Superluminal and parelectric effects in rubidium vapour and ammonia gas

Active Metamaterials with Negative Static Electric Susceptibility

“…Here, G was deliberately chosen to produce a value of χ z (0) that is approximately in the middle of the region of interest − 1 < χ z (0) < 0. The magnitude of this value is of the order of 10 3 times greater than that predicted theoretically for pumped ammonia gas . By changing G , the value of χ z (0) could be readily tuned (Figure S1, Supporting Information).…”

“…, and analogous to the levitation of a diamagnetic material in a static magnetic field), or as the levitation of a ferroelectric body above a piece of negative static electric susceptibility material (as considered in refs. and somewhat analogous to the levitation of a ferromagnet above a superconductor). Further, a charged body may be expected to be capable of levitation above a piece of negative static electric susceptibility material, with potential application in a new type of particle trap (as proposed in refs.…”

“…The question of negative static electric susceptibility values greater than minus one but less than zero is not addressed by such arguments, and it is negative values in this range that we consider here. The possibility of negative static electric susceptibility in metastable systems with inverted populations has been discussed tentatively by Sanders and predicted unequivocally by Chiao et al: the latter authors provide a quantitative estimate for the value of the static electric susceptibility of χ (0) = −3.15 × 10 −4 at a pressure of 1 Torr and a temperature of 180 K in ammonia gas pumped by a carbon dioxide laser . However, this scenario may reasonably be considered a negative static electric susceptibility state that is induced in the ammonia gas by the pump laser, as opposed to a material with intrinsic negative static electric susceptibility.…”

“…Further, a charged body may be expected to be capable of levitation above a piece of negative static electric susceptibility material, with potential application in a new type of particle trap (as proposed in refs. : an effect with no direct magnetic analog due to the absence of magnetic monopoles). Our demonstration of effective negative static electric susceptibility, with large magnitudes and at room temperature and pressure, brings such possibilities a step closer.…”

Superfluorescence in a continuously pumped medium

“…Given in the interaction picture, the atomic operators of interest are the lowering operator R = b)(a e'"' and the populations of the transition levels N. =~a )(a, N"=~b )(b~. (3) The ground state is eliminated explicitly from the equations by using the conservation of population N +Nb+Ng= 1. x-polarized electric field) p, =e(a~x b) In . order to get high gain the decay rate y, must be much smaller than both yb and the pump rate w .…”