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Xu Z, Ni C, Cheng Y, Dong L, Wu L. Photo-Excited Metasurface for Tunable Terahertz Reflective Circular Polarization Conversion and Anomalous Beam Deflection at Two Frequencies Independently. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1846. [PMID: 37368276 DOI: 10.3390/nano13121846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/08/2023] [Accepted: 06/10/2023] [Indexed: 06/28/2023]
Abstract
In this paper, a photo-excited metasurface (MS) based on hybrid patterned photoconductive silicon (Si) structures was proposed in the terahertz (THz) region, which can realize the tunable reflective circular polarization (CP) conversion and beam deflection effect at two frequencies independently. The unit cell of the proposed MS consists of a metal circular-ring (CR), Si ellipse-shaped-patch (ESP) and circular-double-split-ring (CDSR) structure, a middle dielectric substrate, and a bottom metal ground plane. By altering the external infrared-beam pumping power, it is possible to modify the electric conductivity of both the Si ESP and CDSR components. By varying the conductivity of the Si array in this manner, the proposed MS can achieve a reflective CP conversion efficiency that ranges from 0% to 96.6% at a lower frequency of 0.65 THz, and from 0% to 89.3% at a higher frequency of 1.37 THz. Furthermore, the corresponding modulation depth of this MS is as high as 96.6% and 89.3% at two distinct and independent frequencies, respectively. Moreover, at the lower and higher frequencies, the 2π phase shift can also be achieved by respectively rotating the oriented angle (αi) of the Si ESP and CDSR structures. Finally, an MS supercell is constructed for the reflective CP beam deflection, and the efficiency is dynamically tuned from 0% to 99% at the two independent frequencies. Due to its excellent photo-excited response, the proposed MS may find potential applications in active functional THz wavefront devices, such as modulators, switches, and deflectors.
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Affiliation(s)
- Zhixiang Xu
- School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
| | - Cheng Ni
- School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
| | - Yongzhi Cheng
- School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
- Engineering Research Center for Metallurgical Automation and Detecting Technology Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China
- Hubei Longzhong Laboratory, Xiangyang 441000, China
| | - Linhui Dong
- School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
| | - Ling Wu
- School of Physics and Electronic Information Engineering, Hubei Engineering University, Xiaogan 432000, China
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2
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Bao J, Chen X, Liu K, Zhan Y, Li H, Zhang S, Xu Y, Tian Z, Cao T. Nonvolatile chirality switching in terahertz chalcogenide metasurfaces. MICROSYSTEMS & NANOENGINEERING 2022; 8:112. [PMID: 36193224 PMCID: PMC9525255 DOI: 10.1038/s41378-022-00445-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 07/17/2022] [Accepted: 07/29/2022] [Indexed: 06/16/2023]
Abstract
Actively controlling the polarization states of terahertz (THz) waves is essential for polarization-sensitive spectroscopy, which has various applications in anisotropy imaging, noncontact Hall measurement, and vibrational circular dichroism. In the THz regime, the lack of a polarization modulator hinders the development of this spectroscopy. We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials (CMMs) integrated with Ge2Sb2Te5 (GST225) active components can achieve nonvolatile and continuously tunable optical activity in the THz region. A THz time-domain spectroscopic system was used to characterize the device, showing a tunable ellipticity (from ‒36° to 0°) and rotation of the plane polarization (from 32° to 0°) at approximately 0.73 THz by varying the GST225 state from amorphous (AM) to crystalline (CR). Moreover, a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225, which can create intermediate states, having regions of both AM and CR states. Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state. Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.
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Affiliation(s)
- Jiaxin Bao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Xieyu Chen
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Kuan Liu
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Yu Zhan
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Haiyang Li
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Shoujun Zhang
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Yihan Xu
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Zhen Tian
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Tun Cao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
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Yin S, Zeng D, Chen Y, Huang W, Zhang C, Zhang W, E Y. Optically Controlled Terahertz Dynamic Beam Splitter with Adjustable Split Ratio. NANOMATERIALS 2022; 12:nano12071169. [PMID: 35407287 PMCID: PMC9000664 DOI: 10.3390/nano12071169] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 03/26/2022] [Accepted: 03/30/2022] [Indexed: 11/16/2022]
Abstract
The beam splitter is an important functional device due to its ability to steer the propagation of electromagnetic waves. The split-ratio-variable splitter is of significance for optical, terahertz and microwave systems. Here, we are the first (to our knowledge) to propose an optically controlled dynamic beam splitter with adjustable split ratio in the terahertz region. Based on the metasurface containing two sets of reversed phase-gradient supercells, we split the terahertz wave into two symmetrical beams. Associated with the reconfigurable pump laser pattern programmed with the spatial light modulator, dynamic modulation of the split ratio varying from 1:1 to 15:1 is achieved. Meanwhile, the beam splitter works at a split angle of 36° for each beam. Additionally, we obtain an exponential relationship between the split ratio and the illumination proportion, which can be used as theoretical guidance for beam splitting with an arbitrary split ratio. Our novel beam splitter shows an outstanding level of performance in terms of the adjustable split ratio and stable split angles and can be used as an advanced method to develop active functional devices applied to terahertz systems and communications.
