LED lighting could be aided by diode lasers

Laser-LED combination lighting could be the outcome of US government research that has found that the human eye finds diode laser generated white light as comfortable as LEDs.

The researchers from the US government's Sandia National Laboratories have proposed combination lighting that has blue and red diode lasers with yellow and green LEDs, while blue diode lasers could be used for phosphor based lighting, a technique used by LED lights.

Conceived at Sandia, an experiment on laser light comfort was carried out with 40 volunteers at the University of New Mexico’s Center for High Technology Materials. The volunteers had to give their views on how comfortable the illumination of a fruit bowl was, but were not told when it was lit by LEDs, diode lasers or incandescent light bulbs. They reported that they felt no significance difference between LEDs and diode lasers.

Sandia's scientists state that LEDs lose efficiency at currents above 0.5amps while diode lasers’ efficiency improves at higher currents. Diode lasers could provide a range of colours that a user could choose from or they could select spot lights, as laser light can be directed.

According to the Sandia researchers little work had been done on diode lasers, because of an assumption that human eyes would find the light unpleasant. This is because while sunlight blends a wide spectrum of wavelengths diode lasers emit four narrow-band wavelengths, blue, red, green and yellow. Diode laser light is also ten times narrower than LEDs.

‘What we showed is that diode lasers are a worthy path to pursue for lighting,’ said Sandia researcher Jeff Tsao. ‘Before these [comfort] tests, our research in this direction was stopped before it could get started. The typical response was, “Are you kidding?” So finally it seemed like, in order to go further, one really had to answer this very basic question first.’

However, what could hold back diode lasers is their cost and performance. Sandia researchers admit that diode lasers are more expensive to fabricate than LEDs, red diodes are not as good as yellow ones, and green lasers are not efficient enough for commercial lighting.

Sandia is a US Department of Energy’s National Nuclear Security Administration laboratory that has facilities in New Mexico and California. Sandia is operated and managed by the Sandia corporation, a Lockheed Martin subsidiary.

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