Modeling of K and Rb DPALs

A comprehensive three-dimensional modeling of static K diode pumped alkali laser (DPAL) and flowing-gas K and Rb DPALs is carried out. The cases of He/CH4 and pure He buffer gases are investigated and the output power and optical efficiency calculated for various pump powers, mole fractions of methane, buffer gas pressures and flow velocities. The model considers the processes of excitation of high levels of K and Rb, ionization, ion-electron recombination and heating of electrons which affect the diffusion coefficient of K and Rb ions. It explains the experimentally observed sharp increase in power in static K DPAL caused by the addition of a few percent of methane to He buffer gas and its decrease with further increase in the methane percentage [B.V. Zhdanov et al, Opt. Exp. 25, 30793 (2017)]. The predictions of the model for different He/CH4 mixtures are presented and verified by comparing them with experimental results for K flowing-gas DPAL [A. J. Wallerstein, Ph.D. dissertation (Air Force Institute of Technology, 2018)] and with the calculated results obtained using a simplified three-level model based on one-dimensional gas dynamics approach reported by A. Gavrielides et al [J. Opt. Soc. Am. B 35, 2202 (2018)].

[1]  O. Heavens.  Radiative Transition Probabilities of the Lower Excited States of the Alkali Metals , 1961 .

[2]  Velocity dependence of the performance of flowing-gas K DPAL with He and He/CH4 buffer gases: 3D CFD modeling and comparison with experimental results , 2020 .

[3]  J. E. Sansonetti.  Wavelengths, Transition Probabilities, and Energy Levels for the Spectra of Rubidium (Rb I through Rb XXXVII) , 2006 .

[4]  R. Knize,et al.  Collisional excitation transfer and quenching in Rb(5P) -methane mixtures , 2018, Physical Review A.

[5]  M. K. Shaffer,et al.  Low pressure cesium and potassium Diode Pumped Alkali Lasers: pros and cons , 2015, SPIE Security + Defence.

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

[7]  G. Pitz,et al.  Recent advances in optically pumped alkali lasers , 2017 .

[8]  Karol Waichman,et al.  CFD DPAL modeling for various schemes of flow configurations , 2014, Security and Defence.

[9]  Michael R. Hawks,et al.  Analytic treatment of beam quality and power efficiency in a high-power transverse flow diode pumped alkali laser , 2018, Journal of the Optical Society of America B.

[10]  Boris D. Barmashenko,et al.  Detailed analysis of kinetic and fluid dynamic processes in diode-pumped alkali lasers , 2013 .

[11]  Christopher A. Rice,et al.  Excitation of higher lying energy states in a rubidium DPAL , 2018, LASE.

[12]  K. Waichman,et al.  Dependence of static K DPAL performance on addition of methane to He buffer gas: 3D CFD modeling and comparison with experimental results , 2019, Journal of the Optical Society of America B.

[13]  Q. Lu,et al.  Choice of alkali element for DPAL scaling, a numerical study , 2013 .

[14]  A. Wallerstein.  Kinetics of Higher Lying Potassium States after Excitation of the D2 Transition in the Presence of Helium , 2018 .

[15]  Karol Waichman,et al.  CFD assisted simulation of temperature distribution and laser power in pulsed and CW pumped static gas DPALs , 2015, SPIE Security + Defence.

[16]  Charlton D. Lewis,et al.  Temperature dependence of the fine structure mixing induced by 4He and 3He in K and Rb Diode Pumped Alkali Lasers , 2020, Applied Physics B.

[17]  Eric M. Guild,et al.  Advancements in flowing diode pumped alkali lasers , 2016, SPIE LASE.

[18]  Karol Waichman,et al.  Computational fluid dynamics modeling of subsonic flowing-gas diode-pumped alkali lasers: comparison with semi-analytical model calculations and with experimental results , 2014 .

[19]  G. Perram,et al.  Excitation of higher lying states in a potassium diode-pumped alkali laser , 2019, Applied Physics B.

[20]  Xiaojun Xu,et al.  Ionization degree measurement in the gain medium of a hydrocarbon-free rubidium vapor laser operating in pulsed and CW modes. , 2017, Optics express.