Sensors

Research

17 pages, 8079 KiB

Open AccessArticle

Polarization-Insensitive Waveguide Schottky Photodetectors Based on Mode Hybridization Effects in Asymmetric Plasmonic Waveguides

by Qian Li, Junjie Tu, Yang Tian and Yanli Zhao

Sensors 2020, 20(23), 6885; https://doi.org/10.3390/s20236885 - 2 Dec 2020

Cited by 2 | Viewed by 1931

Abstract

Two types of configurations are theoretically proposed to achieve high responsivity polarization-insensitive waveguide Schottky photodetectors, i.e., a dual-layer structure for 1.55 µm and a single-layer structure for 2 µm wavelength band. Mode hybridization effects between quasi-TM modes and sa_b¹ modes in [...] Read more.

Two types of configurations are theoretically proposed to achieve high responsivity polarization-insensitive waveguide Schottky photodetectors, i.e., a dual-layer structure for 1.55 µm and a single-layer structure for 2 µm wavelength band. Mode hybridization effects between quasi-TM modes and sa_b¹ modes in plasmonic waveguides are first presented and further investigated under diverse metal types with different thicknesses in this work. By utilizing the mode hybridization effects between quasi-TE mode and aa_b⁰ mode, and also quasi-TM and sa_b¹ mode in our proposed hybrid plasmonic waveguide, light absorption enhancement can be achieved under both TE and TM incidence within ultrathin and short metal stripes, thus resulting in a considerable responsivity for Si-based sub-bandgap photodetection. For 1.55 µm wavelength, the Au-6 nm-thick device can achieve absorptance of 99.6%/87.6% and responsivity of 138 mA·W⁻¹/121.2 mA·W⁻¹ under TE/TM incidence. Meanwhile, the Au-5 nm-thick device can achieve absorptance of 98.4%/90.2% and responsivity of 89 mA·W⁻¹/81.7 mA·W⁻¹ under TE/TM incidence in 2 µm wavelength band. The ultra-compact polarization-insensitive waveguide Schottky photodetectors may have promising applications in large scale all-Si photonic integrated circuits for high-speed optical communication. Full article

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

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12 pages, 1264 KiB

Open AccessArticle

Dual Oxygen and Temperature Luminescence Learning Sensor with Parallel Inference

by Francesca Venturini, Umberto Michelucci and Michael Baumgartner

Sensors 2020, 20(17), 4886; https://doi.org/10.3390/s20174886 - 28 Aug 2020

Cited by 7 | Viewed by 3554

Abstract

A well-known approach to the optical measure of oxygen is based on the quenching of luminescence by molecular oxygen. The main challenge for this measuring method is the determination of an accurate mathematical model for the sensor response. The reason is the dependence [...] Read more.

A well-known approach to the optical measure of oxygen is based on the quenching of luminescence by molecular oxygen. The main challenge for this measuring method is the determination of an accurate mathematical model for the sensor response. The reason is the dependence of the sensor signal from multiple parameters (like oxygen concentration and temperature), which are cross interfering in a sensor-specific way. The common solution is to measure the different parameters separately, for example, with different sensors. Then, an approximate model is developed where these effects are parametrized ad hoc. In this work, we describe a new approach for the development of a learning sensor with parallel inference that overcomes all these difficulties. With this approach we show how to generate automatically and autonomously a very large dataset of measurements and how to use it for the training of the proposed neural-network-based signal processing. Furthermore, we demonstrate how the sensor exploits the cross-sensitivity of multiple parameters to extract them from a single set of optical measurements without any a priori mathematical model with unprecedented accuracy. Finally, we propose a completely new metric to characterize the performance of neural-network-based sensors, the Error Limited Accuracy. In general, the methods described here are not limited to oxygen and temperature sensing. They can be similarly applied for the sensing with multiple luminophores, whenever the underlying mathematical model is not known or too complex. Full article

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

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15 pages, 3453 KiB

Open AccessArticle

One-Step Assembly of Fluorescence-Based Cyanide Sensors from Inexpensive, Off-The-Shelf Materials

by Gregory E. Fernandes, Ya-Wen Chang, Akash Sharma and Sarah Tutt

Sensors 2020, 20(16), 4488; https://doi.org/10.3390/s20164488 - 11 Aug 2020

Cited by 3 | Viewed by 3758

Abstract

We report a simple and versatile approach to assemble sensitive and selective fluorescence “turn-on” sensors for cyanide by combining three off-the-shelf materials; namely fluorescent dye, 1-vinyl imidazole polymer, and cupric chloride. The cyanide-sensing species is a non-fluorescent fluorophore-polymer-Cu²⁺ complex; which forms as [...] Read more.

