SUPERFLUORESCENCE FROM OPTICALLY TRAPPED CALCIUM ATOMS

We have studied superfluorescence (SF) under highly unfavorable condit ions of rapid collisional and radiative distribution in a Doppler-broa dened medium. Nanosecond SF pulses at 5.5 mu m were generated on the C a 4s4p P-1(1)-3d4s D-1(2) transition from a column of calcium vapor bu ffered with Ar by optically pumping the 4s(2) S-1(0)-4s4p P-1(1) trans ition. The Rabi frequency associated with the intense pump pulse preve nts the occurrence of SF while the pump laser is on. As a result, the predicted scaling laws that describe the properties of SF in a transve rsely excited system, such as peak heights, pulse widths, and delay ti mes, are shown to apply in our situation in which the conditions resem ble swept excitation. The delay times were found to be in agreement wi th a fully quantum mechanical calculation which describes the initiati on of SF. Measurements of the densities of the three levels, the absol ute SF photon yield, and the spatial distribution of the excited state s indicate that the system has a quantum yield of unity. The SF intens ity increases with an increase in Ar pressure due to collisional redis tribution until the collisional dephasing rate inhibits SF. The condit ions describing the transition of SF to amplified spontaneous emission allow us to measure the collisional broadening rate for the SF transi tion. [S1050-2947(98)02611-0].