Quantum Nondemolition Measurement of an Atomic Intensity Using Crossed Opto-Atomic Kerr Effect
Recent experiments1 have demonstrated that atoms can be reflected off an evanescent wave created by total internal reflection of a laser beam in a dielectric prism. One difficulty of such experiments is the detection of the atoms after reflection. To date, fluorescence techniques consisting in collecting the photons spontaneously emitted by the atoms after absorption from a probe laser have been used. Such detection methods are destructive: recoils during absorption-fluorescence cycles induce such a large momentum spread that most atoms do not fall onto the laser spot at the following bounce. Recently, non destructive techniques have been suggested for circumventing this inconvenience, which are based on refraction index variations in the presence of atoms2,3 A conceptually simple method consists in monitoring the phase of the very laser producing the evanescent wave2: because the phase-shift associated with total internal reflection depends on the refractive index of the boundary media, one expects the laser phase to exhibit variations correlated with the presence of atoms in the evanescent wave. Reciprocally, the laser intensity fluctuations lead to variations of the repulsive optical potential barrier, hence to fluctuations of the phase-shift experienced by the atoms during reflection at the evanescent wave mirror.
KeywordsAtomic Beam Total Internal Reflection Evanescent Wave Atomic Intensity Numerical Flux
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