Laser-induced raman and fluorescence spectrum testing system
By achieving laser energy multiplication and signal collection within the laser resonant cavity, the problem of low laser excitation efficiency in existing technologies is solved, enabling efficient detection of gas and liquid samples and reducing system cost and debugging difficulty.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CHEN XINGHAI
- Filing Date
- 2024-11-15
- Publication Date
- 2026-05-21
AI Technical Summary
Existing laser-excited Raman and fluorescence spectroscopy testing systems have low excitation efficiency and weak signals when detecting gases and liquids. Furthermore, existing technical solutions are costly, difficult to debug, and only suitable for specific samples, and cannot efficiently collect non-unidirectional signals.
A dual-beam-waist laser resonant cavity, consisting of a harmonic separation mirror, a first cavity mirror, a second cavity mirror, and a focusing lens, is used to multiply the laser energy through laser frequency doubling and reflection within the resonant cavity, and to collect and analyze the signal in conjunction with a spectral detection unit.
It achieves an order-of-magnitude increase in laser energy, improves signal collection efficiency, reduces costs, is applicable to solid, gas, and liquid samples, reduces sample volume requirements, and enhances detection sensitivity.
Smart Images
Figure CN2024132156_21052026_PF_FP_ABST
Abstract
Description
A laser-induced Raman and fluorescence spectroscopy testing system Technical Field
[0001] This invention relates to the field of spectroscopic testing technology, specifically to a laser-induced Raman and fluorescence spectroscopy testing system. Background Technology
[0002] With the continuous development of laser technology, Raman and fluorescence detection technologies using lasers as excitation sources are becoming increasingly widespread. In practical applications, a wide variety of objects can be detected, including solids, liquids, and gases, all of which can be detected using lasers as excitation sources for Raman and fluorescence signals. Technical issues
[0003] Conventional Raman and fluorescence detection systems mostly employ a point-excitation, point-collection testing method. This involves focusing a laser beam onto the sample, and then collecting the fluorescence or scattered (Raman, Rayleigh) signal generated by the laser beam on the sample using a collection optical path. Existing laser-excited Raman and fluorescence spectroscopy systems are suitable for non-transparent samples such as solids and powders. However, for transparent substances such as gases and liquids, the absorption and scattering cross-sections for excitation light are low, resulting in weaker fluorescence or Raman signals. Especially for gaseous samples, multiple reflections and increased pressure are necessary to improve excitation efficiency.
[0004] To address the aforementioned issues, one existing technology utilizes hollow photonic crystal fibers to enhance gas Raman signals. This involves focusing excitation light into the hollow photonic crystal fiber while simultaneously filling the fiber with the gas to be measured at atmospheric pressure or increased pressure. The laser undergoes multiple reflections within the fiber to excite the gas, and the resulting Raman scattering signal is also reflected multiple times within the fiber before exiting through the fiber outlet and being collected by a collection lens and detected by a spectrometer. However, this approach suffers from several drawbacks. The core diameter of the photonic crystal fiber is typically only a few micrometers. Coupled with a microscope objective, this usually requires a micro-Raman optics system, resulting in high system cost and adjustment difficulty. Furthermore, laser coupling into the fiber can easily cause ablation of the fiber optic cut surface. Frequent recutting of the fiber optic cut and adjustment of the coupling path are necessary. Hollow photonic crystal fibers are not readily available in mass production and are only manufactured by a few research institutions, leading to high costs. This technology is only suitable for gas detection and not for liquids. It can only collect and detect signals that satisfy total internal reflection in the direction of laser transmission.
[0005] Existing technology two employs a multi-cavity method to enhance Raman signals: Multiple reflection cavities effectively prolong the interaction time between the laser and gas molecules by allowing the laser to reflect multiple times between the cavity mirrors. Signal detection is achieved by collecting Raman or fluorescence spectral signals generated by the interaction of the laser with matter in the same direction as the laser transmission. However, in this technology, the reflectivity of the multi-cavity mirrors directly determines the number of laser reflections within the cavity. Gain efficiency can only be improved by increasing laser power and reflectivity, typically achieving only a gain of a few tens of times. The detected substance needs to fill the multi-cavity, requiring a large sample volume. Only signals in the same direction as the laser transmission path can be collected, resulting in low signal collection efficiency. This technology is generally only suitable for gas detection.
