|Student Name:||Major Jeffrey Gallagher|
|Location:||AFIT Buidling 640 Room 217|
|Date & Time:||05/17/2013 at 1300|
|Abstract:|| The Doppler-broadened two-photon absorption(TPA) cross-section for the 5 2S1/2 ? 5 2D5/2 transition in Rb is measured using direct absorption methods. The selection rule |?F| ? 2 applied to both isotopes yields 17 transitions in 3 Doppler limited lines. A detailed model of the intensity profile was also developed to account for a focused Gaussian beam(with a M2 value of 1.09) propagating through a two-?photon absorption medium. A peak absorbance of 24% was observed for an intensity of 6.28 kW/cm2 at the focus and a Rb density of 4.6 x 10^15 cm-3 and a path length of 15 cm. Alkali concentrations from 1.6?8.5 x 10^15 cm-?3 were monitored in the far wing of the D2 line. Extracting the hyperfine broadened TPA cross?section from 87 test configurations, while varying the pump power, alkali concentration and focal length, yielded a statistical average of 7.6 x 10?21 cm4/W. This cross-?section is sufficient for a pulsed dye laser to bleach the pump transition in the Two?Photon Pumped Alkali Laser(TPAL) that lases at 420 nm and 5.2 ?m.