title: Amplifying Sommerfeld precursors and producing a discontinuous index of refraction with gains and losses.
abstract: We show that for specially designed linear dispersive media with one absorption line and one gain line the Sommerfeld precursors of a pulse can be amplified leading to an earlier detection of the signal. Also, we show that in some systems with one strong absorption line, a carefully placed gain resonance must induce a discontinuity in the imaginary part of the frequency dependent index of refraction and in the first derivative of its real part.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: Ribeiro
authors.forename: M L
authors.initials: ML
authors.lastname: Cohen