to adjust the movement of the focusing spot in the z direction.

[0038] In this embodiment, in order to make the light beam reaching the microscope objective lens 15 not move when adjusting the x-axis displacement stage 10 and the y-axis displacement stage 12, it is necessary to finely adjust the filter 8, the second reflector 9 and the third reflector 11, so that the light beam between the filter 8 and the second reflector 9 is strictly parallel to the front-back movement direction of the x-axis displacement stage, and the light beam between the second reflector 9 and the third reflector 11 is strictly parallel to the left-right movement direction of the y-axis displacement stage. In this embodiment, strictly parallel means that when moving within the range of the x-axis and y-axis displacement stages, the movement amount of the light beam reaching the microscope objective lens 15 is less than one tenth of the incident aperture of the objective lens.

[0039] In this embodiment, the microscope objective lens 15 and its supporting illumination imaging system are placed together on the z-axis translation stage 13, ensuring that when the optical path is moved in the z direction, the optical path between the microscope system and the microscope objective lens 15 remains unchanged, thereby maintaining the imaging clarity.

[0040] In this embodiment, the laser generating assembly includes a laser 1, an optical parametric amplifier 2, an optical wavelength selector 3 and an optical intensity regulator 4 which are sequentially arranged on an optical path. The laser 1 generates an excitation light source which is incident on the optical parametric amplifier 2 to adjust the laser wavelength. The optical wavelength selector 3 is a monochromator, a double monochromator or a filter, which is used to select excitation light of a suitable bandwidth. The optical intensity regulator 4 is used to adjust the power of the excitation light.

[0041] In this embodiment, the laser polarization adjustment component includes a first polarizer 6 and a first wave plate 7 which are arranged in sequence. The first polarizer 6 is used to adjust the polarization state of the excitation light, and the first wave plate 7 is used to change the polarization state of the excitation light to make it become left-handed or right-handed circularly polarized light, or linear polarized light in any direction.

[0042] In this embodiment, the filter 8 is used to reflect short-wavelength excitation light and transmit long-wavelength fluorescence. The excitation light is reflected by the filter 8 and horizontally incident on the second reflector 9 along the x-axis displacement stage 10. The second reflector 9 is placed at 45° to reflect the excitation light parallel to the x-axis displacement direction to the y-axis displacement direction. The third reflector 11 is placed at 45° to reflect the excitation light parallel to the y-axis displacement direction to the z-axis displacement direction. The first thin film beam splitter 14 is used to transmit most of the excitation light and fluorescence, and reflect the illumination light and a small part of the excitation light and fluorescence, so that the illumination imaging system is coupled to the optical path. The microscope objective 15 is used to focus the excitation light onto the surface of the sample to be tested 16, and at the same time collect the long-wavelength fluorescence generated by the sample to be tested 16.

[0043] In this embodiment, the fluorescence polarization adjustment component includes a second wave plate 21 and a second polarizer 22, wherein the second wave plate 21 is used to adjust the polarization state of the fluorescence. The second polarizer 22 is used to detect the polarization state of the fluorescence. The spectrum detection module 23 is used to measure the fluorescence spectrum and / or the fluorescence lifetime, and the first polarizer 6 and the second polarizer 22 are Glan prisms.

[0044] In this embodiment, the excitation light is incident on the filter 8 at a small angle, which prevents the filter 8 from changing the polarization state of the excitation light. In this embodiment, the small angle refers to an incident angle of less than 5 degrees.

[0045] In this embodiment, the first polarizer 6 and the second polarizer 22 are of exactly the same model, and the first wave plate 7 and the second wave plate 21 are of exactly the same model. Through the "common mode suppression" effect, the system error caused by the inconsistency of polarization components is greatly eliminated.

[0046] In this embodiment, a microscope system is also included which is placed on the z-axis translation stage 13, and the microscope system is used to perform microscopic imaging on the sample to be tested. The microscope system includes a first thin film beam splitter 14, a microscope objective lens 15, a second thin film beam splitter 17, an imaging camera 18, a fourth reflector 19 and an illumination light source 20. The first thin film beam splitter 14 and the microscope objective lens 15 are sequentially arranged between the third reflector and the sample surface, the second thin film beam splitter 17 and the fourth reflector 19 are sequentially arranged on one side of the first thin film beam splitter 14, the imaging camera 18 is arranged on one side of the second thin film beam splitter 17, and the illumination light source 20 is arranged on one side of the fourth reflector 19.

[0047] In this embodiment, the polarization adjustment of the excitation light adopts a solution of keeping the first polarizer 6 stationary and rotating the first wave plate, thereby avoiding the movement of the excitation light beam caused by the rotation of the polarizer.

[0048] In this embodiment, the polarization of fluorescence is adjusted by keeping the second polarizer 22 stationary and rotating the second wave plate 21, thereby avoiding the movement of the fluorescent light beam caused by the rotation of the polarizer, while ensuring that the polarization state of the light incident on the spectral detection module remains unchanged, thereby avoiding the polarization measurement error caused by the polarization sensitivity effect of the spectral detection module 23.

[0049] This embodiment also includes a computer 24, which is connected to the laser generating component, the laser polarization adjusting component, the filter 8, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module 23; and is used to control the laser generating component, the laser polarization adjusting component, the filter 8, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module 23, and receive the measurement results of the spectrum detection module 23 and the imaging image of the microscope system.

[0050] In this embodiment, the computer 24 is also connected to the x-axis translation stage 10, the y-axis translation stage 12 and the z-axis translation stage 13, and is used to control the x-axis translation stage 10, the y-axis translation stage 12 and the z-axis translation stage 13, so that the focused light spot moves along the x, y and z axes relative to the surface of the sample to be measured, thereby achieving precise coupling between the sample to be measured and the focused light spot.

[0051] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, the patent owner may make various variations or modifications within the scope of the appended claims. As long as they do not exceed the protection scope described in the claims of the present invention, they should be within the protection scope of the present invention.

Claims

1. A polarization-resolved fluorescence testing system based on a three-dimensional movable optical path, characterized in that: include: A laser generating component, used for generating excitation light; A laser polarization adjustment component, used to adjust the polarization state of the excitation light; A filter, used for reflecting the excitation light and transmitting the fluorescence emitted by the sample; A three-dimensional independent optical path displacement component is used to three-dimensionally adjust the optical path so that the focused light spot can be independently moved in three axes of x, y and z on the surface of the sample; A microscope system, used for illuminating and microscopically imaging the surface morphology, excitation light and fluorescence of the sample; A fluorescence polarization adjustment component, used for adjusting the polarization state of fluorescence; and a spectrum detection module, used for detecting the spectrum and lifetime of the fluorescence; The laser polarization adjustment component comprises a first polarizer and a first wave plate which are arranged in sequence, wherein the first polarizer is used to adjust the polarization state of the excitation light, and the first wave plate is used to change the polarization state of the excitation light; The three-dimensional independent optical path displacement component includes an x-axis displacement stage, a y-axis displacement stage, a z-axis displacement stage, a second reflector placed on the x-axis displacement stage, and a third reflector placed on the y-axis displacement stage. The y-axis displacement stage is arranged on the x-axis displacement stage, and the z-axis displacement stage is arranged on the y-axis displacement stage. The x-axis displacement stage is used to realize the x-axis movement of the light spot focused on the sample surface, the y-axis displacement stage is used to realize the y-axis movement of the light spot focused on the sample surface, and the z-axis displacement stage is used to realize the z-axis movement of the light spot focused on the sample surface. The second reflector is used to vertically reflect the excitation light from the x-axis displacement stage to the y-axis displacement stage, and the third reflector is used to vertically reflect the excitation light from the y-axis displacement stage to the z-axis displacement stage. Also included is a microscope system placed on the z-axis translation stage, the microscope system is used to perform microscopic imaging on the sample, the microscope system includes a first thin film beam splitter, a microscope objective lens, a second thin film beam splitter, an imaging camera, a fourth reflector and an illumination light source, the first thin film beam splitter and the microscope objective lens are sequentially arranged between the third reflector and the sample surface, the second thin film beam splitter and the fourth reflector are sequentially arranged on one side of the first thin film beam splitter, the imaging camera is arranged on one side of the second thin film beam splitter, and the illumination light source is arranged on one side of the fourth reflector; The fluorescence polarization adjustment component includes a second wave plate and a second polarizer, the second wave plate is used to adjust the polarization state of the fluorescence emitted by the sample, and the second polarizer is used to detect the polarization state of the fluorescence emitted by the sample.

2. The polarization-resolved fluorescence testing system based on a three-dimensional movable optical path according to claim 1, characterized in that: The laser generating assembly includes a laser, an optical parametric amplifier, an optical wavelength selector and a light intensity regulator which are sequentially arranged on an optical path. The laser is used to generate excitation light, the optical parametric amplifier is used to adjust the wavelength of the excitation light, the optical wavelength selector is used to select the wavelength of the excitation light, and the light intensity regulator is used to adjust the light intensity of the excitation light.

3. The polarization-resolved fluorescence testing system based on a three-dimensional movable optical path according to claim 1, characterized in that: The incident angle of the incident light of the filter is less than 5 degrees.

4. The polarization-resolved fluorescence testing system based on a three-dimensional movable optical path according to claim 1, characterized in that: The laser beam of the excitation light reflected by the filter to the second reflector is parallel to the displacement direction of the x-axis translation stage.

5. The polarization-resolved fluorescence testing system based on a three-dimensional movable optical path according to claim 1, characterized in that: The laser beam of the excitation light reflected by the second reflector to the third reflector is parallel to the displacement direction of the y-axis displacement stage.

6. The polarization-resolved fluorescence testing system based on a three-dimensional movable optical path according to claim 1, characterized in that: The system also includes a computer, which is connected to the laser generating component, the laser polarization adjusting component, the filter, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module; and is used to control the laser generating component, the laser polarization adjusting component, the filter, the three-dimensional independent optical path displacement component, the microscope system, the fluorescence polarization adjusting component and the spectrum detection module, and receive the measurement result of the spectrum detection module and the imaging image of the microscope system.

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