Coherent laser spectroscopy of rubidium atoms

Light speed reduction to 17 metres per second in an ultracold atomic gas

Abstract: Techniques that use quantum interference effects are being actively investigated to manipulate the optical properties of quantum systems1. One such example is electromagnetically induced transparency, a quantum effect that permits the propagation of light pulses through an otherwise opaque medium2,3,4,5. Here we report an experimental demonstration of electromagnetically induced transparency in an ultracold gas of sodium atoms, in which the optical pulses propagate at twenty million times slower than the speed of light in a vacuum. The gas is cooled to nanokelvin temperatures by laser and evaporative cooling6,7,8,9,10. The quantum interference controlling the optical properties of the medium is set up by a ‘coupling’ laser beam propagating at a right angle to the pulsed ‘probe’ beam. At nanokelvin temperatures, the variation of refractive index with probe frequency can be made very steep. In conjunction with the high atomic density, this results in the exceptionally low light speeds observed. By cooling the cloud below the transition temperature for Bose–Einstein condensation11,12,13 (causing a macroscopic population of alkali atoms in the quantum ground state of the confining potential), we observe even lower pulse propagation velocities (17?m?s−1) owing to the increased atom density. We report an inferred nonlinear refractive index of 0.18?cm2?W−1 and find that the system shows exceptionally large optical nonlinearities, which are of potential fundamental and technological interest for quantum optics.

Electromagnetically Induced Transparency

Abstract: Electromagnetically induced transparency is a technique for eliminating the effect of a medium on a propagating beam of electromagnetic radiation EIT may also be used, but under more limited conditions, to eliminate optical self‐focusing and defocusing and to improve the transmission of laser beams through inhomogeneous refracting gases and metal vapors, as figure 1 illustrates The technique may be used to create large populations of coherently driven uniformly phased atoms, thereby making possible new types of optoelectronic devices

Observation of electromagnetically induced transparency

Abstract: We report the results of an experiment showing how an opaque atomic transition in neutral Strontium may be rendered transparent to radiation at its resonance frequency. This is accomplished by applying an electromagnetic coupling field (Fig. 1) between the upper state 4d5d1D2 of the transition and another state 4d5p1D2; of the atom. When the Rabi frequency of the coupling field exceeds the inhomogeneous width of the 5s5p1P1–4d5d1D2; transition, the medium becomes transparent on line center.

Coherent Population Trapping in Laser Spectroscopy

Abstract: Publisher Summary This chapter describes the coherent population trapping in laser spectroscopy. Coherent population trapping may be also described as the pumping of the atomic system in a particular state, the coherent superposition of the atomic states, which is a nonabsorbing state. The exciting radiation creates an atomic coherence, such that the atom's evolution is prepared exactly out of phase with the incoming radiation and no absorption takes place. The chapter discusses the basic properties of an atomic system prepared with the coherent population-trapping superposition of states and outlines experimental observations concerned with the establishment of coherent trapping in different discrete systems. The chapter also discusses the theoretical and experimental aspects of trapping that involve states of the continuum and reviews the theoretical and experimental features associated with coherent population trapping in laser cooling, adiabatic transfer, lasing without inversion, pulse matching, and photon statistics. The theoretical aspect of coherent population trapping created by spontaneous emission is also discussed in the chapter.

Elements of Quantum Optics

Abstract: Classical Electromagnetic Fields.- Classical Nonlinear Optics.- Quantum Mechanical Background.- Mixtures and the Density Operator.- CW Field Interactions.- Mechanical Effects of Light.- to Laser Theory.- Optical Bistability.- Saturation Spectroscopy.- Three and Four Wave Mixing.- Time-Varying Phenomena in Cavities.- Coherent Transients.- Field Quantization.- Interaction Between Atoms and Quantized Fields.- System-Reservoir Interactions.- Resonance Fluorescence.- Squeezed States of Light.- Cavity Quantum Electrodynamics.- Quantum Theory of a Laser.- Entanglement, Bell Inequalities and Quantum Information.