DOCSLIB.ORG

Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept micromachines Review Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept Catharina Latz 1,* , Thomas Asshauer 2, Christian Rathjen 2 and Alireza Mirshahi 1 1 Dardenne Eye Hospital, D-53173 Bonn, Germany; [email protected] 2 Ziemer Ophthalmic Systems, CH-2562 Port, Switzerland; [email protected] (T.A.); [email protected] (C.R.) * Correspondence: [email protected] Abstract: This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled. Keywords: femtosecond laser; fs-assisted cataract surgery; laser-assisted ophthalmic surgery; high pulse frequency; low energy Citation: Latz, C.; Asshauer, T.; 1. Introduction Rathjen, C.; Mirshahi, A. Laser technology and ophthalmic surgery have shaped each other over the past Femtosecond-Laser Assisted Surgery 40 years. The optically transparent structures of the eye, namely cornea, lens, and vitreous of the Eye: Overview and Impact of body, allow for delivery of the laser energy at different focal depths, thereby giving access the Low-Energy Concept. to surgical interventions without having to open or mechanically enter the eye (Figure1). Micromachines 2021, 12, 122. Other types of lasers, with various wavelengths, pulse durations, and power levels, interact https://doi.org/10.3390/mi12020122 with eye tissues in a range of different ways. For continuous laser irradiation of low to moderate average power (mW range), photochemical and thermal effects induced by the Academic Editor: Rebeca Martínez absorbed light are the dominant laser–tissue interactions. Depending on the wavelengths Vázquez used, specific types of molecules can be optically excited to trigger chemical reactions, or Received: 15 December 2020 local heating of specific tissue can be achieved. If temperatures above 60 ◦C are reached, Accepted: 18 January 2021 7 Published: 24 January 2021 tissue coagulation will occur. When pulsed laser light with intensities between 10 and 109 W/cm2 interacts with strongly absorbing tissue, near-surface material can be removed Publisher’s Note: MDPI stays neutral explosively. This effect is called “photoablation”. In ophthalmology, it is applied to change with regard to jurisdictional claims in the curvature of the cornea with pulsed UV light from excimer lasers. For shorter pulse 11 2 published maps and institutional affil- durations in the ps to fs range and even higher intensities above 10 W/cm , more exotic iations. interactions can be achieved, as will be explained in detail below. A more comprehensive general overview of laser–tissue interaction mechanisms can be found in excellent quality in several text books [1,2]. The first reported ophthalmic use of short pulse lasers at near-infrared wavelengths was in 1979 by Aron-Rosa, who treated posterior capsule opacification (PCO) after cataract Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. surgery [3]. In 1989, Stern et al. demonstrated that by decreasing pulse width of ultrashort- −9 −15 This article is an open access article pulsed lasers from nano- to femtoseconds (ns: 10 s, fs: 10 s), ablation profiles showed distributed under the terms and higher precision and less collateral damage [4]. At the same time, optical coherence conditions of the Creative Commons tomography developed and provided noninvasive three-dimensional (3D) in vivo imaging Attribution (CC BY) license (https:// with fine resolution in both lateral and axial dimensions at a micrometer level [5]. These creativecommons.org/licenses/by/ developments offered ophthalmic surgeons a tool for high precision cutting and visual 4.0/). control through imaging, and ultimately allowed a gamut of treatment applications for Micromachines 2021, 12, 122. https://doi.org/10.3390/mi12020122 https://www.mdpi.com/journal/micromachines Micromachines 2021, 12, x 2 of 22 Micromachines 2021, 12, 122 2 of 21 cutting and visual control through imaging, and ultimately allowed a gamut of treatment theseapplications lasers within for these the field lasers of ophthalmology.within the field Recent of ophthalmology. changes in the Recent numerical changes aperture in the of thenumerical laser focusing aperture optics of the and laser the focusing repetition optics rate of and the the laser repetition sources haverate of further the laser decreased sources collateralhave further damage decreased while collateral increasing damage precision. while This increasing review articleprecision. gives This an review overview article of thegives technical an overview backgrounds of the te ofchnical femtosecond backgrounds lasers of and femtos OCTecond imaging lasers as and well OCT as imaging clinical applicationsas well as clinical in ophthalmic applications surgery in ophthalmic today. surgery today. FigureFigure 1. 