Experimental Observation Of Optical Amplification In Silicon Nanocrystals

Abstract

Silicon, as an indirect band gap semiconductor, is a poor light emitter and, therefore, has been considered as unsuitable for optoelectronic application. The situation has been changed with discovery of light emission from porous silicon [1], but due to instability and relatively poor light emission, this material has not yet found functional application. Recent discovery of optical gain in silicon nanocrystals embedded in various matrices promises soon fabrication of silicon laser [4]. The light amplification was demonstrated by pump and probe technique using picosecond light pumping pulses and variable strip method (VSM). The similar observation of amplified spontaneous emission was found by an experiment with nanosecond light pumping pulses [5]. In this paper we provide further evidences for the optical gain in nanocrystaline silicon in fused silica matrix by using VSM and continuous wave laser excitation. Moreover, due to observed strong spatial directionality and narrow line width, these findings are direct evidences for the lasing emission in nanocrystalline silicon.