There have been concerted efforts to develop high-energy diode-pumped alkali vapor lasers (DPAL). These hybrid gas phase / solid-state laser systems offer possibilities for constructing high-powered lasers that have high beam quality. DPAL's utilize excitation of the alkali metal 2P3/22S1/2 transition, followed by collisional relaxation and lasing on the 2P1/2-2S1/2 line. Considerable progress has been made, but there are technical challenges associated with the reactivity of the metal atoms.
Rare gas atoms (Rg) excited to the np5(n+1)s 3P2 configuration are metastable and have spectral properties that are closely similar to those of the alkali metals. In principle, optically pumped lasers can be constructed using excitation of the np5(n+1)p np5(n+1)s transitions. We have demonstrated gain and lasing for optically pumped Ne*, Ar*, Kr* and Xe*. Three-level lasing schemes were used, with He as the collisional energy transfer agent that established the population inversion. These laser systems have the advantage using inert reagents that are gases at room temperature, with excellent potential for closed-cycle, multi-wavelength operation.
The primary technical difficulty for the rare gas laser is the discharge production of sufficient Rg* metastables in the presence of >200 Torr of He. We have developed a high frequency pulsed discharge that yields >10^13 /cm^3 Ar* in the presence of He at pressures up to 730 Torr. Using this discharge, a diode pumped Ar* laser providing 4.1 W of continuous wave output has been demonstrated, with an optical conversion efficiency of 31%. Further development of the pulsed discharge system, lasing demonstrations with Xe* and preliminary experiments with dielectric barrier discharges will be discussed.