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Journal articles on the topic 'Terahertz fiber'

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Published: 7 July 2024

Last updated: 7 July 2024

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1

Sultana, Jakeya, Md Saiful Islam, Cristiano M. B. Cordeiro, Alex Dinovitser, Mayank Kaushik, Brian W.-H. Ng, and Derek Abbott. "Terahertz Hollow Core Antiresonant Fiber with Metamaterial Cladding." Fibers 8, no. 2 (February 17, 2020): 14. http://dx.doi.org/10.3390/fib8020014.

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A hollow core antiresonant photonic crystal fiber (HC-ARPCF) with metal inclusions is numerically analyzed for transmission of terahertz (THz) waves. The propagation of fundamental and higher order modes are investigated and the results are compared with conventional dielectric antiresonant (AR) fiber designs. Simulation results show that broadband terahertz radiation can be guided with six times lower loss in such hollow core fibers with metallic inclusions, compared to tube lattice fiber, covering a single mode bandwidth (BW) of 700 GHz.

2

Im, Kwang-Hee, David K. Hsu, Chien-Ping Chiou, Daniel J. Barnard, Jong-An Jung, and In-Young Yang. "Terahertz Wave Approach and Application on FRP Composites." Advances in Materials Science and Engineering 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/563962.

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Terahertz (THz) applications have emerged as one of the most new powerful nondestructive evaluation (NDE) techniques. A new T-ray time-domain spectroscopy system was utilized for detecting and evaluating orientation influence in carbon fiber-reinforced plastics (CFRPs) composite laminates. Investigation of terahertz time-domain spectroscopy (THz-TDS) was made, and reflection and transmission configurations were studied as a nondestructive evaluation technique. Here, the CFRP composites derived their excellent mechanical strength, stiffness, and electrical conductivity from carbon fibers. Especially, the electrical conductivity of the CFRP composites depends on the direction of unidirectional fibers since carbon fibers are electrically conducting while the epoxy matrix is not. In order to solve various material properties, the index of refraction (n) and the absorption coefficient (α) are derived in reflective and transmission configurations using the terahertz time-domain spectroscopy. Also, for a 48-ply thermoplastic polyphenylene-sulfide-(PPS-) based CFRP solid laminate and nonconducting materials, the terahertz scanning images were made at the angles ranged from0°to180°with respect to the nominal fiber axis. So, the images were mapped out based on the electrical field (E-field) direction in the CFRP solid laminates. It is found that the conductivity (σ) depends on the angles of the nominal axis in the unidirectional fiber.

3

Hasan, Md Rabiul, S. Ali, and S. A. Emi. "Ultra-low material loss microstructure fiber for terahertz guidance." Photonics Letters of Poland 9, no. 2 (July 1, 2017): 66. http://dx.doi.org/10.4302/plp.v9i2.679.

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In this letter, we numerically demonstrate a hybrid-core microstructure fiber for low-loss terahertz guidance. Finite element method with circular perfectly matched layer boundary condition is applied to characterize the guiding properties. It is shown that by using a triangular-core inside a square lattice microstructure exhibits ultra-low effective material loss (EML) of 0.169 dB/cm and low confinement loss of 0.087 dB/cm at the operating frequency of 0.75 THz. We also discuss how other guiding properties including power fraction, single mode propagation and dispersion vary with changing of core diameter and operating frequencies. This low-loss microstructure fiber can be effectively used in numerous applications in the THz regime. Full Text: PDF ReferencesJ. J. Bai, J. N. Li, H. Zhang, H. Fang, S. J. Chang, "A porous terahertz fiber with randomly distributed air holes", Appl. Phys. B 103, 2 (2011). CrossRef S. Atakaramians, S. Afshar, B. M. Fischer, D. Abbott, T. M. Monro, "Porous fibers: a novel approach to low loss THz waveguides", Opt. Express 16, 12 (2008). CrossRef K. Wang, D. M. Mittleman, "Metal wires for terahertz wave guiding", Nature 432, 7015 (2004). CrossRef R. Islam, G. K. M. Hasanuzzaman, M. S. Habib, S. Rana, M. A. G. Khan, "Low-loss rotated porous core hexagonal single-mode fiber in THz regime", Opt. Fiber Technol. 24, (2015). CrossRef M. I. Hasan, S. M. A. Razzak, G. K. M. Hasanuzzaman, M. S.Habib, "Ultra-Low Material Loss and Dispersion Flattened Fiber for THz Transmission", IEEE Photon. Technol. Lett. 26, 23 (2014). CrossRef S. F. Kaijage, Z. Ouyang, X. Jin, "Porous-Core Photonic Crystal Fiber for Low Loss Terahertz Wave Guiding", IEEE Photon. Technol. Lett. 25, 15 (2013). CrossRef M. R. Hasan, M. A. Islam, A. A. Rifat, "A single mode porous-core square lattice photonic crystal fiber for THz wave propagation", J. Eur. Opt. Soc. Rapid Publ. 12, 1 (2016). CrossRef M. R. Hasan, M. A. Islam, M. S. Anower, S. M. A. Razzak, "Low-loss and bend-insensitive terahertz fiber using a rhombic-shaped core", Appl. Opt. 55, 30 (2016). CrossRef S. Ali et al. "Ultra-low loss THz waveguide with flat EML and near zero flat dispersion properties", in 9th Int. Conf. on Elect. and Comp. Eng., IEEE, (2016). CrossRef K. Nielsen, H. K. Rasmussen, A. J. Adam, P. C. Planken, O. Bang, P. U. Jepsen, "Bendable, low-loss Topas fibers for the terahertz frequency range", Opt. Express 17, 10 (2009). CrossRef A. W. Snyder, J. D. Love, Optical waveguide theory (London, Chapman & Hall 1983). DirectLink L. Vincetti, A. Polemi, in Antennas and Propagation Society International Symposium, IEEE (2009)G. P. Agrawal, Nonlinear fiber optics (Boston, Academic Press 1989). CrossRef B. S. Williams, "Terahertz quantum-cascade lasers", Nat. Photon. 1, 9 (2007). CrossRef H. W. Hubers et al. "Terahertz quantum cascade laser as local oscillator in a heterodyne receiver", Opt. Express 13, 15 (2005). CrossRef

