Optical gain at 1.54um in nanocrystal Si sensitized, Er-doped silica waveguide using top-pumping 470nm LED

Abstract

Optical gain from Erbium doped Silicon Rich Silicon Oxide(SRSO) optical waveguide amplifier top-pumped with an 470nm visible LED array is investigated. Er doped SRSO thin films, which consist of Si nanoclusters embedded inside a SiO$_2$ matrix, were prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition with co-sputtering of erbium target using SiH$_4$ and O$_2$ as source gases. After deposition, the samples were rapid thermal annealed at 950 ℃ for 5 min in order to precipitate the excess Si atoms into nc-Si. The Composition of waveguide amplifier is 1 at.% excess Si and ~ 0.06 at.% Er. The presence of nc-Si raises the refractive index of the material to 1.46, automatically providing the refractive index contrast necessary for waveguiding. Thus, ridge-type, single-mode waveguides were formed by defining 1.1 cm long, 9 ㎛ width, 0.3 ㎛ high ridges using photolithography and buffered oxide etching process, followed by mechanical polishing. Optical absorption measurements indicate Er-related absorption of ~ 3dB/cm, consistent with increased Er absorption cross-section by nc-Si. Signal enhancement was observed when the waveguide was pumped from the top using a 470nm visible LED array. simulation of high pump power using 477nm line of an Ar laser showed signal enhancement of 3dB/cm, indicating full inversion.