Detection of protein aggregation with a Bloch surface wave based sensor

We present the innovative application of a Bloch surface wave based sensor to the detection of protein aggregation. In Hen Egg White Lysozyme (HEWL) solutions, aggregates are discriminated from the monomeric forms in a label-free detection scheme

Polarization-selective optical nanostructures for optical MEMS integration

Optical nanostructures have the potential to provide useful new functionalities, using materials and fabrication methods that are compatible with standard silicon-based processes. For example, it has been shown that a nanoscale grating coated with a metal layer produces polarization-selective reflectivity [1,2], based on the combined effects of form birefringence and a resonant cavity [3]. In this work, we adapt this design approach to develop two devices optimized to operate around 1.55 μm wavelength: a polarizing beam splitter, and a polarization-selective reflector. Such devices are of particular interest as they may provide optical properties such as polarization selectivity or enhanced reflectivity using nanostructures compatible with optical micro-electro-mechanical systems (MEMS)

Enhanced light trapping in realistic thin film solar cells using one-dimensional gratings

Finding the optimal structure to enhance light trapping in thin film silicon solar cells has attracted much attention in the previous decades. However, because of problems in integrating theory and experiment, there are only few comprehensive contributions that provide guidelines for the optimal design of such structures. In this work, a realistic thin film solar cell with almost conformal layers based on a one-dimensional metallic grating back-reflector is investigated through experiment and theory. The external quantum efficiency of the cell is obtained with the aid of both theory and experiment for different angles of incidence and in both polarizations to validate the computational method and to show the impact of guided mode excitation. Different substrate shapes that are compatible with solar cell fabrication are then considered and the effect of geometrical parameters on the short circuit current density of the device is investigated. Calculations show that among the investigated shapes, trinagular gratings with a very sharp slope in one side, so called sawtooth gratings, are the most promising one-dimensional grating for light trapping. Furthermore, the role of material property is discussed specifically in the back-reflector by simulating aluminum and silver back-reflectors. It is shown that the blue response of the solar cells is similar almost regardless of the back-reflector material but their red response is viable to change due to variation in resonant properties of the structure

Microlenses with annular amplitude and phase masks

We present theoretical and experimental investigations of microlenses with both amplitude and phase masks. The light field in the focal region has been measured with a high resolution Mach-Zehnder interferometer with z-scan. The experimental results show good agreement with simulation. We show that we can obtain effects as diverse as squeezing or expansion in longitudinal and lateral directions, focal point splitting and focal shift. These effects may be of interest for applications such as Shack-Hartmann wavefront sensing, integral imaging, optical tweezers and confocal microscopy

Near-field study of dielectric surface lens

In this work, we design, fabricate and experimentally characterize a surface structured lens within an ultra thin polymer layer deposited on a Bloch Surface Waves (BSWs) suspended dielectric platform. The near-field (SNOM) measurements demonstrate that the lens is able to manipulate the propagation of the surface waves. Experimental result shows good agreement with the simulation calculated using the finite difference time-domain (FDTD). This work opens a way to realize surface structured integrated all-optical systems and the study of fundamental optical phenomena

A virtual optical probe based on localized Surface Plasmon Polaritons

A confined, evanescent nano-source based on the excitation of Surface Plasmon Polaritons (SPP) on structured thin metal films is proposed. With the help of a suitable cavity, we numerically demonstrate that it is possible to trap SPP over a spatial region smaller than the diffraction limit. In particular, the enhanced plasmonic field associated with the zero-order cavity mode can be used as a virtual probe in scanning near-field microscopy systems. The proposed device shows both the advantages of a localized, non-radiating source and the high sensitivity of SPP-based sensors. The lateral resolution is limited by the lateral extension of the virtual probe. Results from simulated scans of small objects reveal that details with feature sizes down to 50 nm can be detected. © 2005 Optical Society of America