24 Jan 2012
The frequency-doubled 532 nm diode unveiled at Photonics West indicates that green sources remain the subject of much attention.
With several pico-projector developers poised to exploit green laser diodes, and other potential end-users also waiting in the wings, the announcement at Photonics West of a new 532 nm compact diode from QD Laser could mark another step on the road towards successful development of the technology.
It also indicates that frequency-doubling of a 1064 nm seed source remains at present the method of choice for many developers wishing to create a green-laser module, with direct-emission green sources still more expensive and complicated in comparison.
The QD Laser source is a frequency-doubled high-power device, housed in a module of approximately 0.5 cm3 total volume. The company has said that its prototype module developed green light output of more than 100 mW under continuous wave conditions and high-speed modulation of above 100 Mhz. According to the test results, the linewidth of the output was less than 0.01 nm, and the 100 mW output power was obtained with power dissipation of about 900 mW, equating to a wall-plug efficiency of more than 10 percent.
QD Laser has already started shipping samples of a 5 mW output version of the module, and is planning to start sample shipments of a version capable of exceeding 50 mW from the second quarter of 2012. Mass production of the product is scheduled to begin in the fourth quarter.
The module's small dimensions should make it particularly attractive for manufacturers of ultra-compact projection systems in consumer electronics, an arena where the difficulties in developing a suitable green source to complement the more readily available red and blue laser sources has been identified as one of the several barriers currently holding back wider adoption.
Established in 2006 as a spin-out from Fujitsu, QD Laser was among the developers noted by analysts Yole Développement in 2010 as working on proprietary solutions to the generation of a green-laser source and employing a frequency-doubling method to get the job done. That report predicted that direct-emission green sources from the likes of Osram and Sumitomo would have started to appear by mid-2011, but it has since become clear that the technical challenges and pricing pressures involved remain considerable.
As a result, all sides are still jockeying for position. Recent moves have seen Finnish-developer EpiCrystals demonstrate its own frequency-doubled GaAs green laser with a claimed wall-plug efficiency of 8 percent, expected to be available from early 2012 at a price of $45 in volumes exceeding 10,000 units.
Meanwhile MicroVision, based in Redmond, Washington, announced at this year's CES that it had developed a new generation of its PicoP display engine that incorporates a direct-emission green source. MicroVision has indicated that it expects market availability of direct green laser diodes to occur during 2012, and will begin providing early samples of the PicoP Gen2 HD laser display engine to selected OEMs for their own testing and evaluation in the first quarter of the year.