Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Exciting breakthrough in 2-D lasers

21.10.2015

Berkeley Lab researchers demonstrate atomically thin excitonic laser

An important step towards next-generation ultra-compact photonic and optoelectronic devices has been taken with the realization of a two-dimensional excitonic laser. Scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) embedded a monolayer of tungsten disulfide into a special microdisk resonator to achieve bright excitonic lasing at visible light wavelengths.


In this 2-D excitonic laser, the sandwiching of a monolayer of tungsten disulfide between the two dielectric layers of a microdisk resonator creates the potential for ultralow-threshold lasing.

Credit: Xiang Zhang, Berkeley Lab

"Our observation of high-quality excitonic lasing from a single molecular layer of tungsten disulfide marks a major step towards two-dimensional on-chip optoelectronics for high-performance optical communication and computing applications," says Xiang Zhang, director of Berkeley Lab's Materials Sciences Division and the leader of this study.

Zhang, who also holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper describing this research in the journal Nature Photonics. The paper is titled "Monolayer excitonic laser." The lead authors are Yu Ye and Zi Jing Wong, members of Zhang's research group, plus Xiufang Lu, Xingjie Ni, Hanyu Zhu, Xianhui Chen and Yuan Wang.

Among the most talked about class of materials in the world of nanotechnology today are two-dimensional (2D) transition metal dichalcogenides (TMDCs). These 2D semiconductors offer superior energy efficiency and conduct electrons much faster than silicon.

Furthermore, unlike graphene, the other highly touted 2D semiconductor, TMDCs have natural bandgaps that allow their electrical conductance to be switched "on and off," making them more device-ready than graphene. Tungsten disulfide in a single molecular layer is widely regarded as one of the most promising TMDCs for photonic and optoelectronic applications. However, until now, coherent light emission, or lasing, considered essential for "on-chip" applications, had not been realized in this material.

"TMDCs have shown exceptionally strong light-matter interactions that result in extraordinary excitonic properties," Zhang says. "These properties arise from the quantum confinement and crystal symmetry effect on the electronic band structure as the material is thinned down to a monolayer. However, for 2D lasing, the design and fabrication of microcavities that provide a high optical mode confinement factor and high quality, or Q, factor is required."

In a previous study, Zhang and his research group had developed a "whispering gallery microcavity" for plasmons, electromagnetic waves that roll across the surfaces of metals. Based on the principle behind whispering galleries - where words spoken softly beneath a domed ceiling can be clearly heard on the opposite side of the chamber - this micro-sized metallic cavity for plasmons strengthened and greatly enhanced the Q factor of light emissions. In this new study, Zhang and his group were able to adapt this microcavity technology from plasmons to excitons - photoexcited electrons/hole pairs within a single layer of molecules.

"For our excitonic laser, we dropped the metal coating and designed a microdisk resonator that supports a dielectric whispering gallery mode rather than a plasmonic mode, and gives us a high Q factor with low power consumption," says co-lead author Ye. "When a monolayer of tungsten disulfide - serving as the gain medium - is sandwiched between the two dielectric layers of the resonator, we create the potential for ultralow-threshold lasing."

In addition to its photonic and optoelectronic applications, this 2D excitonic laser technology also has potential for valleytronic applications, in which digital information is encoded in the spin and momentum of an electron moving through a crystal lattice as a wave with energy peaks and valleys. Valleytronics is seen as an alternative to spintronics for quantum computing.

"TMDCs such as tungsten disulfide provide unique access to spin and valley degrees of freedom," says co-lead author Wong. "Selective excitation of the carrier population in one set of two distinct valleys can further lead to lasing in the confined valley, paving the way for easily-tunable circularly polarized lasers. The demand for circularly polarized coherent light sources is high, ranging from three-dimensional displays to effective spin sources in spintronics, and information carriers in quantum computation."

###

This research was supported by the United States Air Force Office of Scientific Research and by the DOE Office of Science through the Light-Material Interaction in Energy Conversion Energy Frontier Research Center.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Media Contact

Lynn Yarris
lcyarris@lbl.gov
510-486-5375

 @BerkeleyLab

http://www.lbl.gov 

Lynn Yarris | EurekAlert!

Further reports about: disulfide graphene lasers monolayer optoelectronic properties spintronics

More articles from Physics and Astronomy:

nachricht New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center

nachricht Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>