1.Cross-section Cross-section of of the the eye. eye. Cornea, Cornea, crystalline crystalline lens, lens, and and vitreous vitreous body body are are transparent transparent in in the the healthy eye. healthy eye. 2.2. LaserLaser TechnologyTechnology 2.1.2.1. Solid-StateSolid-State LasersLasers inin OphthalmologyOphthalmology 2.1.1. Nd:YAG Laser with Ns Pulse Durations 2.1.1. Nd:YAG Laser with Ns Pulse Durations The first type of short-pulsed laser at near-infrared wavelengths successfully used in The first type of short-pulsed laser at near-infrared wavelengths successfully used in ophthalmology was the Q-switched Nd:YAG solid-state laser. Its wavelength of 1064 nm is ophthalmology was the Q-switched Nd:YAG solid-state laser. Its wavelength of 1064 nm transmitted by all the visually transparent structures in the eye (cornea, lens, and vitreous is transmitted by all the visually transparent structures in the eye (cornea, lens, and body). Their pulse durations are a few nanoseconds (ns), and for ophthalmic applications, vitreous body). Their pulse durations are a few nanoseconds (ns), and for ophthalmic pulse energies in the range of 0.3–10 mJ are typically used [6]. applications, pulse energies in the range of 0.3–10 mJ are typically used [6]. When Nd:YAG laser pulses are strongly focused at a location inside the eye, to spot When Nd:YAG laser pulses are strongly focused at a location inside the eye, to spot sizes in the order of a few microns, the combination of short pulse duration focusing sizes in the order of a few microns, the combination of short pulse duration focusing to to minimal spot sizes creates very high intensities at the laser focus, above 1011 W/cm2. minimal spot sizes creates very high intensities at the laser focus, above 1011 W/cm2. Under Under these conditions, a phenomenon called “optical breakdown” occurs. In the first step,these multiphoton conditions, absorptiona phenomenon leads called to ionization ”optical of breakdown” some tissue molecules,occurs. In the creating first freestep, electrons.multiphoton In the absorption subsequent leads second to step,ionization these “seed” of some electrons tissue absorb molecules, photon creating energy andfree areelectrons. thus accelerated. In the subsequent After repeated second photon step, th absorptions,ese ”seed” electrons electrons absorb reach photon a sufficiently energy high and kineticare thus energy accelerated. to ionize After themselves repeated morephoton molecules absorptions, by impact electrons ionization, reach a sufficiently creating more high freekinetic electrons. energy Ifto the ionize laser themselves irradiation more is intense molecules enough by impact to overcome ionization, electron creating losses, more an avalanchefree electrons. effect If occurs the laser [2]. irradiation is intense enough to overcome electron losses, an avalancheWhen effect the extremely occurs [2]. fast rising electron density exceeds values of approximately 1020/cmWhen3, a “plasmathe extremely state of fast matter” rising (cloud electron of ions density and free exceeds electrons) values is created of approximately at the laser focus1020/cm [2].3, Thisa ”plasma plasma state is highly of matter” absorbing (cloud forof ions photons and free of all electrons) wavelengths. is created Therefore, at the laser the restfocus of [2]. the laserThis plasma pulse is is directly highly absorbedabsorbing by fo ther photons plasma, of increasingall wavelengths. its temperature Therefore, and the energyrest of densitythe laser (Figure pulse 2is). directly absorbed by the plasma, increasing its temperature and energyThe density hot plasma (Figure cloud 2). rapidly recombines to a hot gas, with a thermalization time of the energy initially carried by free electrons of a few picoseconds to tens of ps [7]. This time is much shorter than the acoustic transit time from the center of the focus to the periphery Micromachines 2021, 12, x 3 of 22 The hot plasma cloud rapidly recombines to a hot gas, with a thermalization time of Micromachines 2021, 12, 122 the energy initially carried by free electrons of a few picoseconds to tens of ps [7].3 This of 21 time is much shorter than the acoustic transit time
Load more

Recommended publications
  • Early-Stage Dynamics of Chloride Ion–Pumping Rhodopsin Revealed by a Femtosecond X-Ray Laser
    Early-stage dynamics of chloride ion–pumping rhodopsin revealed by a femtosecond X-ray laser Ji-Hye Yuna,1, Xuanxuan Lib,c,1, Jianing Yued, Jae-Hyun Parka, Zeyu Jina, Chufeng Lie, Hao Hue, Yingchen Shib,c, Suraj Pandeyf, Sergio Carbajog, Sébastien Boutetg, Mark S. Hunterg, Mengning Liangg, Raymond G. Sierrag, Thomas J. Laneg, Liang Zhoud, Uwe Weierstalle, Nadia A. Zatsepine,h, Mio Ohkii, Jeremy R. H. Tamei, Sam-Yong Parki, John C. H. Spencee, Wenkai Zhangd, Marius Schmidtf,2, Weontae Leea,2, and Haiguang Liub,d,2 aDepartment of Biochemistry, College of Life Sciences and Biotechnology, Yonsei University, Seodaemun-gu, 120-749 Seoul, South Korea; bComplex Systems Division, Beijing Computational Science Research Center, Haidian, 100193 Beijing, People’s Republic of China; cDepartment of Engineering Physics, Tsinghua University, 100086 Beijing, People’s Republic of China; dDepartment of Physics, Beijing Normal University, Haidian, 100875 Beijing, People’s Republic of China; eDepartment of Physics, Arizona State University, Tempe, AZ 85287; fPhysics Department, University of Wisconsin, Milwaukee, Milwaukee, WI 53201; gLinac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025; hDepartment of Chemistry and Physics, Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia; and iDrug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 230-0045 Yokohama, Japan Edited by Nicholas K. Sauter, Lawrence Berkeley National Laboratory, Berkeley, CA, and accepted by Editorial Board Member Axel T. Brunger February 21, 2021 (received for review September 30, 2020) Chloride ion–pumping rhodopsin (ClR) in some marine bacteria uti- an acceptor aspartate (13–15).
    [Show full text]
  • Comparing Femtosecond Lasers an Analysis of Commercially Available Platforms for Refractive Surgery
    REFRACTIVE SURGERY FEATURE STORY Comparing Femtosecond Lasers An analysis of commercially available platforms for refractive surgery. BY JAY S. PEPOSE, MD, PHD, AND HOLGER LUBATSCHOWSKI, PHD ith the increasing popularity and expanding A BCD applications of femtosecond lasers in oph- thalmology,1,2 refractive surgery in particular, W a common question among practitioners is, how do the platforms differ? Currently commercially avail- able in the United States are the IntraLase FS (Advanced Medical Optics, Inc., Santa Ana, CA), Femto LDV (Ziemer Ophthalmic Systems Group, Port, Switzerland), Femtec (20/10 Perfect Vision AG, Heidelberg, Germany), and VisuMax femtosecond laser system (Carl Zeiss Meditec, Inc., Dublin, CA). A meaningful comparison requires some basic concepts of femtosecond laser physics and tissue interactions,3-5 important aspects of which are reviewed in this article. Figure 1. The course of a photodisruptive process is shown.Due BASIC PRINCIPLES to multiphoton absorption in the focus of the laser beam,plasma How short is ultrashort? The definition of a femtosec- develops (A).Depending on the laser parameter,the diameter ond is 10-15 seconds (ie, one millionth of a billionth of a varies between 0.5 µm to several micrometers.The expanding second). Putting that information into comprehensible plasma drives as a shock wave,which transforms after a few terms, it takes 1.2 seconds for light to travel from the microns to an acoustic transient (B).In addition to the shock moon to an earthbound observer’s retinas. In 100 fem- wave’s generation,the expanding plasma has pushed the sur- toseconds, light traverses 30 µm—around one-third the rounding medium away from its center,which results in a cavita- thickness of a human hair.