4

T. V., Smitha, Madhura S, Shreya N, and Sahana Udupa. "Optical Waveguides and Terahertz Signal by Finite Element Method: A Survey." June 2021 3, no. 2 (June 3, 2021): 68–86. http://dx.doi.org/10.36548/jsws.2021.2.002.

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This paper examines the use of the Finite Element Method (FEM) in the field of optical waveguides and terahertz signals, with the main goal of explaining how this method aids in recent advances in this field. The basics of FEM are briefly reviewed, and the technique's application to waveguide discontinuity analysis is observed. Second-order and higher-order derivatives result from optical waveguide modeling, which is significant for information exchange and many other nonlinear phenomena. The use of FEM in the improvised design of hexagonal sort air hole porous core microstructure fibers, which produces hexagonal structure cladding and rectangular-shaped air holes in the fiber core for excellent terahertz signal transmission, was also observed. These modifications were intended to improve the fiber's properties in comparison to other structures. This approach verifies that the fiber has high birefringence, low material loss, a high-power fraction, and minimal dispersion varia-tion. The features of square-type microstructure fiber are investigated. A folded-shaped po-rous cladding design is recognized for sensing applications. This type of photonic crystal fiber is also known as FP-PCF since it features circular air holes. The most approximate findings of this application are obtained using FEM. In comparison to many other approach-es for various applications, it is evident that FEM is a powerful and numerically efficient tool. This work does a survey of optical waveguides and terahertz signals using the Finite Element Method. Terahertz signals can be used in conjunction with electromagnetic waves to identify viruses. Thus, Terahertz signals are employed in real-world applications such as fuel adulteration, liquid metal synthesis, and virus detection.

5

Habib, Md Ahasan, and Md Shamim Anower. "Square Porous Core Microstructure Fiber for Low Loss Terahertz Applications-=SUP=-*-=/SUP=-." Журнал технической физики 126, no. 5 (2019): 690. http://dx.doi.org/10.21883/os.2019.05.47671.335-18.

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AbstractA new kind of square lattice porous core microstructure fiber is proposed for promising low loss terahertz applications. To analyze the guiding characteristics of proposed fiber Finite Element Method (FEM) based Comsol V4.2 software is used. The proposed fiber structure is very simple and easy to realize. The numerical results ensures that this proposed microstructure fiber exhibits low effective absorption loss of 0.06 cm^–1, low confinement loss of 9.2 × 10^–3 cm^–1, low bending loss of 8.8 × 10^–9 dB/m, and very high power fraction of 47% through the core at 1 THz simultaneously. Moreover, our proposed fiber offers very low dispersion variation of 0.85 ± 0.12 ps/THz/cm over a wide range of frequency from 0.7 to 1.15 THz. The investigated results indicates that this fiber will be a good candidate in terahertz signal transmission as well as different terahertz devices.

6

Im, Kwang-Hee, Sun-Kyu Kim, Jong-An Jung, Young-Tae Cho, Yong-Deuck Woo, and Chien-Ping Chiou. "NDE Terahertz Wave Techniques for Measurement of Defect Detection on Composite Panels of Honeycomb Sandwiches." Electronics 9, no. 9 (August 21, 2020): 1360. http://dx.doi.org/10.3390/electronics9091360.

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Terahertz wave (T-ray) technologies have become a popular topic in scientific research over the last two decades, and can be utilized in nondestructive evaluation (NDE) techniques. This study suggests an optimal scanning technique method for honeycomb sandwich composite panels, where skins were utilized with two different skins, namely, carbon fiber-reinforced plastic (CFRP) skin and glass fiber-reinforced plastic (GFRP) skin, as layers of the panel surfaces. Foreign objects were artificially inserted between the skins and honeycomb cells in the honeycomb sandwich composite panels. For this experiment, optimal T-ray scanning methods were performed to examine defects based on the angle between the one-ply thin fiber skin axis and the angle of the electric field (E-field) according to the amount of conductivity of the honeycomb sandwich composite panels. In order to confirm the fundamental characteristics of the terahertz waves, the refractive index values of the GFRP composites were experimentally obtained and analyzed, with the data agreeing with known solutions. Terahertz waves (T-rays) were shown to have limited penetration in honeycomb sandwich composite panels when utilized with a skin of carbon fibers. Therefore, T-rays were found to interact with the electrical conductivity and electric field direction of honeycomb sandwich composite panels with glass fiber skins. The T-ray images were obtained regardless of the electric field direction and the fiber direction. In the honeycomb sandwich composite panels with carbon fiber skins, the T-ray images with higher signal-to-noise (S/N) ratios depended on the scanning angle between the angle of the carbon fiber and the angle of the electric field. Thus, the angle of optimum detection measurement was confirmed to be 90° between the E-field and the fiber direction, particularly when using a carbon fiber skin.

7

Lu, Ja-Yu, Chin-Ping Yu, Hung-Chung Chang, Hung-Wen Chen, Yu-Tai Li, Ci-Ling Pan, and Chi-Kuang Sun. "Terahertz air-core microstructure fiber." Applied Physics Letters 92, no. 6 (February 11, 2008): 064105. http://dx.doi.org/10.1063/1.2839576.

