Abstract
We show that an appropriately designed chalcogenide metasurface allows the enhancement of harmonic generation in the UV range, a regime that conventional wisdom deems inaccessible because of ...absorption. Here we exploit a combination of the photonic band structure that forms when stacking As
2
S
3
metasurfaces, phase-locking, nonlinear dispersion, and improved field localization to enhance third harmonic conversion efficiency. We demonstrate an improvement of two orders of magnitude with respect to the single layer counterpart notwithstanding the fact that the harmonic signal is tuned deep in the absorption range at 285 nm.
We investigated the statistical properties of partially coherent optical vortex beams scattered by a $\mathcal {PT}$ dipole, consisting of a pair of point particles having balanced gain and loss. The ...formalism of second-order classical coherence theory is adopted, together with the first Born approximation, to obtain the cross-spectral density of the scattered field. It is shown that the radiated pattern depends strongly on the coherence properties of the incident beam and on the non-Hermitian properties of the dipole. The spectral density for the scattered radiation is ruled by two terms, one associated to the vortex structure and the other independent of the topological charge, and the competition between these terms dictates the directional properties of the scattered radiation. When they have same order of magnitude, the scattered profile resembles that of an incoherent system, with radiation being emitted in all directions in the three-dimensional space, regardless of the dipole's gain and loss properties. Depending on the gain and loss present in the dipole, the system may scatter light in some preferable directions. All of these effects are accompanied by a change in the spectral degree of coherence of the scattered field.
A facile, cost-effective, and manufacturable method to produce gold−polymer nanocomposite plasmonic nanorod arrays in high-aspect-ratio nanoporous alumina templates is reported, where the formation ...of gold nanoparticles and the polymerization of a photosensitive polymer by ultraviolet light are simultaneously performed. Transverse mode coupling within a two-dimensional array of the nanocomposite rods results in a progression of resonant modes in the visible and infrared spectral regions when illuminated at normal incidence, a phenomenon previously observed in nanoarrays of solid gold rods in an alumina template. Finite element full-wave analysis in a three-dimensional computational domain confirms our hypothesis that nanoparticles, arranged in a columnar structure, will show a response similar to that of solid gold rods. These studies demonstrate a new simple method of plasmonic nanoarray fabrication, apparently obviating the need for a cumbersome electrochemical process to grow nanoarrays.
Light–matter interactions at a particular point in a material may be dominated by properties of the medium at this point, or they could be affected by the electromagnetic properties of the medium in ...the surrounding regions. In the former case, the medium is said to be local, while in the latter, it is nonlocal. Recent studies of light–matter interactions in composite optical metamaterials showed that nonlocal effects enable new optical phenomena that are not acounted for by the conventional, local effective medium description. Up until now the majority of studies focused on metamaterials with spatially uniform material parameters. However, optical metamaterials with electromagnetic material parameters gradually changing from positive to negative values, so-called transition materials, have been predicted to induce a strong enhancement of the local electric or magnetic field in the vicinity of the zero refractive index point. This opens new opportunities for sensing and low-intensity nonlinear optical applications. Here, we analyze the field enhancement in realistic transition metamaterials consisting of an array of plasmonic cone-shaped rods embedded in a dielectric matrix and demonstrate that optical nonlocality is required to adequately describe this optical response. This work enables the design and practical applications of this new emerging metamaterial platform.
A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the ...transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.
We demonstrate a tunable dispersion slope compensator using a linearly chirped fiber Bragg grating and a thin-film heater that provides a variable quadratic temperature gradient along the grating. We ...achieved 2-10-ps/nm/sup 2/ compensation over 3 nm suitable for 160-Gb/s return-to-zero signals.
We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG). A theoretical model for dispersion compensation in transmission based on the ...dispersive properties of the periodic structure is developed. A figure of merit is defined for optimization of the grating parameters for maximum recompression of dispersion-broadened optical pulses in long-haul communication systems. Numerical examples confirm that nearly perfect compensation with very low insertion losses can be achieved for many practical cases of interest.
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