Experimental Studies in Quantum Optics using Diode Lasers

Abstract

This thesis discusses experimental studies with vapor cells containing rubidium (Rb) or cesium (Cs) atoms. Transitions in the atoms (D1 and D2 lines) are accessed using diode lasers. Experiments are performed at room temperature in 3 different kinds of vapour cells|pure, with a buffer gas of neon at 20 torr, or with paraffn (anti-relaxation) coating on the walls. The diode lasers are stabilized using grating feedback, so that the linewidth after stabilization is of order 1 MHz, which is about 5 times smaller than the typical natural linewidth of the hyper ne transitions used in this study. The first part of the thesis discusses the role of dressed-state interference in the phenomenon of EIT in the 3 types of three-levels systems studied - lambda, ladder, and vee. Values from hyper ne transitions in 87Rb are used to get realistic linewidths for the different systems. The second part of the thesis discusses the differences between two well studied and related phenomena coherent population trapping (CPT) and electromagnetically induced transparency (EIT). Whenever possible, the differences are highlighted with experiments using magnetic sublevels of the Fg = 1 ! Fe = 1 hyper ne transition in the D2 line of 87Rb. The third part of the thesis discusses the phenomena of coherent population pumping in a bright state (CBS), a phenomenon which has enhanced absorption at line centre. The experiments are done using magnetic sublevels of the closed Fg = 2 ! Fe = 3 hyper ne transition in 87Rb. The last part of the thesis discusses using the phenomena of CPT to access the clock transition in Cs. The required phase-coherent probe and control beams are derived by frequency modulating a single laser. The frequency modulation is done using a fiber coupled electro-optic modulator (EOM).