Submit to Sensors Review for Sensors Propose a Special Issue

Journal Browser

► Journal Browser

Sensing with Infrared and Terahertz Technologies

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: closed (15 April 2023) | Viewed by 23307

Share This Special Issue

Special Issue Editors

Prof. Dr. Qijie Wang

E-Mail Website
Guest Editor

Centre for OptoElectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, Singapore 639798, Singapore
Interests: mid- and far-infrared lasers; 2D-material-based mid-IR and THz optoelectronic devices; infrared plasmonic and metamaterial devices
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Hua Li

E-Mail Website
Guest Editor

Key Laboratory of Terahertz Solid State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning road, Shanghai 200050, China
Interests: terahertz and mid-infrared lasers; intersub-band-based optoelectronic devices; terahertz frequency combs and applications

Dr. Peng Wang

E-Mail Website
Guest Editor

State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
Interests: infrared detector; photodetector; phototransistor; optoelectronic devices; device physics; thin films; low-dimensional materials; two-dimensional materials
Special Issues, Collections and Topics in MDPI journals

Dr. Ya Zhang

E-Mail Website
Guest Editor

Institute of Engineering, Tokyo University of Agriculture and Technology, Tokyo 1848588, Japan
Interests: terahertz; MEMS sensor; nonlinear oscillation; mode coupling

Special Issue Information

Dear Colleagues,

The big leaps in optoelectronics have drawn increasing attention from scientific researchers and application engineers. The Optoelectronics Global Conference (OGC) was created to connect fundamental research and industrial applications in optoelectronics. This summer, the OGC 2021 will be held at the Exhibition & Convention Center in Shenzhen, China on 31 August–3 September 2021 (http://www.ipsogc.org).

The conference aims to promote interaction and exchange between various disciplines among professionals in academia and industry at home and abroad. The OGC will be an ideal platform for scholars, researchers, and professionals to exchange insights and discuss the development of the optoelectronics industry. It will be a perfect gathering to learn about new perspectives, technologies, and trends which might push the boundaries of technology and eventually create a broader future for optoelectronics applications. Nine symposia are being arranged in the conference, with topics covering precision optics, optical communications, lasers, infrared applications, and fiber sensors. The “Near-infrared, Mid-infrared and Far-infrared Technologies and Applications” Symposium is of particular interest.

Sensing with infrared and terahertz technologies, which strongly interacts with physics, chemistry, material science, life science, etc., has great applications in environmental monitoring, communication radar, national security, and astronomical observations. Further developments in these applications in the infrared and terahertz field require innovations in lasers, detectors, and systems. In this Special Issue, we welcome original research articles and review articles that can provide readers with current research trends and solutions for sensors, systems, and applications employing infrared and terahertz technologies. In addition, a few highly qualified papers selected and extended from the OGC 2021 will be included in the Special Issue.

Prof. Dr. Qijie Wang
Prof. Dr. Hua Li
Dr. Peng Wang
Dr. Ya Zhang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Infrared sensing
Quantum cascade lasers
Two-dimensional materials and devices
Terahertz radiation sources and detectors
Device physics
IR sensing technology and application
Advanced IR materials
Infrared photonics for sensing

Published Papers (11 papers)

Download All Papers

Research

Jump to: Review

18 pages, 2750 KiB

Open AccessArticle

Calibration Method for Airborne Infrared Optical Systems in a Non-Thermal Equilibrium State

by Mingyuan Dong, Honghai Shen, Ping Jia, Yang Sun, Chao Liang, Fan Zhang and Jinghua Hou

Sensors 2023, 23(14), 6326; https://0-doi-org.brum.beds.ac.uk/10.3390/s23146326 - 12 Jul 2023

Viewed by 872

Abstract

Airborne infrared optical systems equipped with multiple cooled infrared cameras are commonly utilized for quantitative radiometry and thermometry measurements. Radiometric calibration is crucial for ensuring the accuracy and quantitative application of remote sensing camera data. Conventional radiometric calibration methods that consider internal stray radiation are usually based on the assumption that the entire system is in thermal equilibrium. However, this assumption leads to significant errors when applying the radiometric calibration results in actual mission scenarios. To address this issue, we analyzed the changes in optical temperature within the system and developed a simplified model to account for the internal stray radiation in the non-thermal equilibrium state. Building upon this model, we proposed an enhanced radiometric calibration method, which was applied to the absolute radiometric calibration procedure of the system. The radiometric calibration experiment, conducted on the medium-wave channel of the system within a temperature test chamber, demonstrated that the proposed method can achieve a calibration accuracy exceeding 3.78% within an ambient temperature range of −30 °C to 15 °C. Additionally, the maximum temperature measurement error was found to be less than ±1.01 °C. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

11 pages, 2223 KiB

Open AccessArticle

Auto-Calibrated Charge-Sensitive Infrared Phototransistor at 9.3 µm

by Mohsen Bahrehmand, Djamal Gacemi, Angela Vasanelli, Lianhe Li, Alexander Giles Davies, Edmund Linfield, Carlo Sirtori and Yanko Todorov

Sensors 2023, 23(7), 3635; https://0-doi-org.brum.beds.ac.uk/10.3390/s23073635 - 31 Mar 2023

Cited by 2 | Viewed by 1423

Abstract

Charge-sensitive infrared photo-transistors (CSIP) are quantum detectors of mid-infrared radiation

(λ = 4 µ m - 14 µ m)

which have been reported to have outstanding figures of merit and sensitivities that allow single photon detection. The typical absorbing [...] Read more.

Charge-sensitive infrared photo-transistors (CSIP) are quantum detectors of mid-infrared radiation

(λ = 4 µ m - 14 µ m)

which have been reported to have outstanding figures of merit and sensitivities that allow single photon detection. The typical absorbing region of a CSIP consists of an Al_xGa_1-xAs quantum heterostructure, where a GaAs quantum well, where the absorption takes place, is followed by a triangular barrier with a graded x(Al) composition that connects the quantum well to a source-drain channel. Here, we report a CSIP designed to work for a 9.3 µm wavelength where the Al composition is kept constant and the triangular barrier is replaced by tunnel-coupled quantum wells. This design is thus conceptually closer to quantum cascade detectors (QCDs) which are an established technology for detection in the mid-infrared range. While previously reported structures use metal gratings in order to couple infrared radiation in the absorbing quantum well, here, we employ a 45° wedge facet coupling geometry that allows a simplified and reliable estimation of the incident photon flux Φ in the device. Remarkably, these detectors have an “auto-calibrated” nature, which enables the precise assessment of the photon flux Φ solely by measuring the electrical characteristics and from knowledge of the device geometry. We identify an operation regime where CSIP detectors can be directly compared to other unipolar quantum detectors such as quantum well infrared photodetectors (QWIPs) and QCDs and we estimate the corresponding detector figure of merit under cryogenic conditions. The maximum responsivity R = 720 A/W and a photoconductive gain G~2.7 × 10⁴ were measured, and were an order of magnitude larger than those for QCDs and quantum well infrared photodetectors (QWIPs). We also comment on the benefit of nano-antenna concepts to increase the efficiency of CSIP in the photon-counting regime. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

20 pages, 30150 KiB

Open AccessArticle

Enhanced Terahertz Fingerprint Sensing Mechanism Study of Tiny Molecules Based on Tunable Spoof Surface Plasmon Polaritons on Composite Periodic Groove Structures

by Ruiqi Zhao, Yu Feng, Haotian Ling, Xudong Zou, Meng Wang and Guizhen Lu

Sensors 2023, 23(5), 2496; https://0-doi-org.brum.beds.ac.uk/10.3390/s23052496 - 23 Feb 2023

Cited by 4 | Viewed by 1730

Abstract

Highly sensitive detection of enhanced terahertz (THz) fingerprint absorption spectrum of trace-amount tiny molecules is essential for biosensing. THz surface plasmon resonance (SPR) sensors based on Otto prism-coupled attenuated total reflection (OPC-ATR) configuration have been recognized as a promising technology in biomedical detection applications. However, THz-SPR sensors based on the traditional OPC-ATR configuration have long been associated with low sensitivity, poor tunability, low refractive index resolution, large sample consumption, and lack of fingerprint analysis. Here, we propose an enhanced tunable high-sensitivity and trace-amount THz-SPR biosensor based on a composite periodic groove structure (CPGS). The elaborate geometric design of the spoof surface plasmon polaritons (SSPPs) metasurface increases the number of electromagnetic hot spots on the surface of the CPGS, improves the near-field enhancement effect of SSPPs, and enhances the interaction between THz wave and the sample. The results show that the sensitivity (S), figure of merit (FOM) and Q-factor (Q) can be increased to 6.55 THz/RIU, 4234.06 1/RIU and 629.28, respectively, when the refractive index range of the sample to measure is between 1 and 1.05 with the resolution

1.54 \times 10^{- 5}

RIU. Moreover, by making use of the high structural tunability of CPGS, the best sensitivity (SPR frequency shift) can be obtained when the resonant frequency of the metamaterial approaches the biological molecule oscillation. These advantages make CPGS a strong candidate for the high-sensitivity detection of trace-amount biochemical samples. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

12 pages, 681 KiB

Open AccessArticle

Probing the Molecular Dynamics of Aqueous Binary Solutions with THz Time-Domain Ellipsometry

by Zahra Mazaheri, Gian Paolo Papari and Antonello Andreone

Sensors 2023, 23(4), 2292; https://0-doi-org.brum.beds.ac.uk/10.3390/s23042292 - 18 Feb 2023

Cited by 1 | Viewed by 1134

Abstract

Using a customized time-domain ellipsometer operating in the THz range, the molecular dynamics of a liquid binary solution based on water and isopropyl alcohol (2-propanol) is investigated. The setup is capable of detecting small changes in the optical properties of the mixture within a single measurement. The complex dielectric response of samples with different concentrations is studied through the direct measurement of the ellipsometric parameters. The results are described using an effective Debye model, from which the relaxation parameters associated with different activation energies can be consistently extracted. Significant deviations between experimental data and the theoretical expectations at an intermediate volume percentage of 2-propanol in water are observed and interpreted as produced by competing effects: the creation/destruction of hydrogen bonding on the one hand, and the presence of cluster/aggregation between water and alcohol molecules on the other. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

13 pages, 54802 KiB

Open AccessEditor’s ChoiceArticle

Using Deep Learning with Thermal Imaging for Human Detection in Heavy Smoke Scenarios

by Pei-Fen Tsai, Chia-Hung Liao and Shyan-Ming Yuan

Sensors 2022, 22(14), 5351; https://0-doi-org.brum.beds.ac.uk/10.3390/s22145351 - 18 Jul 2022

Cited by 14 | Viewed by 6541

Abstract

In this study, we propose using a thermal imaging camera (TIC) with a deep learning model as an intelligent human detection approach during emergency evacuations in a low-visibility smoky fire scenarios. We use low-wavelength infrared (LWIR) images taken by a TIC qualified with the National Fire Protection Association (NFPA) 1801 standards as input to the YOLOv4 model for real-time object detection. The model trained with a single Nvidia GeForce 2070 can achieve >95% precision for the location of people in a low-visibility smoky scenario with 30.1 frames per second (FPS). This real-time result can be reported to control centers as useful information to help provide timely rescue and provide protection to firefighters before entering dangerous smoky fire situations. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

13 pages, 3542 KiB

Open AccessCommunication

Thermal and Optical Properties of Porous Nanomesh Structures for Sensitive Terahertz Bolometric Detection

by Ryoko Yamamoto, Akira Kojima, Nobuyoshi Koshida, Isao Morohashi, Kazuhiko Hirakawa and Ya Zhang

Sensors 2022, 22(14), 5109; https://0-doi-org.brum.beds.ac.uk/10.3390/s22145109 - 07 Jul 2022

