Multilayer beamsplitter polarizers for key UV-FUV spectral lines of solar polarimetry.

Multilayer beamsplitter polarizers have been developed for improved solar polarimetry at key spectral lines. The advantage of beamsplitter polarizers is that a single device separates s from p polarization; this helps minimize attenuation and enables a more compact and lighter polarimeter, which is important for space instruments. Polarizers based on Al/AlF3 multilayers were prepared for both C IV (155 nm) and Mg II (280 nm) lines, and based on Al/MgF2 multilayers for H Lyman α line (121.6 nm). Polarizers were designed to mainly reflect (transmit) s (p) polarization. Beamsplitter performance and throughput are shown to compare advantageously with polarizers in the literature. Beamsplitter polarizers kept a valuable performance after several years of ageing.

Sensing by means of nonlinear optics with functionalized GaAs/AlGaAs photonic crystals.

We report on specific functionalization of GaAs/AlGaAs photonic structures for molecular sensing via the optical second harmonic generation signal in the visible range exhibited by these nanostructures. Functionalization has been achieved by peptides selected by the phage display technology, revealing specific recognition for semiconducting surfaces. These small peptides when biotinylated serve for controlled placement of biotin onto the substrate to capture then streptavidin. Functionalization (with biotinylated peptide) and molecular recognition (of streptavidin) events both result in enhancing the nonlinear optical response of the samples. Adsorption and infiltration of biomolecules into the GaAs/AlGaAs photonic structure were monitored by atomic force and scanning electron microscopy combined with Energy Dispersive X-ray spectroscopy. We demonstrate that once functionalized with specific peptides, photonic structures could be used as miniature biosensors down to femtomolar detection sensitivity, by monitoring changes in the second harmonic signal when molecules are captured. Our results prove the outstanding sensitivity of the nonlinear approach in biosensing with photonic crystal waveguides as compared to linear absorption techniques on the same samples. The present work is expected to pioneer development of a new class of extremely small affinity-based biosensors with high sensitivity and demonstrates that photonic structures support device functionality that includes strongly confined and localized nonlinear radiation emission and detection processes.

DNASER I: layout and data analysis.

We present the DNA analyzer (DNASER), a novel bioinstrumentation for real-time acquisition and elaboration of images from fluorescent DNA microarrays. A white light beam illuminates the target sample allowing the images grabbing on a high sensibility and wide-band charge-coupled device camera (ORCA II-Hamamatsu). This high-performance device permits to acquire images faster and of higher quality than the traditional systems. The DNA microarrays images are processed to recognize the DNA chip spots, to analyze their superficial distribution on the glass slide and to evaluate their geometric and intensity properties. Differently form conventional techniques, the spots analysis is fully automated and the DNASER does not require any additional information about the DNA microarray geometry. The DNASER hardware and software architecture is illustrated. Preliminary results are shown from experiments performed on real DNA samples.

Optical properties of scandium films in the far and the extreme ultraviolet.

The optical properties of thin Sc films deposited in ultrahigh-vacuum conditions have been investigated in the 6.7-174.4-nm spectral range. We measured transmittance and multiangle reflectance in situ in the 53.6-174.4 nm spectral range and used these measurements to obtain the complex refractive index of a Sc film at every individual wavelength investigated. Transmittance measurements were made of Sc samples that were deposited over grids coated with a support C film. The transmittance and the extinction coefficient of Sc films at wavelengths shorter than 30 nm were measured ex situ. The ex situ samples were protected with an additional top C film before their removal from vacuum. To our knowledge, these are the first optical measurements of Sc films reported in the spectral ranges cited.