28 November 2012

Manipulating nanoscale ‘rainbows’ for solar cells and TV screens

The manipulation of light is a core photonics activity performed in numerous ways for numerous practical effects. For example, consider the design of lasers for purposes as diverse as repairing a retina to restore vision and downloading a movie over the internet onto a tablet for viewing.

Anatoly Zayats and his team at King's College
London have created artificial "rainbows" at
the nanoscale. The technology has potential
for use in solar energy generation, optical
computing, and more.
Amazing as those human-scale applications are, imagine manipulating multiple colors of light on a structure about 100 times smaller than the width of a human hair -- and then applying that for the very practical effects of sensing toxins, improving solar cell efficiency, enabling optical circuits for tele- and data communications, and improving flat-screen display.

A team of researchers led by Anatoly Zayats in the Biophysics and Nanotechnology Group at King’s College London reported recently in Nature’s Scientific Reports that they had demonstrated how to separate and even rearrange a spectrum of colors and create artificial “rainbows” using nanoscale structures on a metal surface.

The researchers trapped light of different colors at different positions at a dimension on the order of a few micrometers, an unprecedented scale in previous research, on a gold film.

"Nanostructures of various kinds are being considered for solar cell applications to boost light absorption efficiency," Zayats said in a King’s College press release. "Our results mean that we do not need to keep solar cells illuminated at a fixed angle without compromising the efficiency of light coupling in a wide range of wavelengths. When used in reverse for screens and displays, this will lead to wider viewing angles for all possible colors.”

The group’s nanoscale rainbows differ from actual rainbows in the sense that researchers were able to manipulate where the colors would appear by controlling the nanostructure’s parameters. They also discovered the possibility of separating colors on different sides of the nanostructures.

The effects demonstrated could also provide color sensitivity in infrared imaging systems for security and product control and enable construction of microscale spectrometers for sensing applications.

Zayats, who is a Fellow of SPIE, told about other applications of plasmonic effects and nanostructured metals in a recent SPIE Newsroom video interview. He will have further updates in an invited paper titled “Integrated nanophotonic devices based on plasmonics” to be presented next February at SPIE Photonics West in San Francisco.

13 November 2012

Heating up: remote sensing and global warming

Two polar bears on an iceberg. ©Eric Lefranc/Solent

After droughts, floods, and a “superstorm” this year, people everywhere are talking about the weather. Some people taking the long-term view are urging us all to not only talk but to think much more deeply -- and even to do something -- about climate change.

"Something extraordinary is going on in the world,” noted New York Times op-ed columnist Nicholas Kristof as Hurricane Sandy began to dissipate. In a column headlined, “Will climate get some respect now?” Kristof recalled the amazement of Eskimos in Alaska toward the changes they were seeing: "from melting permafrost to robins (for which their Inupiat language has no word), and even a (shivering) porcupine."

Across the Atlantic, Fiona Harvey wrote last week in The Guardian under the headline “Climate change 'likely to be more severe than some models predict'” that the latest climate models predict higher temperature rises along with more extreme weather. In other words, expect more droughts such as the UK and the USA saw last summer, more disruptions of the Indian monsoon, and more intense hurricanes like Katrina in 2005 and last month’s Sandy.

Doing something, with photonics

Photonics is playing an enormous role in climate modeling and in our understanding of what is entailed in managing climate-related changes.

On the other side of the world from where Hurricane Sandy was wreaking havoc, a group of scientists and engineers whose work is to develop and build tools that read weather systems, predict and track storm activity, and model climate change were reporting at SPIE Asia-Pacific Remote Sensing on their latest work.

As symposium chair Toshio Iguchi of Japan’s National Institute of Information and Communications Technology noted in welcoming conference attendees, they were meeting in the very same facility where the Kyoto Protocol to the United Nations Framework Convention on Climate Change was adopted in 1997.

Reports last month in Kyoto covered projects such as:
  • ground-based observation of dust aerosols and their impact on climate over northwest China
  • monitoring surface climate using satellite measurements in the USA
  • connections between vegetation activity and local climate in East Asia mutual verification in Japan between satellite data and climate model simulation results
  • modeling CO2 fluctuations on the surface of the Earth via observations from the GOSAT Project (Global Greenhouse Gas Observation by Satellite).

More reports were heard in September in Edinburgh at the SPIE Remote Sensing conference. Plenary speaker Mitchell Roffer (Roffer’s Ocean Fishing Forecasting Service) talked about applications of satellite visualization and data fusion products for assessing the health of ocean fisheries such as tuna, mackerel, squid, and marlin, as well as mapping oil-dispersant-and-water mixtures in oil spills, notably in the Gulf of Mexico during the Deepwater Horizon spill in 2010.

Conference papers in Edinburgh discussed:
  • impacts of climate change on Romanian mountain forests
  • instruments used in projects in China, Canada, Russia, and USA to monitor the forces of climate and their impacts on numerous human and environmental factors
  • the amount and rate of evaporation of moisture from the land surface
  • ocean salinity and the consequent change in which creatures and plants can live in those habitats.

