In this review paper some recent advances on optical sensors based on photonic crystal fibres are reported. The different strategies successfully applied in order to obtain feasible and reliable monitoring systems in several application fields, including medicine, biology, environment sustainability, communications systems are highlighted. Emphasis is given to the exploitation of integrated systems and/or single elements based on photonic crystal fibers employing Bragg gratings (FBGs), long period gratings (LPGs), interferometers, plasmon propagation, off-set spliced fibers, evanescent field and hollow core geometries. Examples of recent optical fiber sensors for the measurement of strain, temperature, displacement, air flow, pressure, liquid-level, magnetic field, and hydrocarbon detection are briefly described.

In this work, the inverted micro-Stereolithography (SLA) is used to show the potential of such additive manufacturing (AM) technology at prototyping super-shaped dielectric resonator antennas (S-DRAs) rapidly and accurately. The S-DRAs, which exhibit 3D complex geometries, were designed to operate at 3.5 GHz, suitable for the assessment of 5G communications in the mid band. Initially, a cross-starred-shaped S-DRA was designed and manufactured via the inverted micro-SLA by means of a photopolymer resin as material. As no information about the used material was available from literature and supplier, the dielectric properties of the photopolymer resin were characterized. Moreover, in the view of challenging further the SLA capability, several prototypes, based on the cross star shaped geometry but exhibiting a twist of variable angles along the longitudinal axis, were fabricated and tested. In order to compare the antennas performance in relation to the material volume and sizes, rectangular and cylindrical DRAs were also realized using same material and technology. Scattering parameter S11, gain, bandwidth (BW), efficiency and co- and cross-polarization of all antennas were measured. The experimental results showed that twisted S-DRAs exhibit same performance of the basic cross-starred-shaped antenna, due to the invariance to symmetry of the basic Gielis geometry. The measured gain is about 2.5 dB over a range of 1 GHz in the frequency range of interest; the BW measured for all S-DRAs is about 10%, whereas the efficiency is about 80% at 3.5 GHz. Finally, better performance in terms of bandwidth is shown by the S-DRAs, considering their dramatic volume reduction (~85%) compared to classic rectangular and cylindrical DRAs and other DRA examples already reported in the state of the art.

A review on the recent progress in modeling and fabrication of medium infrared (Mid-IR) fiber lasers is reported. The main objective is to illustrate some recent examples of continuous wave optical sources at wavelengths longer than those commonly employed in telecom applications and allowing high beam quality. A small number of Mid-IR lasers, among the large variety of schemes, glasses, dopants and pumping schemes reported in literature, is selected on the basis of their slope efficiency and threshold pump power. In particular, tellurite, fluoride and chalcogenide fiber lasers are considered. More details are given with reference to the novel pumping schemes.

In this paper, we numerically and experimentally demonstrate that few-layer Chemical Vapour Deposition graphene can be employed for the fabrication of fully optical transparent antennas for microwave applications. We show that planar graphene-based antennas, having a size of tens of square centimeters, can achieve relatively high gain over a wide operating bandwidth (>3.5 GHz) simultaneously covering the GPS, WiFi, Bluetooth, and 5G bands. The measured 3D radiation patterns show dipole-, quadruple-, and hexapole-behavior. These findings open up routes for the realization of innovative devices where “invisible and hidden” antennas could be integrated in smart windows or photovoltaic systems, fostering configurations for camouflage, and communications systems. Furthermore, the possibility to handle different radiation patterns could allow the engineering of complex systems such as antenna arrays devoted to beam-steering, beam-forming, and healthcare applications. Finally, combining graphene transparency and flexibility could also pave the way for the realization of wearable devices, demanding invisibility, which operate on the surface of the human body or can be integrated in transparent devices (for example, in contact lenses) reducing their invasiveness.

A time-dependent numerical model of a dysprosiumdoped ZBLAN glass fiber is developed in order to design a pulsed laser emitting at about 3μm wavelength, by employing an in-band pumping scheme. A number of design parameters are changed to optimize the laser performance. Gain-switching regime with an output signal peak power close to 59W and a full width at half maximum (FWHM) pulse duration shorter than 184 ns is simulated for a fiber with dopant concentration of 2000 ppm, by employing a pulsed input pump with a peak power of 5W and a repetition rate of 100 kHz at the wavelength of 2.8 μm. These characteristics are very promising and theoretically predict the feasibility of a laser which can find application in many areas such as chemical, biological and environmental monitoring.