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Temperini ME, Polito R, Intze A, Gillibert R, Berkmann F, Baldassarre L, Giliberti V, Ortolani M. A mid-infrared laser microscope for the time-resolved study of light-induced protein conformational changes. Rev Sci Instrum 2023; 94:064102. [PMID: 37862502 DOI: 10.1063/5.0136676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 05/26/2023] [Indexed: 10/22/2023]
Abstract
We have developed a confocal laser microscope operating in the mid-infrared range for the study of light-sensitive proteins, such as rhodopsins. The microscope features a co-aligned infrared and visible illumination path for the selective excitation and probing of proteins located in the IR focus only. An external-cavity tunable quantum cascade laser provides a wavelength tuning range (5.80-6.35 µm or 1570-1724 cm-1) suitable for studying protein conformational changes as a function of time delay after visible light excitation with a pulsed LED. Using cryogen-free detectors, the relative changes in the infrared absorption of rhodopsin thin films around 10-4 have been observed with a time resolution down to 30 ms. The measured full-width at half maximum of the Airy disk at λ = 6.08 µm in transmission mode with a confocal arrangement of apertures is 6.6 µm or 1.1λ. Dark-adapted sample replacement at the beginning of each photocycle is then enabled by exchanging the illuminated thin-film location with the microscope mapping stage synchronized to data acquisition and LED excitation and by averaging hundreds of time traces acquired in different nearby locations within a homogeneous film area. We demonstrate that this instrument provides crucial advantages for time-resolved IR studies of rhodopsin thin films with a slow photocycle. Time-resolved studies of inhomogeneous samples may also be possible with the presented instrument.
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Affiliation(s)
- Maria Eleonora Temperini
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
- Center for Life Nano & Neuro Science CL2NS, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome 00161, Italy
| | - Raffaella Polito
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
| | - Antonia Intze
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
- Center for Life Nano & Neuro Science CL2NS, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome 00161, Italy
| | - Raymond Gillibert
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
| | - Fritz Berkmann
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
| | - Leonetta Baldassarre
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
| | - Valeria Giliberti
- Center for Life Nano & Neuro Science CL2NS, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome 00161, Italy
| | - Michele Ortolani
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, Rome 00185, Italy
- Center for Life Nano & Neuro Science CL2NS, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome 00161, Italy
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Barnett J, Wehmeier L, Heßler A, Lewin M, Pries J, Wuttig M, Klopf JM, Kehr SC, Eng LM, Taubner T. Far-Infrared Near-Field Optical Imaging and Kelvin Probe Force Microscopy of Laser-Crystallized and -Amorphized Phase Change Material Ge 3Sb 2Te 6. Nano Lett 2021; 21:9012-9020. [PMID: 34665620 DOI: 10.1021/acs.nanolett.1c02353] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Chalcogenide phase change materials reversibly switch between non-volatile states with vastly different optical properties, enabling novel active nanophotonic devices. However, a fundamental understanding of their laser-switching behavior is lacking and the resulting local optical properties are unclear at the nanoscale. Here, we combine infrared scattering-type scanning near-field optical microscopy (SNOM) and Kelvin probe force microscopy (KPFM) to investigate four states of laser-switched Ge3Sb2Te6 (as-deposited amorphous, crystallized, reamorphized, and recrystallized) with nanometer lateral resolution. We find SNOM to be especially sensitive to differences between crystalline and amorphous states, while KPFM has higher sensitivity to changes introduced by melt-quenching. Using illumination from a free-electron laser, we use the higher sensitivity to free charge carriers of far-infrared (THz) SNOM compared to mid-infrared SNOM and find evidence that the local conductivity of crystalline states depends on the switching process. This insight into the local switching of optical properties is essential for developing active nanophotonic devices.
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Affiliation(s)
- Julian Barnett
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Lukas Wehmeier
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, 01062 Dresden, Germany
| | - Andreas Heßler
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Martin Lewin
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Julian Pries
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Matthias Wuttig
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - J Michael Klopf
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Susanne C Kehr
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Lukas M Eng
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, 01062 Dresden, Germany
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
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Niessen K, Deng Y, Markelz AG. Near-field THz micropolarimetry. Opt Express 2019; 27:28036-28047. [PMID: 31684561 PMCID: PMC6825620 DOI: 10.1364/oe.27.028036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 08/09/2019] [Accepted: 08/11/2019] [Indexed: 05/30/2023]
Abstract
We introduce a method for rapid determination of anisotropic terahertz absorption with sub micron resolution and high spectral integrity in the terahertz range. The method is ideal for microscopic and environmentally sensitive materials such as 2-D materials and protein crystals where the anisotropic absorption is critical to understanding underlying physics. We introduce the idea of using an iso-response relationship between the THz polarization and electro optic probe polarization to enable stationary sample polarization measurements covering a full 2π polarization dependence measurement.
