R. Spano

Ultrafast All-Optical Switching in a Silicon-Nanocrystal-Based Silicon Slot Waveguide at Telecom Wavelengths

We demonstrate experimentally all-optical switching on a silicon chip at telecom wavelengths. The switching device comprises a compact ring resonator formed by horizontal silicon slot waveguides filled with highly nonlinear silicon nanocrystals in silica. When pumping at power levels about 100 mW using 10 ps pulses, more than 50% modulation depth is observed at the switch output. The switch performs about 1 order of magnitude faster than previous approaches on silicon and is fully fabricated using complementary metal oxide semiconductor technologies.

Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm

We present a detailed investigation of the different processes responsible for the optical nonlinearities of silicon nanocrystals at 1550 nm. Through z-scan measurements, the bound-electronic and excited carrier contributions to the nonlinear refraction were measured in presence of two-photon absorption. A study of the nonlinear response at different excitation powers has permitted to determine the change in the refractive index per unit of photo-excited carrier density sigma(r) and the value of the real bound-electronic nonlinear refraction n(2be) as a function of the nanocrystals size. Moreover at high excitation power, a saturation of the nonlinear absorption was observed due to band-filling effects.

Linear and nonlinear optical properties of Si nanocrystals in SiO2 deposited by plasma-enhanced chemical-vapor deposition

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 24at.%. 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 0.80eV in the nanosecond regime and at 1.50eV 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∼−10−8cm2∕W) and nonlinear absorption coefficient (β∼10−6cm∕W). Under femtosecond excitation conditions, a smaller nonlinear refractive index is found (n2∼10−12cm2∕W), typical of nonlinearities arisi...

Silicon Nanocrystals as an Enabling Material for Silicon Photonics

Silicon nanocrystals (Si-nc) is an enabling material for silicon photonics, which is no longer an emerging field of research but an available technology with the first commercial products available on the market. In this paper, properties and applications of Si-nc in silicon photonics are reviewed. After a brief history of silicon photonics, the limitations of silicon as a light emitter are discussed and the strategies to overcome them are briefly treated, with particular attention to the recent achievements. Emphasis is given to the visible optical gain properties of Si-nc and to its sensitization effect on Er ions to achieve infrared light amplification. The state of the art of Si-nc applied in a few photonic components is reviewed and discussed. The possibility to exploit Si-nc for solar cells is also presented. In addition, nonlinear optical effects, which enable fast all-optical switches, are described.

Group velocity dispersion in horizontal slot waveguides filled by Si nanocrystals

A study of group velocity dispersion of horizontal slot waveguides filled by Si nanocrystals with different Silicon concentrations has revealed a change in the sign of GVD from negative to positive values across the third telecom window.

Non-Linear Optical Properties of Si Nanocrystals

Nonlinear optical refraction and absorption have been measured on Si nanocrystals grown by plasma-enhanced- chemical-vapour-deposition. Strong nonlinearities were found at 830 nm and at 1552 nm. Different behaviours, depending on the pump-pulse duration, have been observed

Nonlinear properties of Silicon nanocrystals at 1550 nm and their application in slot waveguides

The nonlinear refractive index of Silicon nanocrystals was measured by the z-scan technique. The results were used to estimate the magnitude of the self-phase modulation (SPM) effect in slot waveguide structures filled by Silicon nanocrystals.

Nonlinear Optical Properties of Si Nanocrystals

Nonlinear optical refraction and absorption have been measured on Si nanocrystals grown by plasma-enhanced- chemical-vapour-deposition. Strong nonlinearities were found at 830 nm and at 1552 nm. Different behaviours, depending on the pump-pulse duration, have been observed

Non linear optical properties of Silicon nanocrystals for applications in photonic logic gates devices.

A systematic study of silicon nanocrystals (Si-ncs) nonlinearities at 1550 nm was carried out in view of the realization of an all optical Mach-Zehender interferometer (MZI).

Experimental characterization of Mach-Zehnder interferometers with coupled ring resonators in Silicon nanocrystals horizontal slot waveguides

We report the fabrication and characterization of both symmetric and asymmetric Mach-Zehnder interferometers (MZIs) with ring resonators (RRs) coupled to both MZI arms using silicon nanocrystals horizontal slot waveguides. Observed transmission dips are due to both MZI destructive interference and resonances of the coupled RRs. Since the slot is filled with a nonlinear material (silicon nanocrystals) the measured structures could be used to implement high-speed all-optical switches entirely fabricated using CMOS processes.