Contrary to our normal expectations, LEDs can exhibit optical efficiencies well above 100%–but only if you re-define “input power” in a unique way.

I am a firm believer in the laws of thermodynamics and their plain-spoken corollary, “When it comes to energy, there is no free lunch.” That’s why I automatically dismiss any article or ad promising efficiency of 100% or better

That’s why I was shocked when I saw the headline “8000% efficient LED enables ultralow-power data transmission” in a recent article in Laser Focus World.

It turns out, though, that the headline was correct. The improved efficiency has to do with how and where you measure input and output powers, plus the subtleties of LEDs and quantum mechanics. To quote the start of the article:

Certain LEDs, when heated and then run at a very low power, exhibit wall-plug efficiencies [electrical-to-optical power-conversion efficiency] of more than 100%; this effect is explained by the existence of thermoelectric pumping of the LED… The setup transmitted 3 kbit/sec at a bit-error rate of 3 x 10-3 and an energy expenditure per bit of only 40 fJ.

Roughly speaking, the LED is pumped with thermal energy in advance, then the energy is parceled out via optical data bits, while the LED itself does not need to consume additional corresponding power. (This effect goes by several names: electro-luminescent or EL cooling, electroluminescent refrigeration, thermophotonic cooling, and optothermionic refrigeration.)

Traditionally LEDs were viewed as an excellent lighting alternative offering significant energy savings, albeit with inferior visual performance compared to some lighting options.

Over the past few years, the energy savings LEDs provide have continued to grow at an impressive pace. In fact today´s LEDs are more than twice as efficient as LEDs from just five years ago, offering 25-30% energy savings compared to CCFLs and up to 80% savings compared to incandescent bulbs. These eye-catching energy savings have been accompanied by significant space savings and enhanced visual performance.

Key developments in LED manufacturing, specifically enhanced equipment, improved processes and superior materials, have allowed the latest generation of LEDs to provide a powerful combination of excellent light output, visual performance and space savings. Let’s look at each development closer.

Fireflies … they’ve allowed us to image the bloodstream and they’ve inspired the creation of a light that could run on waste. Now, they’ve helped an international team of scientists get over 50 percent more light out of existing LED bulbs. The secret lies in the insects’ scales.

More specifically, the secret lies in the scales of the Photuris firefly.

In all types of fireflies, their bioluminescence is emitted through the cuticle of their exoskeleton.

It was discovered that in the Photuris genus, however, scales in the cuticle possessed optical qualities that boosted the amount of light that could get through. These qualities were concentrated along the jagged edges of the roof-shingle-like scales.

A record-setting 1mm2 infrared chip prototype from Osram Opto Semiconductor broke through a barrier by achieving an efficiency of up to 72% at 100 milliamps using thin-film technology. Under laboratory conditions at 930 milliwatts from an operating current of 1 amp, its light output is 25% higher than currently available solutions.

The 850-nanometer wavelength is ideal for infrared illumination such as for surveillance tasks and CCTV camera applications.

The chip is expected to be in production in mid-2013

The new MK-R LEDs make the next generation of 100+ lumens-per-watt system possible for high-lumen applications, including outdoor and indoor directional applications, such as halogen replacement lamps. MK-R LEDs are available in EasyWhite® color temperatures, providing the LED industry’s best color consistency for designs that use only one LED. For systems that use multiple LEDs, MK-R enables manufacturers to use fewer LEDs while still maintaining light output and quality, which translates to lower system cost.

“Cree just announced production power LEDs reaching 200 lumen/watt. Approximately doubling the previous peak LED light efficiency, the new LEDs will require less cooling. This should enable the MK-R series to finally provide direct no-hassle replacements to popular form-factors such as MR-16 spots and incandescent lighting in general.”

A trick of the light evolved by silvery fish to avoid predators could help improve optical devices like LEDs, according to a study in Nature Photonics.

The research took a look at how fish such as sardines and herring reflect light without polarising it.

these fish avoid reflecting polarised light by having two types of reflective crystals in their skins.

In photonics, this property could be used to make more efficient low-loss devices and brighter LED lamps, the researchers say.

In 1962, 50 years ago today, Nick Holonyak Jr. and his team at GE invented the Light Emitting Diode. While LED lights are almost everywhere today — from bridges to headlights to keychain flashlights that are brighter than the sun — their initial development was ripe with uncertainty and competitive research. A direct result of another groundbreaking technology of its day, the laser, LEDs have continued to evolve and now illuminate our homes and transmit our data.

Wired Design caught up with Holonyak, now a professor at the University of Illinois, to ask him about the history, and future, of LEDs.