Flowing-gas diode pumped alkali lasers: theoretical analysis of transonic vs supersonic and subsonic devices

Abstract

We examine transonic diode pumped alkali laser (DPAL) devices as a simpler alternative to supersonic devices, suggested by B.D. Barmashenko and S. Rosenwaks [Appl. Phys. Lett. 102, 141108 (2013)], where complex hardware, including supersonic nozzle, diffuser and high power mechanical pump, is required for continuous closed cycle operation. Three-dimensional computational fluid dynamics modeling of transonic (Mach number M ~0.9) Cs and K DPALs, taking into account the kinetic processes in the lasing medium is reported. The performance of these lasers is compared with that of supersonic (M ~2.5) and subsonic (M ~0.2) DPALs. For Cs DPAL the maximum achievable power of transonic device is lower than that of supersonic, with the same resonator and Cs density at the laser section inlet, by only ~3% implying that supersonic operation mode has only small advantage over transonic. On the other hand, for subsonic laser the maximum power is by 7% lower than in transonic, showing larger advantage of transonic over subsonic operation mode. The power achieved in supersonic and transonic K DPALs is higher than in subsonic by ~80% and ~20%, respectively, showing a considerable advantage of supersonic device over transonic and of transonic over subsonic.

Double-Cycle Alternating-Flow Diode Pumped Potassium Vapor Laser

“…It was found that for the long-term continuous operation of supersonic DPAL, cyclic operation is required to save gas [8]. Subsequent comparison of the output performance of K-DPAL and Cs-DPAL at supersonic, subsonic, and transonic speeds [9][10][11][12] reveals that supersonic speeds are superior to transonic speeds, and transonic speeds are superior to subsonic speeds, while the maximum output power of K-DPAL is higher than that of supersonic Cs-DPAL at supersonic speeds [13,14]. In order to realize high-pressure and high-speed gas flow, ultra-high-power mechanical pumps are required, which is the key to the long-term continuous operation of supersonic recirculating flow-type DPAL.…”

Simulations on flowing-gas DPALs with non-equilibrium potassium vapor

“…Theoretically, Yacoby, E., Waichman, K., Barmashenko, B. D et al developed theoretical models of subsonic and supersonic DPAL in 2012-2017 [5][6][7][8][9][10][11][12][13][14][15][16], showing the positive effect of airflow on laser performance with megawatt laser power. Up to now, in all studies, alkali vapors are obtained by saturated vapors, and the atomic number density of gain medium is determined by the operating temperature.…”

Simulation and analysis of the time evolution of laser power and temperature in static pulsed XPALs

“…Therefore, they introduced gas flow into the system to reduce the temperature gradient [13] and applied fluid methods to the CW XPAL system, with good simulation results being achieved [14] . In another approach, Yacoby et al performed in-depth fluid dynamic studies of alkali vapor lasers with super-fast gas flows [15,16] . However, those systems all need nozzle devices to produce sonic-level gas flow.…”

“…In another approach, Yacoby et al. performed in-depth fluid dynamic studies of alkali vapor lasers with super-fast gas flows [15, 16] . However, those systems all need nozzle devices to produce sonic-level gas flow.…”