Investigation of the Atmospheric Propagation of Alkali Lasers in a Maritime Environment Using Tunable Diode Laser Atmospheric Spectroscopy.

摘要

A field deployable Tunable Diode Laser Atmospheric Spectroscopy (TDLAS) device has been used to investigate the atmospheric absorption of Diode Pumped Alkali Laser (DPAL) wavelengths at a distance of 2,000 meters in a maritime environment. The spectral regions surrounding the cesium (Cs) and rubidium (Rb) DPAL emission lines were examined in order to determine the effects of absorption by the (000)--->(003) and (000)--->(102) water vapor vibrational bands over a distance of 2 km. This data was compared with data previously collected at shorter path lengths and the scaling of absorbance with various factors was analyzed. Spectral data for the Cs spectral region were analyzed to determine temperature and concentration estimates with statistical errors of between 0.1 and 1.14 deg. C and 11 and 1x10(to the 14th power). Temperature and pressure estimates were within 6% and 25%, respectively, of those reported by the weather station at the test site. The rotational dependence of broadening rates was investigated. By analyzing the widths of two widely spaced rotational lines, it was found that the observed linewidths were approximately 25% higher than those reported in existing spectral databases with a scaling ratio of the observed rates approximately 5% below the ratio of the reported values.