Experimental Study of Lasing Without Population Inversion in Ruby.

Lasing without inversion (LWI) is a new field in quantum optics that will lead to new lasers from material that is difficult or impossible for population inversion. So far, the study of LWI is limited to atomic vapors. This dissertation focuses on the study of LWI in a solid medium. We have demonstrated gain without population inversion in ruby. In three-level system of ruby, R_2 coherent driving laser field induces transparency at R_1 transition line center. Any atom in the R_1 excited state | E(^2E) contributes to gain with destructive quantum interference. Those atoms are from R_2 excited state via nonradiative decay. We have also observed reduced R_1 absorption line when the Zeeman states of ground level are coupled with 16.3 GHz microwave field.