Optical gain at the F-band of oxidized silicon nanocrystals

In this paper we present time-resolved optical gain spectroscopy using the variable stripe length technique in combination with the shifting excitation spot technique under pumping with nanosecond laser pulses. Measurements reveal positive optical gain on a nanosecond time scale at 430 nm (F-band), accompanied by spectral narrowing and a threshold behaviour of the amplified spontaneous emission as a function of the excitation intensity. We show that the presence of the slow-red (S-band) emission component critically influences the observation of stimulated emission from the F-band.