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Nonlinear optical properties of multicomponent tellurite glasses doped with Er 3+ ions were investigated by open aperture Z-scan measurements. Compositional and linear optical properties of the glasses were examined by the energy dispersive X-ray spectrum and UV–vis–NIR absorption spectrum analysis respectively. The mechanism behind the optical nonlinearity and optical limiting efficiency was successfully explained by evaluating the physical properties such as density, refractive index and polarizability of the glasses. The nonlinear properties critically depend on the polarizability, which is found to increase with the addition of Er 3+ ions by the creation of non-bridging oxygen ions. By the systematic addition of Er 3+ ions, we have dictated the physical properties and thus tuned the optical limiting efficiency of the glasses. This makes the Er 3+ -doped multicomponent tellurite glasses flexible tunable optical limiters for potential device applications. [ABSTRACT FROM AUTHOR]

We report the nonlinear optical properties of graphene oxide (GO), reduced graphene oxide (rGO), sulfonated graphene oxide (S-rGO), and sparingly sulfonated water soluble graphene (WSG), measured under ultrafast (100 fs) and short pulse (300 ps, 50 ns) laser excitations at 800 nm, employing the open aperture Z-scan technique. The samples exhibit typical third order nonlinear optical behaviour including two-photon absorption (2 PA), reverse saturable absorption (RSA), and saturable absorption (SA). A significant variation in the nature of nonlinear absorption is seen when the laser pulse duration is changed. For example, RSA is prominent under nanosecond (ns) excitation, 2 PA is prevalent under femtosecond (fs) excitation, and SA is dominant under picosecond (ps) excitation. For comparison purposes the measurements are repeated using 5 ns laser pulses at 532 nm. RSA is enhanced in WSG in the nanosecond excitation domain, which can be attributed to the covalent bonding between p-phenyl-SO 3 H groups and sp 2 graphitic planes. WSG exhibits a switching behaviour from SA to RSA upon increasing the excitation intensity under fs excitation. Results show that these graphene derivatives are potentially useful for saturable absorber and optical limiter device applications. [ABSTRACT FROM AUTHOR]

Hetero atom doped graphene - metal nanoparticle hybrids have received increasing attention owing to their unique electronic properties, large specific surface area, very high conductivity and more electronic interactions. Herein, we report for the first time a hydrothermal assisted strategy for developing novel class of nitrogen (N) and sulfur (S) co-doped graphene/Ag nano morphotypes (sphere, cube and wire) hybrids for enhanced optical limiting (OL) and surface-enhanced Raman scattering (SERS) applications. Two probe molecules, Rhodamine 6G and para-aminothiophenol, are chosen to determine the enhancement performance of the as-prepared SERS-active substrate. Our results signified that the Ag nanocube-N, S codoped graphene hybrid based SERS-active substrate presents excellent performances for sensing R6G with an enhancement factor of 1.07 × 10 7 . Further, this SERS substrate reveals outstanding capability to detect P -ATP molecules with detection limit of approximately 1.0 × 10 −12  M. Moreover, the non-linear optical absorption studies results show that the OL properties were appreciably enhanced after the insertion of Ag nanostructures on the NSG surface. Thus, OL properties of the two-dimensional N, S-codoped graphene can be effectively modified by absorbing AgNPs of different morphology on its surface. All of the results signify that these hybrid structures will show extended applications for SERS sensing and optoelectronic fields. [ABSTRACT FROM AUTHOR]