Modeling of static and flowing-gas diode pumped alkali lasers

A simple, semi-analytical model of diode pumped alkali lasers (DPALs), applicable to both static and flowing-gas devices, is reported. Unlike other models, assuming a 3-level scheme of the laser and neglecting influence of the temperature on the lasing power, it takes into account temperature rise and losses of alkali atoms due to ionization and chemical reactions, resulting in a decrease of the pump absorption and slope efficiency. The applicability of the model is demonstrated by (1) obtaining good agreement with measurements in a static DPAL [B.V. Zhdanov, J. Sell and R.J. Knize, Electron. Lett. 44, 582 (2008)], (2) predicting the dependence of power on the flow velocity in flowing-gas DPALs and (3) checking the effect of using a buffer gas with high molar heat capacity and large relaxation rate constant between the 2P3/2 and 2P1/2 fine-structure levels of the of the alkali atom. It is found that ionization processes have a small effect on the laser operation, whereas chemical reactions of alkali atoms with hydrocarbons strongly affect the lasing power. The power strongly increases with flow velocity and by replacing, e.g., ethane by propane as a buffer gas the power may be further increased by up to 30%. 8 kW is achievable for 20 kW pump at flow velocity of 20 m/s.

[1]  Luc Barbier,et al.  Experimental study of Penning and Hornbeck-Molnar ionisation of rubidium atoms excited in a high s or d level (5d⩽nl⩽11s) , 1987 .

[2]  Xiaojun Xu,et al.  Modeling, numerical approach, and power scaling of alkali vapor lasers in side-pumped configuration with flowing medium , 2011 .

[3]  L. Krause,et al.  Inelastic Collisions Between Excited Alkali Atoms and Molecules X. Temperature Dependence of Cross Sections for 2P1/2↔2P3/2 Mixing in Cesium, Induced in Collisions with Deuterated Hydrogens, Ethanes, and Propanes , 1974 .

[4]  William F. Krupke,et al.  Diode pumped alkali lasers (DPALs)—A review (rev1) , 2012 .

[5]  V. K. Kanz,et al.  End-pumped continuous-wave alkali vapor lasers: experiment, model, and power scaling , 2004 .

[6]  G. Perram,et al.  A three-level analytic model for alkali metal vapor lasers: part I. Narrowband optical pumping , 2010 .

[7]  Gordon D. Hager,et al.  A study of collisional quenching and radiation-trapping kinetics for Rb(5p) in the presence of methane and ethane using time-resolved fluorescence , 2009 .

[8]  M. K. Shaffer,et al.  Photoionization in alkali lasers. , 2011, Optics express.

[9]  Qi Zhu,et al.  Analysis of temperature distributions in diode-pumped alkali vapor lasers , 2010 .

[10]  Andrew C. Tam,et al.  Particle formation by resonant laser light in alkali-metal vapor , 1975 .

[11]  Glen P. Perram,et al.  Transfer between the cesium62P1/2and62P3/2levels induced by collisions with H2, HD, D2, CH4, C2H6, CF4, and C2F6 , 2011 .

[12]  B. Barmashenko,et al.  Modeling of flowing gas diode pumped alkali lasers: dependence of the operation on the gas velocity and on the nature of the buffer gas. , 2012, Optics letters.

[13]  Boris V. Zhdanov,et al.  Multiple laser diode array pumped Cs laser with 48W output power , 2008 .

[14]  V. A. Eroshenko,et al.  Diode-pumped caesium vapour laser with closed-cycle laser-active medium circulation , 2012 .

[15]  E. R. V. Artsdalen.  The Carbon‐Carbon Bond Strengths in Ethane, Propane, and n‐Butane , 1942 .