H. M. Lai

Nonlinear elastic scattering of light from a microdroplet: role of electrostrictively generated acoustic vibrations

An attempt is made to account for the experimentally observed nonlinear elastic scattering of light by a micrometer-sized liquid droplet by the following mechanism: electrostriction produces density inhomogeneities, which perturb the morphology-dependent resonances, leading to a reduction in the quality factor Q; the broadened resonance then causes an increase in the effective cross section, which is the average of the actual cross section over the laser profile. We calculated the density fluctuations by analyzing the acoustic modes of the droplet and then used a recently developed formalism to relate these fluctuations to the increase in the width of the resonance. We found that this mechanism fails, by several orders of magnitude, to explain the observation quantitatively, and we suggest alternative mechanisms.

Cavity QED in microdroplets

Purcells formula for the cavity enhancement of QED rates in terms of the density of states can be generalized to each position inside a cavity, and this local density of states can be explicitly evaluated for simple geometries such as a droplet. The density of states satisfies certain sum rules, which imply that when averaged over frequency and position, there can be no significant change of transition rates compared to the case of an extended medium.

Analytic expressions for far fields and radiation fluxes caused by a moving source in some anisotropic dispersive media

A general method recently developed [Phys. Fluids 29, 1881 (1986)] is applied to calculate analytically the far field and the radiation flux caused by a current source moving in each of a uniaxial nondispersive medium, an isotropic cold plasma, and a cold plasma in an infinite magnetic field. Explicit expressions in terms of space and time are obtained, and particular attention is paid to the complex Doppler situation and the Cerenkov case with and without dispersion.