. 24/7 Space News .
We gather here today to join lasers and anti-lasers
by Staff Writers
Berkeley CA (SPX) Nov 09, 2016

Schematics above show light input (green) entering opposite ends of a single device. When the phase of light input 1 is faster than that of input 2 (left panel), the gain medium dominates, resulting in coherent amplification of the light, or a lasing mode. When the phase of light input 1 is slower than input 2 (right panel), the loss medium dominates, leading to coherent absorption of the input light beams, or an anti-lasing mode. Image courtesy Zi Jing Wong/UC Berkeley. For a larger version of this image please go here.

Bringing opposing forces together in one place is as challenging as you would imagine it to be, but researchers in the field of optical science have done just that. Scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have for the first time created a single device that acts as both a laser and an anti-laser, and they demonstrated these two opposite functions at a frequency within the telecommunications band.

Their findings, reported in a paper to be published Monday, Nov. 7, in the journal Nature Photonics, lay the groundwork for developing a new type of integrated device with the flexibility to operate as a laser, an amplifier, a modulator, and an absorber or detector.

"In a single optical cavity we achieved both coherent light amplification and absorption at the same frequency, a counterintuitive phenomenon because these two states fundamentally contradict each other," said study principal investigator Xiang Zhang, senior faculty scientist at Berkeley Lab's Materials Sciences Division.

"This is important for high-speed modulation of light pulses in optical communication."

Reversing the laser
The concept of anti-lasers, or coherent perfect absorber (CPA), emerged in recent years as something that reverses what a laser does. Instead of strongly amplifying a beam of light, an anti-laser can completely absorb incoming coherent light beams.

While lasers are already ubiquitous in modern life, applications for anti-lasers--first demonstrated five years ago by Yale University researchers--are still being explored. Because anti-lasers can pick up weak coherent signals in the midst of a "noisy" incoherent background, it could be used as an extremely sensitive chemical or biological detector.

A device that can incorporate both capabilities could become a valuable building block for the construction of photonic integrated circuits, the researchers said.

"On-demand control of light from coherent absorption to coherent amplification was never imagined before, and it remains highly sought after in the scientific community," said study lead author Zi Jing Wong, a postdoctoral researcher in Zhang's lab. "This device can potentially enable a very large contrast in modulation with no theoretical limits."

The researchers utilized sophisticated nanofabrication technology to build 824 repeating pairs of gain and loss materials to form the device, which measured 200 micrometers long and 1.5 micrometers wide. A single strand of human hair, by comparison, is about 100 micrometers in diameter.

The gain medium was made out of indium gallium arsenide phosphide, a well-known material used as an amplifier in optical communications. Chromium paired with germanium formed the loss medium. Repeating the pattern created a resonant system in which light bounces back and forth throughout the device to build up the amplification or absorption magnitude.

If one is to send light through such a gain-loss repeating system, an educated guess is that light will experience equal amounts of amplification and absorption, and the light will not change in intensity. However, this is not the case if the system satisfies conditions of parity-time symmetry, which is the key requirement in the device design.

Balance and symmetry
Parity-time symmetry is a concept that evolves from quantum mechanics. In a parity operation, positions are flipped, such as the left hand becoming the right hand, or vice versa.

Now add in the time-reversal operation, which is akin to rewinding a video and observing the action backwards. The time-reversed action of a balloon inflating, for example, would be that same balloon deflating. In optics, the time-reversed counterpart of an amplifying gain medium is an absorbing loss medium.

A system that returns to its original configuration upon performing both parity and time-reversal operations is said to fulfill the condition for parity-time symmetry.

Soon after the discovery of the anti-laser, scientists had predicted that a system exhibiting parity-time symmetry could support both lasers and anti-lasers at the same frequency in the same space. In the device created by Zhang and his group, the magnitude of the gain and loss, the size of the building blocks, and the wavelength of the light moving through combine to create conditions of parity-time symmetry.

When the system is balanced and the gain and loss are equal, there is no net amplification or absorption of the light. But if conditions are perturbed such that the symmetry is broken, coherent amplification and absorption can be observed.

In the experiments, two light beams of equal intensity were directed into opposite ends of the device. The researchers found that by tweaking the phase of one light source, they were able to control whether the light waves spent more time in amplifying or absorbing materials.

Speeding up the phase of one light source results in an interference pattern favoring the gain medium and the emission of amplified coherent light, or a lasing mode. Slowing down the phase of one light source has the opposite effect, resulting in more time spent in the loss medium and the coherent absorption of the beams of light, or an anti-lasing mode.

If the phase of the two wavelengths are equal and they enter the device at the same time, there is neither amplification nor absorption because the light spends equal time in each region.

The researchers targeted a wavelength of about 1,556 nanometers, which is within the band used for optical telecommunications.

"This work is the first demonstration of balanced gain and loss that strictly satisfies conditions of parity-time symmetry, leading to the realization of simultaneous lasing and anti-lasing," said study co-author Liang Feng, former postdoctoral researcher in Zhang's Lab, and now an assistant professor of electrical engineering at the University of Buffalo.

"The successful attainment of both lasing and anti-lasing within a single integrated device is a significant step towards the ultimate light control limit."

Comment on this article using your Disqus, Facebook, Google or Twitter login.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only


Related Links
Lawrence Berkeley National Laboratory
Space Technology News - Applications and Research

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
Using Photonics to Call Home
Greenbelt MD (SPX) Oct 27, 2016
A largely unrecognized field called photonics may provide solutions to some of NASA's most pressing challenges in future spaceflight. Photonics explores the many applications of generating, detecting and manipulating photons, or particles of light that, among other things, make up laser beams. On this day in 1983, the General Conference of Weights and Measures adopted the accepted value for the ... read more

Progress, but uphill slog for women in tech

NavCube could support an X-ray communication test in space

NASA, Navy practice Orion module recovery

Weightless tourism just 4 years away

JCSAT-15 arrives in Kourou for Dec Ariane 5 launch

Aerojet Rocketdyne completes CST launch abort engine hot fire tests

China launches first heavy-lift rocket

NASA Uses Tunnel Approach to Study How Heat Affects SLS Rocket

Mars' ionosphere shaped by crustal magnetic fields

Iron-Loving Bacteria A Model For Mars Life

Opportunity makes small U-turn to reach summit of Spirit Mound

'Millions' needed to continue Europe's Mars mission: ESA chief

Long March-5 reflects China's "greatest advancement" yet in rockets

New heavy-lift carrier rocket boosts China's space dream

Long March-7 being assembled, to transport Tianzhou-1

Kuaizhou-1 scheduled to launch in December

AsiaSat wins patent for effective satellite broadband connectivity to aircraft

Sun-observing MinXSS CubeSat to yield insights into solar flare energetics

Optus achieves full certification of 4 teleports

ISRO's World record bid: Launching 83 satellites on single rocket

We gather here today to join lasers and anti-lasers

Trace metal recombination centers kill LED efficiency

Studying structure to understand function within 'material families'

Study: Math scares everyone, even physicists

What happens to a pathogenic fungus grown in space?

How Planets Like Jupiter Form

Giant Rings Around Exoplanet Turn in the Wrong Direction

Preferentially Earth-sized Planets with Lots of Water

Mystery solved behind birth of Saturn's rings

Last Bits of 2015 Pluto Flyby Data Received on Earth

Uranus may have two undiscovered moons

Possible Clouds on Pluto, Next Target is Reddish

The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.