    [Show full text]
  • Terahertz-Time Domain Spectrometer with 90 Db Peak Dynamic Range
    J Infrared Milli Terahz Waves DOI 10.1007/s10762-014-0085-9 Terahertz-time domain spectrometer with 90 dB peak dynamic range N. Vieweg & F. Rettich & A. Deninger & H. Roehle & R. Dietz & T. Göbel & M. Schell Received: 24 January 2014 /Accepted: 12 June 2014 # The Author(s) 2014. This article is published with open access at Springerlink.com Abstract Many time-domain terahertz applications require systems with high bandwidth, high signal-to-noise ratio and fast measurement speed. In this paper we present a terahertz time-domain spectrometer based on 1550 nm fiber laser technology and InGaAs photocon- ductive switches. The delay stage offers both a high scanning speed of up to 60 traces / s and a flexible adjustment of the measurement range from 15 ps – 200 ps. Owing to a precise reconstruction of the time axis, the system achieves a high dynamic range: a single pulse trace of 50 ps is acquired in only 44 ms, and transformed into a spectrum with a peak dynamic range of 60 dB. With 1000 averages, the dynamic range increases to 90 dB and the measurement time still remains well below one minute. We demonstrate the suitability of the system for spectroscopic measurements and terahertz imaging. Keywords terahertz time domain spectroscopy. femtosecond fiber laser. InGaAs photoconductive switches . terahertz imaging 1 Introduction Terahertz waves feature unique properties: like microwaves, terahertz radiation passes through a plethora of non-conducting materials, including paper, cardboard, plastics, wood, ceramics and glass-fiber composites [1]. In contrast to microwaves, terahertz waves have a smaller wavelength and thus offer sub-millimeter spatial resolution.
    [Show full text]
  • 14. Measuring Ultrashort Laser Pulses I: Autocorrelation the Dilemma the Goal: Measuring the Intensity and Phase Vs
    14. Measuring Ultrashort Laser Pulses I: Autocorrelation The dilemma The goal: measuring the intensity and phase vs. time (or frequency) Why? The Spectrometer and Michelson Interferometer 1D Phase Retrieval Autocorrelation 1D Phase Retrieval E(t) Single-shot autocorrelation E(t–) The Autocorrelation and Spectrum Ambiguities Third-order Autocorrelation Interferometric Autocorrelation 1 The Dilemma In order to measure an event in time, you need a shorter one. To study this event, you need a strobe light pulse that’s shorter. Photograph taken by Harold Edgerton, MIT But then, to measure the strobe light pulse, you need a detector whose response time is even shorter. And so on… So, now, how do you measure the shortest event? 2 Ultrashort laser pulses are the shortest technological events ever created by humans. It’s routine to generate pulses shorter than 10-13 seconds in duration, and researchers have generated pulses only a few fs (10-15 s) long. Such a pulse is to one second as 5 cents is to the US national debt. Such pulses have many applications in physics, chemistry, biology, and engineering. You can measure any event—as long as you’ve got a pulse that’s shorter. So how do you measure the pulse itself? You must use the pulse to measure itself. But that isn’t good enough. It’s only as short as the pulse. It’s not shorter. Techniques based on using the pulse to measure itself are subtle. 3 Why measure an ultrashort laser pulse? To determine the temporal resolution of an experiment using it. To determine whether it can be made even shorter.
    [Show full text]
  • The Effect of Long Timescale Gas Dynamics on Femtosecond Filamentation
    The effect of long timescale gas dynamics on femtosecond filamentation Y.-H. Cheng, J. K. Wahlstrand, N. Jhajj, and H. M. Milchberg* Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA *[email protected] Abstract: Femtosecond laser pulses filamenting in various gases are shown to generate long- lived quasi-stationary cylindrical depressions or ‘holes’ in the gas density. For our experimental conditions, these holes range up to several hundred microns in diameter with gas density depressions up to ~20%. The holes decay by thermal diffusion on millisecond timescales. We show that high repetition rate filamentation and supercontinuum generation can be strongly affected by these holes, which should also affect all other experiments employing intense high repetition rate laser pulses interacting with gases. ©2013 Optical Society of America OCIS codes: (190.5530) Pulse propagation and temporal solitons; (350.6830) Thermal lensing; (320.6629) Supercontinuum generation; (260.5950) Self-focusing. References and Links 1. A. Couairon and A. Mysyrowicz, “Femtosecond filamentation in transparent media,” Phys. Rep. 441(2-4), 47– 189 (2007). 2. P. B. Corkum, C. Rolland, and T. Srinivasan-Rao, “Supercontinuum generation in gases,” Phys. Rev. Lett. 57(18), 2268–2271 (1986). S. A. Trushin, K. Kosma, W. Fuss, and W. E. Schmid, “Sub-10-fs supercontinuum radiation generated by filamentation of few-cycle 800 nm pulses in argon,” Opt. Lett. 32(16), 2432–2434 (2007). 3. N. Zhavoronkov, “Efficient spectral conversion and temporal compression of femtosecond pulses in SF6.,” Opt. Lett. 36(4), 529–531 (2011). 4. C. P. Hauri, R. B.