We report a simple and versatile approach to assemble sensitive and selective fluorescence “turn-on” sensors for cyanide by combining three off-the-shelf materials; namely fluorescent dye, 1-vinyl imidazole polymer, and cupric chloride. The cyanide-sensing species is a non-fluorescent fluorophore-polymer-Cu²⁺ complex; which forms as a result of the imidazole polymer’s ability to bind both fluorophore and fluorescence quencher (Cu²⁺). Cyanide removes Cu²⁺ from these complexes; thereby “turning-on” sensor fluorescence. These sensors are water-soluble and have a detection limit of ~2.5 μM (CN⁻) in water. Our ternary complex-based sensing approach also enables facile emission tuning; we demonstrate the convenient, synthesis-free preparation of blue and green-emitting sensors using distyrylbiphenyl and fluorescein fluorophores, respectively. Furthermore; these ternary complexes are easily immobilized using agarose to create cyanide-sensing hydrogels; which are then used in a simple; novel microdiffusion apparatus to achieve interference-free cyanide analysis of aqueous media. The present study provides an inexpensive approach for portable; interference-free cyanide detection. Full article

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

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15 pages, 2956 KiB

Open AccessArticle

Fiber Optic Particle Plasmon Resonance Biosensor for Label-Free Detection of Nucleic Acids and Its Application to HLA-B27 mRNA Detection in Patients with Ankylosing Spondylitis

by Yen-Ta Tseng, Wan-Yun Li, Ya-Wen Yu, Chang-Yue Chiang, Su-Qin Liu, Lai-Kwan Chau, Ning-Sheng Lai and Cheng-Chung Chou

Sensors 2020, 20(11), 3137; https://doi.org/10.3390/s20113137 - 1 Jun 2020

Cited by 12 | Viewed by 3291

Abstract

We developed a label-free, real-time, and highly sensitive nucleic acid biosensor based on fiber optic particle plasmon resonance (FOPPR). The biosensor employs a single-strand deoxyoligonucleotides (ssDNA) probe, conjugated to immobilized gold nanoparticles on the core surface of an optical fiber. We explore the [...] Read more.

We developed a label-free, real-time, and highly sensitive nucleic acid biosensor based on fiber optic particle plasmon resonance (FOPPR). The biosensor employs a single-strand deoxyoligonucleotides (ssDNA) probe, conjugated to immobilized gold nanoparticles on the core surface of an optical fiber. We explore the steric effects on hybridization affinity and limit of detection (LOD), by using different ssDNA probe designs and surface chemistries, including diluent molecules of different lengths in mixed self-assembled monolayers, ssDNA probes of different oligonucleotide lengths, ssDNA probes in different orientations to accommodate target oligonucleotides with a hybridization region located unevenly in the strand. Based on the optimized ssDNA probe design and surface chemistry, we achieved LOD at sub-nM level, which makes detection of target oligonucleotides as low as 1 fmol possible in the 10-μL sensor chip. Additionally, the FOPPR biosensor shows a good correlation in determining HLA-B27 mRNA, in extracted blood samples from patients with ankylosing spondylitis (AS), with the clinically accepted real-time reverse transcription-polymerase chain reaction (RT-PCR) method. The results from this fundamental study should guide the design of ssDNA probe for anti-sense sensing. Further results through application to HLA-B27 mRNA detection illustrate the feasibility in detecting various nucleic acids of chemical and biological relevance. Full article

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

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12 pages, 2376 KiB

Open AccessArticle

Long Exposure Short Pulse Synchronous Phase Lock Method for Capturing High Dynamic Surface Shape

by Weiqiang Han, Xiaodong Gao, Zhenjie Fan, Le Bai and Bo Liu

Sensors 2020, 20(9), 2550; https://doi.org/10.3390/s20092550 - 30 Apr 2020

Cited by 1 | Viewed by 1809

Abstract

In infrared weak target detection systems, high-frequency vibrating mirrors (VMs) are a core component. The dynamic surface shape of the VM has a direct impact on imaging quality and the optical modulation effect, so its measurement is necessary but also very difficult. Measurement [...] Read more.

