Observation of the transparency of a resonant medium to zero-degree optical pulses

Abstract

Experiments are described in which low-intensity laser pulses of zero area [∫−∞∞E(z,t) dt=0] are propagated through a degenerate resonantly absorbing medium with greatly reduced absorption. These pulses are constructed either electro-optically or by allowing a non-zero-degree pulse to evolve toward zero area by means of a resonant absorption and reradiation process. We observe the transmission of as much as 65% of the energy of such pulses through a resonant absorber which attenuates the same cw laser by e−αL, with αL ≈ 20.

A general theory of self-induced transparency

“…As well as the experiments on ruby [29] with 0-0 pulses Greineisen et al [30] have observed anomalously high transmission for small angle 0 -0 pulses using an N20 laser on both NHa and CO2. The systems are degenerate and illustrate the generalized area theorem that can be derived in this case [27,31] The summation on the right is over 2j -t-1 degenerate levels and the theorem will be satisfied in general only for 0 = 0 since the Km are not necessarily integers.…”

Self-induced transparency and coherent population trapping of ^87Rb vapor in a mode-locked laser

“…The additional contribution of reversing electric field envelope is typical of "zero-area" pulse generation, as has been observed and predicted in absorbers [10,11] and amplifiers [19]. The additional zero-area lobes that cannot be resolved with a fast detector make an exper-imental determination of the pulse area difficult.…”

“…In a mode-locked laser tuned to the resonance of a narrow line absorber, several low-loss options are possible. In "zero-area pulse transmission" [10,11], each successive pulse has opposite phase, or, in frequency space, the atomic resonance is midway between two modes of the comb. Alternatively, each pulse of the train can have sufficient energy density to create a succession of population inversion-return to ground state.…”

Short Pulse Propagation in the Submillimeter Region.

“…The spectrum of a zeropi pulse has a zero at the carrier frequency . This accounts for the low loss observed with zero-degree pulses (Grieneisen et al, 1972) when propagating through a medium whose absorption line was centered with the carrier frequency .…”

“…In this connection one should emphasize the shape of the spectrum of a zero-pi pulse (or a zero degree, the terminology used by Grieneisen et al, 1972Grieneisen et al, , 1973, who considered small signal pro-H perties of pulses with phase reversal). The spectrum of a zeropi pulse has a zero at the carrier frequency .…”