February 16, 2013
Engineers Develop More Efficient Way To Capture Light
April Flowers for redOrbit.com — Your Universe Online
Engineers at the University of Buffalo have created a more efficient way to catch a rainbow than chasing leprechauns. They have created an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research.
The study findings were described in a recent issue of the online journal Scientific Reports.
Qiaoqiang Gan, PhD, an assistant professor of electrical engineering at UB, and a team of graduate students developed a “hyperbolic metamaterial waveguide." The waveguide is an advanced microchip made of alternate ultra-thin film of metal and semiconductors and/or insulators. The waveguide functions by halting and ultimately absorbing each frequency of light at slightly different places in a vertical direction to catch a "rainbow" of wavelengths.
“Electromagnetic absorbers have been studied for many years, especially for military radar systems,” Gan, a researcher within UB´s new Center of Excellence in Materials Informatics, said in a statement. “Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band.
“We are developing ultra-thin films that will slow the light and therefore allow much more efficient absorption, which will address the long existing challenge.”
The photons that make up light move extremely fast -- at the speed of light, making them difficult to tame. The research team relied upon cryogenic gases in their initial attempts to slow light, but cryogenic gases are very cold -- approximately 240 degrees below zero Fahrenheit -- making them extremely difficult to work with outside a laboratory.
Prior to joining the UB team, Gan helped to pioneer a method for slowing light without cryogenic gases. He was part of a team at Lehigh University that made nano-scale-sized grooves in metallic surfaces at different depths. This process altered the optical properties of the metal. The grooves worked to slow light, however, they had limitations; such as the energy of the incident light could not be transferred onto the metal surface efficiently. This hampered its use for practical applications.
Because it is a large area of patterned film that can collect the incident light efficiently, the hyperbolic metamaterial waveguide solves that problem. The wavelength is an artificial medium with subwavelength features whose frequency surface is hyperboloid. This allows it to capture a wide range of wavelengths in frequencies that include the visible, near-infrared, mid-infrared, terahertz and microwaves. This new technology could lead to advancements in an array of fields.
In electronics, for example, a phenomenon called crosstalk exists in which a signal transmitted on one circuit or channel creates an undesired effect in another circuit or channel. The on-chip absorber could potentially nullify this effect.
Solar panels and other energy collecting devices could also sport the new on-chip absorber, perhaps as a thermal absorber in the mid-infrared spectral regions for devices that recycle heat after sundown.
Because the on-chip absorber has the potential to absorb different wavelengths at a multitude of frequencies, it could have applications as a stealth coating material for stealth technology.