The results of optical guidance of flowing particles to the probe volume of Dual-Beam Velocimetry

Abstract

In this study, a new method of microscopic particle’s size and condensation measurement by dual-beam methods is investigated. In this method microscopic particles in a turbulent fluid such as aerosols guide to the interfering fringes of two shifted frequency laser beams by an optical tube (e.g., single-charged Bessel-Gaussian laser beams) instead of mechanical guiding of them. Optical forces such as radiation and photophoretic forces on a particle in a fluid was obtained. It was shown theoretically the Signal-to-Noise Ratio, SNR, and the number of detected photons scattered from the particles cross the fringes will be significantly increased rather than mechanical guiding of them. In addition, the Doppler frequency broadening and angular uncertainty are decreased by new measurement. The condensation of aerosols in the lab was measured by counting the signal burst from particles which traverse light fringes after guided them into a single charge Bessel-Gaussian laser beam. Due to the lack of laboratory facilities, our group can’t determine the frequency Doppler shifted of laser beam to determine the particle’s dimensions.