Light-atom Hybrid Interferometer

Since appearing in the world, interferometers have been widely used in the measurement of various physics parameters, and has become one of the most important tool for precise measurement. The newest technologies of quantum optics and atomic optics has also been used to improve the precision of interferometer. Especially, in 1986 B. Yurke et al. proposed to use parameter process or four-wave mixing process instead of traditional beam splitter to measure the phase, and the sensitivity can reach the ultimate quantum limit of phase measurement, i.e., the Heisenberg limit. Notice that the Hamiltonian in Raman scattering process has exactly the same form as the SU(1,1) Hamiltonian for the parametric process; the Stokes field is equivalent to the signal field and the atomic spin wave is to the idler field. So the parametric amplifiers in the nonconventional SU(1,1) interferometer can be replaced with Raman amplifiers to form an atom-light hybrid interferometer. To achieve a new high-precise interferometer by Raman scattering, a stable stokes input light which is two-photon resonant with Raman pump and has good coherence is needed. Besides, the stimulated Raman scattering with a seed light injected or the enhanced Raman scattering with a spin wave injected can be used for the BS splitting process, but another process with good phase sensitivity to realize the second BS recombining process is still needed. Based on above discussions, our detailed research is listed as follows:1. We accomplish the high-efficient preparation of a stable stokes field, which can be used as the input field for the light-atom hybrid interferometer. This stokes field is obtained through coherent feedback Raman process in thermal Rb87 atomic resembles, and has good coherence feature, also matches two photon resonant condition with the Raman pump light. So it can be a good input field for the light-atom interferometer. During this process, the conversion efficiency is about 40-50% for the Stokes field and 20-30% for the anti-Stokes field, respectively. This part will be discussed in Chapter 2 in details in this thesis.2. We realize a new kind of Raman scattering, named correlated enhanced Raman Scattering, which can be used for the recombining process. This realization is based on the phase correlation between the Stokes and spin wave; or the interference effect between the Stokes light field from injected light field and from injected spin wave. Besides, the constructive interference leads to the Raman conversion efficiency higher than other kinds of Raman processes, such as stimulated Raman process with Stokes seed injection alone or uncorrelated light-atom seeding. Thus, this new type of high-efficient and phase-sensitive Raman scattering process is a good tool to implement wave combination for the light-atom hybrid interferometer. This part will be described in the Chapter 3 in this thesis.3. We realize the light-atom hybrid interferometer, based on the above theory and experiment grounds. The first stimulated Raman scattering process generates the correlated optical and atomic waves, which can act as the BS splitter. Then, phase sensitive enhanced Raman scattering process is used to recombine correlated optical and atomic waves. Based on the two processes, we realize nonlinear light-atom interferometer.This new nonlinear light-atom interferometer is totally different from the traditional optical interferometer or atom interferometer. The output signal is sensitive to both the optical phase and the atomic phase, so light sensitive parameter and atom sensitive parameter can both be measured. Besides, the light and atomic spin wave of the light-atom interferometer is quantum correlated, so this makes the nonlinear interferometer has higher precision and signal noise ratio (SNR) than the traditional linear interferometer. In addition, influence to the sensitivity of the light-atom hybrid interferometer by losses inside the interferometer has been researched in our experiment. This part will be presented in Chapter 4 in this thesis.