Marvin G. Payne

Efficient multiwave mixing in the ultraslow propagation regime and the role of multiphoton quantum destructive interference

We analyze a lifetime-broadened four-state four-wave-mixing (FWM) scheme in the ultraslow propagation regime and show that the generated FWM field can acquire the same group velocity and pulse shape as those of an ultraslow pump field. We show that a new type of induced transparency resulted from multiphoton destructive interference that significantly reduced the pump field loss. Such induced transparency based on multphoton destructive interference may have important applications in other nonlinear optical processes.

Superluminal propagation of an optical pulse in a Doppler-broadened three-state single-channel active Raman gain medium

Using a single-channel active Raman gain medium, we show a 220 +/- 20 ns advance time for an optical pulse of tau(FWHM)=15.4 mu s propagating through a 10 cm medium, a lead time that is comparable to what was reported previously using a two-mode pump field. In addition, we have verified experimentally all the features associated with this single-channel Raman gain system.

Realization of a single and closed Λ-system in a room-temperature three-level coherently prepared resonant medium with narrow D1 hyperfine splittings

A single, closed three-state Λ-system in room-temperature rubidium is investigated experimentally using a copropagating beam parallel-polarization configuration under weakly driven electromagnetically induced transparency (EIT) condition. Compare with the widely used orthogonal-polarization beam EIT configuration where multiple nonclosed Λ-schemes coexist, the parallel-polarizations configuration can completely eliminate the leakage light from the control field. Our state preparation and laser polarization lead to a single and closed Λ-scheme that eliminates the detrimental absorption due to nearby states in atomic species with hyperfine separations smaller than Doppler-broadened line widths, a case where the conventional EIT configuration fails completely.

Significant propagation reduction of an optical pulse in an active Raman gain scheme

We investigate an active Raman gain scheme for significant group velocity reduction. This scheme, which is fundamentally different from the electromagnetically induced transparency scheme, is capable of achieving ultraslow and distortion-free propagation of a pulsed probe field. The group velocity behavior is drastically different from the conventional electromagnetically induced transparency scheme, and the new scheme can be used to accurately determine the decoherence rate of a long-lived state. In addition, the Raman gain scheme has the advantage of being broadly tunable, an important feature that may have potential applications.

High efficiency four-wave mixing at low power densities and low concentrations: The role of coherence

Two transform limited nanosecond lasers are used in a delayed pulse mode to prepare a highly coherent mixture of the ground state and the upper state of a two-photon transition. A picosecond laser co-propagates through the prepared medium at a delayed time and generates a four-wave mixing field. With a carefully chosen time delay, the wave mixing process is phase matched for all detunings and concentrations, and all of the third laser photons can be converted to the mixing field, independent of the intensity of the short-pulse laser. The condition for optimum conversion efficiency does not usually correspond to maximum atomic coherence. In the case of a near resonance short-pulse laser, the condition for phase matching leads to efficient conversion, with the mixing field propagating at the speed of light in vacuum with no distortion.