Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Researchers demonstrate highly directional terahertz laser rays

Schematic diagram of a terahertz quantum cascade laser patterned with a metamaterial collimator. The metamaterial patterns are directly sculpted on the highly doped GaAs facet of the device. Artificial coloring in the figure indicates deep and shallow micron scale grooves, which have different functions. The shallow ‘blue’ grooves efficiently couple laser output into surface electromagnetic waves on the facet and confine the waves to the facet. The deep ‘pink’ grooves form an effective grating that coherently scatters the energy of the surface waves into the far-field.
Schematic diagram of a terahertz quantum cascade laser patterned with a metamaterial collimator. The metamaterial patterns are directly sculpted on the highly doped GaAs facet of the device. Artificial coloring in the figure indicates deep and shallow micron scale grooves, which have different functions. The shallow ‘blue’ grooves efficiently couple laser output into surface electromagnetic waves on the facet and confine the waves to the facet. The deep ‘pink’ grooves form an effective grating that coherently scatters the energy of the surface waves into the far-field.

Abstract:
Advance in metamaterials leads to a new semiconductor laser suitable for security screening, chemical sensing and astronomy

Researchers demonstrate highly directional terahertz laser rays

Cambridge, MA & Leeds, UK | Posted on August 10th, 2010

A collaborative team of applied scientists from Harvard University and the University of Leeds have demonstrated a new terahertz (THz) semiconductor laser that emits beams with a much smaller divergence than conventional THz laser sources. The advance, published in the August 8th issue of Nature Materials, opens the door to a wide range of applications in terahertz science and technology. Harvard has filed a broad patent on the invention.

The finding was spearheaded by postdoctoral fellow Nanfang Yu and Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, both of Harvard's School of Engineering and Applied Sciences (SEAS), and by a team led by Edmund Linfield at the School of Electronic and Electrical Engineering, University of Leeds.

Terahertz rays (T-rays) can penetrate efficiently through paper, clothing, plastic, and many other materials, making them ideal for detecting concealed weapons and biological agents, imaging tumors without harmful side effects, and spotting defects, such as cracks, within materials. THz radiation is also used for high-sensitivity detection of tiny concentrations of interstellar chemicals.

"Unfortunately, present THz semiconductor lasers are not suitable for many of these applications because their beam is widely divergent—similar to how light is emitted from a lamp" says Capasso. "By creating an artificial optical structure on the facet of the laser, we were able to generate highly collimated (i.e., tightly bound) rays from the device. This leads to the efficient collection and high concentration of power without the need for conventional, expensive, and bulky lenses."

Specifically, to get around the conventional limitations, the researchers sculpted an array of sub-wavelength-wide grooves, dubbed a metamaterial, directly on the facet of quantum cascade lasers. The devices emit at a frequency of 3 THz (or a wavelength of one hundred microns), in the invisible part of the spectrum known as the far-infrared.

"Our team was able to reduce the divergence angle of the beam emerging from these semiconductor lasers dramatically, whilst maintaining the high output optical power of identical unpatterned devices," says Linfield. "This type of laser could be used by customs officials to detect illicit substances and by pharmaceutical manufacturers to check the quality of drugs being produced and stored."

The use of metamaterials, artificial materials engineered to provide properties which may not be readily available in Nature, was critical to the researchers' successful demonstration. While metamaterials have potential use in novel applications such as cloaking, negative refraction and high resolution imaging, their use in semiconductor devices has been very limited to date.

"In our case, the metamaterial serves a dual function: strongly confining the THz light emerging from the device to the laser facet and collimating the beam," explains Yu. "The ability of metamaterials to confine strongly THz waves to surfaces makes it possible to manipulate them efficiently for applications such as sensing and THz optical circuits."

Additional co-authors of the study included Qi Jie Wang, formerly of Harvard University and now with the Nanyang Technological University in Singapore; graduate student Mikhail A. Kats and postdoctoral fellow Jonathan A. Fan, both of Harvard University; and postdoctoral fellows Suraj P. Khanna and Lianhe Li and faculty member A. Giles Davies, all from the University of Leeds.

The research was partially supported by the Air Force Office of Scientific Research. The Harvard-based authors also acknowledge the support of the Center for Nanoscale Systems (CNS) at Harvard University, a member of the National Nanotechnology Infrastructure Network (NNIN). The Leeds-based authors acknowledge support from the UK's Engineering and Physical Sciences Research Council.

Quantum Cascade Lasers were first invented and demonstrated by Federico Capasso and his team at Bell Labs in 1994. At the shorter wavelengths of the mid-infrared spectrum these compact millimeter length semiconductor lasers operate routinely at room temperature with high optical powers and are a rapidly growing commercial sector for a wide range of military and civilian applications including infrared countermeasures and chemical sensing. They are made by stacking ultra-thin atomic layers of semiconductor materials on top of each other. By varying the thickness of the layers one can design the energy levels in the structure to create an artificial laser medium.

####

For more information, please click here

Copyright © Harvard University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

A new, tunable device for spintronics: An international team of scientists including physicist Jairo Sinova from the University of Mainz realises a tunable spin-charge converter made of GaAs August 29th, 2014

Nanoscale assembly line August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Govt.-Legislation/Regulation/Funding/Policy

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Leading European communications companies and research organizations have launched an EU project developing the future 5th Generation cellular mobile networks August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Possible Futures

Air Force’s 30-year plan seeks 'strategic agility' August 1st, 2014

IBM Announces $3 Billion Research Initiative to Tackle Chip Grand Challenges for Cloud and Big Data Systems: Scientists and engineers to push limits of silicon technology to 7 nanometers and below and create post-silicon future July 10th, 2014

Virus structure inspires novel understanding of onion-like carbon nanoparticles April 10th, 2014

Local girl does good March 22nd, 2014

Academic/Education

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

RMIT delivers $30m boost to micro and nano-tech August 26th, 2014

SEMATECH and Newly Merged SUNY CNSE/SUNYIT Launch New Patterning Center to Further Advance Materials Development: Center to Provide Access to Critical Tools that Support Semiconductor Technology Node Development August 7th, 2014

Oxford Instruments Asylum Research and the Center for Nanoscale Systems at Harvard University Present a Workshop on AFM Nanomechanical and Nanoelectrical Characterization, Aug. 21-22 August 6th, 2014

Announcements

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

Nanoscale assembly line August 29th, 2014

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Photonics/Optics/Lasers

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

Fonon Announces 3D Metal Sintering Technology: Emerging Additive Nano Powder Manufacturing Technology August 28th, 2014

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Research partnerships

Leading European communications companies and research organizations have launched an EU project developing the future 5th Generation cellular mobile networks August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

The thunder god vine, assisted by nanotechnology, could shake up future cancer treatment: Targeted therapy for hepatocellular carcinoma using nanotechnology August 27th, 2014

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Quantum nanoscience

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

X-ray Laser Probes Tiny Quantum Tornadoes in Superfluid Droplets: SLAC Experiment Reveals Mysterious Order in Liquid Helium August 25th, 2014

Rice physicist emerges as leader in quantum materials research: Nevidomskyy wins both NSF CAREER Award and Cottrell Scholar Award August 20th, 2014

Molecular engineers record an electron's quantum behavior August 14th, 2014

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE