Doe Science news source
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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Filtering Water Better than Nature

Water passes through human-made straws faster than the "gold standard" protein, allowing us to filter seawater.


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North Dakota State University Joins Two National Distributed Computing Groups

The NDSU Center for Computationally Assisted Science and Technology (CCAST) joins OSG (Open Science Grid) and XSEDE (Extreme Science and Engineering Discovery Environment).

DOE Announces Funding for New HPC4Manufacturing Industry Projects

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DOE Announces First Awardees for New HPC4Materials for Severe Environments Program

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Two Argonne Scientists Recognized for a Decade of Breakthroughs

Two scientists with the U.S. Department of Energy's (DOE) Argonne National Laboratory have been named to the Web of Science's Highly Cited List of 2017, ranking in the top 1 percent of their peers by citations and subject area. Materials Scientist Khalil Amine and Energy and Environmental Policy Scientist David Streets say they are thrilled to see their work -- and the laboratory -- recognized in such a way.

Argonne Welcomes Department of Energy Secretary Perry

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Argonne names John Quintana Deputy Laboratory Director for Operations and COO

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Developing Next-Generation Sensing Technologies

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Supporting the Development of Offshore Wind Power Plants

Offshore wind is becoming a reality in the United States, especially in the northeast states. To support this development, the Center for Future Energy System (CFES) at Rensselaer Polytechnic Institute will present a webinar titled "Turbine and Transmission System Technologies for Offshore Wind (OSW) Power Plants." The program will be held on Wednesday, Dec. 20, from 2 to 4 p.m. Advance registration is required.

LLNL Releases Newly Declassified Nuclear Test Videos

Researchers at Lawrence Livermore National Laboratory (LLNL) released 62 newly declassified videos today of atmospheric nuclear tests films that have never before been seen by the public.

NAU Researchers Join DOE Project to Study the Soil Microbiome and Its Effect on Carbon Persistence

NAU Regents' Professor Bruce Hungate, director of the Center for Ecosystem Science and Society (Ecoss), recently joined a new initiative lead by LLNL to study how the soil microbiome controls the mechanisms that regulate the stabilization of the organic matter in soil.


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Remotely Predicting Leaf Age in Tropical Forests

New approach offers data across species, sites, and canopies, providing insights into carbon uptake by forests.

What's the Noise Eating Quantum Bits?

The magnetic noise caused by adsorbed oxygen molecules is "eating at" the phase stability of quantum bits, mitigating the noise is vital for future quantum computers.

Rewritable Wires Could Mean No More Obsolete Circuitry

An electric field switches the conductivity on and off in atomic-scale channels, which could allow for upgrades at will.

Filtering Water Better than Nature

Water passes through human-made straws faster than the "gold standard" protein, allowing us to filter seawater.

Machine Learning Provides a Bridge to the Texture of the Quantum World

Machine learning and neural networks are the foundation of artificial intelligence and image recognition, but now they offer a bridge to see and recognize exotic insulating phases in quantum materials.

A Rare Quantum State Realized in a New Material

A revolutionary material harbors magnetism and massless electrons that travel near the speed of light--for future ultrasensitive, high-efficiency electronics and sensors.

Discovering Secrets of Superfluids

Observed atomic dynamics helps explain bizarre flow without friction that has been puzzling scientists for decades.

An Exotic State of Matter Discovered in 2-D Material

Electrons are forced to the edge of the road on a thin sheet of tungsten ditelluride.

Studying Crowd Behavior at MINERvA

Detector measures the energy a neutrino imparts to protons and neutrons to help explain the nature of matter and the universe.

Tweaking Quantum Dots Powers-Up Double-Pane Solar Windows

Using two types of "designer" quantum dots, researchers are creating double-pane solar windows that generate electricity with greater efficiency and create shading and insulation for good measure. It's all made possible by a new window architecture which utilizes two different layers of low-cost quantum dots tuned to absorb different parts of the solar spectrum.


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