22 research outputs found
Bloch surface waves-controlled emission of organic dyes grafted on a one-dimensional photonic crystal
No full textAn alternative route to plasmon-controlled fluorescence for improving the detection of fluorescence is proposed. In place of a metallic layer, a suitable silicon-based one-dimensional photonic crystal is used to generate a Bloch surface waves-coupled emission from a thin polymeric layer decorated with a fluorescent dye. Fluorescent radiation coupled to Bloch surface waves is strongly polarized and directional, with an angular divergence of 0.3° corresponding to a spectral bandwidth of 3 nm. Within this range, an overall signal enhancement of a factor larger than 500 is obtained as compared to a conventional glass substrate thanks to an additional enhancement mechanism based on dyes excitation via Bloch surface waves
Real-time Amyloid Aggregation Monitoring with a Photonic Crystal-based Approach
No full textWe propose the application of a new label-free optical technique based on photonic nanostructures to real-time monitor the amyloid-beta 1-42 (Aβ(1-42)) fibrillization, including the early stages of the aggregation process, which are related to the onset of the Alzheimer's Disease (AD). The aggregation of Aβ peptides into amyloid fibrils has commonly been associated with neuronal death, which culminates in the clinical features of the incurable degenerative AD. Recent studies revealed that cell toxicity is determined by the formation of soluble oligomeric forms of Aβ peptides in the early stages of aggregation. At this phase, classical amyloid detection techniques lack in sensitivity. Upon a chemical passivation of the sensor surface by means of polyethylene glycol, the proposed approach allows an accurate, real-time monitoring of the refractive index variation of the solution, wherein Aβ(1-42) peptides are aggregating. This measurement is directly related to the aggregation state of the peptide throughout oligomerization and subsequent fibrillization. Our findings open new perspectives in the understanding of the dynamics of amyloid formation, and validate this approach as a new and powerful method to screen aggregation at early stage
Terahertz antireflection properties of sub-wavelength metallic double wire grid structures
No full textA virtual optical probe based on localized Surface Plasmon Polaritons
No full textA 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.OP
Polarization-selective optical nanostructures for optical MEMS integration
No full textOptical 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).OP
Microlenses with annular amplitude and phase masks
No full textWe 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
Enhanced light trapping in realistic thin film solar cells using one-dimensional gratings
No full text
