Time-resolved photoluminescence of all-porous-silicon microcavities

The emission property of a porous silicon layer placed in an optical microcavity is investigated by photoluminescence and time-resolved photoluminescence measurements. The microcavity is formed by an all-porous-silicon Fabry-Perot filter made by two distributed Bragg reflectors separated by a $\lambda$ or $\lambda$/2 porous silicon layer. The main findings are that the spontaneous emission spectrum is drastically modified: the linewidth is narrowed, the time decay of the emission is shortened by a factor of about 2/3 at room temperature, and the peak emission intensity is increased by a factor of more than 10. These facts are caused by the redistribution of the optical modes in the cavity due to the presence of the optical resonator and to the variations in the dielectric environment where the radiative emission takes place.