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Novelli F, Friebel P, Murillo-Sanchez ML, Michael Klopf J, Cattaneo L. Liquid crystal wave plate operating close to 18 THz. OPTICS LETTERS 2024; 49:2061-2064. [PMID: 38621076 DOI: 10.1364/ol.519177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/09/2024] [Indexed: 04/17/2024]
Abstract
Controlling the properties of mid- and far-infrared radiation can provide a means to transiently alter the properties of materials for novel applications. However, a limited number of optical elements are available to control its polarization state. Here we show that a 15-µm thick liquid crystal cell containing 8CB (4-octyl-4'-cyanobiphenyl) in the ordered, smectic A phase can be used as a phase retarder or wave plate. This was tested using the bright, short-pulsed (∼1 ps) radiation centered at 16.5 µm (18.15 THz) that is emitted by a free electron laser at high repetition rate (13 MHz). These results demonstrate a possible tool for the exploration of the mid- and far-infrared range and could be used to develop novel metamaterials or extend multidimensional spectroscopy to this portion of the electromagnetic spectrum.
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Xue J, Fujitsuka M, Tachikawa T, Bao J, Majima T. Charge Trapping in Semiconductor Photocatalysts: A Time- and Space-Domain Perspective. J Am Chem Soc 2024; 146:8787-8799. [PMID: 38520348 DOI: 10.1021/jacs.3c14757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2024]
Abstract
Harnessing solar energy to produce value-added fuels and chemicals through photocatalysis techniques holds promise for establishing a sustainable and environmentally friendly energy economy. The intricate dynamics of photogenerated charge carriers lies at the core of the photocatalysis. The balance between charge trapping and band-edge recombination has a crucial influence on the activity of semiconductor photocatalysts. Consequently, the regulation of traps in photocatalysts becomes the key to optimizing their activities. Nevertheless, our comprehension of charge trapping, compared to that of well-studied charge recombination, remains somewhat limited. This limitation stems from the inherently heterogeneous nature of traps at both temporal and spatial scales, which renders the characterization of charge trapping a formidable challenge. Fortunately, recent advancements in both time-resolved spectroscopy and space-resolved microscopy have paved the way for considerable progress in the investigation and manipulation of charge trapping. In this Perspective, we focus on charge trapping in photocatalysts with the aim of establishing a direct link to their photocatalytic activities. To achieve this, we begin by elucidating the principles of advanced time-resolved spectroscopic techniques such as femtosecond time-resolved transient absorption spectroscopy and space-resolved microscopic methods, such as single-molecule fluorescence microscopy and surface photovoltage microscopy. Additionally, we provide an overview of noteworthy research endeavors dedicated to probing charge trapping using time- and space-resolved techniques. Our attention is then directed toward recent achievements in the manipulation of charge trapping in photocatalysts through defect engineering. Finally, we summarize this Perspective and discuss the future challenges and opportunities that lie ahead in the field.
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Affiliation(s)
- Jiawei Xue
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China
| | - Mamoru Fujitsuka
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
| | - Takashi Tachikawa
- Department of Chemistry, Graduate School of Science and Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan
| | - Jun Bao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China
- iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), University of Science and Technology of China, Hefei, Anhui 230029, China
- Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tetsuro Majima
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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Wang H, Kumar A, Dai S, Lin X, Jacob Z, Oh SH, Menon V, Narimanov E, Kim YD, Wang JP, Avouris P, Martin Moreno L, Caldwell J, Low T. Planar hyperbolic polaritons in 2D van der Waals materials. Nat Commun 2024; 15:69. [PMID: 38167681 PMCID: PMC10761702 DOI: 10.1038/s41467-023-43992-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 11/27/2023] [Indexed: 01/05/2024] Open
Abstract
Anisotropic planar polaritons - hybrid electromagnetic modes mediated by phonons, plasmons, or excitons - in biaxial two-dimensional (2D) van der Waals crystals have attracted significant attention due to their fundamental physics and potential nanophotonic applications. In this Perspective, we review the properties of planar hyperbolic polaritons and the variety of methods that can be used to experimentally tune them. We argue that such natural, planar hyperbolic media should be fairly common in biaxial and uniaxial 2D and 1D van der Waals crystals, and identify the untapped opportunities they could enable for functional (i.e. ferromagnetic, ferroelectric, and piezoelectric) polaritons. Lastly, we provide our perspectives on the technological applications of such planar hyperbolic polaritons.