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Affiliation(s)
- Shan Yin
- Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China; (S.Y.); (D.Z.); (Y.C.)
| | - Dehui Zeng
- Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China; (S.Y.); (D.Z.); (Y.C.)
| | - Yuting Chen
- Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China; (S.Y.); (D.Z.); (Y.C.)
| | - Wei Huang
- Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China; (S.Y.); (D.Z.); (Y.C.)
- Correspondence: (W.H.); (W.Z.)
| | - Cheng Zhang
- Hubei Engineering Research Center of RF-Microwave Technology and Application, School of Science, Wuhan University of Technology, Wuhan 430070, China;
| | - Wentao Zhang
- Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China; (S.Y.); (D.Z.); (Y.C.)
- Correspondence: (W.H.); (W.Z.)
| | - Yiwen E
- The Institute of Optics, University of Rochester, Rochester, NY 14627, USA;
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4
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He Y, Wang Y, Li M, Yang Q, Chen Z, Zhang J, Wen Q. All-optical spatial terahertz modulator with surface-textured and passivated silicon. OPTICS EXPRESS 2021; 29:8914-8925. [PMID: 33820332 DOI: 10.1364/oe.419299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 02/26/2021] [Indexed: 06/12/2023]
Abstract
For a Si-based all-optical spatial terahertz modulator (STM), an enhanced modulation efficiency under low illumination density would be of great significance to exploit the competence of THz technology in real-world applications. We presented here an implementation of such a device by microtexturing and passivating the Si surface, forming a truncated pyramidal array (TPA). This TPA structure with SiO2 passivating coatings not only decreases light reflectance and expands the active area for THz modulation but also remarkably increases the photogenerated carrier lifetime. These 3-fold benefits render Si-TPA superior to bare-Si with respect to the achievable modulation efficiency, especially at low irradiation power. Furthermore such a Si-TPA device is also more applicable than its counterpart that is only passivated by SiO2 nanocoatings, even though the Si-SiO2 has a slightly increased modulation efficiency. These periodically aligned pyramids resembled as a mesa array significantly suppress the lateral diffusion induced by longer diffusion, resulting in an equivalent resolution of bare-Si. This novel Si-TPA based STM is highly desired for realizing a high-performance THz imager and provides a feasible approach to breaking the trade-off between resolution and modulation efficiency.
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Masyukov M, Vozianova A, Grebenchukov A, Gubaidullina K, Zaitsev A, Khodzitsky M. Optically tunable terahertz chiral metasurface based on multi-layered graphene. Sci Rep 2020; 10:3157. [PMID: 32081873 PMCID: PMC7035278 DOI: 10.1038/s41598-020-60097-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 02/06/2020] [Indexed: 02/06/2023] Open
Abstract
Active manipulation of the polarization states at terahertz frequencies is crucially helpful for polarization-sensitive spectroscopy, having significant applications such as non-contact Hall measurements, vibrational circular dichroism measurements and anisotropy imaging. The weakness of polarization manipulation provided by natural materials can be overcomed by chiral metamaterials. Chiral metamaterials have a huge potential to achieve the necessary polarization effects, hence they provide the basis for applications such as ultracompact polarization components. Terahertz chiral metamaterials that allow dynamic polarization modulation of terahertz waves are of great practical interest and still challenging. Here, we show that terahertz metasurface based on the four conjugated “petal” resonators integrated with multi-layered graphene (MLG) can enable dynamically tunable chiroptical response using optical pumping. In particular, a change of ellipticity angle of 20° is observed around 0.76 THz under optical pumping by a 980 nm continuous wave (CW) laser. Furthermore, using temporal coupled-mode theory, our study also reveals that the chiroptical response of the proposed multi-layered graphene-based metasurface is strongly dependent on the influence of optical pumping on the loss parameters of resonance modes, leading to actively controllable polarization states of the transmitted terahertz waves. The present work paves the way for the realization of fundamental terahertz components capable for active polarization manipulation.
