Abstract: Quantum dot/liquid crystal nano-composites are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however, we need to control and stabilize nano-particle dispersion in different liquid crystal host phases and understand how the particles behave in an anisotropic fluid. An ideal system will allow for the controlled assembly of either well-defined nano-particle clusters or a uniform particle distribution. In this paper, we investigate mesogen-functionalized quantum dots for dispersion in cholesteric liquid crystal. These nanoparticles are known to assemble into dense stable packings in the nematic phase, and such structures, when localized in the liquid crystal defects, can potentially enhance the coupling between particles and a cholesteric cavity. Controlling the dispersion and assembly of quantum dots using mesogenic surface ligands, we demonstrate how resonant fluid photonic cavities can result from the co-assembly of luminescent nanoparticles in the presence of cholesteric liquid crystalline ordering.
Abstract: The fluorescence of photosystem I (PSI) trimers in proximity to bimetallic plasmonic nanostructures have been explored by single-molecule spectroscopy (SMS) at cryogenic temperature (1.6 K). PSI serves as a model for biological multichromophore-coupled systems with high potential for biotechnological applications. Plasmonic nanostructures are fabricated by thermal annealing of thin metallic films. The fluorescence of PSI has been intensified due to the coupling with plasmonic nanostructures. Enhancement factors up to 22.9 and 5.1 are observed for individual PSI complexes coupled to Au/Au and Ag/Au samples, respectively. Additionally, a wavelength dependence of fluorescence enhancement is observed, which can be explained by the multichromophoric composition of PSI.
Abstract: Using perturbation expansion of Maxwell equations with the nonlinear boundary condition, a generic propagation equation is derived to describe nonlinear effects, including spectral broadening of pulses, in graphene surface plasmon (GSP) waveguides. A considerable spectral broadening of an initial 100 fs pulse with 0.5 mW peak power in a 25 nm wide and 150 nm long waveguide is demonstrated. The generated supercontinuum covers the spectral range from 6 μm to 13 μm .
Abstract: We investigated the dynamics of a dispersion-managed, passively mode-locked, ultrashort-pulse, Er-doped fiber laser using a single-wall carbon nanotube (SWNT) device. A numerical model was constructed for analysis of the SWNT fiber laser. The initial process of passive mode-locking, the characteristics of the output pulse, and the dynamics inside the cavity were investigated numerically for soliton, dissipative-soliton, and stretched-pulse mode-locking conditions. The dependencies on the total dispersion and recovery time of the SWNTs were also examined. Numerical results showed similar behavior to experimental results.
Abstract: Precise control of particle positioning is desirable in many optical propulsion and sorting applications. Here, we develop an integrated platform for particle manipulation consisting of a combined optical nanofiber and optical tweezers system. We show that consistent and reversible transmission modulations arise when individual silica microspheres are introduced to the nanofiber surface using the optical tweezers. The observed transmission changes depend on both particle and fiber diameter and can be used as a reference point for in situ nanofiber or particle size measurement. Thence, we combine scanning electron microscope (SEM) size measurements with nanofiber transmission data to provide calibration for particle-based fiber assessment. This integrated optical platform provides a method for selective evanescent field manipulation of micron-sized particles and facilitates studies of optical binding and light-particle interaction dynamics.
Abstract: The present work shows how the eccentricity in active nano-particles may lead to very interesting and rather directive near- and far-field radiation patterns. The nano-particle is of a three-layer type and consists of a silica core, a free-space middle layer and an outer silver shell and is excited by a magnetic line source. The constant frequency gain model is included in the silica core, and the eccentricity is introduced through appropriate displacements of the core. It is shown that the eccentricity in a nano-particle, which was initially designed to excite a strong dipole mode, causes a progressively larger excitation of several other (including higher order) modes, this being more so the larger the core displacement. Specifically, eccentric nano-particles are identified with comparable simultaneous excitations of dipole and quadrupole modes, with associated large values of the radiated power and, even more notably, enhanced and directive near- and far-field radiation patterns. The main beam of these patterns is shown to be effectively tailored (enhanced, reshaped and steered) by the direction and amount of the core displacement. The eccentric nano-particles can be additionally gain optimized to boost their near-field response and the radiated power, while retaining the directivity of the gain unoptimized eccentric cases. Owing to their very directive nearand far-field patterns, the proposed eccentric, active three-layer nano-particles may provide alternative strategies towards the design of directive nano-antennas relative to several of the existing solutions.