A beam of sunlight is a mixture of different-colored light, including all the colors of the rainbow. Filtering or blocking a specific color, or colors, is often important in photography, color displays and other imaging techniques.
Altering the size and separation of these nanoscale mirrors changes the color of light that they reflect.
Copyright : 2013 A*STAR Institute of Materials Research and Engineering
An international team of engineers has now fabricated arrays of silver nanoscale pillars that can selectively reflect light of any desired color1. The team, led by Jinghua Teng and Yan Jun Liu at the A*STAR Institute of Materials Research and Engineering in Singapore, show that the color can be selected by varying the size of the pillars.
The stained glass in the windows of a church owes its color in part to an effect called surface plasmon resonance: light passing through the window interacts with electrons in the nanometer-sized metallic impurities that are trapped in the glass.
Light of a specific color, or wavelength, forces these electrons to quickly oscillate. In turn, the oscillating electrons enhance the amount of light transmitted through the glass at this wavelength. Teng, Liu and their co-workers were able to transfer this plasmonic effect from light-transmitting windows to light-reflecting mirrors. “Our compact reflectors could be used for applications including color coding, anti-counterfeiting and product branding,” says Teng.
The researchers deposited 6 nanometers of titanium, followed by 180 nanometers of silver on a quartz substrate. Onto the silver layer, they etched arrays of cylinders with diameters of 300 to 500 nanometers and a center-to-center separation of 320 to 540 nanometers (see image). The resulting gap between some of the pillars was as small as 20 nanometers. To achieve these tiny features, the team used a technique called electron-beam lithography: they scanned a beam of electrons to pattern the required features onto a protective layer placed on top of the silver. Then, they used a stream of charged ion atoms to mill the exposed metal and create the nanopillars.
After construction, Teng, Liu and their team shone white light onto each of the arrays and measured the wavelength of the reflected radiation. Arrays of cylinders of 500 nanometers in diameter and separated by 40 nanometers appeared red because they predominantly reflected light with a wavelength of 630 nanometers. Similarly, pillars with a diameter of 300 nanometers and a separation of 20 nanometers appeared blue as they reflected light with a 490-nanometer wavelength.
“We are now working to further develop this technique to create large-area color displays,” says Teng. “We also aim to develop applications and collaborations with industry.”
Si, G., Zhao, Y., Lv, J., Lu, M., Wang, F. et al. Reflective plasmonic color filters based on lithographically patterned silver nanorod arrays. Nanoscale 5, 6243–6248 (2013).
New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology
Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy