title: Delay times and detector times for optical pulses traversing plasmas and negative refractive media.
abstract: We show that arrival times for electromagnetic pulses measured through the rate of absorption in an ideal impedance matched detector are equivalent to the arrival times using the average flow of optical energy as proposed by Peatross [Phys. Rev. Lett. 84, 2370 (2000)]. We then investigate the transport of optical pulses through dispersive media with negative dielectric permittivity and negative refractive index choosing the geometry such that no resonant effects come into play. For evanescent waves, the definitions of the group delay, and the reshaping delay get interchanged in comparison to propagating waves. The total delay times for the evanescent waves can be negative in an infinite plasma medium even for broadband pulses. The total delay time is, however, positive for broadband pulses in the presence of an interface when the radiation is detected outside the plasma. We find evidence of the Hartman effect for pulses when the distance traversed in the plasma is much smaller than the free space pulse length. We also show that for a negative refractive index medium (NRM) with epsilon(omega)=mu(omega) the reshaping delay for propagating waves is identically zero. The total delay time in NRM is otherwise dominated by the reshaping delay time, and for broadband pulses in NRM the total delay time is subluminal.
authors.affiliation: Department of Physics, Indian Institute of Technology, Kanpur 208016, India.
authors.forename: Lipsa
authors.initials: L
authors.lastname: Nanda
authors.forename: Aakash
authors.initials: A
authors.lastname: Basu
authors.forename: S Anantha
authors.initials: SA
authors.lastname: Ramakrishna