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Photonics
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THz Imaging and Spectroscopy
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THz Imaging and Spectroscopy

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Optical Interaction Science".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 8065

Special Issue Editors

Prof. Dr. Dayan Ban

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Interests: semiconductor quantum devices; optoelectronics; scanning probe microscopy; energy harvesting devices; terahertz and infrared photonics
Special Issues, Collections and Topics in MDPI journals
Dr. Xiaoqiong Qi

E-Mail Website
Guest Editor
School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Interests: semiconductor laser dynamics; terahertz quantum cascade lasers; laser feedback interferometry; terahertz sensing and imaging; skin cancer detection
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Terahertz (THz) radiation is an electromagnetic wave with a frequency lies in between the microwave and infrared regions (frequency: 0.1 ~ 10 THz; wavelength: 3mm ~ 0.03mm). THz wave has many unique properties, including high sensitivity to water content, the ability to penetrate a wide variety of non-conducting materials (clothing, paper, cardboard, wood, masonry, plastic and ceramics, etc.), non-ionizing and non-invasive, and with many biological substances have fingerprints in this frequency band. Recently, THz imaging has attracted significant interest for a wide range of applications, including biomedical imaging and diagnosis, security screening, material characterization and pharmaceutical industry. This Special Issue of Photonics, entitled “THz imaging and spectroscopy”, will be focused on design, improvement, and characterization of promising THz imaging and spectroscopy technologies for various applications. It will cover topics on compact THz sources, novel THz imaging principles and methodologies, as well as fast and effective THz detectors. Both reviews and original research articles are very welcome. We are looking forward to your active participation in this Special Issue.

Prof. Dr. Dayan Ban
Dr. Xiaoqiong Qi
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. Photonics is an international peer-reviewed open access monthly 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 2400 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.

Published Papers (5 papers)

