Photothermal Interferometry Device and Method for Measuring Aerosol Absorption Using Herriot Cell

Abstract

The invention discloses a photo-thermal interference apparatus by using Herriott cell to measure aerosol absorption and a method thereof. According to the invention, three ways of interference light are designed, an upper way and a lower way of interference light are used for detecting gradual change of ambient temperature and phase baseline drift due to platform vibration, and then self-correction is formed, an intermediate way of detection laser transmits in the Herriott cell, under prerequisite that a laser light path is not changed, prolongation with order of magnitude of effective effect length of the detection laser can be obtained by the excitation laser, cooperation of the intermediate way of detection laser as well as the upper way and the lower way of interference light can be used for obtaining the phase change due to excitation laser, and on-line detection of aerosol absorption coefficient is realized. According to the invention, the Herriott cell is used for prolonging the effective effect distance so that the detection sensitivity of a photo-thermal interferometry is greatly increased, and phase difference settlement gets rid of angle interval restriction by a phase modulation-demodulation mode.

Description

Technical field: [0001] The invention relates to a photothermal interference device for measuring aerosol absorption by using a Heriot cell, belonging to the field of optics. Background technique: [0002] When the light beam passes through the atmosphere, the aerosol particles in the atmosphere absorb the light radiation energy, causing changes in the thermal state of the air on the beam transmission path, such as temperature, pressure and density. If the incident light beam is periodically modulated, the local thermal state of the air will change periodically, and the absorption coefficient of the aerosol to be measured can be obtained in real time by measuring the linear fluctuation range of this change with the modulated incident light per unit time. The photothermal interference method is based on the change of the refractive index of the sample gas caused by the thermal conversion of the incident laser radiation energy. Unlike the general absorption spectrum, increasin...

AI Technical Summary

Problems solved by technology

Whether it is a coaxial structure or a grazing structure, up to now, the excitation laser has acted on the detection laser once at most twice, and the effective distance is severely restricted, which hinders the improvement of the sensitivity of the photothermal interference method.

Images