Raman optical path system based on a laboratory optical platform

Abstract

The application provides a Raman optical path system based on a laboratory optical platform, and belongs to the optical field.The system comprises a laser excitation optical path and a Raman scattering signal collection optical path; the Raman scattering signal collection optical path comprises a microscope objective, a spatial light coupler and a spectrometer; the laser excitation optical path is coupled with the Raman scattering signal collection optical path through an edge cut-off filter arranged between the microscope objective and the spatial light coupler; wherein the laser excitation optical path is used for generating laser, the laser is transmitted to the edge cut-off filter, reflected to the microscope objective through the edge cut-off filter, and focused to the sample surface by the microscope objective; the Raman scattering signal reflected by the sample is collected by the microscope objective, transmitted to the edge cut-off filter, filtered by the edge cut-off filter, and then transmitted to the spectrometer through the spatial light coupler. The system has a compact overall structure, and less optical elements are used, so that the system integration can be improved.

Description

Technical Field

[0001] This application belongs to the field of optics, and in particular relates to a Raman optical path system based on a laboratory optical platform. Background Technology

[0002] Raman spectroscopy is a spectroscopic analysis method based on inelastic scattering caused by the interaction of light and matter. Because it can provide information on molecular vibrations and chemical structure, it is widely used in materials science, chemical analysis, biomedical detection, and nanoscience research.

[0003] With the development of micro-nano structure research, higher requirements are placed on the spatial resolution, signal collection efficiency, and system stability of Raman systems. Existing Raman spectroscopy systems typically consist of complex optical path structures composed of multiple sets of mirrors and optical components, which not only results in a large system size but also increases the difficulty of optical adjustment and light energy loss. Therefore, there is a need to design a compact, easily adjustable, highly integrated, and modular Raman optical path system suitable for laboratory settings. Summary of the Invention

[0004] In view of this, this application provides a Raman optical path system based on a laboratory optical platform, aiming to improve the integration of the optical path system, including: The laser excitation optical path and the Raman scattering signal collection optical path; the Raman scattering signal collection optical path includes a microscope objective, a spatial optical coupler, and a spectrometer; The laser excitation optical path is coupled to the Raman scattering signal collection optical path through an edge cutoff filter disposed between the microscope objective and the spatial optical coupler; The laser excitation optical path is used to generate laser light, which is transmitted to the edge cutoff filter, reflected by the edge cutoff filter to the microscope objective, and focused onto the sample surface by the microscope objective. The Raman scattering signal reflected by the sample is collected by the microscope objective, transmitted to the edge cutoff filter, filtered by the edge cutoff filter, and then transmitted to the spectrometer through the spatial optical coupler.

[0005] Optionally, the Raman scattering signal collection optical path further includes: A rotatable mirror is positioned between the microscope objective and the edge cutoff filter.

[0006] Optionally, it also includes: Microscopic imaging and illumination optical path, including illumination sub-optical path and imaging sub-optical path; The illumination sub-optical path is coupled to the Raman scattering signal collection optical path through a first beam splitter disposed between the microscope objective and the spatial optical coupler; The imaging sub-optical path is coupled to the Raman scattering signal collection optical path through a second beam splitter positioned between the microscope objective and the spatial optical coupler; The illumination sub-optical path is used to generate illumination light. After the illumination light is transmitted to the first beam splitter, it is reflected by the first beam splitter to the microscope objective, and after being focused by the microscope objective, it illuminates the sample. The illumination light is reflected by the sample to form imaging light. The imaging light is collected by the microscope objective and then transmitted to the second beam splitter. After being reflected by the second beam splitter, it is collected by the imaging sub-optical path to achieve microscopic imaging of the sample.

[0007] Optionally, the illumination sub-optical path includes: The lighting source, aperture stop, and field stop are arranged sequentially. The aperture stop is used to adjust the numerical aperture of the illumination light, and the field stop is used to adjust the illumination range of the illumination light.

[0008] Optionally, the aperture stop and the back focal plane of the microscope objective are conjugate.

[0009] Optionally, the field stop is conjugate with the sample surface.

