Search results for "photonics"
showing 10 items of 802 documents
BEFORE THE EARTHQUAKE: RECONSTRUCTION AND PRESENTATION OF LOST SITES AND BUILDINGS
2021
Abstract. The paper presents the results of a research aiming at proving the efficacy of perspective restitution from photos for the reconstruction of buildings and sites that disappeared in the past century. The case study is the town of Messina, sited at the north-eastern corner of Sicily (Italy), facing the homonymous strait that divides Sicily from the Italian peninsula; in 1908 Messina and Reggio Calabria, at the opposite side of the strait, were levelled to the ground by a powerful earthquake, followed by a tsunami.No building or monument survived the destruction: a new town with the same name took the site of Messina. Except for few strongly reshaped buildings, the memory of the stre…
EXPLORING DESIS FOR INLAND WATER QUALITY IN SPANISH RESERVOIRS
2022
Abstract. In a first approximation to the use of hyperspectral DESIS data to ocean colour applications in inland waters, we present here a comparison of the DESIS vs. MSI spectra from two reservoirs located in the province of Valencia. Benagerber and Tous are two small, oligo-mesotrophic reservoirs in need of constant water quality monitoring. These preliminary results have shown us the advantages and limitations of DESIS imagery for these types of dark and small lakes, but also pointed out the need for a specific over water atmospheric correction, as well as further understanding of the band combinations that can lead to accurate water quality parameter estimations.
A CASE STUDY OF THE APPLICATION OF HAND-HELD MOBILE LASER SCANNING IN THE PLANNING OF AN ITALIAN FOREST (ALPE DI CATENAIA, TUSCANY)
2021
Abstract. Precision forestry is becoming a key sector for forest planning because it allows complex analyses of forest data to be carried out simply and economically. It contributes to the integration between technicians and operators in the sector by guaranteeing the transparency of the forest management operations (Corona et al., 2017). In the context of the progressive development of technology, we investigated the feasibility of using the hand-held mobile laser scanner (HMLS) system in different types of forest sites and comparison of the characteristics of individual trees (tree height, diameters at breast height) with traditional surveys, applied with the aim to validate the performan…
ARCHITECTURAL SURVEY TECHNIQUES FOR DEGRADATION DIAGNOSTICS. AN APPLICATION FOR THE CULTURAL HERITAGE
2021
Abstract. The great technological development in recent years in the field of architectural survey has made possible increasingly expeditious and less invasive investigations with the aim of acquiring a series of data related to the asset and fundamental for the protection of cultural heritage. In addition, the synergy between the various techniques represents an added value able, not only, to fill possible gaps and lacks arising from application limits of the instruments, but also to enhance the peculiarities of the same. This paper presents an integrated survey activity (range-based, image-based and IR thermography techniques) aimed at applying the combination and collaboration of multipl…
Radiation tolerant fiber Bragg gratings for high temperature monitoring at MGy dose levels
2014
International audience; We report a method for fabricating fiber Bragg gratings (FBG) resistant to very severe environments mixing high radiation doses (up to 3 MGy) and high temperatures (up to 230 degrees C). Such FBGs have been written in two types of radiation resistant optical fibers (pure-silica and fluorine-doped cores) by exposures to a 800 nm femtosecond IR laser at power exceeding 500 mW and then subjected to a thermal annealing treatment of 15 min at 750 degrees C. Under radiation, our study reveals that the radiation induced Bragg wavelength shift (BWS) at a 3 MGy dose is strongly reduced compared to responses of FBGs written with nonoptimized conditions. The BWS remains lower t…
Detuning effects in STIRAP processes in the presence of quantum noise
2011
The Stimulated Raman adiabatic passage (STIRAP) in three-state systems in the presence of quantum noise is considered. A comparison is made between different models, one based on a phenomenological introduction of decays, one traceable back to a microscopic description of the system-environment interaction. Effects related, to off-resonance in the coupling between the involved states are considered.
EFFECTS OF THE MULTIPLE INTERNAL REFLECTION AND SAMPLE THICKNESS CHANGES ON DETERMINATION OF ELECTRO-OPTIC COEFFICIENT VALUES OF A POLYMER FILM
2012
New nonlinear optical (NLO) active organic materials are appealing candidates for optoelectronic and photonic technologies. For the evaluation of new NLO polymer materials for applicability in the mentioned technologies, the most important criteria are their electro-optic (EO) coefficients. We have implemented the Mach–Zehnder interferometric (MZI) method for the determination of EO coefficients of thin organic films. Despite the fact that other multiple optical methods for the determination of thin film EO coefficients are known, the MZI method has been chosen because this particular technique has high sensitivity to phase and intensity modulations in the sample arm of an interferometer an…
Tuneable multicoloured patterns from photonic cross-communication between cholesteric liquid crystal droplets
2014
Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications.
Emission of Rhodamine B in PMMA opals for luminescent solar concentrators
2012
In conventional luminescent solar concentrators (LSC) incident light is absorbed by luminophores and emitted isotropically. Most of the emitted light is trapped inside the LSC by total internal reflection and guided to solar cells at the edges. Light emitted towards the surfaces, however, is lost in the escape cone. Furthermore, when the luminophore emits light in its absorption range, light is lost due to reabsorption. To overcome these losses, we embed the luminescent material in photonic structures to influence the emission characteristics. Directional and spectral redistribution of emission is supposed to enhance the light guiding in LSCs and reduce reabsorption losses. For this purpose…
Direct Bragg grating writing in a hybrid PDMS/silica photonic crystal fiber
2011
Infiltration of materials into the air holes of the PCFs can potentially manipulate their optical properties creating a new category of fibers termed as hybrid PCFs [1] and many devices based on hybrid PCFs have been developed [2–5]. Recently, a hybrid PCF with poly-dimethylsiloxane (PDMS) elastomer inclusions has been demonstrated [6]. PDMS is widely used in the area of photonics and optofluidics. It is highly transparent with a refractive index ∼1.41, conserving the total internal reflection guiding mechanism of the hybrid PCF. When PDMS is irradiated with UV light its refractive index increases [7]. In this paper we present the first example of a Bragg grating directly written using UV l…