Navigation Links
Counting the twists in a helical light beam
Date:1/8/2013

Cambridge, Mass. - January 8, 2013 - At a time when communication networks are scrambling for ways to transmit more data over limited bandwidth, a type of twisted light wave is gaining new attention. Called an optical vortex or vortex beam, this complex beam resembles a corkscrew, with waves that rotate as they travel.

Now, applied physicists at the Harvard School of Engineering and Applied Sciences (SEAS) have created a new device that enables a conventional optical detector (which would normally only measure the light's intensity) to pick up on that rotation.

The device, described in the journal Nature Communications, has the potential to add capacity to future optical communications networks.

"Sophisticated optical detectors for vortex beams have been developed before, but they have always been complex, expensive, and bulky," says principal investigator Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering.

In contrast, the new device simply adds a metallic pattern to the window of a commercially available, low-cost photodetector. Each pattern is designed to couple with a particular type of incoming vortex beam by matching its orbital angular momentumthe number of twists per wavelength in an optical vortex.

Sensitive to the beam's "twistiness," this new detector can effectively distinguish between different types of vortex beams. Existing communications systems maximize bandwidth by sending many messages simultaneously, each a fraction of a wavelength apart; this is known as wavelength division multiplexing. Vortex beams can add an additional level of multiplexing and therefore should expand the capacity of these systems.

"In recent years, researchers have come to realize that there is a limit to the information transfer rate of about 100 terabits per second per fiber for communication systems that use wavelength division multiplexing to increase the capacity of single-mode optical fibers," explains Capasso. "In the future, this capacity could be greatly increased by using vortex beams transmitted on special multicore or multimode fibers. For a transmission system based on this 'spatial division multiplexing' to provide the extra capacity, special detectors capable of sorting out the type of vortex transmitted will be essential."

The new detector is able to tell one type of vortex beam from another due to its precise nanoscale patterning. When a vortex beam with the correct number of coils per wavelength strikes the gold plating on the detector's surface, it encounters a holographic interference pattern that has been etched into the gold. This nanoscale patterning allows the light to excite the metal's electrons in exactly the right way to produce a focused electromagnetic wave, known as a surface plasmon. The light component of this wave then shines through a series of perforations in the gold, and lands on the photodetector below.

If the incoming light doesn't match the interference pattern, the plasmon beam fails to focus or converge and is blocked from reaching the detector.

Capasso's research team has demonstrated this process using vortex beams with orbital angular momentum of −1, 0, and 1.

"In principle, an array of many different couplers and detectors could be set up to read data transmitted on a very large number of channels," says lead author Patrice Genevet, a research associate in applied physics at SEAS. "With this approach, we transform detectors that were originally only sensitive to the intensity of light, so that they monitor the twist of the wavefronts. More than just detecting a specific twisted beam, our detectors gather additional information on the phase of the light beam."

The device's ability to detect and distinguish vortex beams is important for optical communications, but its capabilities may extend beyond what has been demonstrated.

"Using the same holographic approach, the same device patterned in different ways should be able to couple any type of free-space light beam into any type of surface wave," says Genevet.


'/>"/>

Contact: Caroline Perry
cperry@seas.harvard.edu
617-496-1351
Harvard University
Source:Eurekalert  

Related biology technology :

1. 2011 ErgoExpo Attendees Choice Award Winners Announced During Sold Out Expo; Exhibitor Renewal for 2012 Hits 96% and Counting
2. Sequenom Announces Appointment of Carolyn Beaver to Chief Accounting Officer
3. NASA develops super-black material that absorbs light across multiple wavelength bands
4. A light wave of innovation to advance solar energy
5. The Foremost Expert on Morgellons Disease Highlights the Gravity of This Illness
6. BioSpace Spotlights Northwests Life Science Community
7. Multidisciplinary team of researchers develop world’s lightest material
8. Blocked holes can enhance rather than stop light going through
9. Novartis Highlights Advances for Patients With Breast Cancer and Hematological Diseases With Over 160 SABCS and ASH Abstracts
10. New 3-D transistors promising future chips, lighter laptops
11. Sheffield scientists shine a light on the detection of bacterial infection
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Counting the twists in a helical light beam
(Date:9/22/2017)... , ... September 22, 2017 , ... ... recently raised nearly $200,000 via Kickstarter. The proceeds will be used to fund ... the B2v2, exceeding the original Kickstarter goal by nearly 1,000%. , The B2v2 ...
(Date:9/22/2017)... ... September 22, 2017 , ... HOLLOWAY ... a booth at premier packaging event PACK EXPO International in Las Vegas from ... Manufacturers Institute (PMMI). , At this year’s PACK EXPO at the Last Vegas ...
(Date:9/22/2017)... ... September 22, 2017 , ... ... Zalewsky in offering LANAP® and LAPIP™ laser treatments. Drs. Hoge and Zalewsky are ... patients, a minimally invasive and less painful option that produces real results. , ...
(Date:9/22/2017)... (PRWEB) , ... September 22, 2017 , ... ... Rocky Mountain Hobby-Expo in Denver, Colorado October 28 and 29, 2017, to promote ... event is to promote participation in different hobbies, including but not limited to ...
Breaking Biology Technology:
(Date:8/23/2017)... -- The general public,s help is being enlisted in what,s thought to be ... on the human body –and are believed to affect health.  ... The Microbiome Immunity Project is the largest study ... gut. The project's goal is to help advance scientific knowledge of the ... ...
(Date:8/15/2017)... LLC , a medical device company focused on improving the safety ... ISO 13485 Certification, the global standard for medical device quality management ... ... for the early detection of IV infiltrations. ... "This is an important milestone for ivWatch, as it validates our ...
(Date:7/20/2017)... (NYSE: DAL ) customers now can use fingerprints instead of ... Airport (DCA). ... Delta launches biometrics to board aircraft at Reagan Washington National Airport ... Delta,s biometric boarding pass experience that launched in May ... boarding process to allow eligible Delta SkyMiles Members who are enrolled in ...
Breaking Biology News(10 mins):