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8

Nielsen, Kristian, Henrik K. Rasmussen, Peter Uhd Jepsen, and Ole Bang. "Broadband terahertz fiber directional coupler." Optics Letters 35, no. 17 (August 20, 2010): 2879. http://dx.doi.org/10.1364/ol.35.002879.

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9

Zubair, Ahmed, Dmitri E. Tsentalovich, Colin C. Young, Martin S. Heimbeck, Henry O. Everitt, Matteo Pasquali, and Junichiro Kono. "Carbon nanotube fiber terahertz polarizer." Applied Physics Letters 108, no. 14 (April 4, 2016): 141107. http://dx.doi.org/10.1063/1.4945708.

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10

Abramov, Aleksei, Igor Zolotovskii, Vladimir Kamynin, Victor Prikhodko, Aleksei Tregubov, Dmitrii Stoliarov, Marina Yavtushenko, and Andrei Fotiadi. "High-Peak Power Frequency Modulation Pulse Generation in Cascaded Fiber Configurations with Inscribed Fiber Bragg Grating Arrays." Photonics 8, no. 11 (October 24, 2021): 471. http://dx.doi.org/10.3390/photonics8110471.

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We explored the dynamics of frequency-modulated (FM) pulses in a cascaded fiber configuration comprising one active and one passive optical fiber with multiple fiber Bragg gratings (FBGs) of different periods inscribed over the fiber configuration length. We present a theoretical formalism to describe the mechanisms of the FM pulse amplification and pulse compression in such fiber cascades resulting in peak powers up to ~0.7 MW. In combination with the decreasing dispersion fibers, the considered cascade configuration enables pico- and sub-picosecond pulse trains with a sub-terahertz repetition rate and sub-kW peak power generated directly from the continuous optical signal.

11

Xiao, Yue-yu, and Shao-fan Lu. "Terahertz circular fiber polarizers using suspended-core spiral fibers." Applied Optics 56, no. 3 (January 17, 2017): 558. http://dx.doi.org/10.1364/ao.56.000558.

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12

Yang, Jingxuan, and Wei Li. "Design for Terahertz Circular-Core Photonic Crystal Fiber Supporting Orbital Angular Momentum Modes." Photonics 9, no. 9 (August 26, 2022): 607. http://dx.doi.org/10.3390/photonics9090607.

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We propose a new terahertz fiber based on a circular-core photonic crystal fiber (PCF) structure to support high-performance orbital angular momentum (OAM) modes transmission. The modal characteristics of the proposed terahertz fiber were thoroughly analyzed to vary the parameters of air holes radius and the annular thickness by the full-vector finite element method (FEM). The optimal parameters are selected to realize the stable transmission of five-order OAM mode with high mode quality, low confinement loss and wide bandwidth. The mode purity is in excess of 91%, and the confinement loss is less than 10−7 dB/m over the 0.2 THz to 0.55 THz band. Furthermore, the design of this PCF is relatively simple and flexible, since it consists only of circular air holes. Due to its excellent transmission characteristics, the proposed OAM fiber has a potential application in terahertz mode division multiplexing (MDM) communication system.

13

Ponomarev D. S., Lavrukhin D. V., Zenchenko N. V., Glinskiy I. A., Khabibullin R. A., Kurlov V. N., and Zaytsev K. I. "Laser pulse energy localization in a photoconductive THz emitter via sapphire fibers." Technical Physics Letters 48, no. 12 (2022): 8. http://dx.doi.org/10.21883/tpl.2022.12.54936.19332.

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We report a seminal approach for localization of photocarriers in a photoconductive antenna (PCA)-emitter via a focusing element comprising the sapphire fiber. Using numerical simulation, we showed that at a certain ratio between the fiber diameter and antenna gap size (d/g~ 22.5), one can attain a ~ 35-fold enhancement of laser irradiation in the vicinity of the PCA electrodes. This provides the formation of subwavelength electromagnetic wave caustics located at the edges of the PCA electrodes, which potentially promotes an increase in the optical-to-terahertz conversion efficiency. Keywords: terahertz frequency, terahertz emitters, semiconductors, photoconductive antenna, IR radiation.

14

Habib, Ahasan. "Ultra low loss and dispersion flattened microstructure fiber for terahertz applications." Brilliant Engineering 1, no. 3 (January 10, 2020): 1–5. http://dx.doi.org/10.36937/ben.2020.003.001.

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In this paper, a rectangular core hexagonal lattice porous core photonic crystal fiber (PC-PCF) is reported for effectively guiding the terahertz light signal. Finite element method with circular perfectly matched layer boundary condition is employed to find out the propagation characteristics of this proposed porous core fiber. Extensive simulation results of that microstructure fiber over wide frequency range shows that very low effective material loss of 0.035 cm-1, large effective area of 1.79×10-7 m2 and high core power fraction of 36% can be obtained simultaneously. In addition, for same designing condition nearly zero flattened dispersion of 0.46 ± 0.07 ps/THz/cm can be achieved over 600 GHz frequency band in terahertz range. Furthermore, other important parameters like single mode operation, confinement loss and bending loss are also investigated rigorously for the proposed fiber. The excellent results of this optical waveguide will pave the way to implement it in various real life terahertz applications.

15

CROOKER, S. A., and A. J. TAYLOR. "ULTRAFAST COHERENT TERAHERTZ SPECTROSCOPY IN HIGH MAGNETIC FIELDS." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 3385–88. http://dx.doi.org/10.1142/s0217979202014498.

