Biomedical subjects

M M Dignam

Publications and source records attributed to M M Dignam.

3 recordsLinked to original sources

PubMed2006

Spontaneous emission suppression via quantum path interference in coupled microcavities.

We examine theoretically the spontaneous emission rate in optical microstructures with cavity resonances that overlap in both position and frequency. Using projection techniques, we show that the spontaneous emission in such structures can be accurately described by the direct emission and quantum path interference of emission into a few discrete resonant modes, even though the exact infinite-dimensional problem involves a coupling to the continuum of radiation states. Moreover, we obtain an efficient numerical time-domain method for determining the spontaneous emission rate that incorporates these effects, including the suppression of spontaneous emission into some modes.

Journal Article↗

PubMed2003

Infinite-order excitonic BLOCH equations for asymmetric nanostructures.

We present a new exciton-based formalism for calculating the coherent response of asymmetric semiconductor multiple quantum well structures to ultrashort optical pulses valid to infinite order in the optical field and including the self-generated intraband fields. We use these equations to calculate and explain the oscillations with time delay of peaks in the spectrally resolved degenerate four-wave mixing signals from biased semiconductor superlattices, obtaining good agreement with experiment.

Journal Article↗

PubMed2002

Conditions for dynamic localization in generalized ac electric fields.

We examine the conditions for dynamic localization of electrons in a periodic potential due to an applied ac electric field. Using a general one-band model, we establish the surprising result that only electric fields that are discontinuous at all changes of sign can lead to exact dynamic localization. We also develop a general procedure for constructing ac fields that yield dynamic localization and derive an "area condition" for such fields. We confirm this result numerically in a multiband simulation.

Journal Article↗