    [Show full text]
  • Femtosecond Pulse Generation
    Femto-UP 2020-21 School Femtosecond Pulse Generation Adeline Bonvalet Laboratoire d’Optique et Biosciences CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128, Palaiseau, France 1 Definitions Electric field of a 10-fs 800-nm pulse nano 10-9 sec pico 10-12 femto 10-15 2,7 fs atto 10-18 10 fs time 2 Many properties Electric field of a 10-fs 800-nm pulse High peaki power (Energy /Duration) Ultrashorti Duration Spectral Properties i (Frequency Comb) time 3 Time-resolved spectroscopy Electric field of a 10-fs 800-nm pulse Ultrashorti Duration Time-resolved spectroscopy Direct observation of ultrafast motions time Ahmed Zewail, Nobel Prize in chemistry 1999, femtochemistry 4 Imaging Electric field of a 10-fs 800-nm pulse High peaki power (Energy /Duration) Nonlinear microscopy time 5 Material processing Electric field of a 10-fs 800-nm pulse High peaki power (Energy /Duration) Laser matter interaction Drilling, cutting, etching,… time Areas of applications : aeronautics, electronics, medical,6 optics… Light matter interaction Electric field of a 10-fs 800-nm pulse High peaki power (Energy /Duration) Ability to reach extreme conditions (amplified system) Applications : Sources of intense particles beams, X-rays, high energy density science, laboratory astroprophysics … time 7 Metrology Electric field of a 10-fs 800-nm pulse Spectral Properties i (Frequency Comb) Nobel Prize 2005 "for their contributions to the development of laser-based time precision spectroscopy, including the optical frequency comb technique." 8 Outline
    [Show full text]
  • Generation of Electromagnetic Pulses from Plasma Channels Induced By
    Generationofelectromagneticpulsesfromplasmachannels inducedbyfemtosecondlightstrings Chung-ChiehCheng,E.M.Wright,andJ.V.Moloney ArizonaCenterforMathematicalSciences,andOpticalSciencesCenter,UniversityofArizona, Tucson,AZ85721 December04,2000 We present a model that elucidates the physics underlying the generation of an electromagneticpulsefromaplasmachannelresultingfromtheionizationofairbya femtosecond laser pulse. By a new mechanism analogous to nonlinear optical rectification,thelaserpulseinducesadipolemomentintheplasmawhichsubsequently oscillates at the plasma frequency and radiates an electromagnetic pulse with a peak frequency within the far-infrared to microwave region, depending on the electron density,withabandwidtharoundhundredsofgigahertz. PACS:33.80.WzOthermultiphotonprocesses 42.65.ReUltrafastprocesses;opticalpulsegenerationandpulsecompression 52.40.DbElectromagnetic(nonlaser)radiationinteractionswithplasma Recentinvestigationsofthepropagationofintensefemtosecondinfrared(IR)laser pulsesinairshowthatthedynamicalinteractionbetweennonlinearself-focusing, plasmadefocusing,andgroup-velocitydispersioncancauseaninitialbeamtobreakup spatiallyintoseveralfilaments,orlightstrings,withdiametersaroundahundred micronsthatcanmaintainthemselvesoverlongdistances[1,2,3,4,5].Ithasbeen observedexperimentallythatfemtosecondlightstringsinturnproduceplasma channelsbymulti-photonionization(MPI)alongtheirdirectionofpropagationwith lengthsrangingfromtensofcentimeterstoseveralmeters[6,7,8].Observationsofthe electromagneticpulses(EMPs)fromlightstringinducedplasmassuggestthatthese
    [Show full text]
  • Thz Field Engineering in Two-Color Femtosecond Filaments Using
    THz field engineering in two-color femtosecond filaments using chirped and delayed laser pulses A Nguyen, P González de Alaiza Martínez, I Thiele, Stefan Skupin, L Bergé To cite this version: A Nguyen, P González de Alaiza Martínez, I Thiele, Stefan Skupin, L Bergé. THz field engineering in two-color femtosecond filaments using chirped and delayed laser pulses. New Journal of Physics, Institute of Physics: Open Access Journals, 2018, 20 (3), pp.033026. 10.1088/1367-2630/aaa470. hal-01754802 HAL Id: hal-01754802 https://hal.archives-ouvertes.fr/hal-01754802 Submitted on 30 Mar 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. PAPER • OPEN ACCESS Related content - Validity of the unidirectional propagation THz field engineering in two-color femtosecond model: Application to laser-driven terahertz emission J Déchard, A Nguyen, P González de filaments using chirped and delayed laser pulses Alaiza Martínez et al. - Spectral self-action of THz emission from To cite this article: A Nguyen et al 2018 New J. Phys. 20 033026 ionizing two-color laser pulses in gases Eduardo Cabrera-Granado, Yxing Chen, Ihar Babushkin et al. - Intense terahertz radiation and their applications View the article online for updates and enhancements.
