Article
Optics
Yulian He, Yuansheng Wang, Qinghui Yang, Huaiwu Zhang, Qiye Wen
Summary: Surface-modified semiconductors, such as passivated GaAs, show potential for enhancing THz modulation performance with increased MD and faster modulation speed. Despite longer carrier lifetime, passivated GaAs modulator achieves a high MD of up to 94% at speeds of 69 MHz in a wide spectral range.
PHOTONICS RESEARCH
(2021)
Article
Optics
Yu Huang, Dong Li, Yu Liu, Minghao Hu, Weiqiang Yang, Kang Wang, Wenfeng Xiang
Summary: The optical properties of aligned nickel nanowire arrays with different degrees of oxidation were studied for terahertz polarizer applications using THz time-domain spectroscopy. It was found that increasing oxidation levels broadened the transmitted peaks in the frequency-domain spectra and caused a blue shift in peak positions, while also enhancing peak intensity. The transmittance of the arrays increased with annealing temperature, but the degree of polarization and extinction ratio decreased. The study also revealed a correlation between the degree of oxidation and the change in extinction ratio.
Article
Materials Science, Multidisciplinary
Jitao Li, Zhen Yue, Jie Li, Chenglong Zheng, Jingyu Liu, Fan Yang, Hui Li, Yating Zhang, Yan Zhang, Jianquan Yao
Summary: In this work, wavefront-controllable terahertz (THz) meta-polarizers based on all-silicon materials are reported, which have higher integration characteristics than conventional metapolarizers and wavefront-controllable PCMs. These meta-polarizers can generate polarized waves from unpolarized waves and manipulate the wavefront simultaneously, providing a new impact for THz wave manipulations.
SCIENCE CHINA-MATERIALS
(2023)
Article
Physics, Multidisciplinary
Wenfeng Xiang, Xuan Liu, Xiaowei Huang, Qingli Zhou, Haizhong Guo, Songqing Zhao
Summary: A mechanically tunable broadband terahertz modulator based on high-aligned Ni nanowire arrays was proposed, demonstrating effective modulation of THz wave transmittance through mechanical stretching. The modulation depth showed a linear relationship with strain, ranging from 0 to 85% in the frequency range of 0.3 THz to 1.8 THz, with detectable modulation depth of about 15% for a 1% strain change resolution. This flexible Ni NW-based modulator has potential applications in remote strain sensing and wearable devices.
Article
Optics
X. Chen, E. Pickwell-MacPherson
Summary: Traditional terahertz spectroscopy methods have limitations in certain cases, while terahertz ellipsometry, as a self-reference characterization technique with wide adaptability, can be applied to almost all sample types.
Article
Optics
Qi Song, Hao Chen, Min Zhang, Ling Li, Junbo Yang, Peiguang Yan
Summary: Research on high performance THz modulators is crucial for advancing THz photonics applications, requiring modulators with large modulation depth and wide bandwidth. This study presents a Bi nanofilm designed as an electrically controlled THz modulator, demonstrating dynamic modulation of THz waves and broadband modulation performance.
Article
Optics
Xiaolong You, Rajour T. T. Ako, Madhu Bhaskaran, Sharath Sriram, Christophe Fumeaux, Withawat Withayachumnankul
Summary: This paper presents a three-layer metasurface-based planar circular polarizer with strong and broadband chirality, overcoming the limitations of conventional non-planar designs and allowing for adjustable functionality and operating bandwidth. Experimental results show that this structure maintains a 15 dB extinction ratio and a transmission efficiency above 92.7% from 251 to 293 GHz. Furthermore, by adjusting the air gap spacings between the metallic layers, it can operate at nearby frequency ranges and is robust to deviations in the air gap spacings.
LASER & PHOTONICS REVIEWS
(2023)
Article
Optics
ShiNa Tao, ZhiXiong Shen, HongGuan Yu, HuaCai Wang, ShiJun Ge, Wei Hu
Summary: A spatial terahertz wave modulator based on a liquid-crystal-integrated metadevice is proposed, which allows for dynamic reconfiguration and modulation of terahertz waves.