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With an aim towards measuring the high-frequency complex conductivity of correlated electron materials in the regime of low temperatures and high magnetic fields, we introduce a method for performing time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed-field magnets. Miniature, fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 5 K and up to 6 Tesla, for eventual use in higher-field magnets. Maintaining the sub-micron alignment between fiber and antenna during thermal cycling, and obtaining ultrafast (<200fs) optical gating pulses at the end of long optical fibers constitute the major technical challenges of this project. Preliminary data on YBCO superconducting thin films is shown.

16

HE Zhong-jiao, 何忠蛟. "Fiber Bragg Grating Based on a Polymer Terahertz Fiber." ACTA PHOTONICA SINICA 44, no. 4 (2015): 406006. http://dx.doi.org/10.3788/gzxb20154404.0406006.

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17

Yasui, Takeshi, Masaki Nose, Atsushi Ihara, Kohji Kawamoto, Shuko Yokoyama, Hajime Inaba, Kaoru Minoshima, and Tsutomu Araki. "Fiber-based, hybrid terahertz spectrometer using dual fiber combs." Optics Letters 35, no. 10 (May 14, 2010): 1689. http://dx.doi.org/10.1364/ol.35.001689.

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18

Madani, Seyed Ahmad, Manouchehr Bahrami, and Ali Rostami. "Multi-clad optical fiber design for ultra-wideband modulation instability." Physica Scripta 97, no. 4 (March 14, 2022): 045501. http://dx.doi.org/10.1088/1402-4896/ac5a3b.

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Abstract Developments of electro-optic (EO) modulators do not have a satisfactory pace and bandwidth restrictions are still limited to several hundred GHz, thus, obtaining methods that enable using broadband optical channels are key factors in high-speed optical communications. In this paper, Modulation Instability (MI) as an approach in order to improve the performance of EO modulators, is investigated in the anomalous and zero-dispersion regimes of proposed optical fiber. In present conventional optical fibers, MI is observed over a few hundred gigahertz bandwidths at low pump power. In order to obtain ultra-wideband (a few Terahertz) bandwidths and maximum gain in the MI process at low pump power, a new structure for optical fiber is proposed. The genetic algorithm is utilized for performance optimization in optical fiber design. It is shown that the proposed optical fiber is able to support MI for a few Terahertz bands at low pump power (100 mW). Furthermore, in this analysis, it is demonstrated that higher-order dispersion terms have a strong impact on modulation instability. Finally, it is concluded that the geometrical and optical parameters of optical fiber are key factors to control modulation instability parameters (gain and bandwidth). The proposed optical fiber can be used as an optical booster in order to compensate frequency response of EO modulators, which is a considerable step forward in high-speed optical communication.

19

Świderski, Waldemar, and Martyna Strąg. "Comparative Studies of GFRP Composites Using Pulsed Thermography and Transmission Terahertz Non-Destructive Testing Methods." Pomiary Automatyka Robotyka 27, no. 3 (September 16, 2023): 33–37. http://dx.doi.org/10.14313/par_249/33.

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Composites are materials that have replaced traditional construction materials in numerous applications in various fields. Due to the possibility of creating the required material properties, fiber-reinforced composites are most often used. Despite competition from carbon and aramid fibers, the earliest glass fibers produced are used in many applications. One of the areas where glass fiber reinforced composites (GFRP) make a significant contribution to structural applications is aviation. Because both during production and operation, composites are exposed to damage, which often occurs in the internal structure of the composite, works are being carried out to develop the most effective method of non-destructive testing to detect such damage. The article presents a comparison of the results of non-destructive testing of glass fiber-reinforced composite samples. A comparison of the results of the possibility of detecting defects in the form of milled holes of different diameters and depths inside the samples was made. These damages are not optically visible on both surfaces of the samples. In non-destructive testing, infrared thermography and transmission terahertz methods were used. The obtained results indicate a great possibility of using terahertz radiation, especially in thicker structures of the GFRP composite, where thermographic methods are not as effective as in thin ones.

20

Zhang, Zhuo, Yandong Gong, Ke Li, and Guobin Ren. "Investigation on fiber‐based terahertz source." Microwave and Optical Technology Letters 63, no. 10 (June 28, 2021): 2675–80. http://dx.doi.org/10.1002/mop.32943.

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21

Zhou, Shu Fan, Hau Ping Chan, Laurence Reekie, Yuk Tak Chow, Po Sheun Chung, and Kwai Man Luk. "Polymer Fiber Polarizer for Terahertz Applications." IEEE Photonics Technology Letters 24, no. 17 (September 2012): 1490–92. http://dx.doi.org/10.1109/lpt.2012.2206021.

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22

Tang, Jian, Zhigang Zhang, Deng Luo, Ming Chen, and Hui Chen. "High birefringence terahertz photonic crystal fiber." Optical Engineering 52, no. 1 (January 8, 2013): 014004. http://dx.doi.org/10.1117/1.oe.52.1.014004.

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23

Huang, Yu-Wei, Tzu-Fang Tseng, Chung-Chiu Kuo, Yuh-Jing Hwang, and Chi-Kuang Sun. "Fiber-based swept-source terahertz radar." Optics Letters 35, no. 9 (April 22, 2010): 1344. http://dx.doi.org/10.1364/ol.35.001344.

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24

Hameed, Mohamed Farhat O., Mohamed Saleh M. Esmail, and Salah S. A. Obayya. "Terahertz photonic crystal fiber polarization rotator." Journal of the Optical Society of America B 37, no. 10 (September 8, 2020): 2865. http://dx.doi.org/10.1364/josab.399165.

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Lopato, Przemyslaw. "Automatic defect recognition for pulsed terahertz inspection of basalt fiber reinforced composites." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 35, no. 4 (July 4, 2016): 1346–59. http://dx.doi.org/10.1108/compel-09-2015-0351.

