Optical hysteresis in mesoporous silicon microcavities

We report on the observation of transient optical bistability in mesoporous silicon microcavity resonators in transmission and reflection when illuminated by a 532nm nanosecond pulsed laser. The properties of the bistablility such as the hysteresis area, the onset and damaged threshold intensities are shown to be porosity dependent. Our model suggests that the bistability is due to the induced nonlinear refractive index changes and the transient lifetime increases with increasing porosity. The role of surface states in the bistability process was also investigated by passivating the internal porous surface using the hydrosilylation chemistry.