Enhancement of Doppler spectroscopy to transverse direction by using optical vortex.

ABSTRACT: Tunable diode laser absorption spectroscopy (TDLAS) is a valuable method for measuring particle flow velocities in plasma. However, conventional TDLAS using a plane-wave beam is sensitive only to the laser propagation direction. This limitation is particularly unfavorable for the observation of the particle transportation perpendicularly incident on the material in the plasma-material interaction. In this paper, we show for the first time that flow measurements perpendicular to the beam direction are possible by replacing the probe beam with an optical vortex beam. Because an optical vortex has a helical wavefront, particles moving in its field experience an azimuthal Doppler shift in addition to the translational Doppler shift. Assuming a uniform gas flow across the optical vortex, the az

SUBMITTER: Minagawa H 

PROVIDER: S-EPMC10505230 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature