A kind of photonic crystal structure with modulation of the refractive index is investigated both experimentally and theoretically for exploiting electromagnetically induced transparency(EIT).The combination of EIT with periodically modulated refractive index medium gives rise to high efficiency reflection as well as forbidden transmission in a threelevel atomic system coupled by standing wave.We show an accurate theoretical simulation via transfer-matrix theory,automatically accounting for multilayer reflections,thus fully demonstrate the existence of photonic crystal structure in atomic vapor.
The high-resolution photoassociation spectrum of the ultracold cesium molecular 0_u^+ state below the 6S 1/2 + 6P 1/2 limit is presented in this paper. The saturation of the photoassociation scattering probability is observed from the dependence of the trap-loss probability on the photoassociation laser intensity. The corresponding resonant line width is also demonstrated to increase linearly with increasing photoassociation laser intensity. Our experimental data have good consistency with the theoretical saturation model of Bohn and Julienne Bohn J L and Julienne P S 1999 Phys. Rev. A 60 1].
A single cesium atom is trapped in a far-off-resonance optical dipole trap(FORT) from the magneto-optical trap(MOT) and directly imaged by using a charge-coupled device(CCD) camera.The binary single-atom steps and photon anti-bunching are observed by a photon-counting-based HBT system using fluorescence light.The average atom dwelling time in the FORT is about 9 s.To reduce the background noise in the detection procedure we employ a weak probe laser tuned to the D 1 line to illuminate the single atom from the direction perpendicular to the large-numerical-aperture collimation system.The second order degree of coherence g(2)()=0.12±0.02 is obtained directly from the fluorescence light of the single atom without deducting the background.The background light has been suppressed to 10 counts per 50 ms,which is much lower compared with the reported results.The measured g(2)() is in good agreement with theoretical analysis.The system provides a simple and efficient method to manipulate and measure single neutral atoms,and opens a way to create an efficient controlled single-photon source.
GUO YanQiang LI Gang ZHANG YanFeng ZHANG PengFei WANG JunMin ZHANG TianCai
We experimentally investigate the optical cavity for various coupled regimes with an injected squeezed vacuum state. We measure the quantum fluctuation spectra of the reflected field of an optical cavity using the homodyne detection and present the spectral dependence on the absorption and dispersion properties of the cavity in the under-coupled, critically-coupled, and over-coupled regimes. The spectra lineshape is phase sensitive with the phase shift induced by the cavity. Moreover, we find that the over-coupled optical cavity has obvious advantage in the manipulation of quantum fluctuation.
