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Stimulated emission from silicon-nanocrystal planar waveguides grown via phase separation and thermal crystallization of SiO/SiO2 superlattices is presented. Under high power pulsed excitation, positive optical gain can be observed once a good optical confinement in the waveguide is achieved and the silicon nanocrystals have proper size. A critical tradeoff between Auger nonradiative recombination processes and stimulated emission is observed. The measured large gain values are explained by the small size dispersion in these silicon nanocrystals. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we present the waveguiding properties of a set of mono-dispersed silicon nanocrystal Si-nc superlattices. The measured modal refractive indices (obtained by the m-line technique) of different samples can only be explained by assuming a negative “form birefringence” of about 1% originating from the particular structure of the active core, i.e., a periodical set of parallel planes of two different materials. By means of a simple model for the ordinary and extraordinary refractive indices in this kind of structures, by using the information from TEM images and the nominal growth parameters, and by considering as free parameters the upper size of the diameter of Si-nc, we are able to fit the m-line measurements in a unique way. We also report gain measurements on this set of samples, showing that, under high power pulsed excitation, positive optical gain is observed in samples that provide both good light confinement inside the waveguide and the right Si-nc dimension. [Copyright &y& Elsevier]

We investigate the optical properties of planar waveguides where the core layer is formed by a silicon nanocrystals (Si-nc)/SiO2 superlattice. M-line measurements of the different waveguides yield the mode indices, which can be modeled by assuming anisotropic optical properties of the core layer. This anisotropy is related to the superlattice, i.e., it is a form birefringence. By modeling the m-line measurements with the structural data obtained by transmission electron microscopy analysis, we determine for each waveguide the value of the form birefringence, an upper limit of the nanocrystals size and their refractive index. Values of the form birefringence as high as 1% have been found. [ABSTRACT FROM AUTHOR]