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Research

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10 pages, 1746 KiB  
Article
Rapid Determination of Ochratoxin A in Black Tea Using Terahertz Ultrasensitive Biosensor
by Gan Chen, Bingwei Liu, Ping Lu and Yan Peng
Photonics 2024, 11(1), 9; https://doi.org/10.3390/photonics11010009 - 22 Dec 2023
Viewed by 809
Abstract
Ochratoxin A (OTA), which is highly toxic and carcinogenic, is easily produced in cereal crops, dry herbs, and other foods under improper storage. Traditional detection methods, including high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), can detect OTA accurately, but there are [...] Read more.
Ochratoxin A (OTA), which is highly toxic and carcinogenic, is easily produced in cereal crops, dry herbs, and other foods under improper storage. Traditional detection methods, including high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), can detect OTA accurately, but there are many problems such as long period, high cost, and poor reproducibility. Therefore, developing a rapid, non-destructive, and highly sensitive method for OTA detection is essential. In this paper, we used a surface plasmon resonance (SPR) biosensor combined with terahertz (THz) spectroscopy to quantify OTA. As a result, the concentration range of OTA in acetonitrile solution was up to 0–20 pg/μL, with a detection limit of 1 pg/μL, which can meet the requirements for OTA detection in most foods. Further, we applied this method to black tea, and the detection limit was up to 1 pg/mg, which is 500 times higher than UV spectrophotometry, and completely meets the EU regulations. This study shows that the combination of terahertz spectroscopy and an SPR biosensor is a promising approach to achieve a simple, rapid, and low-cost method for trace substance quantification in foods and drugs. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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10 pages, 2839 KiB  
Article
Low-Concentration Biological Sample Detection Using an Asymmetric Split Resonator Terahertz Metamaterial
by Yanchun Shen, Xiaoming Li, Jinlan Wang, Hongmei Liu, Junhao Jing, Xinxin Deng and Dongshan Wei
Photonics 2023, 10(2), 111; https://doi.org/10.3390/photonics10020111 - 21 Jan 2023
Cited by 4 | Viewed by 1459
Abstract
A simple and efficient THz metamaterial based on an asymmetric double split square array resonator was designed and fabricated. The sensitivity and Q value of the metamaterial sensor were theoretically analyzed to be 278 GHz/RIU and 11, respectively. Three typical biological samples with [...] Read more.
A simple and efficient THz metamaterial based on an asymmetric double split square array resonator was designed and fabricated. The sensitivity and Q value of the metamaterial sensor were theoretically analyzed to be 278 GHz/RIU and 11, respectively. Three typical biological samples with different concentrations were measured to validate the sensitivity of the THz metamaterial. For the bovine serum albumin (BSA) protein solution, the lowest detectable concentration (LDC) can reach to 1 μM, which is comparable to most recent reports. For the Staphylococcus aureus bacteria, the LDC is 1 × 103 cells/mL, and for the K-citrate solution, the LDC is 0.1 mM. Our studies indicate that the THz metamaterial may be effectively applied in the low-concentration detection of biological samples. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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10 pages, 1110 KiB  
Communication
Diamond Photoconductive Antenna for Terahertz Generation Equipped with Buried Graphite Electrodes
by Taras Viktorovich Kononenko, Kuralai Khamitzhanovna Ashikkalieva, Vitali Viktorovich Kononenko, Evgeny Viktorovich Zavedeev, Margarita Alexandrovna Dezhkina, Maxim Sergeevich Komlenok, Evgeny Evseevich Ashkinazi, Vladimir Valentinovich Bukin and Vitaly Ivanovich Konov
Photonics 2023, 10(1), 75; https://doi.org/10.3390/photonics10010075 - 09 Jan 2023
Cited by 2 | Viewed by 1501
Abstract
It has been shown recently that a photoconductive antenna (PCA) based on a nitrogen-doped diamond can be effectively excited by the second harmonic of a Ti:sapphire laser (λ = 400 nm). The THz emission performance of the PCA can be significantly increased if [...] Read more.
It has been shown recently that a photoconductive antenna (PCA) based on a nitrogen-doped diamond can be effectively excited by the second harmonic of a Ti:sapphire laser (λ = 400 nm). The THz emission performance of the PCA can be significantly increased if a much stronger electric field is created between the close-located electrodes. To produce a homogeneous electric field over the entire excited diamond volume, the laser fabrication of deep-buried graphite electrodes inside the diamond crystal was proposed. Several electrodes consisting of the arrays of buried pillars connected by the surface graphite stripes were produced inside an HPHT diamond crystal using femtosecond and nanosecond laser pulses. Combining different pairs of the electrodes, a series of PCAs with various electrode interspaces was formed. The THz emission of the PCAs equipped with the buried electrodes was measured at different values of excitation fluence and bias voltage (DC and pulsed) and compared with the emission of the same diamond crystal when the bias voltage was applied to the surface electrodes on the opposite faces. All examined PCAs have demonstrated the square-law dependencies of the THz fluence on the field strength, while the saturation fluence fluctuated in the range of 1200–1600 µJ/cm2. The THz emission performance was found to be approximately the same for the PCAs with the surface electrodes and with the buried electrodes spaced at a distance of 1.4–3.5 mm. However, it noticeably decreased when the distance between the buried electrodes was reduced to 0.5 mm. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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13 pages, 6043 KiB  
Article
High-Speed 600 GHz-Band Terahertz Imaging Scanner System with Enhanced Focal Depth
by Yaheng Wang, Li Yi, Masayoshi Tonouchi and Tadao Nagatsuma
Photonics 2022, 9(12), 913; https://doi.org/10.3390/photonics9120913 - 28 Nov 2022
Cited by 3 | Viewed by 2519
Abstract
Lenses/mirrors with fast data acquisition speeds and extended focal depths have practical importance in terahertz (THz) imaging systems. Thus, a high-speed 600 GHz-band THz imaging scanner system with enhanced focal depth is presented in this work. A polygon mirror with a 250 Hz [...] Read more.
Lenses/mirrors with fast data acquisition speeds and extended focal depths have practical importance in terahertz (THz) imaging systems. Thus, a high-speed 600 GHz-band THz imaging scanner system with enhanced focal depth is presented in this work. A polygon mirror with a 250 Hz scanning frequency and an integrated off-axis parabolic (OAP) mirror with an ~170 mm focal depth were employed for 2D imaging. The simulation and experimental results show that a spatial resolution of ~2 mm can be achieved as the imaging distance varies from ~85 to 255 mm. The proposed system was applied to image a hidden metal object as a potential security application, demonstrating that this system can image targets with an enhanced focal depth. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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Review

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36 pages, 12783 KiB  
Review
Urinary Metabolic Biomarker Profiling for Cancer Diagnosis by Terahertz Spectroscopy: Review and Perspective
by Andreja Abina, Tjaša Korošec, Uroš Puc, Mojca Jazbinšek and Aleksander Zidanšek
Photonics 2023, 10(9), 1051; https://doi.org/10.3390/photonics10091051 - 15 Sep 2023
Cited by 3 | Viewed by 1093
Abstract
In the last decade, terahertz (THz) technologies have been introduced to the detection, identification, and quantification of biomolecules in various biological samples. This review focuses on substances that represent important biomarkers in the urine associated with various cancers and their treatments. From a [...] Read more.
In the last decade, terahertz (THz) technologies have been introduced to the detection, identification, and quantification of biomolecules in various biological samples. This review focuses on substances that represent important biomarkers in the urine associated with various cancers and their treatments. From a diagnostic point of view, urine liquid biopsy is particularly important because it allows the non-invasive and rapid collection of large volumes of samples. In this review, the THz spectral responses of substances considered metabolic biomarkers in urine and obtained in previous studies are collected. In addition, the findings from the relatively small number of prior studies that have already been carried out on urine samples are summarised. In this context, we also present the different THz methods used for urine analysis. Finally, a brief discussion is given, presenting perspectives for future research in this field, interpreted based on the results of previous studies. This work provides important information on the further application of THz techniques in biomedicine for detecting and monitoring urinary biomarkers for various diseases, including cancer. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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