Cited by 2 | Viewed by 1510

Abstract

Terahertz (THz) electromagnetic waves are attractive for use in nondestructive and biocompatible sensing applications. Thermal sensors are widely used for THz detection owing to the small photon energies of THz radiation, where this requires materials with low thermal conductivity and a small heat capacity to ensure the sensitive and fast operation of the sensors. In this study, we investigated the thermal and optical properties of porous nanomesh structures for sensitive THz bolometric detection. Nanometer (nm)-scale hole array structures were formed on gallium arsenide (GaAs) microelectromechanical system (MEMS) beams to improve their thermal properties. The thermal conductance of the porous MEMS beams was obtained by measuring their thermal bandwidths; it was found to decrease by as much as ~90% when the porosity (P) of the porous nanostructure was increased to ~0.69. We also measured the THz absorptance of the porous hole array structure. The results show that although the porous nanostructure has a much smaller area than the bulk material, it maintained a high coefficient of THz absorptance because the featured size was much smaller than the THz wavelength. The measured absorptance agreed well with that calculated by using the Drude model. These results demonstrate that the porous nanomesh structure is promising for developing highly sensitive THz thermal sensors. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

7 pages, 8118 KiB

Open AccessCommunication

Real-Time Megapixel Electro-Optical Imaging of THz Beams with Probe Power Normalization

by François Blanchard, Takashi Arikawa and Koichiro Tanaka

Sensors 2022, 22(12), 4482; https://0-doi-org.brum.beds.ac.uk/10.3390/s22124482 - 14 Jun 2022

Cited by 8 | Viewed by 1567

Abstract

In this work, we present a simple method to improve the spatial uniformity of two-dimensional electro-optical imaging of terahertz (THz) beams. In this system, near-field THz images are captured by fully illuminating a sample using conventional optical microscope objectives. Unfortunately, due to the linear relationship between the optical probe power and the measured THz electric field, any spatial variation in probe intensity translates directly into a variation of the recorded THz electric field. Using a single normalized background frame information map as a calibration tool prior to recording a sequence of THz images, we show a full recovery of a two-dimensional flat field for various combinations of magnification factors. Our results suggest that the implementation of dynamic intensity profile correction is a promising avenue for real-time electro-optical imaging of THz beams. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

10 pages, 1552 KiB

Open AccessArticle

Simulated and Experimental Verification for a Terahertz Specific Finite Rate of Innovation Signal Processing Method

by Xavier E. Ramirez Barker, Rayko I. Stanchev, Arturo I. Hernandez Serrano and Emma Pickwell-MacPherson

Sensors 2022, 22(9), 3387; https://0-doi-org.brum.beds.ac.uk/10.3390/s22093387 - 28 Apr 2022

Cited by 1 | Viewed by 1310

Abstract

Recently, finite rate of innovation methods have been successfully applied to achieve low sampling rates in many areas, such as for ultrasound and radio signals. However, to the best of our knowledge, there are no journal publications applying this to real terahertz signals. In this work, we mathematically describe a finite rate of innovation method applied specifically to terahertz signals both experimentally and in simulation. To demonstrate our method, we applied it to randomized simulated signals with and without the presence of noise and to simple experimental measurements. We found excellent agreement between the simulated signals and those recreated based on results from our method, with this success also being replicated experimentally. These results were obtained at relatively low sampling rates, compared to standard methods, which is a key advantage to using a finite rate of innovation method as it allows for faster data acquisition and signal processing. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

9 pages, 2601 KiB

Open AccessCommunication

Terahertz Spectral Properties of 5-Substituted Uracils

by Kaixuan Li, Ding Li and Yan Zhang

Sensors 2021, 21(24), 8292; https://0-doi-org.brum.beds.ac.uk/10.3390/s21248292 - 11 Dec 2021

