An approach to optical-property profiling of a planar-waveguide structure of Si nanocrystals embedded in SiO_2

摘要

The structure of Si nanocrystals (nc-Si) embedded in SiO_2 is promising for achieving optical gain and waveguiding with the advantage of full compatibility with the matured Si technology. In this paper, we report an approach to optical-constant profiling for such a planar waveguide structure formed by Si ion implantation into a SiO_2 thin film based on spectroscopic ellipsometry (SE). With the nc-Si optical constants calculated from the Forouhi-Bloomer model and the nc-Si depth profile obtained from secondary ion mass spectroscopy (SIMS) measurements, the optical properties at a given depth are simulated with the Maxwell-Garnett effective medium approximation (EMA). Then an SE fitting is carried out, and the optical constants of nc-Si are extracted from the best fitting. Finally, the depth profile of optical constants of the structure is obtained from the EMA calculation. The result also suggests that the structure has a very low optical loss in the visible to infrared spectral range.