Detection method using evanescent waves in photoacoustic spectrum and device thereof
A technology of photoacoustic spectroscopy and detection methods, which is applied in measurement devices, material analysis by optical means, instruments, etc., can solve the problems of waste of light source, inability to realize, and affecting detection sensitivity.
Active Publication Date: 2020-04-28
GENUINE LASERS CORP
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[0005] 1. The design of the photoacoustic cell affects the detection sensitivity. The longer the cavity length and the smaller the volume of the photoacoustic cell, it is conducive to the enhancement of the photoacoustic signal and can improve the detection sensitivity; however, the light source beam should avoid shining on the cavity wall In order to avoid background noise, the volume of the cavity is limited by the size of the incident light beam, so the detection sensitivity cannot be improved, and a lower detection limit cannot be achieved
[0006] 2. The resonant photoacoustic cell mainly uses the mode matching effect of light waves and sound waves in the cavity to achieve the effect of resonance amplification; however, the light source beam is incident in the cavity, and the standing wave formed by the relative sound wave in the cavity At the antinode and wave node, the intensity and amplitude of the light source are the same, and the effect of resonance enhancement and amplification cannot be achieved at the antinode of the standing wave, while the light source at the wave node is wasteful
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[0043] First, the present invention provides a detection method, which mainly uses evanescent wave in photoacoustic spectrum to control the light output position of the light source in the photoacoustic cell relative to the position where the amplitude of the sound wave is the largest, so that the modes of the light wave and the sound wave in the photoacoustic cell It can be matched to achieve the amplification effect to achieve high detection sensitivity and low detection limit.
[0044] Such as figure 2 Shown is a schematic structural view of the detection device of the present invention, the detection device of the present invention at least includes: a light source 21, a resonant cavity 22, an optical fiber 23, a sensor 24 and an analysis unit 25; wherein: the light source 21 According to the radiation characteristics, light sources can be divided into two types: incoherent light sources and coherent laser light sources. Compared with incoherent light sources, laser ligh...
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The invention relates to a detection method using evanescent waves in a photoacoustic spectrum and a device thereof. The detection method comprises the steps of providing a resonant cavity filled withgas to be detected and providing an optical fiber to generate an evanescent field in the resonant cavity, wherein the gas to be detected is excited by the evanescent field to generate a photoacousticeffect, a sound wave is generated in the resonant cavity, the sound wave resonates in the resonant cavity to form a standing wave, and the position of the evanescent field is opposite to an antinodeof the standing wave. According to the detection method provided by the invention, high detection sensitivity and low detection limit can be realized in the photoacoustic spectrum.
Description
technical field [0001] The invention relates to a detection method and a device thereof which can realize high detection sensitivity and low detection limit in photoacoustic spectroscopy. Background technique [0002] Photoacoustic spectroscopy technology is based on the photoacoustic effect. It can be used to qualitatively and quantitatively detect various substances in solutions or liquid media or gases and solids by directly measuring the heat energy generated by substances due to the absorption of light energy. And used in gas detection system, such as figure 1 As shown, the excitation light is generated by modulating the monochromatic light source 11 (intensity modulation / wavelength modulation) and coupled into the photoacoustic cell 12; specific gas molecules in the photoacoustic cell 12 absorb light energy and are excited to transition to the vibration level High-energy state, and then convert energy into kinetic energy through a radiation-free transition, forming a ...
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IPC IPC(8): G01N21/17
CPCG01N21/1702G01N2021/1704
Inventor 陈依希
Owner GENUINE LASERS CORP