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Affiliation(s)
- Maxim Masyukov
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia.
| | - Anna Vozianova
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia.,International Scientific and Research Institute of Bioengineering, ITMO University, St. Petersburg, 197101, Russia
| | - Alexander Grebenchukov
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia.,International Scientific and Research Institute of Bioengineering, ITMO University, St. Petersburg, 197101, Russia
| | - Kseniya Gubaidullina
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia
| | - Anton Zaitsev
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia
| | - Mikhail Khodzitsky
- Terahertz Biomedicine Laboratory, ITMO University, St. Petersburg, 199034, Russia.,International Scientific and Research Institute of Bioengineering, ITMO University, St. Petersburg, 197101, Russia
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6
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Khorloo M, Cheng Y, Zhang H, Chen M, Sung HHY, Williams ID, Lam JWY, Tang BZ. Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures. Chem Sci 2019; 11:997-1005. [PMID: 34084354 PMCID: PMC8146380 DOI: 10.1039/c9sc04239c] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications. A polymorphic AIEgen is capable of selective growth in amorphous and crystalline polymer phases with distinct color for microstructure visualization.![]()
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Affiliation(s)
- Michidmaa Khorloo
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China
| | - Yanhua Cheng
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China .,State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University Shanghai 201620 China
| | - Haoke Zhang
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China .,HKUST-Shenzhen Research Institute No. 9 Yuexing 1st RD, South Area, Hi-tech Park, Nanshan Shenzhen 518057 China
| | - Ming Chen
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China
| | - Herman H Y Sung
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China
| | - Ian D Williams
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China
| | - Jacky W Y Lam
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China .,HKUST-Shenzhen Research Institute No. 9 Yuexing 1st RD, South Area, Hi-tech Park, Nanshan Shenzhen 518057 China
| | - Ben Zhong Tang
- Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China .,HKUST-Shenzhen Research Institute No. 9 Yuexing 1st RD, South Area, Hi-tech Park, Nanshan Shenzhen 518057 China.,Center for Aggregation-Induced Emission, SCUT-HKUST Joint Research Institute, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology Guangzhou China
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7
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Kim TT, Oh SS, Kim HD, Park HS, Hess O, Min B, Zhang S. Electrical access to critical coupling of circularly polarized waves in graphene chiral metamaterials. SCIENCE ADVANCES 2017; 3:e1701377. [PMID: 28975151 PMCID: PMC5621972 DOI: 10.1126/sciadv.1701377] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 09/11/2017] [Indexed: 05/25/2023]
Abstract
Active control of polarization states of electromagnetic waves is highly desirable because of its diverse applications in information processing, telecommunications, and spectroscopy. However, despite the recent advances using artificial materials, most active polarization control schemes require optical stimuli necessitating complex optical setups. We experimentally demonstrate an alternative-direct electrical tuning of the polarization state of terahertz waves. Combining a chiral metamaterial with a gated single-layer sheet of graphene, we show that transmission of a terahertz wave with one circular polarization can be electrically controlled without affecting that of the other circular polarization, leading to large-intensity modulation depths (>99%) with a low gate voltage. This effective control of polarization is made possible by the full accessibility of three coupling regimes, that is, underdamped, critically damped, and overdamped regimes by electrical control of the graphene properties.
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Affiliation(s)
- Teun-Teun Kim
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 16419, Republic of Korea
- Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sang Soon Oh
- Blackett Laboratory, Department of Physics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Hyeon-Don Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Hyun Sung Park
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Ortwin Hess
- Blackett Laboratory, Department of Physics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Bumki Min
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Shuang Zhang
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
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8
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Wang Z, Cheng F, Winsor T, Liu Y. Optical chiral metamaterials: a review of the fundamentals, fabrication methods and applications. NANOTECHNOLOGY 2016; 27:412001. [PMID: 27606801 DOI: 10.1088/0957-4484/27/41/412001] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Optical chiral metamaterials have recently attracted considerable attention because they offer new and exciting opportunities for fundamental research and practical applications. Through pragmatic designs, the chiroptical response of chiral metamaterials can be several orders of magnitude higher than that of natural chiral materials. Meanwhile, the local chiral fields can be enhanced by plasmonic resonances to drive a wide range of physical and chemical processes in both linear and nonlinear regimes. In this review, we will discuss the fundamental principles of chiral metamaterials, various optical chiral metamaterials realized by different nanofabrication approaches, and the applications and future prospects of this emerging field.
