As everyone is aware, Strategies Unlimited is the leader in both laser research and LED lighting research, and rarely do the applications of these two widely different light “sources” usually overlap. Lasers can be used for illumination tasks such as semiconductor inspection where a laser illuminates a semiconductor wafer when one looks for defects, but when it comes to general illumination of white light used by us humans for vision, this task almost has always been the domain of LEDs, or at least it has until very recently.
In just the last year, interest in laser light sources is starting to gain momentum in three areas; 1) laser automotive headlights, 2) laser cinema projection, and 3) laser light bulbs. In 2015, several high-end European automotive manufacturers have introduced automobiles which incorporated laser headlights. By the end of 2015, there were already 18 movie theaters worldwide which have incorporated laser illuminated projection systems. And finally in 2015, the University of California at Santa Barbara was awarded a $2.37M grant from the Department of Energy to develop a low-cost, high-efficiency laser light bulb. Conducting the research is Dr. Shuji Nakamura, one of the co-inventors of the blue LED, the device that is principally responsible for all the LED lighting we have today, the device which won him the Nobel Prize in Physics in 2014.
While it’s clear that the laser is starting to be looked at seriously as a light source, what is really not so clear to many is why? Aren’t LED’s really pretty good, and what can the laser offer that LEDs and other light sources can’t? When we look for the answer to that question, we find that there is not just one answer, but many. In fact the real motivation to transition to lasers from other light sources seems to vary with the application. Let’s look at the three applications above and see what the motivation to use lasers is.
We’ll start by looking at automotive headlights, which have used light sources through the years ranging from acetylene and oil, to incandescent lamps, Xenon high-intensity discharge lamps, and LEDs. Certainly automotive headlights have evolved through the years but why now lasers? I have spoken with BMW and Audi, and they say they can get a brighter light intensity from lasers that can be tighter focused. BMW claims that the light it can get from lasers more than doubles the range they can get from LEDs. In addition, the laser die is 100 times smaller than with an LED, which in turns gives car designers more flexibility including installing the laser module a distance from the actual headlight window and feeding the light via fiber cable.
One benefit that laser headlights don’t bring to automotive headlights is cost. I’m told that laser headlights are at least twice the cost of LED headlights, and can be considerably more than that. The BMW i8 was the first car which offered laser headlights as an option. The car lists for $135,925 and that is without the laser headlight option which adds another $10,500 to the price.
Laser cinema projection has a complete different set of advantages than does laser headlights. Here the light source that is being replaced is a high-wattage xenon bulb with a limited life. These xenon bulbs range from 1 kW to 15 kW depending on how big the screen is and whether 3D is employed or not. 3D requires much more light than a non-3D movie because 3D glasses reduce a good part of the light reaching viewer’s eyes.
Xenon bulbs not only use lots of power, and produce large amounts of heat, they are also very costly to replace (up to $6000 per bulb) and their life can be as short as 500 to 600 hours. All these negatives make a laser source seem ideal by comparison. Laser sources can be more energy efficient than xenon bulbs, last in excess of 20,000 hours, and don’t require replacement. Laser projection also offers two other advantages that xenon bulbs don’t; 1) They can be centrally located in a theater and be remote from the projector allowing the projector to be made smaller, and 2) perhaps most important of all, they can be brighter than the brightest xenon bulb, which is very important for very large screen 3D theaters. For example the Metreon IMAX Theatre in San Francisco has an 80’ x 100’ screen but still shows movies in 3D. That combination would be impossible in a theater powered by a xenon bulb.
So lasers in cinema projection and laser automotive headlights clearly offer some advantages over other light sources, but can a laser light bulb be potentially better than the $3, 120 lm/watt efficiency LED bulb that you can purchase at any Home Depot today? The answer is not yet, but maybe soon, and this is due to a different advantage than for cinema or headlights. While LED bulbs today are very bright and cheap and energy efficient, they contain one flaw. LEDs become less power efficient the harder they are driven, while laser diodes become more efficient. Why this is important is because the only way to get more light from an LED die is to make a larger die or many smaller dies, and more silicon means more cost. A laser diode die can be driven higher to produce more light and it becomes more efficient in the process. In other-words, laser light bulbs could not only be potentially more efficient than LED bulbs, but also potentially cheaper as well. Only time and more research will tell for sure.
Should laser bulbs eventually replace LED bulbs, and Dr. Nakamura believes they will, this could become yet another large market for lasers. The current lighting market is over $61B worldwide, with LEDs representing almost 40% of that, and this doesn’t even include automotive headlights and cinema projection bulbs. In any case, the future for laser lighting seems very bright indeed.