Study On Rb-ar Excimer Pumped Alkali Laser

Diode Pumped Alkali Laser (DPAL) has been identified as one of the mostpromising high energy lasers due to its high quantum efficiency and combination ofsolid-state laser’s compactness, high efficiency and gas laser’s easy thermalmanagement. However, DPAL is facing some difficulties: the bandwidth of diode laseris too broad for the alkali resonate line, and the small hydrocarbon molecule may reactwith alkali atoms at elevated temperature. Excimer pumped alkali laser (XPAL) wasproposed to solve these problems. By pumping broad blue spectral satellites which isproduced by alkali-rare gas atomic collision pairs, the absorption bandwidth iscomparable to the bandwidth of commercial diode laser and the hydrocarbon would notbe needed any more. Thus XPAL may solve the difficulties of DPAL. However, XPALhas not been pumped with cw source since the day it was proposed, in addition,investigations with pulsed pumping shows it needs high pump intensity. To study thesequalities of XPAL clearly is important in choosing the right direction of DPAL.Main works of this paper are as follows:First, time-depended rate equation modeling of four-level XPAL is developed, thethreshold pump intensity and absorption efficiency for CW XPAL are calculated. Forthe character of high pump intensity and low absorption, influence of bandwidth ofpump source on absorption is calculated and it indicates broad absorption character canjust keep the efficiency stable but can’t improve it. Influences of length and temperatureof the gain cell on absorption and laser of XPAL are analyzed. When the pump centershifts, XPAL are affected much smaller than DPAL did.Further, the blue satellite of Rb-Ar excimer is confirmed by measure thetransmittance of Rb and Ar mixture. The fluorescence of Rb D2line was seen bypumping the blue satellite with a self-made OPO, indicating the possibility ofpopulation invertion of the scheme. Experiment of four-level XPAL was designed andcarried out using the15ns OPO. Lasing on780nm of Rb D2line was achieved at June2010, and it is the first report of lasing by XPAL scheme in China. The waveform oflaser pulse was measured and the pulse energy increasing with temperature wasdemonstrated.Last, inverted injected pumping unstable resonator configuration was proposed todecrease high threshold and increase low absorption efficiency.