In infrared weak target detection systems, high-frequency vibrating mirrors (VMs) are a core component. The dynamic surface shape of the VM has a direct impact on imaging quality and the optical modulation effect, so its measurement is necessary but also very difficult. Measurement of the dynamic surface shape of VMs requires a transiently acquired image series, but traditional methods cannot perform this task, as, when the VM is vibrating at a frequency of 3033 Hz, using high-speed cameras to acquire the images would result in frame rates exceeding 1.34 MFPS, which is currently technically impossible. In this paper, we propose the long exposure short pulse synchronous phase lock (LSPL) method, which can capture the dynamic surface shape using a camera working at 10 FPS. In addition, our proposed approach uses a single laser pulse and can achieve the dynamic surface shape measurement on a single frame image. Full article

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

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14 pages, 8428 KiB

Open AccessArticle

Improve Temporal Fourier Transform Profilometry for Complex Dynamic Three-Dimensional Shape Measurement

by Yihang Liu, Qican Zhang, Haihua Zhang, Zhoujie Wu and Wenjing Chen

Sensors 2020, 20(7), 1808; https://doi.org/10.3390/s20071808 - 25 Mar 2020

Cited by 20 | Viewed by 3293

Abstract

The high-speed three-dimensional (3-D) shape measurement technique has become more and more popular recently, because of the strong demand for dynamic scene measurement. The single-shot nature of Fourier Transform Profilometry (FTP) makes it highly suitable for the 3-D shape measurement of dynamic scenes. [...] Read more.

The high-speed three-dimensional (3-D) shape measurement technique has become more and more popular recently, because of the strong demand for dynamic scene measurement. The single-shot nature of Fourier Transform Profilometry (FTP) makes it highly suitable for the 3-D shape measurement of dynamic scenes. However, due to the band-pass filter, FTP method has limitations for measuring objects with sharp edges, abrupt change or non-uniform reflectivity. In this paper, an improved Temporal Fourier Transform Profilometry (TFTP) algorithm combined with the 3-D phase unwrapping algorithm based on a reference plane is presented, and the measurement of one deformed fringe pattern producing a new 3-D shape of an isolated abrupt objects has been achieved. Improved TFTP method avoids band-pass filter in spatial domain and unwraps 3-D phase distribution along the temporal axis based on the reference plane. The high-frequency information of the measured object can be well preserved, and each pixel is processed separately. Experiments verify that our method can be well applied to a dynamic 3-D shape measurement with isolated, sharp edges or abrupt change. A high-speed and low-cost structured light pattern sequence projection has also been presented, it is capable of projection frequencies in the kHz level. Using the proposed 3-D shape measurement algorithm with the self-made mechanical projector, we demonstrated dynamic 3-D reconstruction with a rate of 297 Hz, which is mainly limited by the speed of the camera. Full article

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

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Review

Jump to: Research, Other

20 pages, 5397 KiB

Open AccessReview

Advances in Random Fiber Lasers and Their Sensing Application

by Hong Chen, Shaohua Gao, Mingjiang Zhang, Jianzhong Zhang, Lijun Qiao, Tao Wang, Fei Gao, Xinxin Hu, Shichuan Li and Yicheng Zhu

Sensors 2020, 20(21), 6122; https://doi.org/10.3390/s20216122 - 28 Oct 2020

Cited by 37 | Viewed by 4302

Abstract

Compared with conventional laser, random laser (RL) has no resonant cavity, reducing the requirement of cavity design. In recent years, the random fiber laser (RFL), a novel kind of RL, has made great progress in theories and experiments. The RFL has a simpler [...] Read more.

Compared with conventional laser, random laser (RL) has no resonant cavity, reducing the requirement of cavity design. In recent years, the random fiber laser (RFL), a novel kind of RL, has made great progress in theories and experiments. The RFL has a simpler structure, a more flexible design, and higher reliability. It has valuable applications for earth sciences, biological life sciences, and national defense security, due to these unique properties. This paper reviews the development of RFLs in the last decade, including their configurations based on various optical fibers and their output properties, especially the method of control. Moreover, we also introduce their applications in the optical fiber sensing system, which is a very important and practical orientation to study. Finally, this paper presents the prospects of RFLs. Full article

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

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Other

Jump to: Research, Review

9 pages, 3373 KiB

Open AccessLetter

Thermo-Optical Tuning Cascaded Double Ring Sensor with Large Measurement Range

by Zhiping Yang, Yanlu Wang, Chang Su, Liyang Shao, Jian-Jun He and Mingyu Li

Sensors 2020, 20(18), 5149; https://doi.org/10.3390/s20185149 - 9 Sep 2020

Cited by 5 | Viewed by 2420

Abstract

In this paper, a thermo-optic tuning optical waveguide sensor system based on a cascaded double micro-ring resonator is investigated. The system consists of a micro-ring resonator with the microheater as a reference ring and a micro-ring resonator with removing the upper cladding layers [...] Read more.

