Nicolai F. Hartmann
Los Alamos National Laboratory
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Publication
Featured researches published by Nicolai F. Hartmann.
ACS Nano | 2018
Noémie Danné; Mijin Kim; Antoine G. Godin; Hyejin Kwon; Zhenghong Gao; Xiaojian Wu; Nicolai F. Hartmann; Stephen K. Doorn; Brahim Lounis; YuHuang Wang; Laurent Cognet
The intrinsic near-infrared photoluminescence observed in long single-walled carbon nanotubes is known to be quenched in ultrashort nanotubes due to their tiny size as compared to the exciton diffusion length in these materials (>100 nm). Here, we show that intense photoluminescence can be created in ultrashort nanotubes (∼40 nm length) upon incorporation of exciton-trapping sp3 defect sites. Using super-resolution photoluminescence imaging at <25 nm resolution, we directly show the preferential localization of excitons at the nanotube ends, which separate by less than 40 nm and behave as independent emitters. This unexpected observation opens the possibility to synthesize fluorescent ultrashort nanotubes-a goal that has been long thought impossible-for bioimaging applications, where bright near-infrared photoluminescence and small size are highly desirable, and for quantum information science, where high quality and well-controlled near-infrared single photon emitters are needed.
Nano Letters | 2018
Akihiro Ishii; Xiaowei He; Nicolai F. Hartmann; Hidenori Machiya; Han Htoon; Stephen K. Doorn; Y. K. Kato
Single-walled carbon nanotubes are a promising material as quantum light sources at room temperature and as nanoscale light sources for integrated photonic circuits on silicon. Here, we show that the integration of dopant states in carbon nanotubes and silicon microcavities can provide bright and high-purity single-photon emitters on a silicon photonics platform at room temperature. We perform photoluminescence spectroscopy and observe the enhancement of emission from the dopant states by a factor of ∼50, and cavity-enhanced radiative decay is confirmed using time-resolved measurements, in which a ∼30% decrease of emission lifetime is observed. The statistics of photons emitted from the cavity-coupled dopant states are investigated by photon-correlation measurements, and high-purity single photon generation is observed. The excitation power dependence of photon emission statistics shows that the degree of photon antibunching can be kept high even when the excitation power increases, while the single-photon emission rate can be increased to ∼1.7 × 107 Hz.
ACS Nano | 2018
Xiaowei He; Kirill A. Velizhanin; George Bullard; Yusong Bai; Jean-Hubert Olivier; Nicolai F. Hartmann; Brendan J. Gifford; Svetlana Kilina; Sergei Tretiak; Han Htoon; Michael J. Therien; Stephen K. Doorn
Photoluminescent sp3 defect states introduced to single wall carbon nanotubes (SWCNTs) through low-level covalent functionalization create new photophysical behaviors and functionality as a result of defect sites acting as exciton traps. Evaluation of relaxation dynamics in varying dielectric environments can aid in advancing a more complete description of defect-state relaxation pathways and electronic structure. Here, we exploit helical wrapping polymers as a route to suspending (6,5) SWCNTs covalently functionalized with 4-methoxybenzene in solvent systems including H2O, D2O, methanol, dimethylformamide, tetrahydrofuran, and toluene, spanning a range of dielectric constants from 80 to 3. Defect-state photoluminescence decays were measured as a function of emission wavelength and solvent environment. Emission decays are biexponential, with short lifetime components on the order of 65 ps and long components ranging from around 100 to 350 ps. Both short and long decay components increase as emission wavelength increases, while only the long lifetime component shows a solvent dependence. We demonstrate that the wavelength dependence is a consequence of thermal detrapping of defect-state excitons to produce mobile E11 excitons, providing an important mechanism for loss of defect-state population. Deeper trap states (i.e., those emitting at longer wavelengths) result in a decreased rate for thermal loss. The solvent-independent behavior of the short lifetime component is consistent with its assignment as the characteristic time for redistribution of exciton population between bright and dark defect states. The solvent dependence of the long lifetime component is shown to be consistent with relaxation via an electronic to vibrational energy transfer mechanism, in which energy is resonantly lost to solvent vibrations in a complementary mechanism to multiphonon decay processes.
Nature Photonics | 2017
Xiaowei He; Nicolai F. Hartmann; Xuedan Ma; Younghee Kim; Rachelle Ihly; Jeffrey L. Blackburn; Weilu Gao; Junichiro Kono; Yohei Yomogida; Atsushi Hirano; Takeshi Tanaka; Hiromichi Kataura; Han Htoon; Stephen K. Doorn
Journal of Physical Chemistry C | 2016
Mijin Kim; Lyudmyla Adamska; Nicolai F. Hartmann; Hyejin Kwon; Jin Liu; Kirill A. Velizhanin; Yanmei Piao; Lyndsey R. Powell; Brendan Meany; Stephen K. Doorn; Sergei Tretiak; YuHuang Wang
Nanoscale | 2015
Nicolai F. Hartmann; Sibel Ebru Yalcin; Lyudmyla Adamska; Erik H. Hároz; Xuedan Ma; Sergei Tretiak; Han Htoon; Stephen K. Doorn
Advanced Functional Materials | 2015
Xuedan Ma; Jon K. Baldwin; Nicolai F. Hartmann; Stephen K. Doorn; Han Htoon
Journal of the American Chemical Society | 2017
Christina J. Hanson; Nicolai F. Hartmann; Ajay Singh; Xuedan Ma; William J. I. DeBenedetti; Joanna L. Casson; John K. Grey; Yves J. Chabal; Anton V. Malko; Milan Sykora; Andrei Piryatinski; Han Htoon; Jennifer A. Hollingsworth
conference on lasers and electro optics | 2018
Aleksandr Vaskin; Sheng Liu; Matthias Zilk; Stefan Fasold; Benjamin Leung; Miao-Chan Tsai; Yuanmu Yang; Polina P. Vabishchevich; Xiaowei He; Younghee Kim; Nicolai F. Hartmann; Sadhvikas Addamane; Gordon A. Keeler; George T. Wang; Han Htoon; Stephen K. Doorn; Ganesh Balakrishnan; Thomas Pertsch; Michael B. Sinclair; Igal Brener; Isabelle Staude
arxiv:physics.app-ph | 2018
Noémie Danné; Mijin Kim; Antoine G. Godin; Hyejin Kwon; Zhenghong Gao; Xiaojian Wu; Nicolai F. Hartmann; Stephen K. Doorn; Brahim Lounis; YuHuang Wang; Laurent Cognet