Massimiliano Dispenza

Outstanding Poling Stability of a New Cross-Linked Nonlinear Optical (NLO) Material from a Low Molecular Weight Chromophore

In this paper we report the synthesis and characterization of a trihydroxylated nonlinear optical (NLO) azochromophore and its functionalization with 2,4-tolylendiisocyanate (TDI) to give an amorphous mixture of isomers that was used as a starting compound for the preparation of cross-linked electro-optic (EO) thin films. An unedited type of thermal cross-linking reaction was used, exploiting the reactivity of isocyanate groups themselves in the presence of N,N-dimethylacetamide, without the addition of any hydroxylated comonomer as usual in the preparation of polyurethanes. Thin films were prepared by spin coating and corona poled during thermal cross-linking. A d(33) value of 33 pm/V was obtained by second-harmonic generation (SHG) measurements on poled films, and an excellent stability of SHG signal was shown upon aging at 130 °C and during dynamic thermal stability measurements.

A surface plasmon resonance-based biochip to reveal traces of ephedrine

Ephedrine is a crucial chemical precursor for clandestinely produced amphetamine and its related drugs. Also, ephedrine is intentionally added to illegal preparations of methamphetamine or amphetamine because it is cheaper than the other two drugs. Consequently there is a pressing need to prevent the entry of ephedrine into commerce. Therefore the challenge calls for non-invasive techniques that provide data on the presence of ephedrine even in trace amounts. In this paper we describe the synthesis of a new ephedrine derivative with a carbon linker featuring an amino reactive group, and its conjugation to the glutamine binding protein (GlnBP) from E. coli as a carrier protein for the production of polyclonal antibodies against ephedrine. Proof-of-principle results of an efficient SPR-based indirect competitive immunoassay for the detection and quantification of ephedrine are presented. The detection limit of the assay was about 33 ng ml−1.

Towards a THz backward wave amplifier in European OPTHER project

Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable technological effort is being undertaken, in terms of technological development, THz device design and integration. The ultimate goal is to develop a miniaturised THz amplifier based on vacuum-tube principles The main target specifications of the OPTHER amplifier are the following: - Operating frequency: in the band 0.3 to 2 THz - Output power: > 10 mW ( 10 dBm ) - Gain: 10 to 20 dB. The project is in the middle of its duration. Design and simulations have shown that these targets can be met with a proper device configuration and careful optimization of the different parts of the amplifier. Two parallel schemes will be employed for amplifier realisation: THz Drive Signal Amplifier and Optically Modulated Beam THz Amplifier.

A Feature Selection Strategy for the Development of a New Drug Sensing System

In order to efficiently detect four drug precursor molecules in presence of interfering species and background air, using a EC-QCLPAS sensor operating in the mid-infrared region, a complex strategy of spectral response simulation has been developed. In this context, spectra of gases from literature databases have been collected, denoised by means of the Wavelet Transform and mixed together according to a concentration matrix, which was specifically designed to represent a comprehensive combination of possible realistic cases. To scale database spectra to the appropriate concentration levels, an ad-hoc algorithm based on a sigmoidal transfer function has been used. In this way the baseline shape and intensity is preserved. Afterwards, a preliminary wavelength selection has been carried out to exclude noisy regions. The optimal range has finally been defined by maximizing the classification efficiency for all the target gases by means of Partial Least Squares-Discriminant Analysis.

Toward a Compact Instrument for Detecting Drug Precursors in Different Environments

Law enforcement agencies world-wide are keenly aware that chemical control is a crucial element to monitor the manufacture and distribution of illegal narcotics and synthetic substances. For this purpose components able to perform chemical identifications in contexts such as custom offices are needed, where inspection of trucks, cars, containers, as well as people and baggage, is required.

Antenna-coupled heterostructure field effect transistors for integrated terahertz heterodyne mixers

We present the realization of high electron mobility transistors on GaN-heterostructures usable for mixing and rectification in the THz range. Device fabrication is fully compatible with industrial processes employed for millimetre wave integrated circuits. On-chip, integrated, polarization-sensitive, planar antennas were designed to allow selective coupling of THz radiation to the three terminals of field effect transistors in order to explore different mixing schemes for frequencies well above the cutoff frequency for amplification. The polarization dependence of the spectral response in the 0.18-0.40 THz range clearly demonstrated the possible use as integrated heterodyne mixers.

Silicon-organic hybrid fabrication platform for integrated circuits

The combination of CMOS compatible Silicon-On-Insulator (SOI) fabrication technology with organic cover materials constitutes the Silicon-Organic Hybrid (SOH) fabrication platform, which shows innovative functionality for the making of integrated optical circuits. We report on experimental demonstrations of essential building blocks for transceivers, while relying only on well-known SOI processing steps and simple post processing of the organic materials.

Coupling of lithium niobate disk resonators to integrated waveguides

Whispering gallery mode (WGM) disk resonators fabricated in single crystals can have high Q factors within their transparency bandwidth and may have application both in fundamental and applied optics. Lithium niobate (LN) resonators thanks to their electro-optical properties may be used in particular as tunable filters, modulators, and delay lines. A critical step toward the actual application of these devices is the implementation of a robust and efficient coupling system. High index prisms are typically used for this purpose. In this work we demonstrate coupling to high-Q WGM LN disks from an integrated optical LN waveguide. The waveguides are made by proton exchange in X-cut LN. The disks with diameters of about 5 mm and thickness of 1 mm are made from commercial Z-cut LN wafers by core drilling a cylinder and thereafter polishing the edges into a spheroidal profile. Both resonance linewidth and cavity photon lifetime measurements were performed to calculate the Q factor of the resonator, which is in excess of 108.

A new optical method for a fast and simple detection of ephedrine

In this work we describe the synthesis of a new ephedrine derivative with a carbon linker featuring an amino reactive group, and its conjugation to the glutamine binding protein (GlnBP) from E. coli as a carrier protein for the production of polyclonal antibodies in rabbits against ephedrine. Proof-of-principle results that an efficient SPR-based indirect competitive immunoassay for the detection and quantification of ephedrine are presented. The detection limit of this assay was found to be about 33ng/ml.