[0006] Existing technology three employs a multi-cavity method to enhance Raman signals: Similar to existing technology two, the laser is passed through a confocal cavity, and the laser is reflected through the focal point of the confocal cavity. Signal detection is achieved by collecting the spectrum generated by the interaction between the laser and matter at the focal point. Compared with existing technology two, the confocal cavity collects the signal generated at the focal point, requiring a smaller sample amount. However, this technology has no gain within the cavity, and the structure and reflectivity of the confocal cavity directly determine the number of times the laser is reflected within the cavity. Gain efficiency can only be improved by increasing the laser power and reflectivity, typically achieving only a gain output of a few tens of times. The signal can only be enhanced by multiple reflections at the focal point.
[0007] In view of this, there is an urgent need for a laser-induced Raman and fluorescence spectroscopy testing system. Technical solutions
[0008] To address the problems existing in the prior art, the present invention solves this problem using the following technical structure.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] A laser-induced Raman and fluorescence spectroscopy testing system includes: a laser module, a harmonic separation mirror, a frequency doubling crystal, a first cavity mirror, a sample cell, a second cavity mirror, and a spectral detection unit;
[0011] The laser output from the laser module passes sequentially through a harmonic separator, a frequency doubling crystal, and a first cavity mirror.
[0012] The harmonic separation mirror is coated with a high-transmittance film on the side closest to the laser module and a high-reflectance film on the side closest to the frequency doubling crystal. The harmonic separation mirror separates the laser from the frequency doubling crystal and reflects the laser of the required wavelength back to the sample cell.
[0013] The first cavity mirror is used to reflect the laser from the frequency doubling crystal back to the frequency doubling crystal;
[0014] The second cavity mirror is used to reflect the laser from the sample cell back into the sample cell;
[0015] The spectral detection unit is used to analyze and detect the sample in the sample cell.
[0016] A further feature is that,
[0017] The laser module includes a pump laser, a waveplate, and a first focusing lens. The laser output from the pump laser passes sequentially through the waveplate, the first focusing lens, and a harmonic separator.
[0018] A Faraday optical isolator is provided between the pump laser and the waveplate.
[0019] The waveplate is a half-waveplate.
[0020] A second focusing lens is provided between the harmonic separation mirror and the sample cell.
[0021] It also includes a collection mirror for collecting and reflecting scattered or fluorescent signals generated by the sample, a collimating lens for collimating scattered and fluorescent signals from the sample cell, and a laser filter, the collimated laser passing through the laser filter into the spectral detection unit.
[0022] It also includes a third focusing lens, which focuses the laser light entering the spectral detection unit.
[0023] The spectral detection unit includes a slit, a collimating lens, a beam splitter, and an area array detector. The laser from the sample passes through the slit, collimating lens, beam splitter, and area array detector in sequence.
[0024] The spectral detection unit also includes a fourth focusing lens, which is disposed between the beam splitter and the area array detector.
[0025] The spectral detection unit includes a linear array detector. Beneficial effects
[0026] The following beneficial effects can be achieved by using the structure described above in this invention:
[0027] A harmonic separator, a first cavity mirror, a second focusing lens, and a second cavity mirror constitute a dual-beam-waist laser resonator. The first and second cavity mirrors are spherical mirrors, each coated with different high-reflectivity films. The first cavity mirror is confocal with the first focusing lens, and the second cavity mirror is confocal with the second focusing lens. The two beam-waist focal points of the laser resonator are located at the frequency-doubling crystal and the sample cell, respectively, to achieve optimal frequency doubling efficiency and sample excitation efficiency. Attached Figure Description
[0028] Figure 1 is a structural schematic diagram of Embodiment 1 of this application;
[0029] Figure 2 is a structural schematic diagram of Embodiment 2 of this application;
[0030] Figure 3 is a structural schematic diagram of Embodiment 3 of this application.