Article
Nanoscience & Nanotechnology
Armin Solemanifar, Xiao Guo, Bogdan C. Donose, Karl Bertling, Bronwyn Laycock, Aleksandar D. Rakic
Summary: In this study, a non-destructive measurement technique based on terahertz scanning near-field microscope was used to investigate the conductivity of synthetic peptide nanowires. The results showed that the sample incorporating aromatic residues was about six times more conductive than the negative control. This is the first quantitative nano-scale terahertz s-SNOM investigation of peptides, which demonstrates the suitability of the non-destructive approach in combination with designer peptides as model test subjects.
Article
Optics
Dip Sarker, Partha Pratim Nakti, Md Ishfak Tahmid, Md Asaduz Zaman Mamun, Ahmed Zubair
Summary: This study proposed tunable surface plasmon resonance-based graphene nanoribbon (GNR) terahertz (THz) polarizers with high ER, broad tunability, near-perfect degree of polarization, and low insertion loss. The operating frequency of these polarizers can be adjusted by changing parameters like GNR width. The optimized THz polarizer showed comparable performance to commercially available ones, making them promising for various photonic applications.
Review
Engineering, Electrical & Electronic
Michael B. Johnston, Hannah J. Joyce
Summary: This article discusses the physical origins and experimental observations of polarization anisotropy in semiconductor nanowires, and how these phenomena are utilized in devices for detecting and modulating terahertz radiation. These novel terahertz devices are expected to find applications in various fields, including high-speed terahertz communications and molecular fingerprinting.
PROGRESS IN QUANTUM ELECTRONICS
(2022)
Article
Multidisciplinary Sciences
Saeedeh Ahadi, Mohammad Neshat, Mohammad Kazem Moravvej-Farshi
Summary: The study proposes a terahertz modulator based on split-ring resonators, achieving signal modulation through adjustment of bias voltage. The modulator excites LC resonances or dipole resonances at different frequencies under different voltages, with modulation depths reaching 45% to 87%.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Multidisciplinary
Huan Wang, Jiajun Linghu, Xuezhi Wang, Qiyi Zhao, Hao Shen
Summary: An angular-dependent THz modulator with hybrid metal-graphene metastructures is reported in this study. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the modulator can reach similar to 37.6% at 0.62 THz with a gate voltage of -3 V. This hybrid device offers a useful method for THz applications where angle-dependent modulation is needed, such as angle sensors or angular-resolved spectroscopy.
Article
Optics
Shoujun Zhang, Xieyu Chen, Kuan Liu, Haiyang Li, Yuehong Xu, Xiaohan Jiang, Yihan Xu, Qingwei Wang, Tun Cao, Zhen Tian
Summary: Researchers have achieved large-area, reversible, and repeated switching of chalcogenide phase change materials (PCM) with the help of optical and thermal stimuli, and incorporated them into metasurface designs to realize nonvolatile, reconfigurable, multilevel, and broadband terahertz modulators. Experimental results demonstrate the feasibility of multilevel modulation of THz waves in a wide frequency range, and the modulators are reusable and nonvolatile, holding great potential for various applications.
Article
Computer Science, Interdisciplinary Applications
Nazariy Jaworski, Nazariy Andrushchak, Mykhailo Lobur, Marek Iwaniec
Summary: In this study, a finite element model of a terahertz substrate-based wire grid polarizer is developed and implemented using COMSOL software. The simulation results show excellent agreement with known experimental and simulation data.
MATHEMATICS AND COMPUTERS IN SIMULATION
(2021)
Article
Nanoscience & Nanotechnology
Tuomas Haggren, Julie Tournet, Chennupati Jagadish, Hark Hoe Tan, Jani Oksanen
Summary: A scalable multilayer epitaxial lift-off process is demonstrated, which allows efficient removal of epitaxially grown materials from their host substrate without external strains. The films retain good integrity after lift-off and can be further processed into devices. Cost analysis shows a 4-to-6-fold reduction in cost compared to the single-layer epitaxial lift-off process, making it significant for III-V photovoltaics and other technologies relying on thin-film III-V semiconductors.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Optics
Wei Wen Wong, Naiyin Wang, Chennupati Jagadish, Hark Hoe Tan
Summary: This study presents a novel approach to realize on-chip microlasers with directional emission in an all-dielectric, bottom-up grown material system. By coupling the laser emission into a vertical nanowire, efficient optical coupling is achieved and the emission directivity and side mode suppression can be improved by tuning the geometric parameters of the system.
