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An approach to optical-property profiling of a planar-waveguide structure of Si nanocrystals embedded in SiO2

The structure of Si nanocrystals (nc-Si) embedded in SiO2 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 SiO2 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.