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14 pages, 3679 KiB

Open AccessArticle

Optical Fibers Use in On-Chip Fabry–Pérot Refractometry to Achieve High Q-Factor: Modeling and Experimental Assessment

by Mohamed Abdelsalam Mansour, Alaa M. Ali, Frédéric Marty, Tarik Bourouina and Noha Gaber

Photonics 2024, 11(9), 852; https://doi.org/10.3390/photonics11090852 - 10 Sep 2024

Cited by 2 | Viewed by 1296

This paper investigates the integration of optical fibers into an on-chip Fabry–Pérot (FP) resonator to achieve high-quality (Q) factors, which is favorable in sensing applications. Initially designed for high-speed data transmission, optical fibers are now utilized in sensing applications because of their flexibility and sensitivity to optical phenomena. This article focuses on the role of single-mode fibers (SMF) and the geometry of different structures in enhancing light confinement within FP resonators. Two distinct on-chip designs utilizing SMFs are demonstrated, modeled, and experimentally evaluated. One achieves a Q-factor higher than 5200, demonstrating significant improvement in light confinement, while the other maximizes the spectral range between the resonant modes’ peaks, maximizing the sensing range through the wavelength shift. This is supported by visualized simulation and coupling efficiencies calculations for fundamental and higher-order modes for comprehensive analysis. Comparison with existing literature is also made, underscoring the advancements achieved by the presented approaches. The findings contribute to the development of microscale refractive index sensing applications, highlighting the vital role of optical fiber integration for high-performance sensing. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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13 pages, 18121 KiB

Open AccessArticle

Demonstration of a Transportable Fabry–Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes

by Clayton Forssén, Isak Silander, Johan Zakrisson, Eynas Amer, David Szabo, Thomas Bock, André Kussike, Tom Rubin, Domenico Mari, Stefano Pasqualin, Zaccaria Silvestri, Djilali Bentouati, Ove Axner and Martin Zelan

Sensors 2024, 24(1), 7; https://doi.org/10.3390/s24010007 - 19 Dec 2023

Cited by 2 | Viewed by 1358

Abstract

Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10–90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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19 pages, 26682 KiB

Open AccessArticle

The Short-Term Performances of Two Independent Gas Modulated Refractometers for Pressure Assessments

by Clayton Forssén, Isak Silander, Johan Zakrisson, Ove Axner and Martin Zelan

Sensors 2021, 21(18), 6272; https://doi.org/10.3390/s21186272 - 18 Sep 2021

Cited by 9 | Viewed by 2326

Abstract

Refractometry is a powerful technique for pressure assessments that, due to the recent redefinition of the SI system, also offers a new route to realizing the SI unit of pressure, the Pascal. Gas modulation refractometry (GAMOR) is a methodology that has demonstrated an [...] Read more.

10^{- 7}

region. However, its short-term performance, which is of importance for a variety of applications, has not yet been scrutinized. To assess this, we investigated the short-term performance (in terms of precision) of two similar, but independent, dual Fabry–Perot cavity refractometers utilizing the GAMOR methodology. Both systems assessed the same pressure produced by a dead weight piston gauge. That way, their short-term responses were assessed without being compromised by any pressure fluctuations produced by the piston gauge or the gas delivery system. We found that the two refractometer systems have a significantly higher degree of concordance (in the

10^{- 8}

range at 1 s) than what either of them has with the piston gauge. This shows that the refractometry systems under scrutiny are capable of assessing rapidly varying pressures (with bandwidths up to 2 Hz) with precision in the

10^{- 8}

range. Full article

(This article belongs to the Special Issue Optical Gas Sensing: Media, Mechanisms and Applications)

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10 pages, 2261 KiB

Open AccessArticle

Design of Fiber-Tip Refractive Index Sensor Based on Resonant Waveguide Grating with Enhanced Peak Intensity

by Yicun Yao, Yanru Xie, Nan-Kuang Chen, Ivonne Pfalzgraf, Sergiy Suntsov, Detlef Kip and Yingying Ren

Appl. Sci. 2021, 11(15), 6737; https://doi.org/10.3390/app11156737 - 22 Jul 2021

Cited by 2 | Viewed by 2343

Abstract

Resonant waveguide gratings (RWG) are widely used as on-chip refractometers due to their relatively high sensitivity to ambient refractive index changes, their possibility of parallel high-throughput detection and their easy fabrication. In the last two decades, efforts have been made to integrate RWG sensors onto fiber facets, although practical application is still hindered by the limited resonant peak intensity caused by the low coupling efficiency between the reflected beam and the fiber mode. In this work, we propose a new compact RWG fiber-optic sensor with an additional Fabry-Pérot cavity, which is directly integrated onto the tip of a single-mode fiber. By introducing such a resonant structure, a strongly enhanced peak reflectance and improved figure of merit are achieved, while, at the same time, the grating size can be greatly reduced, thus allowing for spatial multiplexing of many sensors on a tip of a single multi-core fiber. This paves the way for the development of probe-like reflective fiber-tip RWG sensors, which are of great interest for multi-channel biochemical sensing and for real-time medical diagnostics. Full article