LASER & PHOTONICS REVIEWS
(2023)
Article
Chemistry, Multidisciplinary
Heon Jin, Michael D. Farrar, James M. Ball, Akash Dasgupta, Pietro Caprioglio, Sudarshan Narayanan, Robert D. J. Oliver, Florine M. Rombach, Benjamin W. J. Putland, Michael B. Johnston, Henry J. Snaith
Summary: Mixed lead-tin halide perovskites show potential for high-efficiency tandem solar cells, but solution processing of thick films is challenging due to rapid crystallization and rough surfaces. This study improves the conformality of subsequent layers using alumina nanoparticles on the surface of rough films, resulting in a 65% increase in maximum-power-point efficiency and 28% improvement in steady-state V-OC. The nanoparticles also enhance device stability, with a six-fold increase in lifetime compared to pristine films.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Adam D. Wright, Jay. B. Patel, Michael B. Johnston, Laura M. Herz
Summary: Understanding the mechanism of light-induced halide segregation is important for using mixed-halide perovskites in multijunction solar cells. Photoluminescence spectroscopy reveals that increasing temperature and light intensity can counteract halide segregation. The acceleration and deceleration of halide segregation with temperature are attributed to the trade-off between temperature activation and entropic factors. High light intensities can also reverse halide segregation, but only temporarily. These findings contribute to a better understanding of halide segregation and the development of efficient and stable perovskite solar cells.
ADVANCED MATERIALS
(2023)
Article
Physics, Applied
Alfred Leitenstorfer, Andrey S. Moskalenko, Tobias Kampfrath, Junichiro Kono, Enrique Castro-Camus, Kun Peng, Naser Qureshi, Dmitry Turchinovich, Koichiro Tanaka, Andrea G. Markelz, Martina Havenith, Cameron Hough, Hannah J. Joyce, Willie J. Padilla, Binbin Zhou, Ki-Yong Kim, Xi-Cheng Zhang, Peter Uhd Jepsen, Sukhdeep Dhillon, Miriam Vitiello, Edmund Linfield, A. Giles Davies, Matthias C. Hoffmann, Roger Lewis, Masayoshi Tonouchi, Pernille Klarskov, Tom S. Seifert, Yaroslav A. Gerasimenko, Dragan Mihailovic, Rupert Huber, Jessica L. Boland, Oleg Mitrofanov, Paul Dean, Brian N. Ellison, Peter G. Huggard, Simon P. Rea, Christopher Walker, David T. Leisawitz, Jian Rong Gao, Chong Li, Qin Chen, Gintaras Valusis, Vincent P. Wallace, Emma Pickwell-MacPherson, Xiaobang Shang, Jeffrey Hesler, Nick Ridler, Cyril C. Renaud, Ingmar Kallfass, Tadao Nagatsuma, J. Axel Zeitler, Don Arnone, Michael B. Johnston, John Cunningham
Summary: THz radiation covers a wide spectral range and has diverse applications in various scientific disciplines. The demands for advanced THz technology in radio astronomy, weather forecasting, security imaging, telecommunications, and other fields have driven the development of related technologies. It is important to explore both the scientific and technical aspects to meet the growing needs.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Jun-Wei Liao, Zhen-Ting Huang, Chia-Hung Wu, Nikita Gagrani, Hark Hoe Tan, Chennupati Jagadish, Kuo-Ping Chen, Tien-Chang Lu
Summary: In this study, localized surface plasmon lasing at room temperature in the communication band was achieved using metallic nanoholes as plasmonic nanocavity and InP nanowires as gain medium. Optimization of laser performance was demonstrated through coupling between two metallic nanoholes, allowing for manipulation of lasing properties. These plasmonic nanolasers offer lower power consumption, smaller mode volumes, and higher spontaneous emission coupling factors, making them promising for high-density sensing and photonic integrated circuits.
Article
Chemistry, Multidisciplinary
Teja Potocnik, Oliver Burton, Marcel Reutzel, David Schmitt, Jan Philipp Bange, Stefan Mathias, Fabian R. Geisenhof, R. Thomas Weitz, Linyuan Xin, Hannah J. Joyce, Stephan Hofmann, Jack A. Alexander-Webber
Summary: This study introduces spectroscopic ellipsometric contrast microscopy (SECM) as a tool for mapping twist angle disorder in optically resonant twisted bilayer graphene, confirming the accuracy and fast characterization of SECM.
