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Nanocomposities are random media containing domains or inclusions that are on the nanometric size scale. The optical properties of composite materials can be adjusted by controlling the constituents and morphology of the composite structure. The optical nanocomposite approach offers opportunities to produce high-performance and relatively low-cost optoelectronic media suitable for many applications. 1 "Stimulated Raman scattering (SRS)" is one of the first discovered nonlinear optical effects: a pump laser beam enters a nonlinear medium and spontaneous generation and amplification lead to a beam at a frequency different from the pump. SRS belongs to a class of nonlinear optical processes that can be called quasi-resonant. Although none of the fields is in resonance with the vibrations in the lattice of the medium (optical phonons), the difference between the pump and generated beam equals the transition frequency. 2 SRS is used in tunable laser development, high energy pulse compression, etc. One of the most important perspectives is the realization of micro/nanosources, with improved performances.In bulk semiconductors, lasing by SRS was first discovered in GaP. 3 Most recently, Raman lasers have been demonstrated in silicon microwaveguides. 4 SRS from spherical droplets and microspheres, with diameters 5À20 μm, has been also observed using both pulsed and continuous wave probe beams. 5 Except for a report of SRS from individual single walled carbon nanotubes, 6 the observation of SRS from semiconductor nanowires 7 and from silicon nanocrystals, 8,9 we find no other evidence for this important nonlinear optic effect in nanostructured materials.In this paper, the microstructural and the optical characterizations of glasses with composition 30K 2 O 3 30Nb 2 O 5 3 40 SiO 2 (KNS 30À30À40) with different thermal treatments were carried out by differential thermal analysis (DTA), highresolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), ellipsometry, and Raman spectroscopy. Our findings prove that as a consequence of the thermal treatment, a nanostructuring process is obtained, which can be considered a powerful tool to make functional nanocomposite glassy materials especially for optical applications. 10,11 In addition, strong changes in the Raman spectra of nanocomposite material with respect to KNS glass are proved and discussed. Finally, a significant enhancement of Raman gain (up to 25 times higher) and of its bandwidth of both KNS glasses and nanocomposite material with respect to SiO 2 glass is reported. ABSTRACT:The optical properties of composite materials can be adjusted by controlling the constituents and morphology of the composite structure. The optical nanocomposite approach offers opportunities to produce high-performance and relatively low-cost optoelectronic media suitable for many applications. In this paper, a nanocomposite material obtained by a high niobium content glass belonging to the K 2 OÀNb 2 O 5 ÀSiO 2 (KNS) glass-forming system is prepared and characterized. We focu...

In this paper, the optical dispersion properties and the Raman gain of sodium phosphate glasses containing niobium oxide at increasing concentrations have been systematically investigated, with the aim of establishing a potential enhancement of the Raman gain and its bandwidth with respect to silica. A broadening of the bandwidth and a higher peak Raman gain (approximately 17 times) than in silica glass have been observed at high niobium oxide molar content. Our findings point out that sodium–niobium–phosphate glasses could be utilized for the realization of Raman amplifiers.

In this work, we present the first experimental evidence of negative dielectric susceptibility in a two-dimensional silicon photonic crystal (PhC) with negative refractive index behavior. In the frequency range in which the effective refractive index n eff is equal to 21, the incident light couples efficiently to the guided modes in the top surface layer of the PhC metamaterial. These modes resemble surface plasmon polariton resonances. This finding was confirmed by ellipsometric measurements, demonstrating the isotropy of the PhC resonances. Such negative index PhC materials may be of use in biosensing applications. Light: Science & Applications (2012) 4 as well as multiplexing. 5 The power of PhCs and their unusual properties arises from the optical bandgap, which can be tailored by design. Recently, PhCs have been used more widely as a metamaterial with an effective negative refractive index.6-10 Light propagating in such a metamaterial can undergo a drastic change in group velocity, causing the light to bend away from the usual direction that is observed with a conventional refracting medium. Owing to the fine control over the optical bandgap of the PhC, the effective refractive index can exhibit optical antimatter behavior.7 For example, a set of circular holes etched vertically into a silicon slab in a hexagonal arrangement can produce an effective resonant refractive index of n eff 521 for light propagating along the length of the slab (perpendicular to the direction of the holes). Such a metamaterial strongly couples incoming light and can be used to transmit data with minimum losses over millimeter distances for lab-on-a-chip applications. 8The reflection spectra of patterned surfaces have been widely studied since the discovery of Wood anomalies in metallic gratings. 11In particular, Fano found a clear connection between the narrow anomalies and surface wave excitation that distinguished broad and sharp anomalies. 12 The theoretical understanding of this phenomenon has been provided by Hessel and Oliner. 13 Similarly, the resonances in PhC slabs have been analyzed in reflection and transmission.14 These resonances have been used to reconstruct the band structure 15 and equifrequency surface 16 of PhCs. Similar to surface plasmon polariton (SPP) resonances, the resonant anomalies allow for the propagation of otherwise forbidden modes. 15 Other analogies with SPP behavior arise for PhCs at frequencies where the refractive index turns negative. In this paper, we present an experimental study of the resonance effects directly connected with negative refractive index properties of PhC. Using standard ellipsometric measurements of the amplitude y and phase D of the ratio between the linear polarization reflection coefficients, we demonstrate that the change in the dielectric function of negative index PhC is similar to the change in the dielectric constant of a plasmonic structure.17 Similar to the Fano resonances, 17,18 the resonances in the y spectrum corresponding to a 180 6 phase change are slightly...