Color of Shock Waves in Photonic Crystals

Unexpected and stunning new physical phenomena result when light interacts with a shock wave or shocklike dielectric modulation propagating through a photonic crystal. These new phenomena include the capture of light at the shock wave front and reemission at a tunable pulse rate and carrier frequency across the band gap, and bandwidth narrowing as opposed to the ubiquitous bandwidth broadening. To our knowledge, these effects do not occur in any other physical system and are all realizable under experimentally accessible conditions. Furthermore, their generality make them amenable to observation in a variety of time-dependent photonic crystal systems, which has significant technological implications.

Figure 1

Schematic of a shock wave moving to the right which compresses the lattice by a factor of 2. Light incident from the right (red arrow) will be converted up in frequency at the shock front and escape to the right. The black arrows indicate the adiabatic evolution of the modes for the lowest two bands.

Figure 2

Large frequency shift. Depicted are four moments in time during a computer simulation of the shock in Eq. (1) moving to the right with $\mathrm{v}=3.4\times {10}^{-4}c$. Time is given in units of $a/c$. The shock front location is indicated by the dotted green line. The light begins the simulation below the gap in the unshocked material at $\omega =0.37$, as in Fig. 1. As the light propagates to the left, most of it is trapped at the shock front until it escapes to the right at $\omega =0.44$.

Figure 3

Bandwidth narrowing. Depicted are two moments in time during computer simulation of the shock in Eq. (1). The shock front is indicated by the dotted green line, and time is given in units of $a/c$. Light is confined between the reflecting shock front on the left and a fixed reflecting surface on the right. As the shock moves to the right with $\mathrm{v}={10}^{-4}c$, the bandwidth of the confined light is decreased by a factor of 4.