Possible Use of Iodine Absorption/Fluorescence Cell in High-Spectral-Resolution Lidar

Abstract

The possibility of using fluorescence from the iodine-blocking filter in HSRL to detect the Mie scattering components in the backscattered signals was studied. An experiment was conducted with an HSRL using an iodine-blocking filter by adding a detector for measuring fluorescence from the iodine cell. Atmospheric backscattering signals were successfully measured, although the detection efficiency was limited by the low optical efficiency of collecting fluorescence from the iodine cell. In the atmospheric measurement, it was also shown that about half of Rayleigh scattering Cabannes line was also absorbed by the iodine cell. To improve the detection performance, a method using detector arrays surrounding the fluorescence cell was considered. The fluorescence excitation spectrum is dependent on the location of the fluorescence detectors, i.e., the penetration depth in the cell. Using this effect, it is possible to separate the Mie and Rayleigh components absorbed in the cell by measuring fluorescence intensity at multiple penetration depths.