arXiv subjects
Publications and source records attributed to L. A. Orozco.
We study the probe spectrum of light generated by spontaneous emission into the mode of a cavity QED system. The probe spectrum has a maximum on-resonance when the number of inverted atoms for an input drive is maximal. For a larger number of atoms N, the maximum splits and develops into a doublet, but its frequencies are different from those of the so-called vacuum Rabi splitting.
We present a lifetime measurements of the 6s level of rubidium. We use a time-correlated single-photon counting technique on two different samples of rubidium atoms. A vapor cell with variable rubidium density and a sample of atoms confined and cooled in a magneto-optical trap. The 5P_{1/2} level serves as the resonant intermediate step for the two step excitation to the 6s level. We detect the decay of the 6s level through the cascade fluorescence of the 5P_{3/2} level at 780 nm. The two samples have different systematic effects, but we obtain consistent results that averaged give a lifetime of 45.57 +- 0.17 ns.
We measure the lifetime of the 8s level on a magneto-optically trapped sample of ^{210}Fr atoms with time-correlated single-photon counting. The 7P_{1/2} state serves as the resonant intermediate level for two-photon excitation of the 8s level completed with a 1300 nm laser. Analysis of the fluorescence decay through the the 7P_{3/2} level gives 53.30 +- 0.44 ns for the 8s level lifetime.
We present lifetime measurements of the 7S1/2 level and the 6p manifold of rubidium. We use a timecorrelated single-photon counting technique on a sample of 85Rb atoms confined and cooled in a magneto-optic trap. The upper state of the 5P1/2 repumping transition serves as the resonant intermediate level for twophoton excitation of the 7s level. A probe laser provides the second step of the excitation, and we detect the decay of atomic fluorescence to the 5P3/2 level at 741 nm. The decay process feeds the 6p manifold that decays to the 5s ground state emitting UV photons. We measure lifetimes of 88.07 +- 0.40 and 120.7 +- 1.2 ns for the 7S1/2 level and 6p manifold, respectively; the hyperfine splitting of the 7S1/2 level is 282.6 +- 1.6 MHz. The agreement with theoretical calculations confirms the understanding of the wave functions involved and provides confidence on the possibility of extracting weak interaction constants from a parity nonconservation measurement.
Detection of a single photon escaping an optical cavity QED system prepares a non-classical state of the electromagnetic field. The evolution of the state can be modified by changing the drive of the cavity. For the appropriate feedback, the conditional state can be captured (stabilized) and then released. This is observed by a conditional intensity measurement that shows suppression of vacuum Rabi oscillations for the length of the feedback pulse and their subsequent return.
We present an optical trap for atoms that we have developed for precision spectroscopy measurements. Cold atoms are captured in a dark region of space inside a blue-detuned hollow laser beam formed by an axicon. We analyze the light potential in a ray optics picture and experimentally demonstrate trapping of laser-cooled metastable xenon atoms.
We present the conditional time evolution of the electromagnetic field produced by a cavity QED system in the strongly coupled regime. We obtain the conditional evolution through a wave-particle correlation function that measures the time evolution of the field after the detection of a photon. A connection exists between this correlation function and the spectrum of squeezing which permits the study of squeezed states in the time domain. We calculate the spectrum of squeezing from the master equation for the reduced density matrix using both the quantum regression theorem and quantum trajectories. Our calculations not only show that spontaneous emission degrades the squeezing signal, but they also point to the dynamical processes that cause this degradation.
We report the creation of an ultracold neutral plasma by photoionization of laser-cooled xenon atoms. The charge carrier density is as high as 2 x 10^9 cm^-3, and the temperatures of electrons and ions are as low as 100 mK and 10 uK, respectively. Plasma behavior is evident in the trapping of electrons by the positive ion cloud when the Debye screening length becomes smaller than the size of the sample. We produce plasmas with parameters such that both electrons and ions are strongly coupled.