Silicon nanocrystals in silica—Novel active waveguides for nanophotonics

Ultrafast decay of femtosecond laser-induced grating in silicon-quantum-dot-based optical waveguides

“…It is almost certain that within the duration of the excitation pulse, nonlinear recombination processes (both radiative and non-radiative) occur in the excited Si-ncs, since, estimating the absorption cross section of Si-ncs at 400 nm for the samples with 20% excess Si concentration to be σ ≈ 2 × 10 −16 cm 2 [9,10] and considering the pump energy density of ∼10 mJ cm −2 , we get the initial mean number of electronhole pairs per nanocrystal as high as 3-5 (nevertheless, we were checking carefully that the pump power density was always below the threshold for irreversible sample changes, i.e. below the threshold for writing down a 'permanent grating' [11]). These nonlinear recombination processes in principle can be described by nonlinear terms in the relevant kinetic equations dealing with the time evolution of the LIG carrier population [4,12] and could manifest themselves through a non-exponential decay of the LIG diffraction efficiency in time.…”

The Synthesis of Silicon Nanocrystals by Ion Implantation

“…The presence of excess silicon increases the refractive index of silicon dioxide and can therefore be used to define a waveguide structure [55]. The near-Gaussian depth distribution produced by silicon implantation is well suited to such applications as it naturally forms an asymmetric slab waveguide that confines light at a known depth beneath the surface.…”

Structure and Properties of Nanoparticles Formed by Ion Implantation

“…Optical gain has been reported in ion-implanted silicon nanocrystal composites [42,43]. The waveguiding properties of silicon nanocrystal layers have been extensively investigated [44] and the relevant optical cross sections are well known (e.g., [45]). …”