Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

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

A 'smart dress' for oil-degrading bacteria July 24th, 2016

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

New probe developed for improved high resolution measurement of brain temperature: Improved accuracy could allow researchers to measure brain temperature in times of trauma when small deviations in temperature can lead to additional brain injury July 23rd, 2016

Govt.-Legislation/Regulation/Funding/Policy

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

Weird quantum effects stretch across hundreds of miles July 21st, 2016

Scientists glimpse inner workings of atomically thin transistors July 21st, 2016

The birth of quantum holography: Making holograms of single light particles! July 21st, 2016

Possible Futures

A 'smart dress' for oil-degrading bacteria July 24th, 2016

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

New probe developed for improved high resolution measurement of brain temperature: Improved accuracy could allow researchers to measure brain temperature in times of trauma when small deviations in temperature can lead to additional brain injury July 23rd, 2016

Academic/Education

News from Quorum: The College of New Jersey use the Quorum Cryo-SEM preparation system in a project to study ice crystals in high altitude clouds July 19th, 2016

Leti and Korea Institute of Science and Technology to Explore Collaboration on Advanced Technologies for Digital Era July 14th, 2016

SUNY Poly Celebrates Its 10th Year Exhibiting at SEMICON West with Cutting Edge Developments in Integrated Photonics and Power Electronics July 8th, 2016

FEI and King Abdullah University of Science and Technology Establish New Electron Microscopy ‘Centre of Excellence’: Centre of Excellence involves materials and life sciences research and technical collaboration July 5th, 2016

Announcements

A 'smart dress' for oil-degrading bacteria July 24th, 2016

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

New probe developed for improved high resolution measurement of brain temperature: Improved accuracy could allow researchers to measure brain temperature in times of trauma when small deviations in temperature can lead to additional brain injury July 23rd, 2016

Photonics/Optics/Lasers

RMIT researchers make leap in measuring quantum states July 21st, 2016

The birth of quantum holography: Making holograms of single light particles! July 21st, 2016

Graphene photodetectors: Thinking outside the 2-D box July 21st, 2016

Scientists develop way to upsize nanostructures into light, flexible 3-D printed materials: Virginia Tech, Livermore National Lab researchers develop hierarchical 3-D printed metallic materials July 20th, 2016

Research partnerships

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

Rice's 'antenna-reactor' catalysts offer best of both worlds: Technology marries light-harvesting nanoantennas to high-reaction-rate catalysts July 18th, 2016

Researchers invent 'smart' thread that collects diagnostic data when sutured into tissue: Advances could pave way for new generation of implantable and wearable diagnostics July 18th, 2016

Leti and Korea Institute of Science and Technology to Explore Collaboration on Advanced Technologies for Digital Era July 14th, 2016

Quantum nanoscience

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

A new spin on reality July 15th, 2016

Physicists couple distant nuclear spins using a single electron: For the first time, researchers at the University of Basel have coupled the nuclear spins of distant atoms using just a single electron July 12th, 2016

Quantum technologies to revolutionize 21st century: Nobel Laureates to discuss impacts at 66th Lindau Meeting July 5th, 2016

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







Car Brands
Buy website traffic