[0031] In the diagram: 1-1, Pump laser; 1-2, Faraday isolator; 1-3, Waveplate; 1-4, First focusing lens; 1-5, Harmonic separator; 1-6, Frequency doubling crystal; 1-7a, First cavity mirror; 1-7b, Second cavity mirror; 1-8, Second focusing lens; 2-1, Sample cell; 2-2, Collecting mirror; 2-3, Collimating lens; 2-4, Laser filter; 2-5, Third focusing lens; 3, Spectral detection unit; 3-1-1, Slit; 3-1-2, Collimating mirror; 3-1-3, Beam splitter; 3-1-4, Fourth focusing mirror; 3-1-5, Area array detector. Embodiments of the present invention
[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0033] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product or device.
[0034] The present application will be further described in detail below with reference to Figures 1-3.
[0035] Example 1, referring to Figure 1, describes a laser-induced Raman and fluorescence spectroscopy testing system, comprising: a laser module, harmonic separation mirrors 1-5, a frequency doubling crystal 1-6, a first cavity mirror 1-7a, a sample cell 2-1, a second cavity mirror 1-7b, and a spectral detection unit 3. The laser output from the laser module passes sequentially through the harmonic separation mirror 1-5, the frequency doubling crystal 1-6, and the first cavity mirror 1-7a. The harmonic separation mirror 1-5 is coated with a high-transmittance film and a high-reflectance film on both sides along the laser transmission direction (from the laser module towards the frequency doubling crystal 1-6). The harmonic separation mirror 1-5 separates the laser from the frequency doubling crystal, reflecting the laser of the desired wavelength to the sample cell 2-1. A second focusing lens 1-8 is provided between 1-5 and sample cell 2-1; a first cavity mirror 1-7a is used to reflect the laser from the frequency doubling crystal back to the frequency doubling crystal 1-6; a second cavity mirror 1-7b is used to fold back the laser from the sample cell (reflect it back to the sample cell); a spectral detection unit 3 is used to analyze and detect the sample at sample cell 2-1. The laser module includes a pump laser 1-1, a Faraday optical isolator 1-2, a waveplate 1-3, and a first focusing lens 1-4. The laser output from the pump laser 1-1 passes sequentially through the Faraday optical isolator 1-2, the waveplate 1-3, the first focusing lens 1-4, and the harmonic separator 1-5. The waveplate 1-3 is a half-waveplate.
[0036] Based on the above structure, the output laser from pump laser 1-1 sequentially passes through Faraday optical isolator 1-2, waveplate 1-3, first focusing lens 1-4, harmonic separator 1-5, and frequency doubling crystal 1-6, finally reaching first cavity mirror 1-7a. When the laser reaches frequency doubling crystal 1-6, it converts the laser into frequency-doubled light (converting a specific wavelength of laser light into half its wavelength). Then, the laser reaches first cavity mirror 1-7a, which multiplies the wavelength by half. The laser and the remaining original wavelength laser are reflected back to the frequency doubling crystal 1-6. After passing through the frequency doubling crystal, they reach the harmonic separation mirror. Then, because the harmonic separation mirror 1-5 is coated with a high-reflection film and a high-transmittance film, the frequency-doubled laser is reflected back to the sample cell 2-1. The remaining laser returns through the high-transmittance film. The second cavity mirror 1-7b is set on the opposite side of the harmonic separation mirror 1-5, reflecting the laser from the sample cell 2-1 back to the sample cell 2-1. The laser returns, thus completing the doubling of the laser energy of the required wavelength.
[0037] As shown in Figure 1, this embodiment also includes a collecting mirror 2-2 for collecting and reflecting the scattered or fluorescent signals generated by the sample, a collimating lens 2-3 for collimating the scattered and fluorescent signals at the sample cell 2-1, a laser filter 2-4, and a third focusing lens 2-5. The collimated laser passes through the laser filter 2-4 and enters the spectral detection unit 3. The third focusing lens 2-5 is used to focus the laser that is about to enter the spectral detection unit. In this way, the laser reflected by the harmonic separation mirror 1-5 reaches the sample cell 2-1, and the gas or liquid sample in the sample cell 2-1 is scattered by the laser excitation. The collection mirror 2-2 and the spectral detection unit 3 are positioned on opposite sides of the sample cell 2-1. The collection mirror 2-2 collects and reflects the scattered or fluorescent signals generated by the sample in the sample cell 2-1 back to the sample cell 2-1, and they all reach the collimating lens 2-3. This reduces the loss of scattered or fluorescent signals generated by the gas or liquid sample in the sample cell 2-1 after laser excitation, and achieves the desired wavelength laser gain. The sample cell 2-1 is collimated by the collimating lens 2-3 and filtered by the laser filter 2-4. Finally, the signal light is focused into the spectral detection unit 3 by the third focusing lens 2-5.