Read all about it

The SPIE Newsroom regularly publishes updates from researchers. A sample of recent papers on remote sensing and climate change includes:

Monitoring global precipitation using satellites: Floods caused by extreme precipitation are one of the most frequent and widespread natural hazards, and more costly and dangerous than ever as population in urban areas increases and the global climate becomes more extreme and variable.
University of California, Irvine, Center for Hydrometeorology and Remote
Sensing (CHRS) Global Network for Water and Development Information for
Arid Lands server for monitoring near-real-time global precipitation distribution.

Improved remote sensing of surface soil moisture: Surface soil moisture plays an important role in the exchange of water and energy between land and the atmosphere, so is important to quantify for use in weather and climate models, flood forecasts, and irrigation management during droughts.

Investigating sensitivity in a Central European landscape: Studies of precipitation and biomass production in the Carpathian Basin that indicate warmer summers in the next century.

Rising lake levels indicate accelerated glacier melting: Satellite-measured elevation data was used to quantify the water levels of the largest lakes in the Tibetan Plateau.

What else needs to be done?
The New York Times noted in a post-Sandy analysis that infrastructure and city planning need attention. "The cost of that single hurricane may well be more than five times greater than that of a usual full year’s worth of the most expensive regulations, which ordinarily cost well under $10 billion annually. True, scientists cannot attribute any particular hurricane to greenhouse gas emissions, but climate change is increasing the risk of costly harm from hurricanes and other natural disasters. Economists of diverse viewpoints concur that if the international community entered into a sensible agreement to reduce greenhouse gas emissions, the economic benefits would greatly outweigh the costs."

05 November 2012

Why bother with STEM ed?

Experts in STEM education (science, technology, education, and mathematics) point out that in teaching, the “how” of science is more important that the “what.” As Shannon Warren, director of a science education partnership grant program in Washington State, noted in a recent magazine feature, learning science means exploring and analyzing, not just memorizing facts and listening to lectures.

The “why” is an equally key question, and one that evokes very personalized responses.
Professor Jin Kang in his lab at Johns Hopkins University
Take Jin Kang’s story, for example. Twenty years ago, Kang was an undergraduate physics student discovering that while he found the theory behind optics and photonics interesting, what he really loved was building lasers and other optical devices.

Kang is now a professor and the chair of the Electrical and Computer Engineering Department at Johns Hopkins University. He conducts research in biophotonics, fiber optics, and optoelectronic devices for applications in medicine and communications.

One of his primary areas of focus areas is developing 3D imaging and sensing systems for guided surgical intervention. He described one of his latest devices ― a “smart” tool with sensors to help guide the surgeon’s eye and hand in microsurgery in a recent SPIE Newsroom video interview.

“I got into optics because I had two great professors,” Kang said. “Under their supervision I built a pulsed ruby laser for holography and other optical devices, which was an indispensable experience that taught me the fundamentals. It made me really appreciate the science."

Photonics enables entertainment, too:
The Grammy-nominated 3D music video
"All Is Not Lost" by OK Go featuring
the dance group Pilobolus was among
presentations shown at the 3D cinema
session at IS&T/SPIE Electronic Imaging

2012 in January in San Francisco, California,
USA. (Photo provided by Eric Kurland, 3D
director and editor of the video.)
The question of “why teach science” also is one with huge implications. Here are just a few answers:

  • Smarter voters, better government: “Exploring and analyzing” defines independent, fact-based thinking ― the driver behind developments such as the polio vaccine, life-saving AIDS treatments, and harnessing solar energy as well as a requirement for healthy democratic government.
  • Jobs: Education is inextricably linked to innovation, and innovation in high technology creates jobs, a message clearly spelled out in the National Research Council report “Optics and Photonics, Essential Technologies for Our Nation,” and the Photonics21 report “Photonics – Our Vision for a Key Enabling Technology of Europe.”
  • Longer, safer, healthier lives: Science solves important problems, such as detecting infrastructure flaws so repairs can be made before a bridge collapses, or identifying exactly where plaque is clogging arteries to aid the surgical team in extending both quality and length of the patient’s life, for just two of thousands of possible examples.

Say it with lasers: Students are experts at sharing photonics.
SPIE Centro de investigaciones en Optica Student Chapter
members in León, Mexico, sent this laser-"drawn" photo
message along with a report on how they spent an education
outreach grant awarded by the society. CIO students present
optics workshops to children and teenagers in isolated
communities situated from 30 to 200 miles from León. More
than 5,000 children and teenagers in 100 communities have
been reached by the chapter's outreach efforts in recent years.
One of the most eloquent answers to the question "why teach science" is found on the website of Photonics Explorer, a program that is progressing toward its goal of bringing photonics education and thereby a greater understanding of science to 2.5 million secondary students across the European Union:

“Every day, our society depends more and more on science and technology. This is not only due to our personal convenience, which often relies on internet access, electrical power or just basic things like clean, drinkable water from the tap. The great challenges we all face together, such as global warming and demographic developments, demand us to (re)search for new answers."

Without a knowledgeable public engaged in the discussion, the website asks, “Who will set the direction and boundaries for research and development? On what basis will citizens decide for or against a specific science policy or a consumer product? Without a basic understanding of scientific facts and reasoning, the public as well as the individual consumer can be easily misled."