A negative value for the nonlinear refraction in graphene is experimentally observed and unambiguously verified by performing a theoretical analysis arising from the conductivity of the graphene monolayer. The nonlinear optical properties of multi-layer graphene are experimentally studied by employing the Z-scan technique. The measurements are carried out at 1150, 1550, 1900 and 2400 nm with a 100-femtosecond laser source. Under laser illumination the multi-layer graphene exhibits a transmittance increase due to saturable absorption, followed by optical limiting due to two-photon absorption. The saturation irradiance Isat and the two-photon absorption coefficient β are measured in the operating wavelength range. Furthermore, an irradiance-dependent nonlinear refraction is observed and discriminated from the conventional nonlinear refraction coefficient n2_, which is not irradiance dependent. The values obtained for the irradiance-dependent nonlinear refraction are in the order of ∼10^-9 cm²W^-1, approximately 8 orders of magnitude larger than any bulk dielectrics.

In this paper we report on successful supercontinuum generation extending from the near to the mid-infrared region in the range 700-2500 nm in a micro-structured fiber made of lead-bismuth-galate glass and pumped in the femtosecond regime with a wavelength of 1540 nm. The flatness of 5 dB is observed in most of the registered spectrum 1000 -2500 nm. The improved spectral and thermo-physical properties of this custom made lead-bismuth-galate glass against tellurite and commercially available heavy oxide SF-57 glasses are presented.

Optical waveguides have been inscribed in periodically poled lithium niobate by femtosecond laser pulses with the multiscan technique. Second harmonic generation experiments from a fundamental wavelength of 1567nm demonstrate that the nonlinear optical coefficient in the waveguides is preserved, yielding a conversion efficiency of 18%W−1.

We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied.

A fan-out device has been fabricated using ultrafast-laser waveguide-inscription that enables each core of a multicore optical fiber (MCF) to be addressed by a single mode fiber held in a fiber V-groove array (FVA). By utilizing the unique three-dimensional fabrication capability of this technique we demonstrate coupling between an FVA consisting of a one-dimensional array of fibers and an MCF consisting of a two-dimensional array of cores. When coupled to all cores of the MCF simultaneously, the average insertion loss per core was 5.0 dB in the 1.55 mum spectral region. Furthermore, the fan-out exhibited low cross-talk and low polarization dependent loss.