Theoretical model and simulations for a cw exciplex pumped alkali laser

Abstract

The Exciplex Pumped Alkali Laser (XPAL) system, which is similar to DPAL (Diode Pumped Alkali vapor Laser), has been demonstrated in mixtures of Cs vapor, Ar, with and without ethane. Unlike DPAL, it uses the broadband absorption blue satellite of the alkali D₂ line, created by naturally occuring collision pairs. For example, Cs-Ar collision pairs have an absorption width which is as wide as the one of commercial semiconductor diode lasers. A continuous wave XPAL four-level theoretical model is presented in this paper. More factors are considered, such as the spectral dependence of pumped laser absorption for broadband pumping and the longitudinal population variation. Some intra-cavity details, such as longitudinal distributions of pumped laser and alkali laser, can also be solved well. The predictions of optical-to-optical efficiency as a function of temperature and pumped laser intensity are presented. The model predicts that there is an optimum value of temperature or pumped laser intensity. The analysis of the influence of cell length on optical-to-optical efficiency shows that a better performance can be achieved when using longer cell. The prediction of influence of Ar concentration and reflectivity of output coupler shows that higher optical-to-optical efficiency could be achieved if lower reflectivity of output coupler and higher Ar concentration are used. The optical-to-optical efficiency as high as 84% achieved by optimizing configuration with the pumped intensity of 5 × 10⁷ W/cm² presented shows that broadband pumped four-level XPAL system has a potential of high optical-to-optical efficiency.

Experimental investigation of a pulsed Rb–Ar excimer-pumped alkali laser

“…Effective approaches to enhancing the absorbed pump energy and conversion efficiency include raising the cell temperature or increasing the cavity length. 28,29) The laser performance with the 40% transmission output mirror is further characterized at temperatures of 413 and 423 K. The corresponding Rb (Ar) densities are 6.15 × 10 13 (1.75 × 10 19 ) and 1.02 × 10 14 (1.71 × 10 19 ) cm −3 , respectively. As shown in Fig.…”

Population inversion in sodium D2 transition based on sodium-ethane excimer pairs

“…Before the pumping laser excites the gain medium, the sodium vapor atom density of the 3 2 S 1∕2 state and excimer density of the X 2 Σ þ 1∕2 state can be calculated. Under the condition of thermal equilibrium, the ratio between the population densities on the X 2 Σ þ 1∕2 state and the 3 2 S 1∕2 state is decided by the equilibrium fraction, just as is shown in [31]…”

“…where f 10 is the equilibrium fraction, n 0 and n 1 are the population densities on the 3 2 S 1∕2 state and the X 2 Σ þ 1∕2 state, respectively, g 0 or g 1 is the degeneracy factor of the 3 2 S 1∕2 state (2) or the X 2 Σ þ 1∕2 state (2), R 0 is the optimal internuclear separation (0.4518 nm for Na-C 2 H 6 ) [21] , ΔR is the range of distances over which the resonance absorption condition is maintained (0.1 nm) [31] , k b is the Boltzmann constant, T is the temperature of the vapor cell, ΔE 10 is the difference in the potential energy between the collision pair state at R 0 and the unbound state (∼114.4 cm −1 ) [21] , and [C 2 H 6 ] is the ethane concentration (1.94 × 10 −19 cm 3 ).…”

Theoretical investigation of the pressure broadening D1 and D2 lines of cesium atoms colliding with ground-state helium atoms

“…In fact, the experimental measurement or theoretically simulation of the absorption-emission spectra must be a crucial tool for determining the physical and chemical properties of the environments of extrasolar giant planets and brown dwarfs. [10][11][12][13][14][15][16] Furthermore, the analysis of the collisionally induced spectral broadening of the D 1 and D 2 lines has played a very significant role in the conceptual design and manufacturing of several new type and efficient lasers, namely, the diode-pumped alkali lasers (DPAL), [7,[17][18][19][20] and the excimer-pumped alkali vapor lasers (XPAL), [21][22][23][24] which was proposed as an alternative to high-power diode-pumped solid-state lasers, and could be used not only for technological applications but also for very important medical application in magnetic resonance imaging.…”