Excimer-pumped alkali vapor lasers (XPALs) are a new class of photoassociation lasers which take
advantage of the spectrally broad absorption profiles of alkali-rare gas collision pairs. In these systems,
transient alkali-rare gas molecules are photopumped from the thermal continuum to a dissociative X<sup>2</sup>Σ<sup>+</sup>
<sub>1/2</sub> interaction potential, subsequently populating the n<sup>2</sup>P<sub>3/2</sub> state of the alkali. The absorption profiles ≥5 nm and
quantum efficiencies >98% have been observed in oscillator experiments, indicating XPAL compatibility
with conventional high power laser diode arrays.
An alternative technique for populating the n<sup>2</sup>P<sub>3/2</sub> state is direct photoexcitation on the n<sup>2</sup>P<sub>3/2</sub>←n<sup>2</sup>S<sub>1/2</sub> atomic
transition. However, because the XPAL scheme employs an off-resonant optical pump, the strengths of
resonantly-enhanced nonlinear processes are minimized. Additionally, the absorption coefficient may be
adjusted by altering the number densities of the lasing species and/or perturbers, a valuable asset in the design
of large volume, high power lasers.
We present an overview of XPAL lasers and their operation, including the characteristics of recently
demonstrated systems photopumped with a pulsed dye laser. Lasing has been observed in Cs at both
894 nm and 852 nm by pumping CsAr or CsKr pairs as well as in Rb at 795 nm by pumping RbKr. These
results highlight the important role of the perturbing species in determining the strength and position of the
excimer absorption profile. It is expected that similar results may be obtained in other gas mixtures as similar
collision pair characteristics have historically been observed in a wide variety of transient diatomic species.
The exciplex pumped alkali laser (XPAL) system was recently demonstrated in mixtures of Cs vapor, Ar, and ethane, by
pumping Cs-Ar atomic collision pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules
(exciplexes or excimers). Because of the addition of atomic collision pairs and exciplex states, modeling of the XPAL
system is far more complicated than classic diode pumped alkali laser (DPAL) modeling. In this paper we discuss
BLAZE-V multi-dimensional modeling of this new laser system and compare with experiments.
Lasing on the 6<sup>2</sup>P<sub>1/2</sub>→6<sup>2</sup>S<sub>1/2</sub>(D1) resonance transition of atomic Cs at 894.3 nm has been demonstrated in mixtures
of Ar, ethane, and Cs vapor by the photoexcitation of ground state Cs-Ar collision pairs and subsequent dissociation
of diatomic, electronically-excited CsAr molecules (exciplexes or excimers). The blue satellites of the alkali D<sub>2</sub> lines
provide a pathway for optically pumping atomic alkali lasers on the principal series (resonance) transitions with
broad linewidth (>2 nm) semiconductor diode lasers. In this paper we discuss different variations of this new laser
system and the experiments of the initial demonstration.