A micro-opto-mechanical oscillator in a droplet

Un esperimento svolto presso la sezione di Napoli dell’Istituto Nazionale di Ottica (INO) del CNR ha mostrato la possibilità di eccitare onde di superficie su piccole gocce liquide per mezzo di un fascio luminoso. Il dispositivo così realizzato si comporta come un vero e proprio micro-oscillatore, costituito però interamente da liquido e mantenuto in forma sferica quasi perfetta dalla sola tensione superficiale.An experiment performed at the Naples Unit of the National Institute of Optics (INO) of the CNR, has shown the possibility to excite surface waves on tiny liquid droplets using a light beam. The resulting optical device serves as a micro-mechanical oscillator, entirely made of liquid with an almost perfect spherical shape due to natural surface tension

How ICTs Shape the Relationship Between the State and the Citizens: Exploring New Paradigms Between Civic Engagement and Social Innovation

The paper investigates the role of Information and Communication Technologies (ICTs) in enabling social innovation and civic engagement. The purpose is to advance a typology for better understanding whether such a phenomenon might contribute to a paradigmatic shift in the relationship between the governments or the administrations and citizens. This framework is set out is based on the review of recent literature on social innovation and ICTs, studying the relationships between government and citizens emerging from 41 cases. The analysis highlights how ICTs underpin innovation in civic engagement initiatives in two main ways: 1) by modernising existing processes and 2) by integrating new services

Absolute frequency measurement of molecular transitions by a direct link to a comb generated around 3-µm

A 3-microm continuous-wave difference-frequency source is directly referenced to a mid-infrared optical frequency comb synthesizer by measuring their beat-note signal by a fast HgCdTe detector. Absolute frequency metrology of molecular vibration spectra is demonstrated by locking the 3-microm coherent radiation to the nearest comb tooth and tuning the comb mode spacing across the Doppler-broadened absorption profile of a CH(4) ro-vibrational transition

Interrogation of fiber Bragg-grating resonators by polarization-spectroscopy laser-frequency locking.

We report on an optically-based technique that provides an efficient way to track static and dynamic strain by locking the frequency of a diode laser to a fiber Bragg-grating Fabry-Pérot cavity. For this purpose, a suitable optical frequency discriminator is generated exploiting the fiber natural birefringence and that resulting from the gratings inscription process. In our scheme, a polarization analyzer detects dispersive-shaped signals centered on the cavity resonances without need for additional optical elements in the resonator or any laser-modulation technique. This method prevents degradation of the resonator quality and maintains the configuration relatively simple, demonstrating static and dynamic mechanical sensing below the picostrain level

Excitation Mechanisms of Whispering Gallery Modes with Direct Light Scattering

AbstractIn optics, whispering gallery modes (WGMs) are modes of light that arise in cylindrically symmetric structures. Their intensity profile is strongly confined around the interface of the structure, and their Q‐factors are some of the highest ever measured with light. Here, the physical mechanisms governing the coupling of a tangential beam into a WGM of a microsphere are analytically demonstrated. For that, Mie theory and the symmetries of light are made use of. It is demonstrated that the coupling mechanism is not related to any evanescent tunnelling effect. Rather, it is shown that it has to do with the angular momentum matching between the available inner WGMs of the sphere and the angular momentum content of the incident beam. The model is valid for any homogeneous sphere, for any wavelength, and for any incident cylindrically symmetric beam, focused or not. It quantitatively predicts the optical coupling efficiency to the resonator for any tangential position of the incident beam. And it sketches four different regimes of interaction depending on the beam position with respect to the sphere, properly matching experimental resonance spectra observed with free‐space laser scattering

Investigating the resonance spectrum of optical frequency combs in fiber-optic cavities

We report a detailed theoretical and experimental study of fiberoptic cavities under broadband excitation by mode-locked laser combs. We calculate the effects of fiber dispersion on the cavity transmission. For any integer ratio between the comb repetition rate and cavity free spectral range, the theoretical resonant output spectrum exhibits a narrow group of resonant teeth, surrounded by minor, unevenly spaced resonances. Also, the central resonance can be rapidly and precisely tuned over the entire comb span by only acting on its repetition rate. Experimental observations are provided by a single-mode fiber ring and a telecom-wavelength comb laser. The resulting spectral pattern agrees very well with our theoretical prediction, allowing a thorough characterization of the cavity dispersion and opening new perspectives for comb spectroscopy in dielectric resonators. © 2013 Optical Society of America

Investigation of refractive index sensing based on Fano resonance in fiber Bragg grating ring resonators.

