Laser Demonstration and Performance Characterization of an Optically Pumped Alkali Laser System

摘要

Diode Pumped Alkali Lasers (DPALs) offer a promising approach for high power lasers in military applications that won't suffer from the long logistical trails of chemical lasers or the thermal management issues of diode pumped solid state lasers. This research focuses on characterizing a DPAL type system to gain a better understanding of using this type of laser as a directed energy weapon. A rubidium laser operating at 795nm is optically pumped by a pulsed titanium sapphire laser to investigate the dynamics of DPALs at pump intensities between 1.3 and 45 kW/cm2 . Linear scaling as high as 32 times threshold is observed, with no evidence of second order kinetics. Comparison of laser characteristics with a quasi-two level analytic model suggests performance near the ideal steady-state limit, with the exception of mode matching. Additionally, the peak power has scaled linearly as high as 1 kW, suggesting aperature scaling to a few cm2 is sufficient to achieve tactical level laser powers. The temporal dynamics of the 100ns pump and rubidium laser pulses are presented, and the continually evolving laser efficiency provides insight into the bottlenecking of the rubidium atoms in the 2P3/2 state. Lastly, multiple excited states of rubidium and cesium were accessed through two photon absorption in the red, and yielded a blue and an IR photon through amplified stimulated emission. Threshold is modest at 0.3mJ/pulse, and slope efficiencies increase dramatically with alkali concentrations and peak at 0.4%, with considerable opportunity for improvement. This versatile system might find applications for IR countermeasures or underwater communications.