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The studies were conducted to assess the structural evolution and nucleation of Si-nanocrystal in silicon-rich silicon oxide films produced by PECVD (plasma enhanced chemical vapor deposition), as a function of the annealing temperature. The findings reveal the active role played by the hydrogen and nitrogen atoms in the formation of Si-nc and in the thermally induced evolution of the deposited films.

Complementary metal-oxide-semiconductor-compatible tunable Fabry-Perot microcavities filled with liquid crystals (LCs) are realized and studied in the near-infrared region. Electric-field-induced shifts of the second-order cavity modes of 127 and 49 nm are obtained for Merck-E7 and Merck-6608 LC, with driving potentials of 5 and 10 V, respectively.

Linear and nonlinear optical properties of silicon suboxide SiOx films deposited by plasma-enhanced chemical-vapor deposition have been studied for different Si excesses up to 24 at. %. The layers have been fully characterized with respect to their atomic composition and the structure of the Si precipitates. Linear refractive index and extinction coefficient have been determined in the whole visible range, enabling to estimate the optical bandgap as a function of the Si nanocrystal size. Nonlinear optical properties have been evaluated by the z-scan technique for two different excitations: at 0.80 eV in the nanosecond regime and at 1.50 eV in the femtosecond regime. Under nanosecond excitation conditions, the nonlinear process is ruled by thermal effects, showing large values of both nonlinear refractive index (n2∼-10-8 cm2/W) and nonlinear absorption coefficient (β∼10-6 cm/W). Under femtosecond excitation conditions, a smaller nonlinear refractive index is found (n2∼10-12 cm2/W), typical of nonlinearities arising from electronic response. The contribution per nanocrystal to the electronic third-order nonlinear susceptibility increases as the size of the Si nanoparticles is reduced, due to the appearance of electronic transitions between discrete levels induced by quantum confinement. [ABSTRACT FROM AUTHOR]

The energy transfer mechanism among silicon nanoparticles (Si-np), both amorphous and crystalline, and Er ions in a silicon dioxide matrix is analyzed. A model is developed in which the internal intraband recombination within Si-np is competitive with the transfer process via an Auger electron-erecyclingE process and the studies have recast the role of Si-np in the sensitization scheme, where they are able to excite very efficiently ions in close proximity to their surface.

Optical properties of directly excited erbium ([Er.sup.3+]) ions are analyzed in silicon rich silicon oxide materials codoped with [Er.sup.3+]. Time resolved [micro]-photoluminescence measurements are used for measuring the spectral dependence of the direct excitation cross section of the [Er.sup.3+] atomic transition.

A systematic study of the linear and nonlinear optical properties of Si[O.sub.x] films deposited on silica by plasma-enhanced chemical-vapor deposition (PECVD) technique is presented. The contribution per nanocrystal to the electronic third-order nonlinear susceptibility is found to increase with reduction in the size of the Si nanoparticles due to the appearance of electronic transitions between discrete levels induced by quantum confinement.

The study and modeling of the structural and optical properties of rib-loaded waveguides working in the 600-900-nm spectral range is presented. A Si nanocrystal rich SiO2 layer with nominal Si excess ranging from 10% to 20% is produced by quadrupole ion implantation of Si into thermal SiO2 formed on a silicon substrate.

Stimulated emission from silicon-nanocrystal planar waveguides grown via phase separation and thermal crystallization of SiO/SiO2 superlattices is presented. The study shows that under high power pulsed excitation, positive optical gain is observed once a good optical confinement in the waveguides is achieved and the silicon nanocrystals have proper size.

Absorption coefficient (αabs) of Er3+ ions coupled to Si nanoclusters (Si-nc) in SiO2 has been determined by optical transmission measurements in rib-loaded waveguides characterized by different refractive indices, thus gauging an Er3+ absorption cross section (σabs) of 0.4–1.2×10-20 cm2 at 1534 nm. Although no significant enhancement due to the presence of Si-nc was observed, a clear dependence on the refractive index has been found. Measurements of the decay lifetime permit one to model the behavior as due to both local and mean field variations caused by the composite nature of the core waveguide layer. [ABSTRACT FROM AUTHOR]