Superluminal optical pulse reflection at 1.5 micron in a double-Lorentzian fiber Bragg grating

Summary form only given. We demonstrate superluminal reflection of picosecond optical pulses at the wavelength of optical communications (1.5 /spl mu/m) using a double- Lorentzian fiber Bragg grating (DL-FBG) as a photonic barrier in which two closely-spaced resonance modes realize in reflection the dispersive properties of a gain-doublet system recently exploited to demonstrate negative group velocities. The use of a FBG presents several advantages as compared to quarter-wave dielectric structures previously used for tunneling experiments at optical wavelengths. First, the weak Bragg scattering per-length realized in a FBG permits the use of long structures, leading to a drastic increase of the time scale involved in tunneling processes. Tunneling and reflection times can thus be precisely measured using direct time-domain optoelectronic means instead of indirect autocorrelation techniques. In addition, the writing techniques of FBG allow the fabrication of FBG with complicated index profiles, such as that needed in a DL-FBG.