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13 pages, 2460 KiB

Open AccessArticle

Design of Transmission-Type Refractive Index Sensor, Based on Silica Planar Lightwave Circuit Using Combination of Refractive Angle and Phase Measurements

by Koichi Maru

Sensors 2019, 19(19), 4095; https://doi.org/10.3390/s19194095 - 22 Sep 2019

Viewed by 2444

Abstract

A transmission-type refractive index sensor, based on planar lightwave circuit (PLC) technology is proposed. In the proposed structure, we introduce a combination of coarse measurements, using the dependence of the angle of refraction and fine measurement, and the dependence of the phase on [...] Read more.

A transmission-type refractive index sensor, based on planar lightwave circuit (PLC) technology is proposed. In the proposed structure, we introduce a combination of coarse measurements, using the dependence of the angle of refraction and fine measurement, and the dependence of the phase on the refractive index to measure the absolute refractive index precisely, without expensive optical measurement equipment. The theoretical model of the proposed refractive index sensor is derived based on Fourier optics and transfer function to simulate its performance. The simulation results for the use of the 2.5%-Δ silica-based PLC technology indicate that the proposed structure has the potential to achieve a refractive index error of approximately 1 × 10⁻⁶ RIU or less when a monitored power deviation of ±0.05 dB is accepted. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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12 pages, 1504 KiB

Open AccessArticle

Molecularly Imprinted Sol-Gel for TNT Detection with Optical Micro-Ring Resonator Sensor Chips

by Ludmila Eisner, Isabel Wilhelm, Günter Flachenecker, Jürgen Hürttlen and Wolfgang Schade

Sensors 2019, 19(18), 3909; https://doi.org/10.3390/s19183909 - 10 Sep 2019

Cited by 10 | Viewed by 2899

Abstract

A sensor for trinitrotoluene (TNT) detection was developed by using a combination of optical micro-ring technology and a receptor coating based on molecularly imprinted sol-gel layers. Two techniques for deposition of receptor layers were compared: Airbrush technology and electrospray ionization. A concentration of [...] Read more.

A sensor for trinitrotoluene (TNT) detection was developed by using a combination of optical micro-ring technology and a receptor coating based on molecularly imprinted sol-gel layers. Two techniques for deposition of receptor layers were compared: Airbrush technology and electrospray ionization. A concentration of less than 5 ppb for TNT in the gas-phase, using electrospray deposition of the receptor layer, was detected. The cross-sensitivities to organic substances and further nitro-based explosives were compared. As a result, the sensitivity to TNT is about one order of magnitude higher in comparison to the explosives 2,4-dinitrotoluene (DNT) or 1,3-dinitrobenzene (DNB) and about four orders of magnitude higher than the organic substances phenol, ethanol, and acetone. The signal response of the sensor is fast, and the compact sensor design enables the deposition of different receptor layers on multiple optical micro-rings on one chip, which allows a more precise analysis and reduction of side effects and false alarms. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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13 pages, 1538 KiB

Open AccessArticle

Optimizing the Limit of Detection of Waveguide-Based Interferometric Biosensor Devices

by Jonas Leuermann, Adrián Fernández-Gavela, Antonia Torres-Cubillo, Sergio Postigo, Alejandro Sánchez-Postigo, Laura M. Lechuga, Robert Halir and Íñigo Molina-Fernández

Sensors 2019, 19(17), 3671; https://doi.org/10.3390/s19173671 - 23 Aug 2019

Cited by 43 | Viewed by 6040

Abstract

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration [...] Read more.

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ∼

10^{- 8} RIU

with a silicon nitride sensor operating at telecom wavelengths. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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10 pages, 5961 KiB

Open AccessArticle

Graphene-Enhanced Surface Plasmon Resonance Liquid Refractive Index Sensor Based on Photonic Crystal Fiber

by Bin Li, Tonglei Cheng, Junxin Chen and Xin Yan

Sensors 2019, 19(17), 3666; https://doi.org/10.3390/s19173666 - 23 Aug 2019

Cited by 42 | Viewed by 4078

Abstract

A surface plasmon resonance (SPR) liquid refractive index sensor based on photonic crystal fiber (PCF) is proposed. The PCF is made of the exposed core structure, and the gold film is formed by electron beam evaporation within its defects. The sensitivity of the [...] Read more.

