Self Phase Modulation and Stimulated Raman Scattering due to High Power Femtosecond Pulse Propagation in Silicon-on-Insulator Waveguides.

Self Phase Modulation (SPM) and Stimulated Raman Scattering (SRS) in silicon waveguides have been observed and will be discussed theoretically using a modified Nonlinear Schrödinger Equation. The high optical peak powers needed for the experiments were obtained by coupling sub-picosecond (200fs) transform limited pulses with a spectral width of 12nm into a single mode silicon waveguide. Spectral broadening up to 50nm has been observed due to Self Phase Modulation. An intensity increase of the idler spectrum around 1650nm at the expense of the 1550nm pump signal has been observed as function of pump power, indicating the presence of Stimulated Raman Scattering

Ultrafast nonlinear all-optical processes in silicon-on-insulator waveguides

In this review we present an overview of the progress made in recent years in the field of integrated silicon-on-insulator (SOI) waveguide photonics with a strong emphasis on third-order nonlinear optical processes. Although the focus is on simple waveguide structures the utilization of complex structures such as microring resonators and photonic crystal structures is briefly discussed as well. Several fabrication methods are explained and methods which improve optical loss, coupling efficiency and polarization dependence are presented. As the demand for bandwidth increases communication systems are forced to use higher bit rates to accommodate the load. A consequence of high-bit-rate systems is that they require short pulses where the importance of waveguide dispersion tailoring becomes increasingly important. The impact of short pulses on the efficiency of all-optical processes is discussed and recent accomplishments in this field are presented. Numerical results of femtosecond, picosecond and nanosecond pulse propagation in SOI waveguides are compared to provide an insight into the physical processes that dominate at these different time scales. In this work we focus on two-photon absorption (TPA), free-carrier absorption (FCA), plasma dispersion and the optical Kerr effect. After describing these nonlinear effects, some other important all-optical processes based on plasma dispersion and the Kerr effect are described, namely cross-absorption modulation (XAM), self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM) and stimulated Raman scattering (SRS). The latter provides the best hope for practical and/or commercial applications and finds its use in amplification and lasing. Furthermore, we present some guidelines for efficient numerical modelling of propagation in SOI waveguides. This review is a good starting point for those who are new in this hot and rapidly emerging field and gives an overview of important considerations that need to be taken into account when designing, fabricating and characterizing SOI waveguides for ultrafast third-order nonlinear all-optical processing

Observation of high-energy neutrinos using Cerenkov detectors embedded deep in Antarctic Ice

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova2, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water3,4 or ice5. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations1.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe