F. De Leonardis

Modeling and design of a novel miniaturized integrated optical sensor for gyroscope systems

In this paper, we report, for the first time to our knowledge, the modeling and the design of a miniaturized integrated optical sensor, based on a multiple quantum-well (MQW) microring laser, to be used in gyroscope systems. The device can be fully integrated on a single chip and used either in low (e.g., vehicles for land transport) or high (e.g., ships, airplanes, spaceborne platforms) sensitivity navigation systems. The model includes the influence of some physical effects, such as quantum noise, lock in, thermal effect, and sidewall roughness-induced losses. Very good performance has been obtained in terms of gyro quantum limit, operating regions of detectable velocity, thermal range of operation, and power consumption. The proposed architecture shows significant manifold advantages with respect to other existing optical solutions: no polarization-induced noise, no use of frequency-locking techniques, negligible bending losses, high cavity quality factor, complete evaluation of the rotation speed, predictable thermal variation of the gyro scale factor, and very high dynamic range.

Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and √ s = 8 TeV by TOTEM

Abstract 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 | t | 0.2 GeV 2 with a significance greater than 7 σ . Two extended parametrisations, with quadratic and cubic polynomials in the exponent, are shown to be well compatible with the data. Using them for the differential cross-section extrapolation to t = 0 , and further applying the optical theorem, yields total cross-section estimates of ( 101.5 ± 2.1 ) mb and ( 101.9 ± 2.1 ) mb , respectively, in agreement with previous TOTEM measurements.

Modeling and design of a novel high-sensitivity electric field silicon-on-insulator sensor based on a whispering-gallery-mode resonator

In this paper, we present the modeling and design of a new approach to a miniaturized electric field sensor, based on a whispering-gallery-mode resonator coupled with a Fabry-Perot cavity in silicon-on-insulator technology. The sensing element consists of a metal oxide semiconductor capacitor, optimized to achieve high electrical sensitivity and low optical losses. The theoretical model of the whole sensor architecture includes the influence of all electrical and optical parameters, including thin oxide thickness, silicon and polysilicon doping concentration, optical losses due to propagation, absorption and scattering, wavelength and amplitude characteristics of the architecture, charge accumulation effects in the capacitor, and thermal effects. The very high sensitivity of this device, demonstrated by simulations, is due to the simultaneous influence of the two coupled resonators and the metal oxide semiconductor structure.

Modeling and Performance of a Guided-Wave Optical Angular-Velocity Sensor Based on Raman Effect in SOI

In this paper, we report, for the first time to the best of our knowledge, the detailed modeling and design of a guided-wave optical angular-velocity sensor based on Raman amplification in a silicon-on-insulator resonant cavity. Theoretical results for continuous-wave Raman laser emission are compared with experiments in the literature, demonstrating very good agreement. The model includes the influence of a number of physical effects on the propagation of both counterpropagating pumps and Stokes waves, such as stimulated Raman scattering, two- photon absorption, free-carrier dispersion, self- and cross-phase- modulation induced by the Kerr effect, and the lock-in effect. Investigation of optical dithering features by intracavity phase modulation is also presented. Performance is derived to optimize the device sensitivity for both medical, robotics, automotive, and entertainment gyro applications.

Wavelength Interrogator for Optical Sensors Based on a Novel Thermo-Optic Tunable Filter in SOI

In this paper, the wavelength interrogation of optical sensors by novel thermo-optic tunable filters with multiple partially reflected slanted mirrors in silicon-on-insulator (SOI) technology is presented. The tunable filter is used both for tunable band selection of broadband light source interrogating the optical sensors, as well as for precise detection of interrogation optical wavelength. New interrogator design is numerically studied by 2-D finite-difference time-domain and finite-element method for a compact structure. The investigation demonstrates the performance of an interrogator on SOI, 1 cm long, having about 1 pm wavelength resolution and 1 ms scanning over 40 nm range at 1550 nm, with an operation power of about 16 mW.

Ultrafast Raman Pulses in SOI Optical Waveguides for Nonlinear Signal Processing

Nonlinear optical signal processing by ultrafast Raman pulses in silicon-on-insulator rib waveguides is theoretically investigated in this paper. Stimulated Raman scattering, two-photon absorption, free carrier dispersion, self- and cross-phase-modulation-induced by Kerr effect, walk-off, group velocity dispersion, pump depletion, self-steeping, and polarization coupling are taken into account by a very general modeling under subpicosecond regime. Raman amplification, multiwavelength conversion, soliton formation, and pulse compression are presented and discussed. Finally, some simulations for generation of higher order Stokes pulses in mid-IR region are given.

Efficient Wavelength Conversion in Optimized SOI Waveguides Via Pulsed Four-Wave Mixing

In this paper a detailed investigation of Four Wave Mixing in Silicon-on-Insulator optical waveguides is carried out under pulsed regime. A number of nonlinear effects, such as two photon absorption, free carrier absorption, self and cross phase modulation are considered in the analysis, as well as walk-off, group velocity dispersion and third order dispersion. The interesting influence of pulsewidth on the space-time evolution of both signal and idler pulses is presented. Optimized phase matching conditions are found to achieve very efficient wavelength conversion in parametric amplification, considering both degenerate and non degenerate processes. Finally, waveguide parameters are optimized for rib and membrane SOI waveguides.

Fiber Bragg grating ring resonators under rotation for angular velocity sensing

In this paper we investigate the possibility of using hybrid resonators based on fiber Bragg grating ring resonators (FBGRRs) and π-shifted FBGRRs (i.e., defective FBGRRs) as rotation sensitive elements for gyroscope applications. In particular, we model the conventional fiber Bragg grating (FBG) with the coupled mode theory by taking into account how the Sagnac effect, induced by the rotation, modifies the eigenvalues, the photonic band gap, and the spectral response of the FBG. Then, on the basis of the FBG model under rotation conditions, the spectral responses of the FBGRR and π-FBGRR have been evaluated, confirming that the Sagnac effect manifests itself with a spectral shift of the eigensolutions. This physical investigation can be exploited for opening new ways in the optical gyroscope platforms.

Enhanced spectral response of π-phase shifted fiber Bragg gratings in closed-loop configuration

The transmission spectrum of a ring resonator enclosing a π-phase shifted fiber Bragg grating (π-FBG) shows a spectral feature at the Bragg wavelength that is much sharper than resonance of the π-FBG alone, and that can be detected with a simple integrated cavity output technique. Hence, the resolution of any sensor based on the fitting of the π-FBG spectral profile can be largely improved by the proposed configuration at no additional fabrication costs and without altering the sensor robustness. A theoretical model shows that the resolution enhancement attainable in the proposed closed-loop geometry depends on the quality factor of the ring resonator. With a commercial grating in a medium-finesse ring, a spectral feature 12 times sharper than the π-FBG resonance is experimentally demonstrated. A larger enhancement is expected in a low-loss, polarization maintaining setup.

Sensitivity analysis of rib waveguides for integrated optical sensors

Sensitivity of rib waveguides designed for evanescent-wave integrated optical sensors is investigated by an improved analytic approach based on Effective Index Method. Proposed procedure is applied to rib guiding structures in different CMOS-compatible technologies and rigorous results obtained by Finite Element Method are used for comparison. Agreement is demonstrated to be good even for high index contrast waveguides.