Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

Home > Press > Cloak and swagger: Engineers use plasmonics to create an invisible photodetector

An image showing light scattering from a silicon nanowire running diagonally from bottom left to top right. The brighter areas are bare silicon while the dimmer sections are coated with gold demonstrating how plasmonic cloaking reduces light scattering in the gold-coated sections. Photo: Stanford Nanocharacterization Lab.
An image showing light scattering from a silicon nanowire running diagonally from bottom left to top right. The brighter areas are bare silicon while the dimmer sections are coated with gold demonstrating how plasmonic cloaking reduces light scattering in the gold-coated sections.

Photo: Stanford Nanocharacterization Lab.

Abstract:
A team of engineers at Stanford and the University of Pennsylvania has for the first time used "plasmonic cloaking" to create a device that can see without being seen - an invisible machine that detects light. It is the first example of what the researchers describe as a new class of devices that controls the flow of light at the nanoscale to produce both optical and electronic functions.

Cloak and swagger: Engineers use plasmonics to create an invisible photodetector

Stanford, CA | Posted on May 21st, 2012

It may not be intuitive, but a coating of reflective metal can actually make something less visible, engineers at Stanford and UPenn have shown. They have created an invisible, light-detecting device that can "see without being seen."

At the heart of the device are silicon nanowires covered by a thin cap of gold. By adjusting the ratio of metal to silicon - a technique the engineers refer to as tuning the geometries - they capitalize on favorable nanoscale physics in which the reflected light from the two materials cancel each other to make the device invisible.

Pengyu Fan is the lead author of a paper demonstrating the new device published online May 20th in the journal Nature Photonics. He is a doctoral candidate in materials science and engineering at Stanford University working in Professor Mark Brongersma's group. Brongersma is senior author of the study.

Cloak of invisiblity

Light detection is well known and relatively simple. Silicon generates electrical current when illuminated and is common in solar panels and light sensors today. The Stanford device, however, is a departure in that for the first time it uses a relatively new concept known as plasmonic cloaking to render the device invisible.

The field of plasmonics studies how light interacts with metal nanostructures and induces tiny oscillating electrical currents along the surfaces of the metal and the semiconductor. These currents, in turn, produce scattered light waves.

By carefully designing their device - by tuning the geometries - the engineers have created a plasmonic cloak in which the scattered light from the metal and semiconductor cancel each other perfectly through a phenomenon known as destructive interference.

The rippling light waves in the metal and semiconductor create a separation of positive and negative charges in the materials - a dipole moment, in technical terms. The key is to create a dipole in the gold that is equal in strength but opposite in sign to the dipole in the silicon. When equally strong positive and negative dipoles meet, they cancel each other and the system becomes invisible.

"We found that a carefully engineered gold shell dramatically alters the optical response of the silicon nanowire," said Fan. "Light absorption in the wire drops slightly - by a factor of just four - but the scattering of light drops by 100 times due to the cloaking effect, becoming invisible."

"It seems counterintuitive," said Brongersma, "but you can cover a semiconductor with metal - even one as reflective as gold - and still have the light get through to the silicon. As we show, the metal not only allows the light to reach the silicon where we can detect the current generated, but it makes the wire invisible, too."

Broadly effective

The engineers have shown that plasmonic cloaking is effective across much of the visible spectrum of light and that the effect works regardless of the angle of incoming light or the shape and placement of the metal-covered nanowires in the device. They likewise demonstrate that other metals commonly used in computer chips, like aluminum and copper, work just as well as gold.

To produce invisibility, what matters above all is the tuning of metal and semiconductor.

"If the dipoles do not align properly, the cloaking effect is lessened, or even lost," said Fan. "Having the right amount of materials at the nanoscale, therefore, is key to producing the greatest degree of cloaking."

In the future, the engineers foresee application for such tunable, metal-semiconductor devices in many relevant areas, including solar cells, sensors, solid-state lighting, chip-scale lasers, and more.

In digital cameras and advanced imaging systems, for instance, plasmonically cloaked pixels might reduce the disruptive cross-talk between neighboring pixels that produces blur. It could therefore lead to sharper, more accurate photos and medical images.

