ENGINEERING RADIATIVE TRANSITIONS OF ALKALI-RARE GAS COLLISION PAIRS

Optical amplifiers that rely on free-free molecular transition for both pumping and amplification will be introduced. A gaseous medium comprised of Cs vapor and Ar is photoexcited through a free-free molecular transition, B $^{2}$$\Sigma$$_{1/2}^{+}$ $\leftarrow$ X $^{2}$$\Sigma$$_{1/2}^{+}$, with a pulse duration of 8 ns. The gain medium is characterized by scanning the probe wavelength and changing the time delay between the pump and probe pulses. It will be shown that the large bandwidth ($>$150 GHz) and reduced lifetime ($\sim$5 ns) make the amplifiers more suitable for high power IR sources. The optical-to-optical efficiency exceeds 28\% in a single pass amplification. The circular polarization of the optical pump increases the efficiency by 20\%. Furthermore, the weak atomic interaction was identified in the gain spectrum of a Cs-Xe gas mixture by implementing the pump-probe method and compared to the simulation based on the Franck-Condon principle. The spectral feature, also known as the red satellite, had been hard to be resolved experimentally because of the wing structure of A$^{2}$$\Pi$$_{3/2}^{+}$ $\leftarrow$ X $^{2}$$\Sigma$$_{1/2}^{+}$ transition. In the simulation, the Franck-Condon overlap integral develops in the region as the phases of the wavefunctions are stationary to each other, which shows that even a shallow feature in the potential curve can contribute the resulting spectrum significantly. This technique can be utilized in precise atomic spectroscopy