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Purpose – The purpose of this paper is to present a system for automatic recognition of defects detected in non-conductive polymer composites using pulsed terahertz imaging. Design/methodology/approach – On the beginning, non-destructive evaluation of composites using electromagnetic waves in terahertz frequency is shortly introduced. Next automatic defects recognition (ADR) algorithm is proposed, focussing on new features calculation. Dimensionality of features space is reduced by using principal component analysis. Finally, results of basalt fiber reinforced composite materials inspection and identification using artificial neural networks is presented and discussed. Findings – It is possible to develop ADR system for non-destructive evaluation of dielectric materials using pulsed terahertz technique. New set of features in time and frequency domains is proposed and verified. Originality/value – ADR in non-destructive testing is utilized in case of digital radiography and ultrasonic testing. Terahertz inspection with pulsed excitation is reported as a source of many useful information about the internal structure of the dielectric material. Up to now ADR based on terahertz non-destructive evaluation systems was not utilized.

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Zhang, Jin, Jiandong Chen, Jie Wang, Jinpeng Lang, Jinbo Zhang, Yan Shen, Hong-Liang Cui, and Changcheng Shi. "Nondestructive evaluation of glass fiber honeycomb sandwich panels using reflective terahertz imaging." Journal of Sandwich Structures & Materials 21, no. 4 (June 6, 2017): 1211–23. http://dx.doi.org/10.1177/1099636217711628.

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The glass fiber honeycomb sandwich panel is an efficient structural configuration which has been widely used in several designs related to air, sea, and land transport systems. Terahertz time domain spectroscopy technology is an effective supplementary method for nondestructive evaluation of composites. Terahertz time domain spectroscopy imaging technology in the reflection configuration was employed to detect the defects of glass fiber honeycomb sandwich panels, such as a skin-core debonding and a foreign inclusion. It was shown in systematic experimental investigation that different defects were detected through terahertz imaging based on different parameters, which were obtained by comparing and analyzing the waveforms in time and/or frequency domain between normal and defective regions of the sample.

27

Guo, Cuijuan, Mengya Su, Jia Shi, Linlin Tian, Wei Xu, Hongli Chen, Hua Bai, Zhitao Xiao, Degang Xu, and Jianquan Yao. "Tunable Temperature Characteristic of Terahertz Bragg Fiber Filled with Liquid Water." Applied Sciences 11, no. 18 (September 7, 2021): 8306. http://dx.doi.org/10.3390/app11188306.

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Hollow-core terahertz (THz) fibers have attracted a lot of research interest due to the low loss and easy inner modification with functional materials. Liquid water has unique properties in the THz region and has been widely investigated in THz emission, sensing, and devices. In this paper, a hollow-core THz Bragg fiber with a water defect layer is proposed. The finite element method is used to verify and analyze the tunable temperature characteristic of the water-filled THz fiber. The numerical analysis results show that the confinement loss and the low-frequency side of the dip near 0.5 THz can be controlled by the temperature of the liquid water. The temperature sensitivity of the THz fiber is obtained at 0.09614 dB·m−1/K at 0.45 THz with a high core power fraction up to 98%. The proposed THz fiber has potential applications in THz interaction with liquid and THz tunable devices.

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Habib, Md Ahasan. "A Refractive Index Based Micro-Structured Sensor for Blood Components Detection in Terahertz Regime." Sensor Letters 18, no. 1 (January 1, 2020): 74–82. http://dx.doi.org/10.1166/sl.2020.4186.

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In this article, a hexagonal packing photonic crystal fiber based optical sensor is presented and analyzed for different blood components identification using terahertz (THz) signal. The numerical analysis of the proposed sensor is performed by using finite element method based software Comsol V5.0. The proposed fiber is investigated in terahertz frequency spectrum from 1.3 THz to 2.5 THz for higher relative sensitivity and numerical aperture as well as lower absorption loss and confinement loss for better sensing applications. The reported hollow core fiber provide better interaction of light and the analytes, so that high relative sensitivity of 83.45%, 81.20%, 80.78%, 79.60% and 78.80% are obtained for RBCs, Hemoglobin, WBCs, Plasma and Water respectively at a particular geometric condition. Moreover, very low confinement loss and absorption loss with high numerical aperture is offered by the proposed sensor in terahertz spectrum. This optical sensor may be an alternative option to detect blood components present in the blood in a very efficient manner.

29

Yang, Rui, Xianyin Dong, Gang Chen, Feng Lin, Zhenhua Huang, Maurizio Manzo, and Haiyan Mao. "Novel Terahertz Spectroscopy Technology for Crystallinity and Crystal Structure Analysis of Cellulose." Polymers 13, no. 1 (December 22, 2020): 6. http://dx.doi.org/10.3390/polym13010006.

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Crystallinity is an essential indicator for evaluating the quality of fiber materials. Terahertz spectroscopy technology has excellent penetrability, no harmful substances, and commendable detection capability of absorption characteristics. The terahertz spectroscopy technology has great application potential in the field of fiber material research, especially for the characterization of the crystallinity of cellulose. In this work, the absorption peak of wood cellulose, microcrystalline cellulose, wood nano cellulose, and cotton nano cellulose were probed in the terahertz band to calculate the crystallinity, and the result compared with XRD and FT-IR analysis. The vibration model of cellulose molecular motion was obtained by density functional theory. The results showed that the average length of wood cellulose (WC) single fiber was 300 μm. The microcrystalline cellulose (MCC) was bar-like, and the average length was 20 μm. The cotton cellulose nanofiber (C-CNF) was a single fibrous substance with a length of 50 μm, while the wood cellulose nanofiber (W-CNF) was with a length of 250 μm. The crystallinity of cellulose samples in THz was calculated as follows: 73% for WC, 78% for MCC, 85% for W-CNF, and 90% for C-CNF. The crystallinity values were obtained by the three methods which were different to some extent. The absorption peak of the terahertz spectra was most obvious when the samples thickness was 1 mm and mixed mass ratio of the polyethylene and cellulose was 1:1. The degree of crystallinity was proportional to the terahertz absorption coefficients of cellulose, the five-movement models of cellulose molecules corresponded to the five absorption peak positions of cellulose.

