Ultrafast switching of photonic density of states in photonic crystals

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Abstract
It is shown theoretically that the photonic density of states (DOS) of three-dimensional semiconductor photonic crystals can be dramatically changed on ultrafast time scales through two photon excitation of free carriers. Calculations for GaAs inverse opals show that the photonic band gap exhibits a large shift in frequency and a change in width with an appropriate excitation pulse. At certain frequencies, the DOS can be switched from a high value to zero, from zero to a high value, and from a high to zero to a high on 100-fs time scales, independent of the relaxation time of the semiconductor. This technique allows for ultrafast control of spontaneous emission and trapping of photons.