    [Show full text]
  • Femtosecond Optics by Tomas Jankauskas
    Femtosecond optics by Tomas Jankauskas Since the introduction of the first sub-picosecond lasers in the 1990s, the market for femtosecond optics Chromatic dispersion has grownrapidly. However, it still cannot compete with longer pulse or CW laser markets. In femtosecond Since the optical spectrum of an ultrashort pulse is very applications problems of conventional optics and broad, group velocity plays a key role in understanding coatings are that they either distort the temporal how ultrashort optics work. Group velocity of a wave characteristics of the pulse, or are damaged by high is the velocity with which the overall shape of waves’ peak power of the pulse. To better understand why this amplitudes propagates through space. It would be happens, let’s look at the basics of the ultrashort world. correct to say that group velocity is the velocity with Though the definition sometimes varies, anultrashort which whole broad electromagnetic ultrashort pulse pulse is an electromagnetic pulse with a time duration propagates. For free space where the refractive index of one picosecond (10-12 second) or less. Since ultrashort is equal to one, group velocity is constant for all phenomena are too fast to be directly measured with components of the pulse. electronic devices such events are sometimes referred Optical materials possess a specific quality, the phase to as ultrafast (the meaning, however, is the same). velocity of light inside the material depends on the Pulse length is inversely proportional to the optical frequency (or wavelength), and equivalently the group spectrum of the laser beam therefore ultrashort pulses velocity depends on the frequency.
    [Show full text]
  • Terahertz Time-Domain Spectroscopy
    PROTOCOL https://doi.org/10.32386/scivpro.000006 Terahertz Time-Domain Spectroscopy C. Ciccarellia, H. Joyceb, J. Robinsonc, F. N. Kholida*, D. Hamaraa, S. Karb, K. Jeonc Time-Domain terahertz spectroscopy (THz TDS) has attracted attention from many scientific disciplines as it enables access- ing the gap between electronic and optical techniques. One application is to probe spintronic dynamics in sub-picosecond time scale. Here, we discuss principles and technical aspects of a typical THz TDS setup. We also show an example of terahertz time-domain data obtained from a Co/Pt thin film calibrant, which is a well-studied spintronic structure emitting strong THz radiation. See video at https://youtu.be/X7vrvQcmy8c Introduction The new THz spectroscopy laboratory at the Maxwell Centre (Caven- dish Laboratory, University of Cambridge) became fully operational in March 2019 (Figure 1). The laboratory was mainly funded by The Winton Programme for the Physics of Sustainability through an Ad- vanced Research Fellowship awarded to Chiara Ciccarelli (Figure 2), in combination with funding from the Royal Society and the Euro- pean Union, belonging to both Chiara Ciccarelli and Hannah Joyce. Time-domain THz Spectroscopy, is a powerful technique for materials characterisation and control.1-4 Technologies to generate THz radiation are now widely available and this is what is allowing a wider use of THz frequencies in new research areas. One of these areas is spintronics.5,6 Spintronics means ‘spin transport electronics’ and indicates elec- Figure 1 | Chiara Ciccarelli (Lecturer at the University of Cambridge) and tronics made of spins as opposed to electronics made of charges.5,6 Dominik Hamara (PhD student).