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Affiliation(s)
- Hongwei Wang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, 315211, Ningbo, China
| | - Anshuman Kumar
- Laboratory of Optics of Quantum Materials, Department of Physics, IIT Bombay, Mumbai, Maharashtra, 400076, India
| | - Siyuan Dai
- Department of Mechanical Engineering, Materials Research and Education Center, Auburn University, Auburn, AL, 36849, USA
| | - Xiao Lin
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Extreme Photonics and Instrumentation, ZJU-Hangzhou Global Science and Technology Innovation Center, College of Information Science and Electronic Engineering, Zhejiang University, 310027, Hangzhou, China
| | - Zubin Jacob
- Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Vinod Menon
- Department of Physics, City College and Graduate Center, City University of New York, New York, NY, 10031, USA
| | - Evgenii Narimanov
- Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Young Duck Kim
- Department of Physics and Department of Information Display, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Jian-Ping Wang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Phaedon Avouris
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
- IBM T. J. Watson Research Center, Yorktown Heights, NY, 10598, USA
| | - Luis Martin Moreno
- Instituto de Nanociencia y Materiales de Aragon (INMA), CSIC-Universidad de Zaragoza, Zaragoza, 50009, Spain
- Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, Zaragoza, 50009, Spain
| | - Joshua Caldwell
- Department of Mechanical Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | - Tony Low
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
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Obst M, Nörenberg T, Álvarez-Pérez G, de Oliveira TVAG, Taboada-Gutiérrez J, Feres FH, Kaps FG, Hatem O, Luferau A, Nikitin AY, Klopf JM, Alonso-González P, Kehr SC, Eng LM. Terahertz Twistoptics-Engineering Canalized Phonon Polaritons. ACS NANO 2023; 17:19313-19322. [PMID: 37738305 DOI: 10.1021/acsnano.3c06477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/24/2023]
Abstract
The terahertz (THz) frequency range is key to studying collective excitations in many crystals and organic molecules. However, due to the large wavelength of THz radiation, the local probing of these excitations in smaller crystalline structures or few-molecule arrangements requires sophisticated methods to confine THz light down to the nanometer length scale, as well as to manipulate such a confined radiation. For this purpose, in recent years, taking advantage of hyperbolic phonon polaritons (HPhPs) in highly anisotropic van der Waals (vdW) materials has emerged as a promising approach, offering a multitude of manipulation options, such as control over the wavefront shape and propagation direction. Here, we demonstrate the THz application of twist-angle-induced HPhP manipulation, designing the propagation of confined THz radiation between 8.39 and 8.98 THz in the vdW material α-molybdenum trioxide (α-MoO3), hence extending twistoptics to this intriguing frequency range. Our images, recorded by near-field optical microscopy, show the frequency- and twist-angle-dependent changes between hyperbolic and elliptic polariton propagation, revealing a polaritonic transition at THz frequencies. As a result, we are able to allocate canalization (highly collimated propagation) of confined THz radiation by carefully adjusting these two parameters, i.e. frequency and twist angle. Specifically, we report polariton canalization in α-MoO3 at 8.67 THz for a twist angle of 50°. Our results demonstrate the precise control and manipulation of confined collective excitations at THz frequencies, particularly offering possibilities for nanophotonic applications.
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Affiliation(s)
- Maximilian Obst
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
| | - Tobias Nörenberg
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
| | - Gonzalo Álvarez-Pérez
- Department of Physics, University of Oviedo, Oviedo 33006, Spain
- Center of Research on Nanomaterials and Nanotechnology CINN (CSIC-Universidad de Oviedo), El Entrego 33940, Spain
| | - Thales V A G de Oliveira
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden 01328, Germany
| | - Javier Taboada-Gutiérrez
- Department of Quantum Matter Physics, Université de Genève, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland
| | - Flávio H Feres
- Gleb Wataghin Physics Institute, University of Campinas (Unicamp), Campinas, Sao Paulo 13083-859, Brazil
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Sao Paulo 13083-100, Brazil
| | - Felix G Kaps
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
| | - Osama Hatem
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
- Department of Engineering Physics and Mathematics, Faculty of Engineering, Tanta University, Tanta 31511, Egypt
| | - Andrei Luferau
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden 01328, Germany
| | - Alexey Y Nikitin
- Donostia International Physics Center (DIPC), Donostia/San Sebastián 20018, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao 48013, Spain
| | - J Michael Klopf
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden 01328, Germany
| | - Pablo Alonso-González
- Department of Physics, University of Oviedo, Oviedo 33006, Spain
- Center of Research on Nanomaterials and Nanotechnology CINN (CSIC-Universidad de Oviedo), El Entrego 33940, Spain
| | - Susanne C Kehr
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
| | - Lukas M Eng
- Institut für Angewandte Physik, Technische Universität Dresden, Dresden 01187, Germany
- Würzburg-Dresden Cluster of Excellence - EXC 2147 (ct.qmat), Dresden 01062, Germany
- Collaborative Research Center 1415, Technische Universität Dresden, Dresden 01069, Germany
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