(This article belongs to the Special Issue Advances in Fiber Optic Sensors and Their Application)

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9 pages, 3405 KiB

Open AccessArticle

High-Q Fabry–Pérot Micro-Cavities for High-Sensitivity Volume Refractometry

by Noha Gaber, Yasser M. Sabry, Mazen Erfan, Frédéric Marty and Tarik Bourouina

Micromachines 2018, 9(2), 54; https://doi.org/10.3390/mi9020054 - 31 Jan 2018

Cited by 15 | Viewed by 4206

Abstract

This work reports a novel structure for a Fabry–Pérot micro cavity that combines the highest reported quality factor for an on-chip Fabry–Pérot resonator that exceeds 9800, and a very high sensitivity for an on-chip volume refractometer based on a Fabry–Pérot cavity that is about 1000 nm/refractive index unit (RIU). The structure consists of two cylindrical Bragg micromirrors that achieve confinement of the Gaussian beam in the plan parallel to the chip substrate, while for the perpendicular plan, external fiber rod lenses (FRLs) are placed in the optical path of the input and the output of the cavity. This novel structure overcomes number of the drawbacks presented in previous designs. The analyte is passed between the mirrors, enabling its detection from the resonance peak wavelengths of the transmission spectra. Mixtures of ethanol and deionized (DI)-water with different ratios are used as analytes with different refractive indices to exploit the device as a micro-opto-fluidic refractometer. The design criteria are detailed and the modeling is based on Gaussian-optics equations, which depicts a scenario closer to reality than the usually used ray-optics modeling. Full article

(This article belongs to the Special Issue Photonic MEMS and Optofluidic Devices)

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11 pages, 4435 KiB

Open AccessArticle

High Sensitivity Refractometer Based on TiO₂-Coated Adiabatic Tapered Optical Fiber via ALD Technology

by Shan Zhu, Fufei Pang, Sujuan Huang, Fang Zou, Qiang Guo, Jianxiang Wen and Tingyun Wang

Sensors 2016, 16(8), 1295; https://doi.org/10.3390/s16081295 - 15 Aug 2016

Cited by 27 | Viewed by 8077

Abstract

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO₂) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed to the higher refractive index of the TiO₂ nanofilm compared to that of silica, an asymmetric Fabry–Perot (F-P) resonator could be constructed along the fiber taper. The central wavelength of the F-P resonator could be controlled by adjusting the thickness of the TiO₂ nanofilm. Such a F-P resonator is sensitive to changes in the surrounding refractive index (SRI), which is utilized to realize a high sensitivity refractometer. The refractometer developed by depositing 50.9-nm-thickness TiO₂ on the tapered fiber shows SRI sensitivity as high as 7096 nm/RIU in the SRI range of 1.3373–1.3500. Due to TiO₂’s advantages of high refractive index, lack of toxicity, and good biocompatibility, this refractometer is expected to have wide applications in the biochemical sensing field. Full article

(This article belongs to the Section Chemical Sensors)

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14 pages, 6669 KiB

Open AccessFeature PaperArticle

Optofluidic Fabry-Pérot Micro-Cavities Comprising Curved Surfaces for Homogeneous Liquid Refractometry—Design, Simulation, and Experimental Performance Assessment

by Noha Gaber, Yasser M. Sabry, Frédéric Marty and Tarik Bourouina

Micromachines 2016, 7(4), 62; https://doi.org/10.3390/mi7040062 - 7 Apr 2016

Cited by 20 | Viewed by 6735

Abstract

In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. The curved surfaces of the tube and the cylindrical mirrors provide three-dimensional light confinement and enable achieving stability for the cavity illuminated by a Gaussian beam input. The resonant optofluidic cavity attains a high-quality factor (Q)—over 2800—which is necessary for a sensitive refractometer, not only by providing a sharp interference spectrum peak that enables accurate tracing of the peak wavelengths shifts, but also by providing steep side peaks, which enables detection of refractive index changes by power level variations when operating at a fixed wavelength. The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the details are met. By experimentally measuring mixtures of acetone-toluene with different ratios, refractive index variations of 0.0005 < Δn < 0.0022 could be detected, with sensitivity as high as 5500 μW/RIU. Full article

(This article belongs to the Special Issue Optofluidics 2015)

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