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Li, Hui Qin, Ji Xian Gong, Jian Fei Zhang, Chang Lei Wang, and Zhen Tian. "Sensing Textile Fibers by THz Time-Domain Spectroscopy." Advanced Materials Research 298 (July 2011): 153–56. http://dx.doi.org/10.4028/www.scientific.net/amr.298.153.

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Along with the booming development of multi-component blending fabrics, the accurate detection of component of fabrics has become a major goal in textile testing. Terahertz sensing technology provides a new way for detecting the materials. THz time-domain spectroscopy (THz-TDS) is a novel spectroscopic technique which measures the electric field of the radiation through a sample and provides the phase and amplitude changes of the radiation, which can provide information unavailable through conventional methods such as microwave and X-ray techniques. In this investigation, THz-TDS technology was introduced into the textile differentiation. Three kinds of cellulose textile fibers, cotton fiber, bamboo fiber and viscose fiber, were prepared as the sample and detected by THz-TDS at room temperature in the absence of vapor. The temporal and frequency signals of the fibers were obtained. In the THz absorption spectrum, the characteristic absorption peaks of textile fibers in THz wave band were found, which can be used to recognize the fibers. This approach provides a novel non-contact examine method for fiber identification in complicated textiles.

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Dorney, Timothy D., William W. Symes, and Daniel M. Mittleman. "Multistatic Reflection Imaging with Terahertz Pulses." International Journal of High Speed Electronics and Systems 13, no. 02 (June 2003): 677–99. http://dx.doi.org/10.1142/s0129156403001855.

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Recent advances in the technique of terahertz time-domain spectroscopy have led to the development of the first fiber-coupled room-temperature broadband terahertz sources and detectors. The fiber coupling permits the repositioning of the emitter and receiver antennas without loss of temporal calibration or alignment, thus enabling multistatic imaging. We describe a new imaging method which exploits this new capability. This technique emulates the data collection and image processing procedures developed for geophysical prospecting. We use a migration procedure to solve the inverse problem; this permits us to reconstruct the location, shape, and refractive index of targets. We show examples for both metallic and dielectric model targets, and we perform velocity analysis on dielectric targets to estimate the refractive indices of imaged components. These results broaden the capabilities of terahertz imaging systems, and also demonstrate the viability of the THz system as a test bed for the exploration of new seismic processing methods.

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Yoon, Young-Jong, Namje Kim, Han-Cheol Ryu, Kiwon Moon, Jun-Hwan Shin, Sang-Pil Han, and Kyung Hyun Park. "Terahertz Time-Domain Spectroscopy and Imaging using Compact Fiber-coupled Terahertz Modules." Korean Journal of Optics and Photonics 25, no. 2 (April 25, 2014): 72–77. http://dx.doi.org/10.3807/kjop.2014.25.2.072.

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Hossain, Md Selim, Md Omar Faruq, Md Masud Rana, Shuvo Sen, Md Dulal Haque, and Mir Mohammad Azad. "Sensitivity analysis for detecting chemicals by the optical chemical sensor based Photonic Crystal Fiber (PCF) in the Terahertz (THz) regime." Physica Scripta 96, no. 12 (December 1, 2021): 125121. http://dx.doi.org/10.1088/1402-4896/ac42ec.

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Abstract This research article demonstrates a good simulation result for identifying and detecting various industrial chemicals in a Terahertz (THz) waveguide with a new heptagonal, five layers of heptagonal photonic fiber elliptic form, heptagonal cladding shape (H-PCF). COMSOL 4.2 software based on finite element (FEM) methods and perfectly matched layers check our composition (PML). The different chemicals are also differentiated and identified by each other in different parameters H-PCF fibers show a high relative sensitivity of ethanol of approximately 86.50 percent after numerical analysis, Benzene around 89.35%, and water around 85.15% at a frequency of around 0.7 THz. In our experiment, we obtained very low confinement losses at 1 terahertz (THz) such as 5.95 × 10−08 dB/m for Ethanol 6.67 × 10−08 dB/m for Benzene, and 5.80 × 10−08 dB/m for water. Regarding these results, we can strongly recommend that our proposed heptagonal photonic crystal fiber (H-PCF) will be more congenial in biomedical, bio-medicine, and industrial areas for the identification and detection of various types of chemicals with the help of a THz waveguide.

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Bezborodov, V. I., V. K. Kiseliov, Y. M. Kuleshov, P. K. Nesterov, S. V. Mizrakhi, I. V. Sherbatko, and M. S. Yanovsky. "Sub-Terahertz Quasi-Optical Reflectometer for CFRP Surface Inspection." Advanced Materials Research 664 (February 2013): 547–50. http://dx.doi.org/10.4028/www.scientific.net/amr.664.547.

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Quasioptical reflectometer based on hollow dielectric beamguide (HDB), terahertz beamguide components and elements has been developed. The reflectometer has been analyzed in terms of its application for nondestructive method for surface and subsurface contamination of carbon fiber reinforced plastic (CFRP). Sub-terahertz (0.1…0.2 THz) measurement results of CFRP samples with different surface contaminations are presented.

