Power/Performance Bits: March 4

Photon glue
Like a spring connecting two swings, light can act as photon glue that binds together the quantum mechanical properties of two vastly different materials and this effect could harness the most useful characteristics from each material for hybrid solar cells and high efficiency lighting, among other applications. To this end, researchers at the University of Michigan and Queens College, City University of New York, used light to create links between organic and inorganic semiconductors in an optical cavity—a mirror-lined nanoscale filament about 1/1,000th the width of a hair.

The researchers said they took the excited states of two principally different materials and combined them into a new quantum mechanical state that shares their best properties, which demonstrates stronger light absorption and possibly enhanced “nonlinear” optical properties useful in optical switching.

In an optical cavity — a filament lined with mirrors — researchers have used light to bind together quantum mechanical states of two disparate materials. The result could one day enable more robust, efficient solar cells and lighting solutions. (Image credit: Tal Galfsky, CUNY)

Developing engineered nonlinear optical materials with properties that surpass naturally occurring materials is important for developing next generation photonic technologies that rely on the quantum properties of light, the researchers pointed out. For example, one could develop an optical switch that uses one photon to turn on or off the path of a second photon. This is basically a light switch that regulates light, one photon at a time—an important building block for quantum communication and computing.

Infrared as a new renewable energy source
While it seems far-fetched, physicists at the Harvard School of Engineering and Applied Sciences (SEAS) envision a device that would harvest energy from Earth’s infrared emissions into outer space.

Heated by the sun, our planet is warm compared to the frigid vacuum beyond. The researchers say recent technological advances, namely, that heat imbalance could soon be transformed into direct-current (DC) power, taking advantage of a vast and untapped energy source.

The researchers admitted it’s not at all obvious, at first, how DC power would be generated by emitting infrared light in free space toward the cold. To generate power by emitting, not by absorbing light, is weird, they said. While it makes sense physically once it is thought about, it’s highly counterintuitive. This is a use of physics at the nanoscale for a completely new application.

Three diode-resistor generator circuits with different temperature inputs. A circuit at thermal equilibrium (A) generates no current; (B) is a conventional rectifier circuit. The Harvard team proposes a twist—shown in (C). (Image source: Federico Capasso and PNAS.)