[0010] Optionally, the imaging sub-optical path includes: An imaging camera and a condenser lens, wherein the condenser lens is used to converge imaging light.

[0011] Optionally, the laser excitation optical path includes: The laser, beam expander collimator, narrowband filter, and polarizer are arranged in sequence. The laser beam generated by the laser is expanded and collimated by the beam expander and collimator before being transmitted to the narrowband filter. The narrowband filter performs narrowband filtering on the laser beam before transmitting it to the polarizer. After the polarization state is adjusted by the polarizer, the laser beam is transmitted to the edge cutoff filter.

[0012] Optionally, the laser is a multi-wavelength laser.

[0013] Optionally, it also includes: An adjustable confocal pinhole structure is set inside a spatial optical coupler, comprising a confocal lens, an adjustable pinhole, and a coupling lens arranged sequentially. The confocal lens 41 and adjustable pinhole 42 can filter out stray light other than the Raman signal of the focal plane, and the light is then emitted through the coupling lens 43 for subsequent spatial coupling.

[0014] The beneficial effects of the technical solution provided in this application include: In the embodiments provided in this application, the laser excitation optical path, the Raman scattering signal collection optical path, and the microscopic imaging and illumination optical path are spatially coupled at the microscope objective by unifying the optical axis. Specifically, the present invention achieves coaxial coupling of the laser excitation optical path, the Raman signal collection optical path, and the microscopic imaging optical path at the same microscope objective by combining an edge cutoff filter, a reflector, and a first beam splitter and a second beam splitter, thereby significantly reducing the complexity of optical path folding and adjustment caused by a large number of reflectors in traditional systems. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 A schematic diagram of a Raman optical path system based on a laboratory optical platform provided in an embodiment of this application; Figure 2 A schematic diagram of an adjustable confocal pinhole structure provided in an embodiment of this application; Figure 3 This is a schematic diagram of a metal-enhanced probe tip provided in an embodiment of this application.

[0017] The attached figures are labeled as follows: 1: Laser excitation optical path; 10: Edge cutoff filter; 100: Sample; 1000: Sample stage; 11: Laser; 12: Beam expander and collimator; 13: Narrowband filter; 14: Polarizer; 2: Raman scattering signal collection optical path; 21: Microscope objective; 22: Spatial optical coupler; 23: Spectrometer; 24: Mirror; 3: Microscopic imaging and illumination optical path; 31: Illumination sub-optical path; 310: First beam splitter; 311: Illumination source; 312: Aperture stop; 313: Field stop; 32: Imaging sub-optical path; 320: Second beam splitter; 321: Imaging camera; 322: Condenser lens; 4: Adjustable confocal pinhole structure; 41: Confocal lens; 42: Adjustable pinhole; 43: Coupler lens; 5: Metal-enhanced probe tip. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] Figure 1 A schematic diagram of a Raman optical path system based on a laboratory optical platform, provided as an embodiment of this application. See also... Figure 1 ,include: The laser excitation optical path 1 and the Raman scattering signal collection optical path 2 include a microscope objective 21, a spatial optical coupler 22, and a spectrometer 23. The laser excitation optical path 1 is coupled to the Raman scattering signal collection optical path 2 through the edge cutoff filter 10 disposed between the microscope objective 21 and the spatial optical coupler 23. The laser excitation optical path 1 is used to generate laser light, which is transmitted to the edge cutoff filter 10, reflected by the edge cutoff filter 10 to the microscope objective 21, and focused by the microscope objective 21 onto the surface of the sample 100. The Raman scattering signal reflected by the sample 100 is collected by the microscope objective 21, transmitted to the edge cutoff filter 10, filtered by the edge cutoff filter 10, and transmitted to the spectrometer 23 through the spatial optical coupler 22.

[0020] In some embodiments, the edge cutoff filter 10 has high reflectivity to incident laser light in a specific wavelength range, causing the excitation light to be reflected into the microscope objective 21.

