Boris Sherman

Spontaneous and Induced Atomic Decay in Photonic Band Structures

Abstract We present a comprehensive quantum electrodynamical analysis of the interaction between a continuum with photonic band gaps (PBGs) or frequency cut-off and an excited two-level atom, which can be either ‘bare’ or ‘dressed’ by coupling to a near-resonant field mode. A diversity of novel features in the atom and field dynamics is shown to arise from the non-Markovian character of radiative decay into such a continuum of modes. Firstly the excited atom is shown to evolve, by spontaneous decay, into a superposition of non-decaying single-photon dressed states, each having an energy in a different PBG, and a decaying component. This superposition is determined by the atomic resonance shift, induced by the spontaneously emitted photon, into or out of a PBG. The main novel feature exhibited by the decaying excited-state component is the occurrence of beats between the shifted atomic resonance frequency and the PBG cut-off frequencies, corresponding to a non-Lorentzian emission spectrum. Secondly the ind...

Quantum electrodynamics in photonic band gaps: atomic-beam interaction with a defect mode

A structural defect in a two-dimensionally periodic dielectric structure may form a local field mode within a photonic band gap in which no other E-polarized field modes exist. We show that such a defect mode can give rise to new quantum-electrodynamic effects in resonant field–atom interaction, owing to the spatially modulated standing-wave character of its field. Atomic-beam motion is considered (a) along an interplanar defect and (b) through a spherical defect. The resonant interaction of a moving two-level atom with the quantized field of these defects can yield hitherto unknown features—oscillatory patterns of the atomic population inversion, fluorescence spectra, and nonclassical field states—that are essentially different from their counterparts in the standard Jaynes–Cummings model, which holds for atomic-beam motion in a spatially uniform single-mode field.

Lasing without inversion in Cherenkov free-electron lasers

Abstract Quantum theory is applied to interference of emission and absorption in a two-section Cerenkov free-electron laser (FEL). A scheme for absorption cancellation with enhanced gain, which resembles “lasing without inversion” in atomic systems, is proposed. This scheme is based on the adjustment of the phases of electrons and light by appropriate dispersion between the two sections. It enables FEL operation even with a broad electron momentum spread. Such a scheme is interesting in the context of FEL operation in the ultraviolet and X-ray regimes.

A holistic metrology approach: multi-channel scatterometry for complex applications

Improvement in metrology performance when using a combination of multiple optical channels vs. standard single optical channel is studied. Two standard applications (gate etch 4x and STI etch 2x) are investigated theoretically and experimentally. The results show that while individual channels might have increased performance for few individual parameters each - it is the combination of channels that provides the best overall performance for all parameters.