CN-121994767-A - Laser-induced fluorescence spectrum rare earth element detection method and system for light field regulation

CN121994767ACN 121994767 ACN121994767 ACN 121994767ACN-121994767-A

Abstract

The invention discloses a method and a system for detecting rare earth elements in a laser-induced fluorescence spectrum under light field regulation and control, and belongs to the technical field of spectrum analysis and optical precision detection. The method adopts a supercontinuum light source to be matched with an acousto-optic tunable filter to realize rapid and accurate tuning of excitation wavelength, converts excitation light into vector beams polarized in an angular direction or a radial direction through a vortex wave plate, then tightly focuses through a high numerical aperture objective lens, and forms remarkable local enhancement of longitudinal electric field or magnetic field components in a focal region, so that electric dipole or magnetic dipole transition fluorescence signals of rare earth ions are selectively enhanced, and fluorescence signals are collected and analyzed through a spectrometer. The method has the advantages of high signal-to-noise ratio, strong specificity and flexible operation, and is suitable for trace detection and space distribution imaging of rare earth elements in geological, material and environmental samples.

Inventors

SHU RONG
XU WEIMING
LIU XIANGFENG
LIU XIALIN
WANG XIZHU

Assignees

中国科学院上海技术物理研究所

Dates

Publication Date: 20260508
Application Date: 20260410

Claims (10)

1. The method for detecting the rare earth element by using the laser-induced fluorescence spectrum is characterized by comprising the following steps of: Step 1, constructing an integrated optical detection system, wherein the system comprises an excitation unit, a collection unit and a correction unit, and the excitation unit comprises a wavelength selection module, a light field regulation module and a high-resolution focusing module which are sequentially arranged along an optical axis; Step 2, selecting excitation light with specific wavelength from a supercontinuum light source by utilizing the wavelength selection module, converting the excitation light into vector light beams of angular polarized light or radial polarized light by utilizing the light field regulation and control module, and focusing the vector light beams to the surface of a sample by utilizing the high-resolution focusing module; Step 3, observing an excitation light spot image corresponding to the vector beam acting on the surface of the sample by using the correction unit, and adjusting the position of the sample to accurately align the excitation light spot image with the region to be detected of the sample; step 4, collecting fluorescent signals generated by sample excitation by using the collecting unit, and acquiring spectrums or images; and 5, carrying out specific identification and quantitative analysis of rare earth elements based on the acquired spectrum or image data.
2. The method for detecting rare earth elements in a light field controlled laser-induced fluorescence spectrum according to claim 1, wherein the wavelength selection module comprises a supercontinuum light source and an acousto-optic tunable filter, an output end of the supercontinuum light source is optically connected with an input end of the acousto-optic tunable filter, and the acousto-optic tunable filter is used for realizing rapid and mechanical-free tuning of excitation wavelength through an electronically controlled radio frequency signal so as to match a characteristic absorption energy level of a target rare earth element.
3. The method for detecting rare earth elements in a light field according to claim 1, wherein the light field adjusting module comprises a half-wave plate and a vortex wave plate, an output end of the half-wave plate is optically connected with an input end of the vortex wave plate, the half-wave plate is used for adjusting a linear polarization direction of excitation light, the vortex wave plate is used for converting the linear polarization light into angular polarization light or radial polarization light, and a fast axis direction of the vortex wave plate is linearly changed with an azimuth angle of a position where the vortex wave plate is located.
4. The method for detecting the rare earth elements by using the laser-induced fluorescence spectrum according to the light field regulation and control of claim 1, wherein the high-resolution focusing module comprises an objective lens with a numerical aperture NA larger than or equal to 0.8 and a nano displacement platform, the objective lens is arranged on an output light path of the light field regulation and control module, the nano displacement platform is used for bearing a sample and is arranged near a focal plane of the objective lens, and is used for tightly focusing a vector light beam on the surface of the sample, and a local enhancement field of a longitudinal electric field or a magnetic field is formed in a focal area, so that an electric dipole transition or a magnetic dipole transition fluorescence signal of rare earth ions is selectively enhanced.
5. The method for detecting the rare earth elements in the fluorescence spectrum by the laser induction of the light field regulation and control according to claim 1, wherein the correction unit comprises a turnover mirror, an imaging lens and an area array camera, the turnover mirror is arranged in a light path of the collection unit, a light beam is switchably guided to the imaging lens, and the output end of the imaging lens is optically connected with the input end of the area array camera and is used for realizing conjugate imaging of the surface of a sample and an excitation light spot, and monitoring in real time and accurately positioning a region to be detected.
6. The method for detecting rare earth elements in a laser-induced fluorescence spectrum by light field regulation according to claim 1, wherein the collecting unit comprises a beam splitter, a filter, a focusing lens and a spectrometer, the beam splitter is arranged at the intersection of the light paths of the exciting unit and the collecting unit, the output end of the beam splitter is optically connected with the input end of the filter, the output end of the filter is optically connected with the input end of the focusing lens, the output end of the focusing lens is optically connected with the input end of the spectrometer, and the filter is a long-wave pass or band-pass filter for filtering excitation light scattering and collecting target fluorescence signals.
7. The method for detecting the rare earth elements by using the laser-induced fluorescence spectrum with the light field regulation and control according to claim 1 is characterized in that the step 5 further comprises the steps of realizing synchronous identification of various rare earth elements by combining excitation wavelength scanning with polarization resolution spectrum, carrying out point-by-point scanning by a nano displacement platform, and combining characteristic fluorescence intensity reconstruction to obtain a two-dimensional space distribution image of the rare earth elements on the surface of a sample.
8. A light field modulated laser induced fluorescence spectrum rare earth element detection system, applied to the method of any one of claims 1-7, comprising: The excitation unit is used for generating a tightly focused excitation light field with tunable wavelength and controllable polarization state and acting on a sample, and comprises a wavelength selection module, a light field regulation module and a high-resolution focusing module which are sequentially and optically connected along an optical axis; The collecting unit is connected with the light path of the excitation unit in a crossing way and is used for collecting and analyzing fluorescent signals generated by the excited sample; and the correction unit is in switchable connection with the light path of the collecting unit and is used for outputting accurate sample space coordinates through imaging positioning and transmitting the accurate sample space coordinates to the excitation unit so as to ensure the accuracy of excitation actions.
9. An electronic device, comprising: One or more processors; a memory for storing one or more programs; Wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the laser-induced fluorescence spectroscopy rare earth element detection method of light field modulation of any one of claims 1-7.
10. A computer readable storage medium having stored thereon executable instructions which, when executed by a processor, enable the processor to implement the laser-induced fluorescence spectrum rare earth element detection method of light field modulation of any one of claims 1-7.