[0021] In some embodiments, the microscope objective 21 is preferably a high numerical aperture objective, such as an objective with an NA greater than or equal to 0.9, which is used not only to focus the excitation light but also to collect Raman scattered light. After the excitation light is focused by the microscope objective 21, a high-intensity, small-spot focused region is formed on the surface of the sample 100, thereby exciting the sample to generate a Raman scattering signal.

[0022] The Raman scattered light generated by sample 100 returns along the opposite path to the incident laser and passes through microscope objective 21 again, where it is collected and collimated for output. Due to the slight difference between the Raman scattering signal and the excitation light wavelength, when the Raman scattered light reaches the edge cutoff filter 10, its long-wavelength Stokes component can pass through the edge cutoff filter 10, while the excitation light and Rayleigh scattering are reflected or blocked.

[0023] In some embodiments, the edge cutoff filter 10 has a strong ability to suppress Rayleigh scattering near the excitation wavelength, allowing only the Raman-shifted signal to pass through, thereby significantly improving the signal-to-noise ratio.

[0024] The filtered Raman scattered light enters the spatial optical coupler 22. Subsequently, the Raman signal is coupled into the spectrometer 23 through the spatial optical coupler 22, where wavelength separation and spectral analysis are performed. Finally, Raman spectral data are acquired through detectors such as CCD, enabling the analysis of information on the sample structure and composition.

[0025] In some embodiments, the Raman scattering signal collecting optical path 2 further includes: A rotatable mirror 24 is disposed between the microscope objective 21 and the edge cutoff filter 10.

[0026] In some embodiments, by providing a rotatable reflector 24, the direction of excitation light input can be switched, enabling the system to adapt to vacuum sample chambers or special experimental environments and improving the system's scalability.

[0027] In some embodiments, the laser excitation optical path 1 includes: The laser 11, beam expander collimator 12, narrowband filter 13, and polarizer 14 are arranged in sequence. The laser generated by the laser 11 is expanded and collimated by the beam expander and collimator 12 and then transmitted to the narrowband filter 13. The narrowband filter 13 performs narrowband filtering on the laser and then transmits it to the polarizer 14. After the polarization state is adjusted by the polarizer 14, the laser is transmitted to the edge cutoff filter 10.

[0028] Laser 1 is used to output monochromatic laser light. After output, the laser light sequentially enters beam expander and collimator 2, which simultaneously performs beam expansion and collimation: on the one hand, by increasing the beam diameter, the divergence angle is reduced, thereby obtaining a smaller diffraction-limited spot during subsequent focusing; on the other hand, collimation correction reduces energy divergence and optical loss during beam propagation. After beam expansion and collimation, the laser light enters narrowband filter 3, which is used to further compress the laser linewidth and filter out plasma lines and spontaneous emission background, thereby improving the monochromaticity of the excitation light. Subsequently, the laser light passes through polarizer 4 for polarization state modulation, forming linearly polarized light in a predetermined direction to enhance the electromagnetic field coupling efficiency near nanostructures or needle tips, thereby improving the intensity of Raman scattering, especially the locally enhanced Raman signal.

[0029] The excitation light modulated as described above propagates along the optical path after being reflected by the edge cutoff filter 10 to the microscope objective 21.

[0030] In some embodiments, the cutoff wavelength of the edge cutoff filter 10 is the wavelength of the laser source.

[0031] In some embodiments, laser 11 is a laser with a wavelength of 532 nm.

[0032] In other embodiments, laser 11 is a multi-wavelength laser, which enhances Raman resonance in different material systems by switching different wavelengths, thereby improving the applicability of the system.

[0033] In some embodiments, it also includes: The microscopic imaging and illumination optical path 3 includes an illumination sub-optical path 31 and an imaging sub-optical path 32; The illumination sub-optical path 31 is coupled to the Raman scattering signal collection optical path 2 via a first beam splitter 310 disposed between the microscope objective 21 and the spatial optical coupler 22. The imaging sub-optical path 32 is coupled to the Raman scattering signal collection optical path 2 via a second beam splitter 320 disposed between the microscope objective 21 and the spatial optical coupler 22. The illumination sub-optical path 31 is used to generate illumination light. After the illumination light is transmitted to the first beam splitter 310, it is reflected by the first beam splitter 310 to the microscope objective 21, and after being focused by the microscope objective 21, it illuminates the sample 100. The illumination light is reflected by the sample to form imaging light. The imaging light is collected by the microscope objective 21 and transmitted to the second beam splitter 320. After being reflected by the second beam splitter 320, it is collected by the imaging sub-optical path 32 to realize the microscopic imaging of the sample.

