Competing ultrafast switching mechanisms in silicon woodpile photonic crystals near telecom wavelengths

In this work, Kerr nonlinearity in photonic crystals has been critically evaluated at instantaneous timescales. Non-degenerate pump-probe experiments is performed on silicon woodpile photonic band gap crystals. The result is the first demonstration of instantaneous Kerr switching in photonic crystals. For the two competing processes, a generalized non-degenerate figure of merit (NFOM) is discussed, which defines the quality of switching for all instantaneous optical switching processes. The NFOM is ultimately suited to identify conditions to switch the density of states, dynamically control spontaneous emission, or trap and release photons from cavities.