"We can even imagine reengineering existing opto-electronic devices to incorporate valuable new functions and to achieve sensor densities not possible today," concluded Brongersma. "There are many emerging opportunities for these photonic building blocks."

Brongersma lab alumnus Professor Linyou Cao and doctoral candidate Farzaneh Afshinmanesh contributed to this research. This work is a collaboration with Professor Nader Engheta and post-doctoral researcher Uday Chettiar from University of Pennsylvania.

By Andrew Myers

Andrew Myers is associate director of communications for the Stanford University School of Engineering.

####

For more information, please click here

Contacts:
Andrew Myers
Associate Director of Communications
650.736.2245


Jamie Beckett
Director of Communications and Alumni Relations
650.736.2241

Copyright © Stanford School of Engineering

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

Starpharma initiates new DEP™ drug delivery program with AstraZeneca July 27th, 2016

Ageing can drive progress: Population ageing is likely to boost medicine, nanotechnology and robotics, but increase political risks July 27th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Imaging

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Display technology/LEDs/SS Lighting/OLEDs

Researchers develop faster, precise silica coating process for quantum dot nanorods July 12th, 2016

Integrated trio of 2-D nanomaterials unlocks graphene electronics applications: Voltage-controlled oscillator developed at UC Riverside could be used in thousands of applications from computers to wearable technologies July 7th, 2016

GraphExeter illuminates bright new future for flexible lighting devices June 23rd, 2016

New nanomaterial offers promise in bendable, wearable electronic devices: Electroplated polymer makes transparent, highly conductive, ultrathin film June 13th, 2016

Chip Technology

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

Nanometrics Reports Second Quarter 2016 Financial Results July 26th, 2016

Ultra-flat circuits will have unique properties: Rice University lab studies 2-D hybrids to see how they differ from common electronics July 25th, 2016

Attosecond physics: Mapping electromagnetic waveforms July 25th, 2016

Sensors

Ultrasensitive sensor using N-doped graphene July 26th, 2016

Integration of novel materials with silicon chips makes new 'smart' devices possible July 25th, 2016

Electron 'spin control' of levitated nanodiamonds could bring advances in sensors, quantum information processing July 20th, 2016

Easier, faster, cheaper: A full-filling approach to making nanotubes of consistent quality: Approach opens a straightforward route for engineering the properties of single-wall carbon nanotubes July 19th, 2016

Discoveries

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

Ultrasensitive sensor using N-doped graphene July 26th, 2016

Announcements

Starpharma initiates new DEP™ drug delivery program with AstraZeneca July 27th, 2016

Ageing can drive progress: Population ageing is likely to boost medicine, nanotechnology and robotics, but increase political risks July 27th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Energy

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

Designing climate-friendly concrete, from the nanoscale up: New understanding of concrete’s properties could increase lifetime of the building material, decrease emissions July 25th, 2016

An accelerated pipeline to open materials research: ORNL workflow system unites imaging, algorithms, and HPC to advance materials discovery and design July 24th, 2016

Researchers discover key mechanism for producing solar cells: Better understanding of perovskite solar cells could boost widespread use July 21st, 2016

Photonics/Optics/Lasers

Attosecond physics: Mapping electromagnetic waveforms July 25th, 2016

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

Research partnerships

New lithium-oxygen battery greatly improves energy efficiency, longevity: New chemistry could overcome key drawbacks of lithium-air batteries July 26th, 2016

Ultrasensitive sensor using N-doped graphene July 26th, 2016

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

Solar/Photovoltaic

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

An accelerated pipeline to open materials research: ORNL workflow system unites imaging, algorithms, and HPC to advance materials discovery and design July 24th, 2016

Researchers discover key mechanism for producing solar cells: Better understanding of perovskite solar cells could boost widespread use July 21st, 2016

The future of perovskite solar cells has just got brighter -- come rain or shine: Korean researchers at POSTECH have succeeded in developing high-efficiency perovskite solar cells that retain excellent performance over two months in a very humid condition July 21st, 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