A surface plasmon resonance (SPR) liquid refractive index sensor based on photonic crystal fiber (PCF) is proposed. The PCF is made of the exposed core structure, and the gold film is formed by electron beam evaporation within its defects. The sensitivity of the sensor is improved by coating graphene on the surface of the gold film. The experimental results show that the sensitivity of the sensor is increased by 390 nm/RIU after the introduction of graphene, and finally to 2290 nm/RIU. The experiment and simulation have a good consistency. Significantly, the sensor can be reused, and the measurement accuracy can be maintained. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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18 pages, 8018 KiB

Open AccessArticle

Toward the Required Detection Limits for Volatile Organic Constituents in Marine Environments with Infrared Evanescent Field Chemical Sensors

by Carina Dettenrieder, Yosef Raichlin, Abraham Katzir and Boris Mizaikoff

Sensors 2019, 19(17), 3644; https://doi.org/10.3390/s19173644 - 21 Aug 2019

Cited by 23 | Viewed by 4296

Abstract

A portable sensor system for the simultaneous detection of multiple environmentally relevant volatile organic compounds (VOCs) in real seawater based on Fourier transform infrared fiber-optic evanescent wave spectroscopy (FT-IR-FEWS) was developed. A cylindrical silver halide (AgX) fiber with an ethylene/propylene copolymer (E/P-co) coated [...] Read more.

A portable sensor system for the simultaneous detection of multiple environmentally relevant volatile organic compounds (VOCs) in real seawater based on Fourier transform infrared fiber-optic evanescent wave spectroscopy (FT-IR-FEWS) was developed. A cylindrical silver halide (AgX) fiber with an ethylene/propylene copolymer (E/P-co) coated flattened segment was used as an active optical transducer. The polymer membrane enriches the hydrophobic analytes, while water is effectively excluded from the penetration depth of the evanescent field. Determination of multicomponent mixtures (i.e., 10 VOCs in real-world seawater samples) collected in Arcachon Bay, France revealed a high accuracy and reproducibility with detection limits down to 560 ppb. The measurement showed no significant influence from changing water conditions (e.g., salinity, turbidity, and temperature or other interfering substances). The time constants for 90% saturation of the polymer ranged from 20 to 60 min. The sensor system is capable of being transported for on-site monitoring of environmental pollutants in aqueous matrices with efficient long-term stability, thus showing great potential to be utilized as an early warning system. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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12 pages, 3419 KiB

Open AccessArticle

Single-Mode Tapered Vertical SU-8 Waveguide Fabricated by E-Beam Lithography for Analyte Sensing

by Yu Xin, Gregory Pandraud, Yongmeng Zhang and Paddy French

Sensors 2019, 19(15), 3383; https://doi.org/10.3390/s19153383 - 1 Aug 2019

Cited by 19 | Viewed by 4465

Abstract

In this paper, we propose a novel vertical SU-8 waveguide for evanescent analyte sensing. The waveguide is designed to possess a vertical and narrow structure to generate evanescent waves on both sides of the waveguide’s surface, aimed at increasing the sensitivity by enlarging [...] Read more.

In this paper, we propose a novel vertical SU-8 waveguide for evanescent analyte sensing. The waveguide is designed to possess a vertical and narrow structure to generate evanescent waves on both sides of the waveguide’s surface, aimed at increasing the sensitivity by enlarging the sensing areas. We performed simulations to monitor the influence of different parameters on the waveguide’s performance, including its height and width. E-beam lithography was used to fabricate the structure, as this one-step direct writing process enables easy, fast, and high-resolution fabrication. Furthermore, it reduces the sidewall roughness and decreases the induced scattering loss, which is a major source of waveguide loss. Couplers were added to improve the coupling efficiency and alignment tolerance, and will contribute to the feasibility of a plug-and-play optical system. Optical measurements show that the transmission loss is 1.03 ± 0.19 dB/cm. The absorption sensitivity was measured to be 4.8 dB per refractive index unit (dB/RIU) for saline solutions with various concentrations. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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8 pages, 2310 KiB

