Physical Review A
Photon echoes in lithium vapor with the use of angled excitation beams
Raymond John Beach, Burton Brody, Sven R. Hartmann
Abstract
Two-pulse photon echoes on the $2^{2}S_{\frac{1}{2}}\ensuremath{-}2^{2}P_{\frac{3}{2}}$ transition in lithium vapor are generated using laser excitation pulses with angular separations of 0.70 and 1.40 mrad. The observed degradation of echo intensity with angling of the excitation pulses is in agreement with theory. The largest echoes radiated by the lithium sample contained ${10}^{9}$ photons; the smallest echoes detected contained only an average of 0.04 photons. This intensity range of greater than ${10}^{10}$ represents measurements made over more than 15 natural lifetimes of the $2^{2}P_{\frac{3}{2}}$ state despite the degradation due to angling. Modulation of the echo signal due to the hyperfine structure of the $2^{2}P_{\frac{3}{2}}$ state is also observed.