Coherent ultraviolet generated by wave packets interacting with chi(3) in Rb and K atoms

摘要

Abstract: Wavepackets formed from the ns and (n-2)d states of Rb and K (n $EQ 8 for K, 11 and 12 for Rb) have been observed by four wave mixing in pump-probe experiments. The temporal behavior of the wavepacket is observed by monitoring the coherent ultraviolet radiation generated near the alkali mp $+2$/P $YLD $+2$/S$-$HLF$/ resonance transitions (7 $LSEQ m $LSEQ 12 for Rb) when a approximately 100 fs, red probe pulse ($lambda approximately 620 nm) is scattered by the wavepacket established by an earlier (identical) pump pulse. The spatial and spectral characteristics of the ultraviolet emission are well-described by axially phase-matched, four wave mixing and all of the prominent frequency components of the wavepackets are associated with energy differences between pairs of excited states for which $Delta$EL $EQ 0 or 2. These results demonstrate that the wavepacket modulates $chi$+(3)$/ of the medium, thus rendering the wavepacket detectable.!12