Description

Laser-induced fluorescence spectrum rare earth element detection method and system for light field regulation Technical Field The invention belongs to the technical field of spectrum analysis and optical precision detection, and particularly relates to a laser-induced fluorescence spectrum rare earth element detection method and system for light field regulation. Background Rare Earth Elements (REEs) play an irreplaceable role in modern high technology industry and leading-edge scientific research due to their unique optical, electrical and magnetic properties. The accurate and rapid in-situ analysis of the content, the type and the spatial distribution is a key technical requirement in the fields of mineral resource evaluation, advanced material research and development, environment monitoring and the like. Currently, accurate quantitative analysis of rare earth elements in laboratories mainly depends on large-scale instrument methods such as inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Although the sensitivity of the method is high, the method has inherent limitations such as complex sample pretreatment, damage to the original state of the sample, incapability of in-situ analysis and real-time analysis. Although X-ray fluorescence spectroscopy (XRF) and Laser Induced Breakdown Spectroscopy (LIBS) can realize in-situ analysis to a certain extent, the resolution capability of the X-ray fluorescence spectroscopy (XRF) and the Laser Induced Breakdown Spectroscopy (LIBS) on the 4f-4f transition spectrums which are complex in rare earth elements and mutually overlapped is limited, and high-specificity identification is difficult to realize. The Laser Induced Fluorescence (LIF) technique has potential in the field of elemental analysis as an optical detection means with high sensitivity that enables non-contact and in-situ analysis. However, when the method is applied to rare earth element detection, a series of technical bottlenecks still exist, namely, a traditional LIF system adopts a laser with fixed wavelength, the characteristic absorption energy levels of different rare earth ions are difficult to flexibly match, the multi-element detection capability of the system is limited, the Magnetic Dipole (MD) transition intensity of the rare earth ions, which is critical to structural analysis, is usually far weaker than Electric Dipole (ED) transition in fluorescence signals of the rare earth ions, the signals are easy to be submerged by noise, important information is lost, and the excitation light spot of the conventional LIF system is large, the spatial resolution is limited, and the visible in-situ analysis of the component distribution of a sample micrometer or even nanometer scale region is difficult to combine with a microscopic imaging technology. Therefore, a laser-induced fluorescence spectrum detection method and a system which can realize rapid tuning of excitation wavelength, effectively enhance weak transition signals and have high spatial resolution in-situ imaging capability are developed, and the method and the system have important scientific significance and application value for promoting the development of rare earth element analysis technology to the directions of higher sensitivity, stronger specificity and better spatial resolution. Disclosure of Invention The invention provides a method and a system for detecting a rare earth element by laser-induced fluorescence spectrum with light field regulation, which utilize an acousto-optic tunable filter (AOTF) to realize rapid and accurate tuning of excitation wavelength to match an excitation state of a target rare earth element, convert excitation light into a vector light beam polarized in an angular direction or a radial direction through a vortex wave plate, tightly focus the vector light beam by utilizing a high numerical aperture objective lens, form a local enhancement field of a longitudinal electric field or a magnetic field component on the surface of a sample, promote electric dipole transition of rare earth ions by the electric field and promote magnetic dipole transition of the rare earth ions by the magnetic field, and realize visual positioning and in-situ spectrum acquisition of a sample micro-area through a conjugate imaging light path. The method is particularly suitable for carrying out high-specificity identification, high-sensitivity detection and micro-area space distribution analysis on rare earth elements, and has important application value in the fields of geological investigation, material science, environmental monitoring and the like. In order to achieve the above purpose, the invention adopts the following technical scheme: The method for detecting the rare earth elements by using the laser-induced fluorescence spectrum with light field regulation comprises the following steps: Step 1, constructing an integrated optical detection system