title: Reversed Doppler effect in photonic crystals.
abstract: Nonrelativistic reversed Doppler shifts have never been observed in nature and have only been speculated to occur in pathological systems with simultaneously negative effective permittivity and permeability. This Letter presents a different, new physical phenomenon that leads to a nonrelativistic reversed Doppler shift in light. It arises when light is reflected from a moving shock wave propagating through a photonic crystal. In addition to reflection of a single frequency, multiple discrete reflected frequencies or a 10 GHz periodic modulation can also be observed when a single carrier frequency of wavelength 1 microm is incident.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. evan@mit.edu
authors.forename: Evan J
authors.initials: EJ
authors.lastname: Reed
authors.forename: Marin
authors.initials: M
authors.lastname: Soljacić
authors.forename: John D
authors.initials: JD
authors.lastname: Joannopoulos