A Broadband and High Precision Comb Spectrometer for Diode-Pumped Alkali Lasers (DPALs)

Diode-pumped alkali lasers (DPALs) have inherently high optical-to-optical efficiency and thus the potential to reach megawatt-class average power lasers with near-diffraction limited beam quality. However, as DPALs scale up in power, a plasma is formed in the gain medium, resulting in lower efficiency and increased gas heating. This ultimately leads to a degradation in laser beam quality and a poor size, weight and power (SWaP) factor. Until now, the electron energy density distribution (EEDF) in a DPAL has only been modeled but not measured experimentally. In this Phase 1 proposal, we will utilize dual frequency comb spectroscopy to obtain spectroscopic information on a number of ionic and neutral transitions, from which we will investigate the feasibility of reliably extracting information on the electron number density and EEDF (or ion density). This will be performed under a variety of buffer gas pressures, laser intensities and densities. It will provide a roadmap for the assembly of an experimental apparatus that will be used to measure key energetic parameters in a DPAL during Phase 2. The data will be used for modeling and design of current and future DPALs. Approved for Public Release | 22-MDA-11339 (13 Dec 22)