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The TOTEM experiment has made a precise measurement of the elastic proton–proton differential cross-section at the centre-of-mass energy s=8 TeV based on a high-statistics data sample obtained with the β⁎=90 m optics. Both the statistical and systematic uncertainties remain below 1%, except for the t -independent contribution from the overall normalisation. This unprecedented precision allows to exclude a purely exponential differential cross-section in the range of four-momentum transfer squared 0.027

The improvement of cascaded second-order nonlinearity h (2) : h (2) effects in a quasiphase-matching (QPM) structure constituted by a periodically poled lithium niobate (PPLN) waveguide is obtained utilizing an integrated metal mirror placed after an additional waveguide segment. The resulting double-pass device, which can be employed for wavelength conversion, is refined by choosing the most advantageous length of the segment waveguide and by taking into account both the thermal and electro-optic effects. In the ideal case of perfect QPM, for a grating length z G4 = 25 mm, the calculated double-pass maximum efficiency is eta dp = 22.86 dB, which is almost the triple of eta sp = 8.20 dB, calculated for the single-pass version (without mirror) for the same value of the pump and signal powers.

The paper is a review on modelling and experimental results regarding microsphere resonators. The applications of the whispering-gallery-modes (WGMs) resonances in conventional glass microspheres to perform chemical spectroscopy, biomedical sensing, low threshold lasing are recalled. The behaviour of silica microsphere coated via silica hafnia 70SiO2-30HfO2 and activated with 0.3% mol Er3+ for NIR operation is described. The feasibility of amplifying systems, operating in Mid-IR wavelength and based on Er3+-doped Ga5Ge20Sb10S65 chalcogenide microspheres coupled to tapered a fiber is discussed. The investigation has been performed via a dedicated 3D numerical model, based on the coupled mode theory and solving the rate equations. The code includes the transitions among the erbium energy levels, the amplified spontaneous emission and the most important secondary transitions pertaining to the ion-ion interactions. The model follows the particle swarm optimization (PSO) approach, allowing both the amplifying system optimization and to perform the microsphere glass spectroscopy.

Two original computer codes for the design of rare-earth-doped dielectric microspheres have been ad hoc developed. The former code is based on a finite-difference time-domain algorithm, suitably extended to model the amplification of the whispering-gallery modes propagating into rare-earth-doped microspheres. It takes into account the wavelength dispersion of the microsphere refractive index and the polarization obtained via the density matrix model. The design of an Er3+-doped silica microsphere coupled with a tapered silica fiber is reported. The latter home-made computer code solves the rate equations and the power propagation equations in frequency domain. The results are in excellent agreement.

Paper reports recent advances in optical nanomaterials, planar microcavity, and spherical microresonators. Bottom-up fabrication and optical assessment of Er3+-activated SiO2-HfO2 waveguide glass ceramic is presented. Concerning confined structures, fabrication by radio-frequency sputtering (RFS) technique of an Er3+-activated microcavity with a quality factor of 171 using oxide-based dielectric materials is demonstrated and fabrication and spectroscopic assessment of Er 3+-activated silica microspheres is presented.

A genetic-algorithm (GA) procedure has been ad hoc implemented to obtain a tool for both design and characterization of rare-earth-doped optical amplifiers and lasers. In particular, the routines performing the selection, crossover, mutation, and elitism operations have been written with the aim to investigate the optimal erbium-doped amplifier or laser configuration. Conversely, the GA can be employed in device characterization to identify those parameters of the erbium-energy-level transitions, which are not directly measurable, e.g., the cross-relaxation and up-conversion coefficients. The GA appears intriguing because of its efficiency and versatility. Its operation strategy is noticeably for the capability to identify solutions in complex multidimensional spaces. In this paper, the GA application for modeling and characterizing erbium-doped photonic-crystal-fiber amplifiers is described in detail.

We report on the design of highly reflecting two-dimensional photonic crystal (2D-PC) mirrors, which can be inte- grated in a short InGaAs QWs laser source, operating around 970 nm. These mirrors consist of a triangular lattice of air holes into the GaAs slab, whose geometrical parameters have been calculated by the effective index method and 2D plane wave expansion method. A 2D finite-difference time-domain (2D-FDTD) model has also been used in order to evaluate the transmission and reflection characteristics of 2D-PC front and back mirrors of the in-plane laser. Finally, a detailed description of the nanotechnology processes necessary for the fabrication of ultra-compact in-plane laser is shown.

This paper describes the optical properties of praseodymium-doped chalcogenide (GeS 2 –Ga 2 S 3 –CsI) thin films deposited by the pulsed laser deposition (PLD) technique using XeCl (308 nm) and KrF (248 nm) excimer lasers. Optical transmission and reflection spectra, at normal incidence, were recorded in the 200–2500 nm spectral region. The optical constants (refractive index n and extinction coefficient k ) versus wavelength, as well as the film thickness, were calculated from these spectra and a computer code. The waveguiding properties of the deposited films were investigated by the prism coupling technique (m-lines spectroscopy). The presence of praseodymium in the doped chalcogenide thin film was analysed by exciting the electrons to the 1 G 4 level and collecting the photoluminescence spectrum in the 1.335 μm region. Moreover, compositional, morphological and structural characteristics of the films were obtained by Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses.

SiO 2 (silica) and ITO (indium tin oxide) films, SiO 2 /ITO bilayers and multilayers and Pr 3+ -doped chalcogenide glass films were deposited by excimer laser (λ = 308, 248 and 193 nm) ablation. Dense, stoichiometric SiO 2 films, almost droplet-free and with low surface roughness (

Praseodymium-doped GeS 2 –Ga 2 S 3 –CsI thin films were prepared by the pulsed laser deposition (PLD) technique. We ablated chalcogenide glass, Pr 3+ -doped, targets in vacuum with XeCl laser pulses (308 nm). The films were deposited on microscope slide glass substrates at room temperature. Film characteristics were investigated by many different techniques. The deposited films were well adhesive to their substrates. They were plain without cracks or corrugations and with stoichiometric composition close to that of the target. Micro-sized droplets were detected on the surface of films. The spectrophotometric measurements of transmittance and reflectance allowed to determine the real and imaginary parts of complex refractive index vs. wavelength, as well as the film thickness, by using a computer code. The waveguide guiding properties of the films deposited were investigated by prism-coupling technique (m-lines spectroscopy).

A two-dimensional photonic crystal microcavity coupled with a waveguide is proposed to realise a high sensitive force sensor, designed on a GaAs membrane. A theoretical model is developed to evaluate the change of the refractive index induced by the application of the force onto a sensing surface. A linear calibration curve is obtained relating the resonant drop position to the applied force.

We propose the simulation and the fabrication of a photonic crystal (PhC) strain-sensitive structure, showing that the optical properties of photonic crystals can be used to realize sensing devices characterized by a high degree of compactness and good resolution. The force/pressure optical sensor has been realized by designing a bulk GaAs/AlGaAs photonic crystal microcavity operating in the wavelength range 1300-1400 nm. The simulations show that the resonant wavelength of the mode localized in the microcavity shifts its spectral position following a linear behaviour when a pressure ranging between 0.25 Gpa and 5 GPa is applied, thus allowing the possibility to achieve pressure resolution of 5.82 nm/GPa. High-resolution electron beam lithography technique followed by inductively coupled plasma process were used to transfer the designed geometry on the sample. (c) 2007 Elsevier B.V. All rights reserved.

We report on the design of highly reflecting two-dimensional photonic crystal (2D-PC) mirrors, which can be integrated in a short InGaAs QWs laser source, operating around 970 nm. These mirrors consist of a triangular lattice of air holes into the GaAs slab, whose geometrical parameters have been calculated by the effective index method and 2D plane wave expansion method. A 2D finite-difference time-domain (2D-FDTD) model has also been used in order to evaluate the transmission and reflection characteristics of 2D-PC front and back mirrors of the in-plane laser. Finally, a detailed description of the nanotechnology processes necessary for the fabrication of ultra-compact in-plane laser is shown.