This paper is an overview of current gyroscopes and their roles based on their applications. The considered gyroscopes include mechanical gyroscopes and optical gyroscopes at macro- and micro-scale. ...Particularly, gyroscope technologies commercially available, such as Mechanical Gyroscopes, silicon MEMS Gyroscopes, Ring Laser Gyroscopes (RLGs) and Fiber-Optic Gyroscopes (FOGs), are discussed. The main features of these gyroscopes and their technologies are linked to their performance.
This theoretical modeling and simulation paper presents designs and projected performance of non-volatile broadband on-chip 1 × 2 and 2 × 2 electro-optical switches operating in the telecommunication ...C-band and based on the silicon-on-insulator technological platform. These optical switches consist of an asymmetric two-waveguide directional coupler and a symmetric three-waveguide directional coupler, in which the optical phase change material Ge 2 Sb 2 Se 4 Te 1 (GSST) is the top cladding layer for one of the silicon strip waveguides. Reversible crossbar switching is attained by the amorphous (Am) to crystalline (Cr) and Cr-to-Am phase transitions in the GSST induced by heating the GSST in contact with an indium tin oxide (ITO) microstrip through Joule heating. We examined device performance in terms of mid-band insertion loss (IL), crosstalk (CT), and 0.3-dB IL bandwidth (BW). The 2 × 2 results were IL = -0.018 dB, CT <; 31.3 dB, and BW = 58 nm for the coupling length Lc of 15.4 μm, and IL = 0.046 dB, CT <; 38.1 dB, and BW = 70 nm for the coupling length Lc of 17.4 μm. Simulations of the 1 × 2 devices at 16.7-μm Lc revealed that IL = 0.083 dB and CT <; 12.8 dB along with an expanded BW of 95 nm. Thermal simulations showed that a 5-V pulse train applied to 10 19 -cm -3 doped ITO would produce crystallization; however, the process of amorphization required a 24-V pulse of 2.9-μs duration to raise the GSST temperature above the melting temperature of 900 K.
Abstract
Colorimetric and electrochemical (bio)sensors are commonly employed in wearable platforms for sweat monitoring; nevertheless, they suffer from low stability of the sensitive element. In ...contrast, mass-(bio)sensors are commonly used for analyte detection at laboratory level only, due to their rigidity. To overcome these limitations, a flexible mass-(bio)sensor for sweat pH sensing is proposed. The device exploits the flexibility of piezoelectric AlN membranes fabricated on a polyimide substrate combined to the sensitive properties of a pH responsive hydrogel based on PEG-DA/CEA molecules. A resonant frequency shift is recorded due to the hydrogel swelling/shrinking at several pH. Our device shows a responsivity of about 12 kHz/pH unit when measured in artificial sweat formulation in the pH range 3–8. To the best of our knowledge, this is the first time that hydrogel mass variations are sensed by a flexible resonator, fostering the development of a new class of compliant and wearable devices.
Recent advances in integrated photonic sensors Passaro, Vittorio M N; de Tullio, Corrado; Troia, Benedetto ...
Sensors (Basel, Switzerland),
11/2012, Letnik:
12, Številka:
11
Journal Article, Book Review
Recenzirano
Odprti dostop
Nowadays, optical devices and circuits are becoming fundamental components in several application fields such as medicine, biotechnology, automotive, aerospace, food quality control, chemistry, to ...name a few. In this context, we propose a complete review on integrated photonic sensors, with specific attention to materials, technologies, architectures and optical sensing principles. To this aim, sensing principles commonly used in optical detection are presented, focusing on sensor performance features such as sensitivity, selectivity and rangeability. Since photonic sensors provide substantial benefits regarding compatibility with CMOS technology and integration on chips characterized by micrometric footprints, design and optimization strategies of photonic devices are widely discussed for sensing applications. In addition, several numerical methods employed in photonic circuits and devices, simulations and design are presented, focusing on their advantages and drawbacks. Finally, recent developments in the field of photonic sensing are reviewed, considering advanced photonic sensor architectures based on linear and non-linear optical effects and to be employed in chemical/biochemical sensing, angular velocity and electric field detection.
The ion-sensitive field-effect transistor is a well-established electronic device typically used for pH sensing. The usability of the device for detecting other biomarkers in easily accessible ...biologic fluids, with dynamic range and resolution compliant with high-impact medical applications, is still an open research topic. Here, we report on an ion-sensitive field-effect transistor that is able to detect the presence of chloride ions in sweat with a limit-of-detection of 0.004 mol/m
. The device is intended for supporting the diagnosis of cystic fibrosis, and it has been designed considering two adjacent domains, namely the semiconductor and the electrolyte containing the ions of interest, by using the finite element method, which models the experimental reality with great accuracy. According to the literature explaining the chemical reactions that take place between the gate oxide and the electrolytic solution, we have concluded that anions directly interact with the hydroxyl surface groups and replace protons previously adsorbed from the surface. The achieved results confirm that such a device can be used to replace the traditional sweat test in the diagnosis and management of cystic fibrosis. In fact, the reported technology is easy-to-use, cost-effective, and non-invasive, leading to earlier and more accurate diagnoses.