    [Show full text]
  • Femtosecond to Millisecond Structural Changes in a Light-Driven Sodium
    1 Femtosecond to millisecond structural changes in a 2 light-driven sodium pump 3 Petr Skopintsev1, David Ehrenberg2,†, Tobias Weinert1,†, Daniel James1, Rajiv K. Kar3, Philip J. M. Johnson4, 4 Dmitry Ozerov5, Antonia Furrer1, Isabelle Martiel6, Florian Dworkowski6, Karol Nass6,7, Gregor Knopp7, 5 Claudio Cirelli7, Christopher Arrell8, Dardan Gashi1,7, Sandra Mous9, Maximilian Wranik1, Thomas Gruhl1, 6 Demet Kekilli1, Steffen Brünle1, Xavier Deupi1, Gebhard F. X. Schertler1,10, Roger M. Benoit1,11, Valerie 7 Panneels1, Przemyslaw Nogly9, Igor Schapiro3, Christopher Milne7, Joachim Heberle2, Jörg Standfuss1 8 9 1Laboratory of Biomolecular Research, Biology and Chemistry Division, Paul Scherrer Institut, 5232 Villigen, Switzerland. 10 2Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Berlin, Germany. 11 3Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel. 12 4Laboratory of Non-linear Optics, Photon Science Division, Paul Scherrer Institut, 5232 Villigen, Switzerland. 13 5Science IT, Paul Scherrer Institut, 5232 Villigen, Switzerland. 14 6Laboratory for Macromolecules and Bioimaging, Photon Science Division, Paul Scherrer Institut, 5232 Villigen, 15 Switzerland. 16 7Laboratory of Femtochemistry, Photon Science Division, Paul Scherrer Institut, 5232 Villigen, Switzerland. 17 8Laboratory for Advanced Photonics, Photon Science Division, Paul Scherrer Institut, 5232 Villigen, Switzerland. 18 9Institute of Molecular Biology and Biophysics,
    [Show full text]
  • Frequency Generation Using BIBO Crystal Pumped with an Optical Parametric Amplifier
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 3 September 2020 doi:10.20944/preprints202009.0064.v1 Communication Green-Yellow-Orange-Red Spectral Range with Sum- frequency Generation Using BIBO Crystal Pumped with an Optical Parametric Amplifier Rafael Quintero-Torres 1 and J.L. Domínguez-Juárez 1,2* 1 Centro de Física Aplicada y Tecnología Avanzada, UNAM, Querétaro, México; [email protected] 2 Cátedras CONACyT, CFATA, UNAM, Juriquilla, Querétaro 76230, México * Correspondence: [email protected] Received: date; Accepted: date; Published: date Abstract: We show broadband sum-frequency generation (SFG) in the Green-Yellow-Orange-Red spectral range using bismuth triborate, BiB3O6 crystal (BIBO) as nonlinear material. We perform a noncollinear phase-matching configuration within BIBO crystal using the remaining light behind the second harmonic generation stage and the infrared idler of an optical parametric amplifier (OPA). The obtained mixing radiation of ultrafast light sources to generate femtosecond pulses across 520.5 to 742.5 nm region is observed. SFG spectrum from single-pass cross-correlation intensity over such visible range is showed. The SFG wavelengths as a function of tunable wavelength idler OPA agrees with the expectations of parametric conversion condition and open the door to practical multi-beam or multi-color sum-frequency generators. Keywords: Sum frequency generation; femtosecond pulses; noncollinear phase matching 1. Introduction The growing field of ultrafast light sources still requires multi-beam or multi-colour systems motivated by scientific, medical and industrial applications[1-4]. Recently, wavelength tunability and intense pulse are needed for industrial manufacturing[5,6], scientific research of medical device fabrication[7], spectroscopy techniques to analyze surfaces and interfaces[8], biological imaging with multiphoton microscopy methodologies[9], time-resolved experiments[10] and many other fundamental applications of modern science.
    [Show full text]