[0034] In some embodiments, the illumination sub-optical path 31 includes: The lighting source 311, the aperture stop 312, and the field stop 313 are arranged sequentially. The aperture stop 312 is used to adjust the numerical aperture of the illumination light, and the field stop 313 is used to adjust the illumination range of the illumination light.

[0035] In some embodiments, the aperture stop 312 and the back focal plane of the microscope objective 21 are conjugate.

[0036] In some embodiments, the field stop 313 is conjugate with the sample surface.

[0037] In some embodiments, the numerical aperture and illumination range of the illumination light are adjusted by aperture stop 312 and field stop 313 respectively, so that the illumination light forms uniform illumination on the sample surface.

[0038] In this process, the aperture stop 312 is conjugate with the back focal plane of the objective lens to adjust the angular distribution of the incident beam, while the field stop 313 is conjugate with the surface of the sample 100 to define the observation area.

[0039] In some embodiments, the imaging sub-optical path 32 includes: An imaging camera 321 and a condenser lens 322 are provided, the condenser lens 322 being used to converge the imaging light. The imaging light converged by the condenser lens 322 is transmitted to the imaging camera 321, thereby realizing microscopic imaging of the sample.

[0040] In the embodiments provided in this application, the laser excitation optical path, the Raman scattering signal collection optical path, and the microscopic imaging and illumination optical path are spatially coupled at the microscope objective 21 through a unified optical axis. Specifically, the present invention achieves coaxial coupling of the laser excitation optical path, the Raman signal collection optical path, and the microscopic imaging optical path at the same microscope objective 21 through the combination of the edge cutoff filter 10, the reflector 24, and the first beam splitter 310 and the second beam splitter 320, thereby significantly reducing the complexity of optical path folding and adjustment caused by a large number of reflectors in traditional systems.

[0041] In some embodiments, the entire optical path system is integrated on a laboratory optical platform and modularly fixed using standard optical brackets, thereby ensuring the system's stability and repeatability.

[0042] In some embodiments, an adjustable confocal pinhole structure is provided in the Raman signal collection path, and the pinhole size can be adjusted to achieve an optimal balance between signal strength and spatial resolution.

[0043] See Figure 2 Specifically, the adjustable confocal pinhole structure 4 is disposed in the spatial optical coupler 22 and consists of a confocal lens 41, an adjustable pinhole 42, and a coupling lens 43. Through the confocal lens 41 and the adjustable pinhole 42, stray light other than the Raman signal of the focal plane can be filtered out, and after being emitted through the coupling lens 43, it is used for subsequent spatial coupling.

[0044] The adjustable pinhole 42 is adjustable in the x and y directions as shown in the figure, and the diameter of the pinhole is also adjustable. It can be selected as a rotary multi-diameter pinhole device or an aperture-type continuously adjustable pinhole, etc. The coupling lens 43 is adjustable in the z direction as shown in the figure.

[0045] In some embodiments, the system of the present invention can be further coupled with a scanning probe microscope to form a localized surface plasmon-enhanced electromagnetic field near the metal tip, thereby enabling tip-enhanced Raman spectroscopy (TERS) measurement and significantly improving the spatial resolution at the nanoscale.

[0046] The specific implementation process is as follows: Install a metal enhancement probe tip 5 that is matched with the microscope objective 21. The metal enhancement probe tip 5 is made of metal materials such as gold and silver that can generate surface plasmon resonance effect. During the application, the metal enhancement probe tip 5 maintains a nanometer-level distance with the sample 100 surface on the sample stage 1000 to form a nanometer-level gap, and keeps synchronized with the beam focused by the microscope objective 21. This enables the beam to be excited by the local surface plasmon resonance enhanced electromagnetic field in the nanometer-level gap of the focusing area, thereby increasing the intensity of the in-situ Raman signal.