Non-Hermitian sensors have been widely studied for the enhanced response of their eigenvalues in the proximity of exceptional points. However, it has been shown that noise is enhanced in the same way ...as sensitivity, thus vanishing the advantages of the exceptional point. Recently, the idea of measuring the frequency splitting of transmission peaks of a non-lasing PT-symmetric sensor has shown the possibility of increasing the signal-to-noise ratio of a sensor close to the so called "transmission peak degeneracy", with respect to an operating condition away from it. Here we analyze a non-Hermitian optical gyroscope, demonstrating that also anti-PT-symmetric Hamiltonians show an enhanced transmission peaks frequency splitting in the proximity of the transmission peak degeneracy. We also perform an analysis on noise and uncertainties and introduce new figures of merit to compare the proposed anti-PT-symmetric sensor with a classical resonant optical gyroscope. When the uncertainties due to fluctuations of parameters are negligible with respect to the uncertainties due to amplitude noise, the non-Hermitian sensor working at the transmission peak degeneracy is demonstrated to operate better than a classical resonant gyroscope in terms of signal-to-noise ratio.
Vascular grafts are artificial conduits properly designed to substitute a diseased blood vessel. However prosthetic fail can occur without premonitory symptoms. Continuous monitoring of the system ...can provide useful information not only to extend the graft's life but also to optimize the patient's therapy. In this respect, various techniques have been used, but all of them affect the mechanical properties of the artificial vessel. To overcome these drawbacks, an ultrathin and flexible smart patch based on piezoelectric Aluminum Nitride (AlN) integrated on the extraluminal surface of the prosthesis is presented. The sensor can be conformally wrapped around the external surface of the prosthesis. Its design, mechanical properties and dimensions are properly characterized and optimized in order to maximize performances and to avoid any interference with the graft structure during its activity. The sensorized graft is tested in vitro using a pulsatile recirculating flow system that mimics the physiological and pathological blood flow conditions. In this way, the ability of the device to measure real-time variations of the hemodynamics parameters has been tested. The obtained high sensitivity of 0.012 V Pa
m
, joint to the inherent biocompatibility and non-toxicity of the used materials, demonstrates that the device can successfully monitor the prosthesis functioning under different conditions, opening new perspectives for real-time vascular graft surveillance.
We investigate graphene-based optical absorbers that exploit guided mode resonances (GMRs) attaining theoretically perfect absorption over a bandwidth of few nanometers (over the visible and ...near-infrared ranges) with a 40-fold increase of the monolayer graphene absorption. We analyze the influence of the geometrical parameters on the absorption rate and the angular response for oblique incidence. Finally, we experimentally verify the theoretical predictions in a one-dimensional, dielectric grating by placing it near either a metallic or a dielectric mirror, thus achieving very good agreement between numerical predictions and experimental results.
Non-Hermitian photonics has attracted increasing attention especially for sensing applications. Two coupled optical systems, designed to work at the "exceptional point", exhibit a strong spectral ...response to perturbations. Due to the enhanced sensitivity of exceptional points, they have been usually suggested as perfect candidates for high resolution sensing. The drawback of these configurations is their undesired sensitivity also to external fluctuations and noise that could eliminate the advantages of exceptional points. Recently, the concept of exceptional surface has been proposed to overcome this problem. In particular, coupling two counterpropagating modes in the same structure prevents differential noise in distinct cavities from affecting the exceptional-point condition. In this work we present a new configuration based on exceptional surfaces to design an optical accelerometer. The strong spectral response guaranteed by exceptional surfaces is used here to demonstrate the enhancement of the sensitivity of a Bragg grating-based optical accelerometer, reaching a value of 3 nm/g at 0.5 g.
This theoretical simulation paper presents designs and projected performance of ∼1550-nm silicon-on-insulator (SOI) and ∼2000-nm Ge-on-Si-on-nitride and Ge-on-nitride 2×2 optical crossbar switches ...based upon a three-waveguide coupler in which the central waveguide is a nanobeam actuated by the thermo-optical (TO) effect. A TO heater stripe is located atop the central nanobeam. To implement accurate and realistic designs, the 3D finite difference time domain approach was employed. The metrics of crossbar switching, insertion loss (IL) and crosstalk (CT) were evaluated for choices of 3-waveguide structure parameters and TO-induced index changes. The predicted ILs and CTs were excellent, enabling the designed devices to be considered as fundamental building blocks in wavelength-division-multiplexed cross-connect (WXC) applications. Proposed here are compact, nonblocking space-and-wavelength routing switches to be constructed in a monolithic, industry-standard SOI chip (and in Ge-on-SON and GON chips). Specifics are given for realizing 16 × 16 × Mλ WXCs as well as reconfigurable, multi-resonant, programmable hexagonal and diamond meshes.
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