Nonlinear Optics with an Atomic Ytterbium Vapor

A theoretical analysis of two-photon cascade emission and four- wave mixing in a three-level atomic system is presented. The specific levels of interest are the $^1$S$_0$, $^3$P$_1$, and $^3$D$_2$ states in atomic ytterbium. Cascade emission along the decay path $^3$D$_2$ $\rightarrow$ $^3$P$_1$ $\rightarrow$ $^1$S$_0$ generates photons at 1479 nm and 556 nm, respectively. For various emission directions, this decay sequence can produce either (i) polarization-entangled photon pairs or (ii) entanglement between the polarization of one of the emitted photons and the Yb nuclear spin. Finally, simultaneous excitation of the $^1$S$_0$ $\rightarrow$ $^3$D$_2 $ two-photon transition (808 nm) and the $^1$S$_0$ $\rightarrow$ $^3$P$_1$ single-photon transition (556 nm) can be used to generate a 1479 nm radiation field (resonant with the $^3$D$_2$ $\rightarrow$ $^3$P$_1$ transition) through four- wave mixing. Experimental progress towards observing these processes will be presented.