Low-power all-optical switching in active semiconductor chirped periodic structures.

We investigate the effects of spatial chirp of the built-in grating on the spectral range and switching power of all-optical switching in active semiconductor periodic structures. We show that a total linear variation in the grating period of as little as 0.24% nearly triples the spectral range of low-power switching. Moreover, the upward-switching power at the onset of bistability is lowered by two orders of magnitude, to a value below 10 nW for typical device-parameter values. These improvements occur for optical signals tuned to the long-wavelength side of the stop band and propagating in the direction of increasing grating period. We also predict the existence of multiple bistable hystereses in devices with large amounts of spatial chirp.