Cited by 2 | Viewed by 2191

Abstract

Applications of terahertz time-domain spectroscopy (THz-TDS) in the fields of chemistry and biomedicine have recently received increased attention. Specifically, THz-TDS is particularly effective for the identification of alkaloid molecules, because it can distinguish the vibration types of base molecules in the THz band and provide a direct characteristic spectrum for the configuration and conformation of biomolecules. However, when THz-TDS technology is used to identify alkaloid molecules, most of them are concentrated in the 0.1–3.0 THz band, limiting the amount of information that can be obtained. In this work, a wide-spectrum THz-TDS system was independently built to explore the absorption spectra of uracil and its 5-substituents in the range of 1.3–6.0 THz. We found that, in the THz band, uracil and its 5-substituents have similar absorption peaks near 4.9 and 3.3 THz, while the 5-substituents have an additional absorption peak in the range of 1.5–2.5 THz. This absorption peak is red-shifted as the relative atomic mass of the 5-substituted atoms increases. Gaussian software was adopted to calculate the absorption spectra of the samples. The simulation conclusions were in good agreement with the experimental results, revealing that the vibration of the base molecule at low frequencies can be attributed to the inter-molecular vibration. This work demonstrates that THz-TDS technology can be used to accurately identify biomolecules with similar molecular structures, reflecting the importance of molecular structure in biological activity. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

9 pages, 3441 KiB

Open AccessCommunication

Carbon Nanotube Far Infrared Detectors with High Responsivity and Superior Polarization Selectivity Based on Engineered Optical Antennas

by Xiansong Ren, Zhaoyu Ji, Binkai Chen, Jing Zhou, Zeshi Chu and Xiaoshuang Chen

Sensors 2021, 21(15), 5221; https://0-doi-org.brum.beds.ac.uk/10.3390/s21155221 - 31 Jul 2021

Cited by 3 | Viewed by 1887

Abstract

Single-wall carbon nanotube (SWCNT) thin films are promising for sensitive uncooled infrared detection based on the photothermoelectric effect. The SWCNT film is usually shaped into a belt and diversely doped to form a p-n junction at the center. Under the illumination of a focused incident light, the temperature gradient from the junction to the contacts leads to photoresponse. When the SWCNTs are aligned in one direction, the photoresponse becomes polarization selective. Although a typical bowtie antenna can improve the responsivity and polarization extinction ratio by deep-subwavelength light focusing, the absolute absorptance of the junction region is only 0.6%. In this work, the antenna was engineered for a higher light coupling efficiency. By integrating a bottom metal plane at a specific distance from the SWCNT film and optimizing the antenna geometries, we achieved ultra-efficient impedance matching between the antenna and the SWCNTs, thus the absorptance of the junction region was further enhanced by 21.3 times and reached 13.5%, which is more than 3 orders of magnitude higher than that of the device without the engineered antenna. The peak responsivity was further enhanced by 19.9 times and responsivity reached 1500 V/W at 1 THz. The resonant frequency can be tuned by changing the size of the antenna. Over the frequency range of 0.5 THz to 1.5 THz, the peak responsivity was further enhanced by 8.1 to 19.9 times, and the polarization extinction ratio was enhanced by 2.7 to 22.3 times. The highest polarization extinction ratio reached 3.04 × 10⁵ at 0.5 THz. The results are based on the numerical simulations of the light and the thermal fields. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures

Figure 1

Review

Jump to: Research

28 pages, 6977 KiB

Open AccessReview

Terahertz Detectors Using Microelectromechanical System Resonators

by Chao Li, Ya Zhang and Kazuhiko Hirakawa

Sensors 2023, 23(13), 5938; https://0-doi-org.brum.beds.ac.uk/10.3390/s23135938 - 26 Jun 2023

Cited by 1 | Viewed by 1904

Abstract

The doubly clamped microelectromechanical system (MEMS) beam resonators exhibit extremely high sensitivity to tiny changes in the resonance frequency owing to their high quality (Q-) factors, even at room temperature. Such a sensitive frequency-shift scheme is very attractive for fast and highly sensitive terahertz (THz) detection. The MEMS resonator absorbs THz radiation and induces a temperature rise, leading to a shift in its resonance frequency. This frequency shift is proportional to the amount of THz radiation absorbed by the resonator and can be detected and quantified, thereby allowing the THz radiation to be measured. In this review, we present an overview of the THz bolometer based on the doubly clamped MEMS beam resonators in the aspects of working principle, readout, detection speed, sensitivity, and attempts at improving the performance. This allows one to have a comprehensive view of such a novel THz detector. Full article

(This article belongs to the Special Issue Sensing with Infrared and Terahertz Technologies)

► Show Figures