[0038] The following detailed explanation uses a 1064nm pump frequency-doubled output 532nm laser for excitation as an example:
[0039] The 1064nm laser 1-1 outputs laser light that passes through a Faraday optical isolator 1-2, a 1 / 4λ waveplate 1-3, a first focusing lens 1-4, and a harmonic separator 1-5 before being focused onto a frequency-doubling crystal 1-6 to generate a 532nm laser. The Faraday optical isolator 1-2 isolates the 1064nm laser light reflected by the first cavity mirror 1-7a from entering the laser, preventing damage. The waveplate 1-3 (in this embodiment, a 1 / 4λ waveplate is used) adjusts the laser polarization direction to achieve phase matching with the frequency-doubling crystal 1-6, achieving optimal frequency doubling efficiency. The harmonic separator 1-5 has a 1064nm high-transmittance film and a 532nm high-reflectance film coated on both sides, allowing the pump 1064nm laser to pass through while the frequency-doubled 532nm laser is highly reflective. The 1064nm laser, after being processed by the frequency doubling crystal 1-6, generates a 532nm laser, and the remaining 1064nm laser. Reflected by the first cavity mirror 1-7a, the laser passes through the frequency doubling crystal 1-6 again, and then the harmonic separation mirror 1-5 separates the 532nm and 1064nm lasers. The 1064nm laser returns to the laser 1-1 along its original path, while the 532nm laser, reflected and focused by the second focusing lens 1-8 onto the sample cell 2-1, is reflected by the second cavity mirror 1-7b and returns along its original path. The harmonic separation mirror 1-5, the first cavity mirror 1-7a, the second focusing lens 1-8, and the second cavity mirror 1-7b form a double-beam-waist 532nm laser resonant cavity. The first cavity mirror 1-7a and the second cavity mirror 1-7b are spherical mirrors, coated with 532nm and 1064nm high-reflectivity films, respectively. The first cavity mirror 1-7a is confocal with the first focusing lens 1-4, and the second cavity mirror 1-7b is confocal with the second focusing lens 1-8. The two beam waist focal points of the 532nm laser resonator are located at positions 1-6 of the frequency doubling crystal and 2-1 of the sample cell, respectively, to achieve optimal frequency doubling efficiency and sample excitation efficiency.
[0040] The aforementioned system structure enables the generation of a 532nm laser from a 1064nm laser frequency-doubled by a crystal within the resonant cavity, achieving power multiplication through cavity resonance. Stability is achieved when the power of the 532nm laser within the cavity and the power of the 532nm laser generated by frequency doubling of the 1064nm laser are equal to the cavity losses. By increasing the 1064nm pump power and improving the frequency doubling efficiency, and controlling the cavity losses (reflection and diffraction losses of the cavity devices and absorption and scattering losses of the sample), the power of the 532nm laser within the cavity can be multiplied by orders of magnitude. Of course, this example only uses a 1064nm pump with frequency doubling to output a 532nm laser; this method can also achieve cavity gain enhancement for other excitation wavelengths, such as a 1570nm pump light frequency doubling to achieve 785nm laser cavity resonance. Alternatively, the frequency doubling crystal can be replaced with a laser crystal such as a YAG crystal, using an 808nm pump to achieve cavity enhancement of the 1064nm laser.
[0041] Example 2, as shown in Figure 2, includes a spectral detection unit comprising a slit, a collimating lens, a beam splitter, and an area array detector. Laser light from the sample sequentially passes through the slit, collimating lens, beam splitter, fourth focusing lens, and area array detector. The signal light is focused onto slit 3-1-1 by the third focusing lens 2-5, then collimated by collimating lens 3-1-3, and then diffracted by beam splitter 3-1-4 to different wavelengths. Finally, the signal light of different wavelengths is focused onto the Y-direction of area array detector 3-1-5 by the fourth focusing lens 3-1-4. The Y-direction of area array detector 3-1-5 corresponds to different wavelength signals, and the X-direction corresponds to the spatial dimension information along the slit length direction. That is, each column of area array detector 3-1-5 corresponds to the spectral information of a point along the slit length direction. By accumulating and integrating the detector signal along the X-direction (accumulating the signal along the X-direction, corresponding to the slit length direction, to achieve signal integration enhancement), line integration detection of the scattered or fluorescent signals generated by laser line excitation can be achieved, improving signal intensity and detection sensitivity. It can also perform individual detection on each point to achieve line imaging and counting detection of signals on the excitation line, such as the detection of microplastics in solution, particulate matter in gas, and abnormal cells in blood.
