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    The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
    • 2017-10-16 12:05:30
    • Article ID: 683028

    Chemical Treatment Improves Quantum Dot Lasers

    Doctored dots release laser light more efficiently, use less power

    • Credit: Los Alamos National Laboratory

      Los Alamos National Laboratory Chemist Jaehoon Lim works on an apparatus that synthesizes quantum dots along with Los Alamos researcher Young-Shin Park (also with the University of New Mexico Center for High-Technology Materials). In a paper published in Nature Nanotechnology, Los Alamos colleagues Kaifeng Wu and Victor Klimov worked with Lim and Park to demonstrate that negatively charged quantum dots show promise for low-power laser applications or quantum dot laser diodes.

    LOS ALAMOS, N.M., Oct. 16, 2017—One of the secrets to making tiny laser devices such as opthalmic surgery scalpels work even more efficiently is the use of tiny semiconductor particles, called quantum dots. In new research at Los Alamos National Laboratory’s Nanotech Team, the ~nanometer-sized dots are being doctored, or “doped,” with additional electrons, a treatment that nudges the dots ever closer to producing the desired laser light with less stimulation and energy loss.

    “When we properly tailor the compositional profile within the particles during their fabrication, and then inject two or more electrons in each dot, they become more able to emit laser light. Importantly, they require considerably less power to initiate the lasing action,” said Victor Klimov, leader of the Nanotech team.

    In order to force a material to emit laser light one has to work toward a “population inversion,” that is, making the number of electrons in a higher-energy electronic state exceed the number that are in a lower-energy state. To achieve this condition normally, one applies an external stimulus (optical or electrical) of a certain power, which should exceed a critical value termed the “optical-gain threshold.” In a recent paradigm-changing advance, Los Alamos researchers demonstrated that by adding extra electrons into their specially designed quantum dots, they can reduce this threshold to virtually zero.

    A standard lasing material, when stimulated by a pump, absorbs light for a time before it starts to lase. On the way to lasing, the material transitions through the state of “optical transparency” when light is neither absorbed nor amplified. By adding extra charge carriers to their quantum dots, the Los Alamos researchers were able to block absorption and create the state of transparency without external stimulation. This implies that even extremely weak pumping can now initiate lasing emission.

    Another important ingredient of this research is a new type of quantum dots with their interiors designed to maintain the lasing-active state for much longer than standard particles do. Normally, the presence of extra electrons would suppress lasing because quantum dot energy is quickly released not as a photon stream but wasteful heat. The new Los Alamos particle design eliminates these parasitic losses, redirecting the particle’s energy into the emission channel.   

    “These studies open exciting opportunities for realizing new types of low-threshold lasing devices that can be fabricated from solution using a variety of substrates and optical cavity designs for applications ranging from fiber optics and large-scale lasing arrays to laser lighting and lab-on-a-chip sensing technologies,” Klimov said.

    The research is described in the journal Nature Nanotechnology this week, authored by project members Kaifeng Wu (a Los Alamos Director’s postdoctoral fellow), Young-Shin Park (guest scientist, University of New Mexico), Jaehoon Lim (Los Alamos postdoctoral research associate) and Victor I. Klimov (Laboratory Fellow, project leader).

    Publication: Kaifeng Wu, Young-Shin Park, Jaehoon Lim, and Victor I. Klimov, “Towards zero-threshold optical gain using charged semiconductor quantum dots,” Nature Nanotechnology.

    Funding: The work on the synthesis of graded quantum dots and studies of Auger recombination in synthesized materials was supported by the DOE Office of Science. The studies of the effect of charging on quantum dot optical gain properties were supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.

    About Los Alamos National Laboratory (www.lanl.gov)

    Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, BWX Technologies, Inc. and URS Corporation for the Department of Energy’s National Nuclear Security Administration.

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    A Breakthrough in the Study of Laser/Plasma Interactions

    A Breakthrough in the Study of Laser/Plasma Interactions

    A new 3D particle-in-cell simulation tool developed by researchers from Lawrence Berkeley National Laboratory and CEA Saclay is enabling cutting-edge simulations of laser/plasma coupling mechanisms. More detailed understanding of these mechanisms is critical to the development of ultra-compact particle accelerators and light sources.

