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A linear oscillator in an optical field

Sergei A. Akhmanov, S. Yu. Nikitin

Published Apr 3, 1997• 0 citations
Publisher

Abstract

Abstract Absorption of light by an oscillator and by an oscillator ensemble. The Bouguer law. Absorption spectroscopy. Decrease in the phase velocity of light propagating in a medium and the index of refraction. An inhomogeneous ensemble of oscillators. Homogeneous and inhomogeneous widths of spectra. Excitation by a short pulse-energy relaxation and dephasing. Principles of frequency- and time-domain spectroscopy.

DOI
10.1093/oso/9780198517955.003.0007

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Abstract Absorption of light by an oscillator and by an oscillator ensemble. The Bouguer law. Absorption spectroscopy. Decrease in the phase velocity of light propagating in a medium and the index of refraction. An inhomogeneous ensemble of oscillators. Homogeneous and inhomogeneous widths of spectra. Excitation by a short pulse-energy relaxation and dephasing. Principles of frequency- and time-domain spectroscopy.
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The resonant absorption, emission, and scattering of light are the fundamental optical processes that have been used both to probe matter and to manipulate light itself. In the last decade there has been essential progress in coherent control of both linear and nonlinear optical responses based on resonant excitation of atomic coherence in multilevel quantum systems. Some interesting and useful phenomena, resulting from coherent control of absorption and the group index, such as electromagnetically induced transparency, lasing without inversion, and ultra-slow group velocity of light have been widely studied. This work is focused on coherent control of refractive index and resonant fluorescence in multilevel medium. \n \nWe suggest two promising schemes for resonant enhancement of the refractive index with eliminated absorption and propose their implementation in transition element doped crystals with excited state absorption and in a cell of Rb atoms at natural abundance. We show how to use one of these schemes for spatial variation of the refractive index via its periodic resonant increase/decrease, remarkably keeping at the same time zero absorption/gain. It opens the way to production of transparent photonic structures (such as distributed Bragg reflectors, holey fibers, or photonic crystals) in a homogeneous resonant atomic media such as dielectrics with homogeneously distributed impurities, atomic, or molecular gases. These optically produced photonic structures could easily be controlled (including switching on/off, changing amplitude and period of modulation) and would be highly selective in frequency, naturally limited by the width of the optical resonance. \n \nWe also derive the optical fluorescence spectra of a three-level medium driven by two coherent fields at the adjacent transitions in a general case when all three transitions are allowed. We show that coherent driving can efficiently control the distribution of intensities between the fluorescent channels. In particular, the total intensity of fluorescence at the transition which is not driven by the optical fields may essentially exceed the fluorescence intensity at the driven transitions under the condition of two-photon resonance. This counter-intuitive effect is due to depletion of the intermediate state via atomic interference.
Abstract We demonstrate the nonreciprocal propagation of optical pulses in a linear dispersive medium with a time-varying refractive index. The change of refractive index with time breaks the time-translation symmetry of the spatially homogeneous medium compelling it to be inherently nonreciprocal. A time-reversal asymmetric field ratio of the counter-propagating optical pulses along with a frequency shift leading to spectral nonreciprocity in such dynamic media have been observed. The findings have emerged a new avenue to realize nonreciprocal light flow in dynamically tuned integration-feasible photonic systems.