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Islam, Raonaqul, Shubi Felix Kaijage, and Sohel Rana. "Low-loss and dispersion flattened terahertz fiber." Optik 229 (March 2021): 166293. http://dx.doi.org/10.1016/j.ijleo.2021.166293.

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Jiang Zi-Wei, Bai Jin-Jun, Hou Yu, Wang Xiang-Hui, and Chang Sheng-Jiang. "Terahertz dual air core fiber directional coupler." Acta Physica Sinica 62, no. 2 (2013): 028702. http://dx.doi.org/10.7498/aps.62.028702.

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Stehr, Dominik, Christopher M. Morris, Christian Schmidt, and Mark S. Sherwin. "High-performance fiber-laser-based terahertz spectrometer." Optics Letters 35, no. 22 (November 9, 2010): 3799. http://dx.doi.org/10.1364/ol.35.003799.

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Goto, Masahiro, Alex Quema, Hiroshi Takahashi, Shingo Ono, and Nobuhiko Sarukura. "Teflon Photonic Crystal Fiber as Terahertz Waveguide." Japanese Journal of Applied Physics 43, No. 2B (February 6, 2004): L317—L319. http://dx.doi.org/10.1143/jjap.43.l317.

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Yi, Minwoo, Kanghee Lee, Jongseok Lim, Youngbin Hong, Young-Dahl Jho, and Jaewook Ahn. "Terahertz waves emitted from an optical fiber." Optics Express 18, no. 13 (June 10, 2010): 13693. http://dx.doi.org/10.1364/oe.18.013693.

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Chen, Zhen, Lei Yuan, Gerald Hefferman, and Tao Wei. "Terahertz Fiber Bragg Grating for Distributed Sensing." IEEE Photonics Technology Letters 27, no. 10 (May 15, 2015): 1084–87. http://dx.doi.org/10.1109/lpt.2015.2407580.

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Chiu, Chui-Min, Hung-Wen Chen, Yu-Ru Huang, Yuh-Jing Hwang, Wen-Jeng Lee, Hsin-Yi Huang, and Chi-Kuang Sun. "All-terahertz fiber-scanning near-field microscopy." Optics Letters 34, no. 7 (March 27, 2009): 1084. http://dx.doi.org/10.1364/ol.34.001084.

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Anthony, Jessienta, Rainer Leonhardt, Alexander Argyros, and Maryanne C. J. Large. "Characterization of a microstructured Zeonex terahertz fiber." Journal of the Optical Society of America B 28, no. 5 (April 8, 2011): 1013. http://dx.doi.org/10.1364/josab.28.001013.

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Ji, Young Bin, Eui Su Lee, Sang-Hoon Kim, Joo-Hiuk Son, and Tae-In Jeon. "A miniaturized fiber-coupled terahertz endoscope system." Optics Express 17, no. 19 (September 10, 2009): 17082. http://dx.doi.org/10.1364/oe.17.017082.

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Im, Kwang Hee, David K. Hsu, Chien Ping Chiou, and Daniel J. Barnard. "T-Ray NDE Inspections on the Fiber Direction of Thermoplastic PPS-Based CFRP Composites." Advanced Materials Research 650 (January 2013): 253–57. http://dx.doi.org/10.4028/www.scientific.net/amr.650.253.

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Terahertz ray (T-ray) imaging has been emerged as one of the most promising new powerful nondestructive evaluation (NDE) techniques, and new application systems are under processing development for the area applications. The terahertz time domain spectroscopy (THz TDS) can be considered as a useful tool using general non-conducting materials; however it is quite limited to conducting materials. In this study, a new time-domain spectroscopy system was utilized for detecting and evaluating layup effect and flaw in FRP composite laminates. In order to solve various material properties, the index of refraction (n) and the absorption coefficient (α) are derived in reflective and transmission configuration using the terahertz time domain spectroscopy. However, the T-ray is limited in order to penetrate a conducting material to some degree. So, investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied for a 48-ply thermoplastic PPS (poly-phenylene sulfide)-based CFRP solid laminate.

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Islam, Md Rakibul, Tabassum Jannat Ritu, and Saeed Mahmud Ullah. "Design and simulation of Zeonex Based Suspended Microstructure Photonic Crystal Fiber for Chemical Sensing Application." Dhaka University Journal of Applied Science and Engineering 7, no. 2 (April 4, 2023): 56–61. http://dx.doi.org/10.3329/dujase.v7i2.65098.

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Over the last few years for sensing applications in terahertz regime photonic crystal fiber (PCF) has gained attention quite extensively. The optical characteristics of photonic crystal fiber can be controlled by fine-tuning of the structural parameters like core radius and effecctive area. In this context, a terahertz sensor based on a hollow-core photonic crystal fiber has been developed for chemical identification in the terahertz frequency range with very low loss. The proposed structure contains hexagonal manner sectored suspension type cladding and hexagonal manner sectored core region, all the sector are formed by zeonex based struts. To investigate the optical characteristics of developed design, finite element method (FEM) based COMSOL multiphysics v.5.4a software has been used. The simulation result shows the sensitivity of 83.37% and 83.63% at the optimum condition in x-polarization mode for ethanol and benzene respectively with low effective material loss of 0.0291 cm−1 and low confinement loss of 1.87×10-13 cm-1. Moreover, the developed design implementation is possible in the existing fabrication method. Physical features and comparative performance analysis are also showed in this research. DUJASE Vol. 7 (2) 56-61, 2022 (July)

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Nellen, S., T. Ishibashi, A. Deninger, R. B. Kohlhaas, L. Liebermeister, M. Schell, and B. Globisch. "Experimental Comparison of UTC- and PIN-Photodiodes for Continuous-Wave Terahertz Generation." Journal of Infrared, Millimeter, and Terahertz Waves 41, no. 4 (December 20, 2019): 343–54. http://dx.doi.org/10.1007/s10762-019-00638-5.