    Researchers Create the First Maps of Two Melatonin Receptors Essential for Sleep

    Researchers Create the First Maps of Two Melatonin Receptors Essential for Sleep

    An international team of researchers used an X-ray laser at the Department of Energy's SLAC National Accelerator Laboratory to create the first detailed maps of two melatonin receptors that tell our bodies when to go to sleep or wake up and guide other biological processes. A better understanding of how they work could enable researchers to design better drugs to combat sleep disorders, cancer and Type 2 diabetes. Their findings were published in two papers today in Nature.

    Capturing the behavior of single-atom catalysts on the move

    Capturing the behavior of single-atom catalysts on the move

    Scientists are excited by the prospect of stripping catalysts down to single atoms. Attached by the millions to a supporting surface, they could offer the ultimate in speed and specificity. Now researchers have taken an important step toward understanding single-atom catalysts by deliberately tweaking how they're attached to the surfaces that support them - in this case the surfaces of nanoparticles.

    Watching Molecules Split in Real Time

    Watching Molecules Split in Real Time

    Using a new X-ray technique, a team of researchers was able to watch in real time as a molecule split apart into two new molecules. The method could be used to look at chemical reactions that other techniques can't catch, for instance in catalysis, photovoltaics, peptide and combustion research. The team, led by researchers from Brown University in collaboration with the Department of Energy's SLAC National Accelerator Laboratory, published their results in March in Angewandte Chemie.

    Capturing Energy Flow in a Plasma by Measuring Scattered Light

    Capturing Energy Flow in a Plasma by Measuring Scattered Light

    First measurements of heat flux in plasmas experientially sheds light on models relying on classical thermal transport.

    Artificial Intelligence and Deep Learning Accelerate Efforts to Develop Clean, Virtually Limitless Fusion Energy

    Artificial Intelligence and Deep Learning Accelerate Efforts to Develop Clean, Virtually Limitless Fusion Energy

    The Fusion Recurrent Neural Network reliably forecasts disruptive and destructive events in tokamaks.

    Spin Flipper Upends Protons

    Spin Flipper Upends Protons

    The spin direction of protons was reversed, for the first time, using a nine-magnet device, potentially helping tease out details about protons that affect medical imaging and more.

    Catalyst Renders Nerve Agents Harmless

    Catalyst Renders Nerve Agents Harmless

    A team of scientists including researchers at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory has studied a catalyst that decomposes nerve agents, eliminating their harmful and lethal effects. The research was published Friday, April 19, in the Journal of Physical Chemistry Letters. "Our work is part of an ongoing, multiagency effort to protect soldiers and civilians from chemical warfare agents (CWAs)," said Anatoly Frenkel, a physicist with a joint appointment at Brookhaven Lab and Stony Brook University and the lead author on the paper.

    Splitting Water Fast! Catalyst Works Faster than Mother Nature

    Splitting Water Fast! Catalyst Works Faster than Mother Nature

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    Sea Quark Spin Surprise!

    Sea Quark Spin Surprise!

    Antiquark spin contribution to proton spin depends on flavor, which could help unlock secrets about the nuclear structure of atoms that make up nearly all visible matter in our universe.


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    Five new innovators join Chain Reaction Innovations in third cohort

    Five new innovators join Chain Reaction Innovations in third cohort

    Five new innovators will be joining Chain Reaction Innovations (CRI), the entrepreneurship program at the U.S. Department of Energy's (DOE's) Argonne National Laboratory, as part of the elite program's third cohort. Announced on Monday, April 22, these innovators were selected following an extensive national solicitation process and two-part pitch competition, with reviews from industry experts, investors, scientists and engineers.

    Department of Energy Announces $20 Million for Artificial Intelligence Research

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    Tim Knewitz named Argonne National Laboratory's Chief Financial Officer

    Tim Knewitz named Argonne National Laboratory's Chief Financial Officer

    The U.S. Department of Energy's Argonne National Laboratory has named Tim Knewitz at its Chief Financial Officer.

    Department of Energy Announces $95 Million for Small Business Research and Development Grants

    U.S. Energy Secretary Rick Perry today announced that the Department of Energy will award 86 grants totaling $95 million to 74 small businesses in 21 states.

    DOE's Science Graduate Student Research Program Selects 70 Students to Pursue Research at DOE Laboratories

    The Department of Energy's (DOE's) Office of Science has selected 70 graduate students from across the nation for its 2018 Solicitation 2 cycle for Office of Science Graduate Student Research (SCGSR) Program.

    Brookhaven Joins the IBM Q Network Hub at Oak Ridge National Lab

    Brookhaven Joins the IBM Q Network Hub at Oak Ridge National Lab

    Brookhaven National Lab has joined the IBM Q Network Hub at Oak Ridge National Lab. This hub is part of an international community of Fortune 500 companies, startups, universities, and research labs working with IBM to advance quantum computing and explore its practical applications.

