Fabrication and stimulated emission of Er-doped nanocrystalline Si waveguides formed on Si substrates by laser ablation

Abstract

Er-doped nanocrystalline Si (nc-Si) waveguides were fabricated on Si substrates and investigated by optical pumping. A stimulated emission at 1540 nm was demonstrated at room temperature. The sizes of the fabricated Er-doped nc-Si waveguides were 5000 nm×200 nm×L, where L is the cavity length and is changed from 1 to 10 mm. Superlinear optical outputs at 1540 nm were observed for the waveguides longer than 3 mm. The threshold of the optical output where the stimulated emission occurs is in the order of 10 MW/cm2, and is demonstrated to depend on the cavity length of the waveguides. A large reduction of decay lifetimes of the light output from a cleavage facet of the Er-doped nc-Si waveguides was observed when the pumping power density exceeded the thresholds indicating an increase of transition probabilities in intra-4f electrons in Er3+ ions caused by the stimulated emission. Better 1540 nm laser performance and lower pumping power density should be obtained by optimizing the device structure and increasing the Er concentration.