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More Is Less: Increased Voltage Switches Off Microlasers

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Lasers that switch off when their pump power is increased could one day make viable optical switches and logic circuits.

Researchers at the Vienna University of Technology, led by professor Stefan Rotter, have demonstrated the phenomenon using a pair of coupled microdisk quantum cascade lasers emitting at terahertz frequencies. The work builds on mathematical models devised by Hakan Türeci, assistant professor of electrical engineering at Princeton University.


An electron microscope image shows two microdisk quantum cascade lasers placed 2 µm apart. Images courtesy of the Vienna University of Technology.


“Loss is something you normally are trying to avoid,” Türeci said. “In this case, we take advantage of it and it gives us a different dimension we can use — a new tool — in controlling optical systems.”

The study involved manipulating regions of gain and loss within the coupled laser system. In experiments, one laser began emitting light when pumped, but when the other was pumped the system switched off.


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Deeper understanding of gain and loss distribution could make microlasers more efficient, and lead to new types of highly accurate sensors and lab-on-chip applications, the researchers said. The mathematical concepts demonstrated could also be applied to electronics, they said.


Manipulating minute areas of gain and loss within individual lasers (shown here as peaks and valleys), researchers were able to create paradoxical interactions between two nearby lasers.


“Our approach provides a whole new set of levers to create unforeseen and useful behaviors,” Türeci said.

The work was funded by the Vienna Science and Technology Fund and the Austrian Science Fund, as well as by the National Science Foundation through a grant for the Mid-Infrared Technologies for Health, the Environment Center (MIRTHE) at Princeton and by DARPA.

The research was published in Nature Communications (doi:10.1038/ncomms5034).

For more information, visit www.tuwien.ac.at or www.princeton.edu/engineering.

Published: June 2014
Glossary
gain
Also known as amplification. 1. The increase in a signal that is transmitted from one point to another through an amplifier. A material that exhibits gain rather than absorption, at certain frequencies for a signal passing through it, is known as an active medium. 2. With reference to optical properties, the term may be defined in two ways: a. the relative brightness of a rear projection screen as compared with a perfect lambertian reflective diffuser; b. the ratio of brightness in footlamberts...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
terahertz
Terahertz (THz) refers to a unit of frequency in the electromagnetic spectrum, denoting waves with frequencies between 0.1 and 10 terahertz. One terahertz is equivalent to one trillion hertz, or cycles per second. The terahertz frequency range falls between the microwave and infrared regions of the electromagnetic spectrum. Key points about terahertz include: Frequency range: The terahertz range spans from approximately 0.1 terahertz (100 gigahertz) to 10 terahertz. This corresponds to...
AmericasAustriaAustrian Science FundBasic ScienceDARPAEuropegainLight SourceslossMIRTHEnanoNational Science FoundationNature CommunicationsNew JerseyPrinceton Universityquantum cascade lasersResearch & TechnologyStefan RotterterahertzVienna University of Technologymicrodisk lasersHakan TüreciVienna Science and Technology FundMid-Infrared Technologies for Health and the Environment CenterLasersLEDs

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