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Luo W, Boselli M, Poumirol JM, Ardizzone I, Teyssier J, van der Marel D, Gariglio S, Triscone JM, Kuzmenko AB. High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces. Nat Commun 2019; 10:2774. [PMID: 31235858 PMCID: PMC6591405 DOI: 10.1038/s41467-019-10672-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 05/21/2019] [Indexed: 11/09/2022] Open
Abstract
Probing the local transport properties of two-dimensional electron systems (2DES) confined at buried interfaces requires a non-invasive technique with a high spatial resolution operating in a broad temperature range. In this paper, we investigate the scattering-type scanning near field optical microscopy as a tool for studying the conducting LaAlO3/SrTiO3 interface from room temperature down to 6 K. We show that the near-field optical signal, in particular its phase component, is highly sensitive to the transport properties of the electron system present at the interface. Our modeling reveals that such sensitivity originates from the interaction of the AFM tip with coupled plasmon-phonon modes with a small penetration depth. The model allows us to quantitatively correlate changes in the optical signal with the variation of the 2DES transport properties induced by cooling and by electrostatic gating. To probe the spatial resolution of the technique, we image conducting nano-channels written in insulating heterostructures with a voltage-biased tip of an atomic force microscope.
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Affiliation(s)
- Weiwei Luo
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Margherita Boselli
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marie Poumirol
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Ivan Ardizzone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jérémie Teyssier
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Dirk van der Marel
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Stefano Gariglio
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marc Triscone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Alexey B Kuzmenko
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland.
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Pustogow A, McLeod AS, Saito Y, Basov DN, Dressel M. Internal strain tunes electronic correlations on the nanoscale. Sci Adv 2018; 4:eaau9123. [PMID: 30555919 PMCID: PMC6294596 DOI: 10.1126/sciadv.aau9123] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 11/15/2018] [Indexed: 06/01/2023]
Abstract
In conventional metals, charge carriers basically move freely. In correlated electron materials, however, the electrons may become localized because of strong Coulomb interactions, resulting in an insulating state. Despite considerable progress in the last decades, elucidating the driving mechanisms that suppress metallic charge transport, the spatial evolution of this phase transition remains poorly understood on a microscopic scale. Here, we use cryogenic scanning near-field optical microscopy to study the metal-to-insulator transition in an electronically driven charge-ordered system with a 20-nm spatial resolution. In contrast to common mean-field considerations, we observe pronounced phase segregation with a sharp boundary between metallic and insulating regions evidencing its first-order nature. Considerable strain in the crystal spatially modulates the effective electronic correlations within a few micrometers, leading to an extended "zebra" pattern of metallic and insulating stripes. We can directly monitor the spatial strain distribution via a gradual enhancement of the optical conductivity as the energy gap is depressed. Our observations shed new light on previous analyses of correlation-driven metal-insulator transitions.
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Affiliation(s)
- A. Pustogow
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - A. S. McLeod
- University of California San Diego, La Jolla, CA 92093, U.S.A
- Department of Physics, Columbia University, New York, NY 92093, U.S.A
| | - Y. Saito
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - D. N. Basov
- University of California San Diego, La Jolla, CA 92093, U.S.A
- Department of Physics, Columbia University, New York, NY 92093, U.S.A
| | - M. Dressel
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
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Döring J, Lang D, Wehmeier L, Kuschewski F, Nörenberg T, Kehr SC, Eng LM. Low-temperature nanospectroscopy of the structural ferroelectric phases in single-crystalline barium titanate. Nanoscale 2018; 10:18074-18079. [PMID: 30230501 DOI: 10.1039/c8nr04081h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We optically investigate the local-scale ferroelectric domain structure of tetragonal, orthorhombic, and rhombohedral barium titanate (BTO) single crystals using scattering-type scanning near-field infrared (IR) optical microscopy (s-SNIM) at temperatures down to 150 K. Thanks to the precisely tunable narrow-band free-electron laser FELBE, we are able to explore the spectral fingerprints and IR resonances of these three phases and their domain orientations in the optical IR near-field. More clearly, every structural phase is analyzed with respect to its near-field resonances close to a wavelength of 17 μm when exploring the (111)-oriented BTO sample surface. Furthermore, near-field imaging at these resonances is performed, that clearly allows for the unambiguous optical identification of different domain orientations. Since our s-SNIM is based on a non-contact scanning force microscope, our s-SNIM findings are backed up by sample-topography and piezoresponse force microscopy (PFM) imaging, providing complementary information in an excellent match to the s-SNIM results.
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Affiliation(s)
- Jonathan Döring
- Institut für Angewandte Physik, Technische Universität Dresden, Nöthnitzer Str. 61, D-01187 Dresden, Germany.
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