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AbstractWe carried out an experimental comparison study of the two most established optoelectronic emitters for continuous-wave (cw) terahertz generation: a uni-traveling-carrier photodiode (UTC-PD) and a pin-photodiode (PIN-PD). Both diodes are commercially available and feature a similar package (fiber-pigtailed housings with a hyper-hemispherical silicon lens). We measured the terahertz output as a function of optical illumination power and bias voltage from 50 GHz up to 1 THz, using a precisely calibrated terahertz power detector. We found that both emitters were comparable in their spectral power under the operating conditions specified by the manufacturers. While the PIN-PD turned out to be more robust against varying operating parameters, the UTC-PD showed no saturation of the emitted terahertz power even for 50 mW optical input power. In addition, we compared the terahertz transmission and infrared (IR) blocking ratio of four different filter materials. These filters are a prerequisite for correct measurements of the absolute terahertz power with thermal detectors.

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Petrov, Nikolai I. "Dispersive Propagation of Terahertz Pulses in a Plasmonic Fiber." Fibers 11, no. 7 (July 14, 2023): 62. http://dx.doi.org/10.3390/fib11070062.

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The dispersion properties of surface plasmon polaritons (SPPs) during propagation on metal wires with a dielectric coating in the terahertz frequency range were investigated theoretically. An analytical expression was obtained for a pulsed electric field using the solution of Maxwell equations taking into account high-order dispersion terms. The influence of the dielectric coating on the distortion of the pulse shape was investigated. Unlike uncoated wire, the propagation of surface plasmon pulses along a coated wire is highly dispersive. It was shown that the coating leads to the appearance of a long-chirped signal with a propagation of only a few millimeters, i.e., when a terahertz pulse propagates along a coated wire, it acquires a long oscillatory tail, the frequency of which depends on time.

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Kolpatzeck, Kevin, Xuan Liu, Lars Häring, Jan C. Balzer, and Andreas Czylwik. "Ultra-High Repetition Rate Terahertz Time-Domain Spectroscopy for Micrometer Layer Thickness Measurement." Sensors 21, no. 16 (August 10, 2021): 5389. http://dx.doi.org/10.3390/s21165389.

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Terahertz time-domain spectroscopy systems driven by monolithic mode-locked laser diodes (MLLDs) exhibit bandwidths exceeding 1 THz and a peak dynamic range that can compete with other state-of-the-art systems. Their main difference compared to fiber-laser-driven systems is their ultra-high repetition rate of typically dozens of GHz. This makes them interesting for applications where the length of the terahertz path may not be precisely known and it enables the use of a very short and potentially fast optical delay unit. However, the phase accuracy of the system is limited by the accuracy with which the delay axes of subsequent measurements are synchronized. In this work, we utilize an all-fiber approach that uses the optical signal from the MLLD in a Mach–Zehnder interferometer to generate a reference signal that we use to synchronize the detected terahertz signals. We demonstrate transmission-mode thickness measurements of stacked layers of 17μm thick low-density polyethylene (LDPE) films.

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Habib, Md Ahasan, Erick Reyes-Vera, Juan Villegas-Aristizabal, and Md Shamim Anower. "Numerical Modeling of a Rectangular Hollow-Core Waveguide for the Detection of Fuel Adulteration in Terahertz Region." Fibers 8, no. 10 (October 8, 2020): 63. http://dx.doi.org/10.3390/fib8100063.

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A petrol adulteration sensor based on a rectangular shaped hollow-core photonic crystal fiber is proposed and numerically analyzed in the terahertz regime. The performance of the proposed sensor was evaluated when it is employed to characterize different kerosene mixtures. In this research, the adulterated fuel sample is filled in the rectangular hollow channel and the electromagnetic signal of the terahertz band is also driven through the same channel. The received signal after the interaction of fuel with the terahertz signal will advise the refractive index of the fuel oil inside the core, which will also bear the information of how much extrinsic component is present in the fuel. The finite element method based simulation shows that the proposed sensor can reach a high relative sensitivity of 89% and presents low confinement losses at 2.8 THz. The reported sensing structure is easily realizable with the conventional manufacturing techniques. Consequently, this proposed fiber may be treated as an essential part of real-life applications of petrol adulteration measurements.

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Ichikawa, Hiroya, Kei Takeya, and Saroj R. Tripathi. "Linear dichroism and birefringence spectra of bamboo and its use as a wave plate in the terahertz frequency region." Optical Materials Express 13, no. 4 (March 10, 2023): 966. http://dx.doi.org/10.1364/ome.485119.

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The applications of terahertz (THz) waves have been increasing rapidly in various fields, and there is a strong demand for efficient, robust, and low-cost optical components working in the terahertz frequency region. Bamboo, being one of the naturally occurring renewable resources, it has the potential to be used as an easily accessible and sustainable material for the fabrication of terahertz optical components. In this article, transmission mode terahertz time domain spectroscopy (THz-TDS) is used to investigate the terahertz properties, such as refractive index and absorption coefficient of three different species of bamboo in a frequency range from 200 GHz to 1 THz. Remarkable features such as birefringence and linear dichroism are observed, and the origin of these properties is primarily attributed to the orientation of fiber in the bamboo. The possibility of fabricating waveplates using bamboo is explored, and a quarter waveplate working in the sub-terahertz frequency region is demonstrated as a proof-of-principle. This wave plate can be used in terahertz sensing and imaging systems.