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We demonstrate coherent control of spontaneous emission from a three-level atom with one resonant frequency near the edge of a photonic band gap. As a result of quantum interference and photon localization, spontaneous emission can be totally suppressed or strongly enhanced depending on the relative phase between the control and pump laser fields. The fractionalized steady state inversion of the atom depends sensitively on the initial conditions, suggesting the possibility of a phase-sensitive, optical memory device on the atomic scale. [S0031-9007 (97)04879-5] PACS numbers: 42.70.Qs, 42.50.Gy, 42.79.VbPhoton localization is a fundamental effect predicted [1] to occur in certain strongly scattering dielectric microstructures. The realization of this effect has been facilitated by the prediction [2,3] and development [4-7] of photonic band gap (PBG) materials. These are lossless materials which exhibit a range of frequencies for which electromagnetic wave propagation is classically forbidden. In addition to strong localization of light [3] at the classical level, these systems lead to the suppression of spontaneous emission [2,8] and the formation of photonatom bound states [9]. Near a photonic band edge, spontaneous emission dynamics is anomalous [10] and leads to a fractionalized steady-state inversion [8,10,11] for a single atom. Nonexponential spontaneous emission decays into frequency-dependent reservoirs, and other nonMarkovian effects in cavities and waveguides have been discussed in the early works of Lewenstein et al. [12]. These studies have been extended to the case of a twolevel atom driven by an external laser field [13]. Unlike these earlier studies, in a PBG system the emitted photon remains partially localized in the vicinity of the emitting atom. This, in turn, leads to long term memory effects and non-Markovian behavior in the collective spontaneous emission from many atoms [14]. These remarkable changes in the radiative properties of atoms and molecules arise purely from the dielectric environment of the PBG host, without the presence of an external field. On the other hand, coherent interaction of atoms with external laser fields can have a profound effect on radiative dynamics [13], even in ordinary vacuum [15][16][17][18][19].In this paper we investigate the combined effects of coherent control and photon localization on spontaneous emission from a three-level atom with one resonant frequency at the edge of a PBG. In our system, a pump laser pulse is used to create an excited state of the atom with an atomic Bloch vector specified by the "area" of the incident pulse. A control, cw, laser field with a specific phase relation to the pump laser pulse stimulates radiative transitions between the upper two excited states.

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We experimentally verify the anomalous phase behavior in metamaterial structures with birefringent materials predicted by Mandatori, et. al. using form birefringent structures. Large birefringence as much as Deltan/n = 0.7 has been achieved by surface-treated form birefringent discs, making compact single layer Mandatori structures viable. With a reduced model of a single layer birefringent structure, the relationship between design parameters (thickness and orientation angle) and device operation and performance parameters (such as the center operation frequency, bandwidth, effective negative index, negative group index of refraction, and the transmission throughput) are derived and verified experimentally. Tunable group index of refraction from strong slow light of ng = 29.6 to fast light of ng = -1.1 are measured experimentally.

The coherent control of cooperative spontaneous emission from two identical non-overlapping three-level atoms in the V-configuration located within a photonic band gap (PBG) material with two resonant frequencies near the upper band edge of the PBG and confined to a region small in comparison to their radiation wavelengths but still greater than their atomic sizes is investigated. The dependencies of cooperative effects in which a photon emitted by one atom is reabsorbed by the other atom on the inter-atomic separation, on the initial state of the two-atom system, on the strength of the driving control laser field, and on the detuning of the atomic resonant frequencies from the upper band edge frequency is analyzed so as to identify the conditions for which these cooperative effects are enhanced or inhibited. Cooperative effects between atoms are shown to be influenced more by the PBG than by the nature of the atomic transitions involved. Excited state populations as well as coherences between excited levels are expressed in terms of timedependent amplitudes which are shown to satisfy coupled integro-differential equations for which analytic solutions are derived under special conditions. Unlike for the case of one atom in a PBG where the fractional non-zero steady state populations on the excited levels as well as the coherence between the excited levels are constants independent of time, in the case of two atoms in PBG these quantities continuously oscillate as a manifestation of beating due to the continuous exchange between the two atoms of the photon trapped by the PBG. The values of these quantities as well as the amplitudes and frequencies of their oscillations depend of the parameters of the system, providing different ways of manipulating the system. The general formalism presented here is shown to recapture the special results of investigations of similar systems in free space when the non-Markovian memory kernels of the PBG are replaced by delta function dependent Markovian memory kernels.