    David Reis named head of PULSE Institute for ultrafast science

    David Reis named head of PULSE Institute for ultrafast science

    Long before David Reis joined the faculty of the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, he was helping lay the groundwork for the lab's first-of-a-kind X-ray free-electron laser, or XFEL, and the revolutionary science that followed its opening in 2009. Now he's director of the PULSE Institute, which was founded by SLAC and Stanford with the express purpose of exploiting the possibilities for ultrafast science at that X-ray laser, the Linac Coherent Light Source (LCLS).

    Head of NSTX-U research is appointed deputy director for research at the Princeton Plasma Physics Laboratory

    Head of NSTX-U research is appointed deputy director for research at the Princeton Plasma Physics Laboratory

    Jon Menard, the head of research on the Princeton Plasma Physics Laboratory's National Spherical Torus Experiment-Upgrade, has been named deputy director for research. Michael Zarnstorff, who held the position for 10 years, will become the chief chief scientist at PPPL, a position that will oversee strategic scientific planning.

    Argonne scientist advances energy sciences through professional leadership

    Argonne scientist advances energy sciences through professional leadership

    Ralph Muehleisen of the U.S. Department of Energy's (DOE) Argonne National Laboratory was recently re-elected to the Board of Directors of IBPSA-USA, the U.S. affiliate of the International Building Performance Simulation Association. IBPSA is a global leader in the promotion of building simulation science and one of the largest professional organizations in the world for building scientists and engineers.

    Brookhaven Lab Publishes Second Edition of Nuclear Nonproliferation Textbook

    Brookhaven Lab Publishes Second Edition of Nuclear Nonproliferation Textbook

    Brookhaven Lab has published the second edition of Deterring Nuclear Proliferation: The Importance of IAEA Safeguards, a textbook that provides a history of the origins of the International Atomic Energy Agency (IAEA) and introduces the ways in which IAEA verifies nation states' nuclear nonproliferation commitments.


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    Capturing Energy Flow in a Plasma by Measuring Scattered Light

    Capturing Energy Flow in a Plasma by Measuring Scattered Light

    First measurements of heat flux in plasmas experientially sheds light on models relying on classical thermal transport.

    Artificial Intelligence and Deep Learning Accelerate Efforts to Develop Clean, Virtually Limitless Fusion Energy

    Artificial Intelligence and Deep Learning Accelerate Efforts to Develop Clean, Virtually Limitless Fusion Energy

    The Fusion Recurrent Neural Network reliably forecasts disruptive and destructive events in tokamaks.

    Spin Flipper Upends Protons

    Spin Flipper Upends Protons

    The spin direction of protons was reversed, for the first time, using a nine-magnet device, potentially helping tease out details about protons that affect medical imaging and more.

    Splitting Water Fast! Catalyst Works Faster than Mother Nature

    Splitting Water Fast! Catalyst Works Faster than Mother Nature

    Design principles lead to a catalyst that splits water in a low pH environment, vital for generating solar fuels.

    Sea Quark Spin Surprise!

    Sea Quark Spin Surprise!

    Antiquark spin contribution to proton spin depends on flavor, which could help unlock secrets about the nuclear structure of atoms that make up nearly all visible matter in our universe.

    The Weak Side of the Proton

    The Weak Side of the Proton

    A precision measurement of the proton's weak charge narrows the search for new physics.

    Fast-Moving Pairs May Solve 35-Year-Old Mystery

    Fast-Moving Pairs May Solve 35-Year-Old Mystery

    Physicists develop a universal mathematical description that suggests that proton-neutron pairs in a nucleus may explain why their associated quarks have lower average momenta than predicted.

    Team Takes Fluoride from Taps and Toothpaste to Batteries

    Team Takes Fluoride from Taps and Toothpaste to Batteries

    With user facilities, researchers devise novel battery chemistries to help make fluoride batteries a reality.

    Quarks Under Pressure in the Proton

    Quarks Under Pressure in the Proton

    Pressure in the middle of a proton is about 10 times higher than in a neutron star.

    Magnetic Levitation of Ultracold Neutrons Yields New Measurement of the Neutron Lifetime

    Magnetic Levitation of Ultracold Neutrons Yields New Measurement of the Neutron Lifetime

    Storing extremely slow neutrons in a novel trap enables precise measurement of a basic property of particle physics.


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