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Affiliation(s)
- Zuojia Wang
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA
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9
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Photo-generated metamaterials induce modulation of CW terahertz quantum cascade lasers. Sci Rep 2015; 5:16207. [PMID: 26549166 PMCID: PMC4637892 DOI: 10.1038/srep16207] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/17/2015] [Indexed: 11/09/2022] Open
Abstract
Periodic patterns of photo-excited carriers on a semiconductor surface profoundly modifies its effective permittivity, creating a stationary all-optical quasi-metallic metamaterial. Intriguingly, one can tailor its artificial birefringence to modulate with unprecedented degrees of freedom both the amplitude and phase of a quantum cascade laser (QCL) subject to optical feedback from such an anisotropic reflector. Here, we conceive and devise a reconfigurable photo-designed Terahertz (THz) modulator and exploit it in a proof-of-concept experiment to control the emission properties of THz QCLs. Photo-exciting sub-wavelength metastructures on silicon, we induce polarization-dependent changes in the intra-cavity THz field, that can be probed by monitoring the voltage across the QCL terminals. This inherently flexible approach promises groundbreaking impact on THz photonics applications, including THz phase modulators, fast switches, and active hyperbolic media.
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Kan T, Isozaki A, Kanda N, Nemoto N, Konishi K, Takahashi H, Kuwata-Gonokami M, Matsumoto K, Shimoyama I. Enantiomeric switching of chiral metamaterial for terahertz polarization modulation employing vertically deformable MEMS spirals. Nat Commun 2015; 6:8422. [PMID: 26423346 PMCID: PMC4600721 DOI: 10.1038/ncomms9422] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 08/19/2015] [Indexed: 11/22/2022] Open
Abstract
Active modulation of the polarization states of terahertz light is indispensable for polarization-sensitive spectroscopy, having important applications such as non-contact Hall measurements, vibrational circular dichroism measurements and anisotropy imaging. In the terahertz region, the lack of a polarization modulator similar to a photoelastic modulator in the visible range hampers expansion of such spectroscopy. A terahertz chiral metamaterial has a huge optical activity unavailable in nature; nevertheless, its modulation is still challenging. Here we demonstrate a handedness-switchable chiral metamaterial for polarization modulation employing vertically deformable Micro Electro Mechanical Systems. Vertical deformation of a planar spiral by a pneumatic force creates a three-dimensional spiral. Enantiomeric switching is realized by selecting the deformation direction, where the polarity of the optical activity is altered while maintaining the spectral shape. A polarization rotation as high as 28° is experimentally observed, thus providing a practical and compact polarization modulator for the terahertz range.
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Affiliation(s)
- Tetsuo Kan
- Department of Mechano-Informatics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Akihiro Isozaki
- IRT Research Initiative, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Natsuki Kanda
- Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198, Japan
- Photon Science Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Natsuki Nemoto
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kuniaki Konishi
- Institute for Photon Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hidetoshi Takahashi
- Department of Mechano-Informatics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Makoto Kuwata-Gonokami
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kiyoshi Matsumoto
- IRT Research Initiative, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Isao Shimoyama
- Department of Mechano-Informatics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- IRT Research Initiative, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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11
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Cao T, Wei C, Mao L. Numerical study of achiral phase-change metamaterials for ultrafast tuning of giant circular conversion dichroism. Sci Rep 2015; 5:14666. [PMID: 26423517 PMCID: PMC4589781 DOI: 10.1038/srep14666] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 09/03/2015] [Indexed: 11/20/2022] Open
Abstract
Control of the polarization of light is highly desirable for detection of material’s chirality since biomolecules have vibrational modes in the optical region. Here, we report an ultrafast tuning of pronounced circular conversion dichroism (CCD) in the mid-infrared (M-IR) region, using an achiral phase change metamaterial (PCMM). Our structure consists of an array of Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) dielectric layer, where the Au square patches occupy the sites of a rectangular lattice. The extrinsically giant 2D chirality appears provided that the rectangular array of the Au squares is illuminated at an oblique incidence, and accomplishes a wide tunable wavelength range between 2664 and 3912 nm in the M-IR regime by switching between the amorphous and crystalline states of the Ge2Sb2Te5. A photothermal model is investigated to study the temporal variation of the temperature of the Ge2Sb2Te5 layer, and shows the advantage of fast transiting the phase of Ge2Sb2Te5 of 3.2 ns under an ultralow incident light intensity of 1.9 μW/μm2. Our design is straightforward to fabricate and will be a promising candidate for controlling electromagnetic (EM) wave in the optical region.