[0042] In Example 3, as shown in Figure 3, in addition to the spectral detection unit described above, the spectral detection unit of the present invention can also employ a linear array detector to detect signals of a specific wavelength after the spectral signal generated by linear excitation has passed through a filter.
[0043] In summary, this application employs a gain resonance method within a resonant cavity to achieve an order-of-magnitude increase in the energy of the excitation light. Furthermore, by utilizing the line transmission characteristics of laser light and the weak absorption and scattering characteristics of laser light by gases and liquids, and leveraging the slit imaging characteristics of an imaging spectrometer, a line excitation and line collection method is adopted to significantly enhance the excitation and signal detection capabilities of the sample. This application is applicable to non-transparent samples such as solids and powders, as well as transparent substances such as gases and liquids. It is easy to implement and, compared to existing technologies, has lower costs, provides intracavity gain, requires less sample volume, and has relatively high signal collection efficiency.
[0044] The above are merely preferred embodiments of this application, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.
Claims
1. A laser induced Raman, fluorescence spectroscopy testing system, characterized by, include: Laser module, harmonic separation mirror, frequency doubling crystal, first cavity mirror, sample cell, second cavity mirror, and spectral detection unit; The laser output from the laser module passes sequentially through a harmonic separator, a frequency doubling crystal, and a first cavity mirror. The harmonic separation mirror is coated with a high-transmittance film on the side closest to the laser module and a high-reflectance film on the side closest to the frequency doubling crystal. The harmonic separation mirror separates the laser from the frequency doubling crystal and reflects the laser of the required wavelength back to the sample cell. The first cavity mirror is used to reflect the laser from the frequency doubling crystal back to the frequency doubling crystal; The second cavity mirror is used to reflect the laser from the sample cell back into the sample cell; The spectral detection unit is used to analyze and detect the sample in the sample cell.
2. The laser-induced Raman, fluorescence spectroscopy testing system according to claim 1, characterized in that: The laser module includes a pump laser, a waveplate, and a first focusing lens. The laser output from the pump laser passes sequentially through the waveplate, the first focusing lens, and a harmonic separator.
3. The laser-induced Raman, fluorescence spectroscopy testing system according to claim 2, characterized in that: A Faraday optical isolator is provided between the pump laser and the waveplate.
4. The laser-induced Raman, fluorescence spectroscopy testing system according to claim 2, characterized in that: The waveplate is a half-waveplate.
5. The laser-induced Raman, fluorescence spectroscopy testing system according to claim 1, characterized in that: A second focusing lens is provided between the harmonic separation mirror and the sample cell.
6. The laser induced Raman, fluorescence spectroscopy testing system according to claim 1, characterized in that: It also includes a collection mirror for collecting and reflecting scattered or fluorescent signals generated by the sample, a collimating lens for collimating scattered and fluorescent signals from the sample cell, and a laser filter, the collimated laser passing through the laser filter into the spectral detection unit.
7. A laser induced Raman, fluorescence spectroscopy testing system according to claim 6, characterized in that: It also includes a third focusing lens, which is disposed between the laser filter and the spectral detection unit.
8. A laser induced Raman, fluorescence spectroscopy testing system according to any one of claims 1 to 7, characterized in that: The spectral detection unit includes a slit, a collimating lens, a beam splitter, and an area array detector. The laser from the sample passes through the slit, collimating lens, beam splitter, and area array detector in sequence.
9. The laser-induced Raman, fluorescence spectroscopy testing system of claim 8, wherein: The spectral detection unit also includes a fourth focusing lens, which is disposed between the beam splitter and the area array detector.
10. A laser induced Raman, fluorescence spectroscopy testing system according to any one of claims 1 to 7, characterized in that: The spectral detection unit includes a linear array detector.