Article
Nanoscience & Nanotechnology
Jessica L. Boland, Djamshid A. Damry, Chelsea Q. Xia, Piet Schoenherr, Dharmalingam Prabhakaran, Laura M. Herz, Thorsten Hesjedal, Michael B. Johnston
Summary: By exploiting band structure topology, both helicity-dependent and helicityindependent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. Narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarization. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21-1.40 THz as the angle is tuned from 15 to 45 degrees. Therefore, Cd3As2 nanowires are considered a promising novel material platform for controllable terahertz emission.
Article
Chemistry, Physical
Karim A. Elmestekawy, Benjamin M. Gallant, Adam D. Wright, Philippe Holzhey, Nakita K. Noel, Michael B. Johnston, Henry J. Snaith, Laura M. Herz
Summary: This study explores the effects of three common solution-based film-fabrication methods on FAPbI3 crystals, and finds that two methods can reduce quantum confinement effects and improve the conversion efficiency and short-circuit current of solar cells. A meta-analysis of 244 articles and 825 photovoltaic devices confirms that PCE rarely exceeds a 20% threshold when these absorption features are present. Therefore, ensuring the absence of these absorption features should be the primary consideration when designing fabrication approaches for high-efficiency FAPbI3 solar cells.
ACS ENERGY LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Bikesh Gupta, Doudou Zhang, Hongjun Chen, Chennupati Jagadish, Hark Hoe Tan, Siva Karuturi
Summary: This study presents a novel approach for fabricating high-performance solar cells based on InP heterojunctions using a solution-processed ferri-hydrite (Fh) electron-selective contact (ESC). The champion cell efficiency of 16.6% is achieved, which is a significant improvement over those from previous studies using other solution-processed ESC materials. The Fh layer not only selectively extracts photogenerated electrons from InP but also simultaneously serves as a surface protection layer, improving the cell's long-term stability.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Wei Wen Wong, Naiyin Wang, Bryan D. D. Esser, Stephen A. A. Church, Li Li, Mark Lockrey, Igor Aharonovich, Patrick Parkinson, Joanne Etheridge, Chennupati Jagadish, Hark Hoe Tan
Summary: In this study, we utilize the selective area epitaxy method to deterministically engineer thousands of microring lasers on a single chip. By elucidating a detailed growth mechanism and controlling the adatom diffusion lengths, we achieve ultrasmooth cavity sidewalls. These engineered devices exhibit a tunable emission wavelength in the telecommunication O-band and show low-threshold lasing with high device efficacy across the chip. This work marks a significant milestone toward the implementation of a fully integrated III-V materials platform for next-generation high-density integrated photonic and optoelectronic circuits.
Article
Engineering, Electrical & Electronic
Yang Wu, Gabriele Restifo Pecorella, Gianluca Verderame, Daniele Annicchiarico, Thanuja Galhena, Stephen Hodge, Hannah Jane Joyce, Patrizia Livreri, Antonio Lombardo
Summary: This article presents an experimental demonstration of a novel microwave gas sensor based on graphene aerogel (GA). The sensor utilizes the porous structure of GA and the modulation of graphene conductivity to detect gases in the air. The results show that the sensor exhibits clear shifts in the scattering parameters of the waveguide upon exposure to different gases, and it also demonstrates excellent reproducibility when exposed to alternating cycles of air and vacuum. These findings open up possibilities for the development of new gas sensors for applications such as breath analysis.
IEEE SENSORS JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Nian Jiang, Saptarsi Ghosh, Martin Frentrup, Simon M. Fairclough, Kagiso Loeto, Gunnar Kusch, Rachel A. Oliver, Hannah J. Joyce
Summary: Understanding the growth mechanisms of III-nitride nanowires is crucial for harnessing their full potential. A systematic study explores the growth of silane-assisted GaN nanowires on c-sapphire substrates, investigating the surface evolution of the substrates during annealing, nitridation, and nucleation steps. Both Ga-polar and N-polar GaN nanowires were grown, with N-polar nanowires exhibiting faster growth. The presence of protuberance structures and ring-like features in N-polar GaN nanowires suggests energetically favorable nucleation sites at inversion domain boundaries, while the impact on device performance is confined to the protuberance structure area.
NANOSCALE ADVANCES
(2023)