Lasers could replace LEDs

Recent announcements from Sandia Labs and BMW suggest lasers could be an alternative to LED-based systems

Sandia conducted tests into the white light generated by diode lasers and discovered the human eye is as comfortable with it as it is with LEDs.

An important difference between lasers and LEDs is the efficiency of each, with LEDs reducing in efficiency at higher currents while lasers improve.

Jeff Tsao examines the set-up (Photo by Randy Montoya)

Sandia researcher Jeff Tsao, who proposed the comparative experiment, said: ‘What we showed is that diode lasers are a worthwhile path to peruse for lighting.’

The tests – reported in LEDs Magazine – took place at University of New Mexico’s Centre for High Technology Materials, where 40 volunteers were seated in front of two near-identical scenes. Each both was illuminated by warm, cool or neutral white LEDs, tungsten-filament incandescent light or a combination of four lasers – blue, red, green, yellow – which combined were tuned to create white light.

Volunteers were asked to chose between alternatives – but were not told which source was being used – 80 times. Jonathan Wierer, involved in planning, calibrating and executing the experiments, said there was a significant preference for the diode-laser-based white light over the warm and cool LED-based white light. There was no statistical preference between the laser-based light and either the neutral LED-based or incandescent white light.

Comparing laser light with an incandescent bulb

Jonathan Wierer, researcher at Sandia, said: ‘We are going to start exploring the challenges of using lasers for solid-state lighting. We are starting to look at topics such as efficiency, quality and economical benefits.

‘We think this idea has potential. It most likely will not have as much universal use as LED-based solid-state lighting, but probably has some potential in specific lighting applications.’

Sandia’s experiment combined the output of four laser colours – blue, red, green and yellow – to create a white light source. The narrow beam is addressed via a suitable optical system.

The Sandia research was published in the 1 July, Optics Express

Driving possibilities

At the same time as Sandia’s research, BMW demonstrated a prototype laser-based headlight system on its i8 Concept car, using blue lasers and phosphors.

BMW used blue lasers to illuminate a remote phosphor system, generating white light.

Driver safety needs to be addressed, insuring lasers are properly directed. BMW said the laser headlamps would be safe, as the illumination would be indirect.

BMW stated: ‘Safety is a key consideration in the development of laser lighting for use in passenger cars. For BMW, the complete eye safety of this technology for all road users and its complete reliability in day-to-day use have top priority.’

BMW quotes around 100 lumens per watt for LED lighting compared with 170 lumens per watt for lasers and that the technology would not change the shape of headlights.

The strength of lasers could open up the possibility of reducing the depth of the highlight, allowing designers to play around with the positioning and body styling.

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