J. E. Field

We show that by applying a strong-coupling field between a metastable state and the upper state of an allowed transition to ground one may obtain a resonantly enhanced third-order susceptibility while at the same time inducing transparency of the media. An improvement in conversion efficiency and parametric gain, as compared to weak-coupling field behavior, of many orders of magnitude is predicted.

An atomic transition that has been made transparent by applying an additional electromagnetic field exhibits a rapidly varying refractive index with zero group velocity dispersion at line center. A 10-cm-long Pb vapor cell at an atom density of 7\ifmmode\times\else\texttimes\fi{}${10}^{15}$ atoms/${\mathrm{cm}}^{3}$ and probed on its 283-nm resonance transition has a calculated optical delay of 83 ns [(c/${\mathit{V}}_{\mathit{G}}$)=250].

We report the observation of electromagnetically induced transparency on the collisionally broadened resonance line of Pb vapor. By applying a 1064-nm laser beam, the transmission at 283 nm is increaesd by at least a factor of exp(10), with nearly all of the Pb atoms remaining in the ground state.

We show a model laser system which operates by an electromagnetically induced interference. Provided that an inversion condition for the thermal radiation field is satisfied, the system lases without atomic population inversion in steady state. The system is pumped by incoherent radiation on the transition on which lasing occurs.

First measurements of the in-flight shape of imploding inertial confinement fusion (ICF) capsules at the National Ignition Facility (NIF) were obtained by using two-dimensional x-ray radiography. The sequence of area-backlit, time-gated pinhole images is analyzed for implosion velocity, low-mode shape and density asymmetries, and the absolute offset and center-of-mass velocity of the capsule shell. The in-flight shell is often observed to be asymmetric even when the concomitant core self-emission is round. $\mathrm{A}\ensuremath{\sim}15\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ shell asymmetry amplitude of the ${Y}_{40}$ spherical harmonic mode was observed for standard NIF ICF hohlraums at a shell radius of $\ensuremath{\sim}200\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ (capsule at $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}$ radial compression). This asymmetry is mitigated by a $\ensuremath{\sim}10%$ increase in the hohlraum length.