In this paper we theoretically investigate a ring resonant cavity obtained by closing on itself a pi-shifted fiber Bragg grating, to be used for refractive index sensing applications. Differently from a conventional pi-shifted fiber Bragg grating, the spectral structure of this cavity is characterized by an asymmetric splitting doublet composed by a right side resonance having an asymmetric Fano profile and a left side resonance having a symmetric Lorentzian profile. The right side resonance shows a narrower and sharper peak than all the other kinds of resonance achievable with both conventional ring resonators and pi-shifted fiber Bragg gratings. A reduction of the resonant linewidth with respect to a conventional pi-shifted Fiber Bragg grating and a fiber ring resonator, having the same physical parameters, is theoretically proved, achieving up to five orders of magnitude improvement with respect to the usual ring resonator. Due to these resonance features, the pi-shifted Bragg grating ring resonator results suitable for RI sensing applications requiring extremely narrow resonances for high resolution measurements. In particular, by assuming a refractive index sensing to detect the presence of sugar in water, the sensor can show a theoretical resolution better than 10(-9) RIU. (C)2015 Optical Society of Americ

Localized strain sensing with fiber Bragg-grating ring cavities

We report the theoretical description and the experimental demonstration of an optical resonator formed by inserting a Fiber Bragg Grating (FBG) in a closed fiber loop. The spectral characteristics of such a resonator strongly depend on the reflectivity of the FBG. In the wavelength region where the FBG reflectivity R is negligible, the system behaves like a conventional ring resonator. On the other hand, when R is not vanishing, a split-mode structure can be observed, associated to the degeneracy removal of two counterpropagating resonant modes. The magnitude of the mode splitting can be used to sense small variations of the FBG physical parameters, such as length, temperature or group index. An example of strain sensing with this setup is reported, showing that the mode splitting is sensitive to a mechanical strain applied to the FBG, while it is almost insensitive to a strain applied to any other point of the resonator. This peculiar feature allows to perform cavity-enhanced, local strain measurements with a reduced sensitivity to environmental perturbations, which represents an important improvement in the framework of the fiber-optic sensors. (C)2013 Optical Society of Americ

Novel laser-based techniques for monitoring of volcanoes

An overview of novel laser techniques suitable for volcanic monitoring, based on different kinds of infrared laser sources, is presented. Their main advantages and drawbacks are discussed focusing on the achievable sensitivity and precision levels in analysis of gaseous species. Some of the most recent experimental results obtained in laboratory development as well as in field tests of home-built laser spectrometers are reported. New perspectives in optical devices aimed at geochemical and geophysical applications are also considered

Health and nutrition studies related to cereal biodiversity: a participatory multi-actor literature review approach

Recently, a large and growing body of literature has investigated the health potential of different wheat species. In particular, a considerable number of studies dealing with nutritional aspects has grown up around the theme of the recovery of ancient wheat varieties (species that have remained unchanged over the last hundred years). According to several studies, indeed, ancient varieties present a healthier nutritional profile than modern ones. In the framework of the European project "CERERE, CEreal REnaissance in Rural Europe: embedding diversity in organic and low-input food systems", this paper aimed to review recent research on the issue of health and nutritional cereal systems by adopting an innovative and participatory multi-actor approach which involved practitioners along with researchers. The participatory approach is the main innovation and peculiarity of this literature review. Nevertheless, the review highlights the many positive effects derived from eating whole and ancient grains such as a significant reduction in the risk of chronic diseases such as cancer, cardiovascular disease, and also a more favorable long-term weight management and increase in satiety. This review may be considered as a fruitful starting point that integrates research results to foster current and future healthier and sustainable practices in cereal systems