About Tissa Gunaratne

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So far Tissa Gunaratne has created 23 blog entries.

Observation of Rapid Exciton–Exciton Annihilation in Monolayer Molybdenum Disulfide

A  publication from Prof. Tony Heinz group with Model IMPULSE from Clark-MXR. Dezheng Sun, Yi Rao, Georg A. Reider, Gugang Chen, Yumeng You, Louis Brézin, Avetik R. Harutyunyan, and Tony F. Heinz Monolayer MoS2 is a direct-gap two-dimensional semiconductor that exhibits strong electron–hole interactions, leading to the formation of stable excitons and trions. Here we report the existence of efficient exciton–exciton annihilation, a four-body interaction, in this material. Exciton–exciton annihilation was identified experimentally in ultrafast transient absorption measurements through the emergence of a decay channel varying quadratically with exciton density. The rate of exciton–exciton annihilation [...]

2018-02-23T21:45:13+00:00 Sep 9, 2016|

Clark-MXR is Laser Institute of America’s Featured Member

August 10, 2016 – An industry leader in Ultrashort Pulse laser based micromachining and the production of ultrafast lasers and laser-based solutions for scientific research and industrial applications, Clark-MXR, Inc. is known for offering unparalleled contract manufacturing services and easy-to-use laser products at a low cost of ownership. See complete CMXR feature

2018-03-05T17:36:35+00:00 Aug 10, 2016|

Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

Re-published from The Journal of Physical Chemistry Letters Jingya Sun, Aniruddha Adhikari, Basamat S. Shaheen, Haoze Yang, and Omar F. Mohammed* Solar and Photovoltaics Engineering Research Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia ABSTRACT: Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. [...]

2018-02-22T20:37:48+00:00 Mar 18, 2016|

Time-resolved Photoemission Study of the Electronic Structure and Dynamics of Chemisorbed Alkali Atoms on Ru(0001)

Clark-MXR Product:  Model IMPULSE Shengmin Zhang, Cong Wang, Xuefeng Cui, Yanan Wang, Adam Argondizzo, Jin Zhao, and Hrvoje Petek Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, & Department of Physics and ICQD/Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei,  China. We investigate the electronic structure and photoexcitation dynamics of alkali atoms (Rb and Cs) chemisorbed on transition-metal Ru(0001) single-crystal surface by angle- and time-resolved multiphoton photoemission. Three- and four-photon photoemission (3PP and 4PP) spectroscopic features due to the σ and π resonances [...]

2018-02-22T22:03:59+00:00 Mar 16, 2016|

DNA Extraction from Geological Samples Assisted with Clark-MXR Femtosecond Laser Micromachining Technology

Traditional techniques used to extract DNA from thin sections of rock samples for amplification and analysis will often introduce contamination from the surrounding material. This is especially true when extracting microscopic inclusion in the presence of nearby unwanted materials. Our femtosecond laser micromachining capability offers a way to address these critical concerns. This image shows a cylinder machined in a thin layer of a rock. The inclusion is isolated with negligible damage to either the center section or the surrounding area. And so that the trapped bio-matter in the middle of the circle can be [...]

2018-02-22T21:51:28+00:00 Feb 11, 2016|

Real-Space Imaging of Carrier Dynamics of Materials Surfaces by Second-Generation Four-Dimensional Scanning Ultrafast Electron Microscopy – Republish

Republished from Imaging of Carrier Dynamics by Second-Generation 4D Scanning UEM enabled by Model IMPULSE from Clark-MXR. A new publication from Prof. Omar Abdelsaboor group at KAUST Jingya Sun, Vasily A. Melnikov, Jafar I. Khan, and Omar F. Mohammed Solar and Photovoltaics Engineering Research Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia Abstract In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion [...]

2018-02-22T21:51:38+00:00 Oct 5, 2015|

Population Inversion and Giant Bandgap Renormalization in Atomically Thin WS2 Layers

Another publication from Prof. Tony Heinz group with Clark-MXR's Model IMPULSE Alexey Chernikov, Claudia Ruppert, Heather M. Hill, Albert F. Rigosi & Tony F. Heinz Nature Photonics 9, 466–470 (2015) Abstract Control of the optical properties of matter on ultrashort timescales is of both fundamental interest and central importance for applications in photonics. It is desirable to achieve pronounced changes over a broad spectral range using the least possible amount of material. Here, we demonstrate a dramatic change over a spectral range of hundreds of meV on the femtosecond timescale in the optical response of [...]

2018-02-22T22:05:29+00:00 Sep 22, 2015|

Chemical Composition of Micrometer-Sized Filaments in an Aragonite Host by a Miniature Laser Ablation/Ionization Mass Spectrometer

Researchers at University of Bern and co-workers used Clark-MXR Model CPA-Series laser to carry out Laser Ablation/Ionization Mass Spectrometry in the quest to search for extraterrestrial life. Tulej Marek, Neubeck Anna, Ivarsson Magnus, Riedo Andreas, Neuland Maike B., Meyer Stefan, and Wurz Peter. Astrobiology. August 2015, 15(8): 669-682. https://doi.org/10.1089/ast.2015.1304 ABSTRACT Detection of extraterrestrial life is an ongoing goal in space exploration, and there is a need for advanced instruments and methods for the detection of signatures of life based on chemical and isotopic composition. Here, we present the first investigation of chemical composition of putative [...]

2018-02-23T21:45:24+00:00 Aug 28, 2015|

Megahertz, High-Order Harmonics for Photoelectron Spectroscopy Generated with Clark-MXR’s Model IMPULSE

March 2015 | Dexter, MI, USA — Recent advancements in high-order harmonic generation (HHG) of vacuum ultraviolet (VUV) at MHz repetition rates provide a wide photon energy range, 13-45eV (up to ~39th harmonic), with ultrafast time resolution. This new publication and related video abstract from Prof. Wolf Widdra group at Martin-Luther-Universität, Halle-Wittenberg, Germany provides a good comparison of traditional techniques with ToF-ARPES using MHz, high-order harmonics. This paper explains ideal conditions for ARPES that can be achieved with Model IMPULSE based High-Order harmonic generation. Fiber-laser based HHG setup for photoemission experiments with one of [...]

2018-03-05T17:46:34+00:00 May 29, 2015|

CARS Microscopy with Spectral Focusing

With the help of spectral focusing, vibrational imaging modalities using multimodal CARS have become invaluable tools in neuroscience. Hans-Erik Swoboda and Tissa Gunaratne Multiphoton/nonlinear laser scanning microscopy has become an important tool to investigate biological phenomena, where high resolution, 3-dimensional imaging with depth resolution is essential to uncover underlying biological functions. Two-photon or multiphoton imaging is preferred to single photon imagining techniques due to several intrinsic advantages of multiphoton techniques. One of the advantages is having a nonlinear intensity dependent absorption. For example, two-photon absorption is restricted to the focal volume so there is virtually [...]

2018-02-23T21:45:40+00:00 May 29, 2015|