The Experimental Research On Raman Scattering Based On Atomic Coherence

In atomic ensemble, if the atoms in ground state have some phase correlation with the atoms in exited state, then the ensemble have atomic coherence which also called atomic spin wave in some literatures. Atomic spin wave is just one result of the atomic collective excitation. The concept atomic spin wave-is redefined based on spin wave which was first proposed by Bloch when he was studying at the crystals, atomic spin wave also push the theory of the interaction between atom and light to a high level. The coupling strength between atom and light can be greatly enhanced by atomic spin wave in atomic ensemble, thus enhances the nonlinearity. In recent years, it was widely studied in the field of quantum communication, quantum memory and other fields. In this thesis, we created atomic spin wave by Raman scattering in hot atomic ensemble, based on which we did some researches as follows.1. A spatial distributed atomic spin wave was created by Raman scattering in a87Rb cell, then we got an enhancement in Raman scattering due to this spin wave, and experimentally studied how the spatial distribution and strength of the spin wave affect the enhancement.2. We created maximal atomic spin wave in Rb atomic ensemble, and observed Rabi-like oscillation between the pump laser and the corresponding Stokes filed, and discussed the effect of spin wave’s intensity to the oscillation frequency. At last, we demonstrated high conversion efficiency from the pump light to the Stokes filed. 3. we theoretically proposed a effective scheme to entangle two atomic ensembles based on single atomic spin ecitation. Furthermore, we experimentally took some preliminary exploration in this scheme. In the regime of lower-energy level, we proved the time correlation between the two atomic spin waves, studied loss of the light’s influence on the visibility of the interference and also the relation between interference visibility and the phase of atomic spin wave.In addition, we also studied the enhancement of Pyridine CARS signal on the surface of random aggregates of gold nanoparticles based on coherence, we observed the enhanced CARS signals. And we also investigated the influence of the bandwidth of probe pulse on the CARS signal, decay of vibrational coherence and the impact of metal surface on decoherence process.