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Affiliation(s)
- Tun Cao
- Department of Biomedical Engineering, Dalian University of Technology, 116024 China (P.R.C) 116024
| | - Chenwei Wei
- Department of Biomedical Engineering, Dalian University of Technology, 116024 China (P.R.C) 116024
| | - Libang Mao
- Department of Biomedical Engineering, Dalian University of Technology, 116024 China (P.R.C) 116024
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12
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Cao T, Wei CW, Mao LB, Wang S. Tuning of giant 2D-chiroptical response using achiral metasurface integrated with graphene. OPTICS EXPRESS 2015; 23:18620-18629. [PMID: 26191920 DOI: 10.1364/oe.23.018620] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Tuning the chiroptical response of a molecule is crucial for detecting the material's chirality. Here, we demonstrate a pronounced circular conversion dichroism (CCD) by using an achiral metasurface (AMS) which is composed of a rectangular reflectarray of Au squares separated from a continuous Au film by a dielectric interlayer. This extrinsically 2D chirality originates from the mutual orientation between the AMS and oblique incident wave. The AMS is further incorporated with graphene to tune the CCD spectra in the mid-infrared (MIR) region by electrically modulating the graphene's Fermi level. This approach offers a high fabrication tolerance and will be a promising candidate for controlling electromagnetic (EM) waves in the MIR region from 1500 to 3000 nm.
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Yin X, Schäferling M, Michel AKU, Tittl A, Wuttig M, Taubner T, Giessen H. Active Chiral Plasmonics. NANO LETTERS 2015; 15:4255-4260. [PMID: 26039735 DOI: 10.1021/nl5042325] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Active control over the handedness of a chiral metamaterial has the potential to serve as key element for highly integrated polarization engineering approaches, polarization sensitive imaging devices, and stereo display technologies. However, this is hard to achieve as it seemingly involves the reconfiguration of the metamolecule from a left-handed into a right-handed enantiomer and vice versa. This type of mechanical actuation is intricate and usually neither monolithically realizable nor viable for high-speed applications. Here, enabled by the phase change material Ge3Sb2Te6 (GST-326), we demonstrate a tunable and switchable mid-infrared plasmonic chiral metamaterial in a proof-of-concept experiment. A large tunability range of the circular dichroism response from λ = 4.15 to 4.90 μm is achieved, and we experimentally demonstrate that the combination of a passive bias-type chiral layer with the active chiral metamaterial allows for switchable chirality, that is, the reversal of the circular dichroism sign, in a fully planar, layered design without the need for geometrical reconfiguration. Because phase change materials can be electrically and optically switched, our designs may open up a path for highly integrated mid-IR polarization engineering devices that can be modulated on ultrafast time scales.
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Affiliation(s)
- Xinghui Yin
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
- §Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Martin Schäferling
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
| | - Ann-Katrin U Michel
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Andreas Tittl
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
| | - Matthias Wuttig
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Thomas Taubner
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Harald Giessen
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
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Steinbusch TP, Tyagi HK, Schaafsma MC, Georgiou G, Gómez Rivas J. Active terahertz beam steering by photo-generated graded index gratings in thin semiconductor films. OPTICS EXPRESS 2014; 22:26559-26571. [PMID: 25401807 DOI: 10.1364/oe.22.026559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate active beam steering of terahertz radiation using a photo-excited thin layer of gallium arsenide. A constant gradient of phase discontinuity along the interface is introduced by an spatially inhomogeneous density of free charge carriers that are photo-generated in the GaAs with an optical pump. The optical pump has been spatially modulated to form the shape of a planar blazed grating. The phase gradient leads to an asymmetry between the +1 and -1 transmission diffracted orders of more than a factor two. Optimization of the grating structure can lead to an asymmetry of more than one order of magnitude. Similar to metasurfaces made of plasmonic antennas, the photo-generated grating is a planar structure that can achieve large beam steering efficiency. Moreover, the photo-generation of such structures provides a platform for active THz beam steering.
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