The Alexandrite Ring Laser: A Spectrally Narrow Lidar Light Source for Atmospheric Fluorescence and Absorption Observations

The Atmospheric Lidar Observatory (ALO) at Utah State University has recently acquired an alexandrite laser, developed by Light Age Incorporated, that is a relatively new type of configuration, ideal for resonance lidar and DIAL observations. Unidirectional ring lasing is established in a tworod cavity, producing single longitudinal and transverse mode (TEM00) pulses up to 200 mJ in energy and having a pulse length of 100 nsec or greater. This paper is, in part, a progress report on the advanced technology behind this new type of alexandrite laser, and how the new performance level will impact atmospheric lidar observations. We have not yet operated the USU alexandrite laser as a lidar transmitter, but have carried out the construction and testing of this and two other similar lasers, one of which is lidar-operational, and the other is currently being installed for the same purpose. This paper reviews some of the salient features of alexandrite as a laser medium, provides details on the current state-of-the-art of this tunable frequency-stabilized laser, and outlines the capabilities for geophysical lidar measurements using the alexandrite laser.