In this paper, a thermo-optic tuning optical waveguide sensor system based on a cascaded double micro-ring resonator is investigated. The system consists of a micro-ring resonator with the microheater as a reference ring and a micro-ring resonator with removing the upper cladding layers as a sensing ring, combined with a microfluidic control. The refractive index change of the sample is measured by the electric power change of the microheater. The experimental results show that the sensitivity of the thermo-optic tuning is 34.231 W/RIU (refractive index units), and the measurement range is 4.325 × 10⁻³ RIU, almost eight times larger than that of the cascaded double micro-ring resonator without thermo-optic tuning for the intensity interrogation. Full article

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

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14 pages, 8792 KiB

Open AccessLetter

Critical Factors for In Vivo Measurements of Human Skin by Terahertz Attenuated Total Reflection Spectroscopy

by Lixia Wang, Sayon Guilavogui, Henghui Yin, Yiping Wu, Xiaofei Zang, Jingya Xie, Li Ding and Lin Chen

Sensors 2020, 20(15), 4256; https://doi.org/10.3390/s20154256 - 30 Jul 2020

Cited by 4 | Viewed by 2629

Abstract

Attenuated total reflection (ATR) geometry is a suitable choice for in vivo measurements of human skin due to the deep penetration of the field into the sample and since it makes it easy to measure the reference spectrum. On the other hand, there [...] Read more.

Attenuated total reflection (ATR) geometry is a suitable choice for in vivo measurements of human skin due to the deep penetration of the field into the sample and since it makes it easy to measure the reference spectrum. On the other hand, there are several critical factors that may affect the terahertz (THz) response in these kinds of experiments. Here, we analyse in detail the influence of the following factors: the contact positions between the thumb and the prism, the contact pressure, the contact duration, and the materials of the prism. Furthermore, we use the THz-ATR technology to evaluate different types of handcream and also establish the theoretical model to investigate the reflectivity after interacting with the skin. The results agree well with experimental ones. Our analysis makes it clear the importance of controlling the above factors during measurements to enable reliable THz response and results which, in turn, may be used to monitor water motion in human skin and to predict possible diseases. Full article

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

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15 pages, 3431 KiB

Open AccessLetter

FDTD Simulation: Simultaneous Measurement of the Refractive Index and the Pressure Using Microdisk Resonator with Two Whispering-Gallery Modes

by Ping Zhang, Dongyue He, Chen Zhang and Zhiruo Yan

Sensors 2020, 20(14), 3955; https://doi.org/10.3390/s20143955 - 16 Jul 2020

Cited by 14 | Viewed by 4678

Abstract

In this paper, an approach to measure both the refractive index (RI) and the pressure simultaneously using two Whispering-Gallery Modes (WGMs) in a microdisk resonator is theoretically proposed. Due to the difference in the energy distribution of the first and second order WGMs, [...] Read more.

In this paper, an approach to measure both the refractive index (RI) and the pressure simultaneously using two Whispering-Gallery Modes (WGMs) in a microdisk resonator is theoretically proposed. Due to the difference in the energy distribution of the first and second order WGMs, the sensitivity of two modes toward the variation of RI and pressure applied to the device show differences. An RI sensitivity of 29.07 nm/RIU and pressure sensitivity of 0.576 pm/kPa for WGM (1,36), and an RI sensitivity of 38.68 nm/RIU and a pressure sensitivity of 0.589 pm/kPa for WGM (2,28) are obtained through the 3D finite-difference time-domain (3D-FDTD) simulation. Dual parametric sensing can be achieved by solving the second-order inverse sensitivity matrix. Therefore, strain–optical coupling behavior is effectively eliminated. The dual sensing scheme we proposed provides a novel approach to overcome the difficulty of multi-sensing applications based on the flexible photonic device. Full article

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

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