[0047] In summary, this invention significantly reduces system complexity while ensuring optical performance through a highly integrated design of the three optical paths for excitation, collection, and imaging, achieving high stability, high efficiency, and high resolution Raman spectroscopy detection.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Raman optical path system based on a laboratory optical platform, characterized in that, include: The laser excitation optical path and the Raman scattering signal collection optical path; the Raman scattering signal collection optical path includes a microscope objective, a spatial optical coupler, and a spectrometer; The laser excitation optical path is coupled to the Raman scattering signal collection optical path through an edge cutoff filter disposed between the microscope objective and the spatial optical coupler; The laser excitation optical path is used to generate laser light, which is transmitted to the edge cutoff filter, reflected by the edge cutoff filter to the microscope objective, and focused onto the sample surface by the microscope objective. The Raman scattering signal reflected by the sample is collected by the microscope objective, transmitted to the edge cutoff filter, filtered by the edge cutoff filter, and then transmitted to the spectrometer through the spatial optical coupler.

2. The Raman optical path system based on a laboratory optical platform according to claim 1, characterized in that, The Raman scattering signal collection optical path also includes: A rotatable mirror is positioned between the microscope objective and the edge cutoff filter.

3. The Raman optical path system based on a laboratory optical platform according to claim 1, characterized in that, Also includes: Microscopic imaging and illumination optical path, including illumination sub-optical path and imaging sub-optical path; The illumination sub-optical path is coupled to the Raman scattering signal collection optical path through a first beam splitter disposed between the microscope objective and the spatial optical coupler; The imaging sub-optical path is coupled to the Raman scattering signal collection optical path through a second beam splitter positioned between the microscope objective and the spatial optical coupler; The illumination sub-optical path is used to generate illumination light. After the illumination light is transmitted to the first beam splitter, it is reflected by the first beam splitter to the microscope objective, and after being focused by the microscope objective, it illuminates the sample. The illumination light is reflected by the sample to form imaging light. After being collected by the microscope objective, the imaging light is transmitted to the second beam splitter. After being reflected by the second beam splitter, it is collected by the imaging sub-optical path to achieve microscopic imaging of the sample.

4. The Raman optical path system based on a laboratory optical platform according to claim 3, characterized in that, The illumination sub-optical path includes: The lighting source, aperture stop, and field stop are arranged sequentially. The aperture stop is used to adjust the numerical aperture of the illumination light, and the field stop is used to adjust the illumination range of the illumination light.

5. The Raman optical path system based on a laboratory optical platform according to claim 4, characterized in that, The aperture stop and the back focal plane of the microscope objective are conjugate.

6. The Raman optical path system based on a laboratory optical platform according to claim 4, characterized in that, The field stop and the sample surface are in a conjugate relationship.

7. The Raman optical path system based on a laboratory optical platform according to claim 4, characterized in that, The imaging sub-optical path includes: An imaging camera and a condenser lens, wherein the condenser lens is used to converge imaging light.

8. The Raman optical path system based on a laboratory optical platform according to claim 1, characterized in that, The laser excitation optical path includes: The laser, beam expander collimator, narrowband filter, and polarizer are arranged in sequence. The laser beam generated by the laser is expanded and collimated by the beam expander and collimator before being transmitted to the narrowband filter. The narrowband filter performs narrowband filtering on the laser beam before transmitting it to the polarizer. After the polarization state is adjusted by the polarizer, the laser beam is transmitted to the edge cutoff filter.

9. The Raman optical path system based on a laboratory optical platform according to claim 8, characterized in that, The laser is a multi-wavelength laser.

10. The Raman optical path system based on a laboratory optical platform according to claim 1, characterized in that, Also includes: An adjustable confocal pinhole structure is set inside a spatial optical coupler, comprising a confocal lens, an adjustable pinhole, and a coupling lens arranged sequentially. The confocal lens 41 and adjustable pinhole 42 can filter out stray light other than the Raman signal of the focal plane, and the light is then emitted through the coupling lens 43 for subsequent spatial coupling.

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