Open AccessArticle

Corrosion Detection by Infrared Attenuated Total Reflection Spectroscopy via Diamond-Like Carbon-Coated Silicon Wafers and Iron-Sensitive Dyes

by Dervis Türkmen, Carina Dettenrieder, Pontus Forsberg, Andreas Mattsson, Fredrik Nikolajeff, Lars Österlund, Mikael Karlsson and Boris Mizaikoff

Sensors 2019, 19(15), 3373; https://doi.org/10.3390/s19153373 - 1 Aug 2019

Cited by 6 | Viewed by 4120

Abstract

The durability of metal-based constructions, especially those containing reinforced concrete, is mainly limited by corrosion processes. Diamond-like carbon (DLC)-coated silicon (Si) wafers provide a chemically inert and mechanically robust sensing interface for application in aggressive environments. In this study, iron-sensitive dyes, i.e., 2,3-dihydroxypyridine [...] Read more.

The durability of metal-based constructions, especially those containing reinforced concrete, is mainly limited by corrosion processes. Diamond-like carbon (DLC)-coated silicon (Si) wafers provide a chemically inert and mechanically robust sensing interface for application in aggressive environments. In this study, iron-sensitive dyes, i.e., 2,3-dihydroxypyridine (DHP) and 1,2-dihydroxybenzol (DHB), were coated onto DLC-modified Si wafers for evaluating the potential of detecting corrosion processes via evanescent field absorption spectroscopy using Fourier-transform infrared spectroscopy. The obtained IR spectra reveal discernible changes of the dye layer after exposure to iron solutions, which indicates that indeed corrosion processes may be studied at molecular level detail. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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13 pages, 7334 KiB

Open AccessArticle

Resonant Grating without a Planar Waveguide Layer as a Refractive Index Sensor

by Sivan Isaacs, Ansar Hajoj, Mohammad Abutoama, Alexander Kozlovsky, Erez Golan and Ibrahim Abdulhalim

Sensors 2019, 19(13), 3003; https://doi.org/10.3390/s19133003 - 8 Jul 2019

Cited by 32 | Viewed by 7171

Abstract

Dielectric grating-based sensors are usually based on the guided mode resonance (GMR) obtained using a thin planar waveguide layer (PWL) adjacent to a thin subwavelength grating layer. In this work, we present a detailed investigation of thick subwavelength dielectric grating structures that exhibit [...] Read more.

Dielectric grating-based sensors are usually based on the guided mode resonance (GMR) obtained using a thin planar waveguide layer (PWL) adjacent to a thin subwavelength grating layer. In this work, we present a detailed investigation of thick subwavelength dielectric grating structures that exhibit reflection resonances above a certain thickness without the need for the waveguide layer, showing great potential for applications in biosensing and tunable filtering. Analytic and numerical results are thoroughly discussed, as well as an experimental demonstration of the structure as a chemical sensor in the SWIR (short wave infrared) spectral range (1200–1800 nm). In comparison to the GMR structure with PWL, the thick grating structure has several unique properties: (i) It gives higher sensitivity when the spaces are filled, with the analyte peaking at certain space values due to an increase in the interaction volume between the analyte and the evanescent optical field between the grating lines; (ii) the TM (transverse magnetic) resonance, in certain cases, provides a better figure of merit; (iii) the sensitivity increases as the grating height increases; (iv) the prediction of the resonance locations based on the effective medium approximation does not give satisfactory results when the grating height is larger than a certain value, and the invalidity becomes more severe as the period increases; (v) a sudden increase in the Q-factor of the resonance occurs at a specific height value accompanied by the high local field enhancement (~10³) characteristic of a nano-antenna type pattern. Rigorous numerical simulations of the field distribution are presented to explain the different observed phenomena. Full article

(This article belongs to the Special Issue Waveguide-Based Sensors)

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