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18 October 2012

Osram Opto launches direct-emitting green laser diodes

Osram Opto Semiconductors GmbH of Regensburg, Germany says that it is now offering its first direct-emitting green diode lasers. The two compact indium gallium nitride (InGaN) laser diodes have optical output powers of 30mW and 50mW, respectively (at 25°C), as well as high beam quality, which is key to the development of miniature projectors for mobile devices such as smartphones and cameras, adds the firm. Other applications include projection units for laser shows, point lasers and line lasers.

Direct green diode lasers are a key step toward powerful pico projectors, eliminating the laborious method of producing green light by doubling the frequency of an infrared laser. The new technology also enables high color rendering and contrast to be achieved, says Osram Opto.

The new PL 520 laser diode’s wavelength range of 515-530nm produces the appropriate green colour for projection applications, the firm notes. Optical output is 50mW and efficiency is typically 5-6% at present. In addition, the PL 515 laser diode offers an output of 30mW in the wavelength range 510-530nm. With a TO-38 package diameter of just 3.8mm the lasers can enable the dimensions of projection units to be reduced considerably. “The commercial breakthrough for compact laser projectors is closer than ever before,” reckons Stephan Haneder, marketing manager for Consumer Lasers at Osram Opto.

Photo: Osram Opto’s PL 520 green direct-emitting laser diode for projection applications.

The firm says that the lasers have high beam quality – i.e. an extremely narrow beam that spreads out only slightly due to its small divergence angle. In the case of pico projectors, which project the laser light with a micro-electromechanical system (MEMS) mirror without any other optics, the size of the light point determines the image resolution. The beam quality is hence particularly important. Both laser diodes therefore operate in single mode (emitting just a single transverse oscillation mode).

Osram Opto says that direct-emitting lasers can be better modulated than other laser types, such as frequency-doubled infrared lasers. This is an key property for MEMS-based projectors, in which the color components per pixel result from the emission time of the laser diode. There is also no need to adjust the focus of the projection image, which is always sharp, even on curved surfaces.

The single-mode lasers open up new possibilities as light sources for laser shows, says Osram Opto, as their high beam quality enables extremely fine structures to be displayed even over large distances. The projectors also benefit from the high thermal stability and small size of the lasers.

Green diode lasers are also suitable as point or line lasers for measuring distances, for example. The human eye is most sensitive in the green spectrum, offering another advantage over red laser light. For the same laser output, and hence the same laser safety class, green light is perceived more easily by the eye than the red light that is usually used. Hence distance meters (such as those used by builders) can be used over larger distances.

Osram Opto says that its green laser was developed as part of the research project ‘MOLAS’ (technologies for ultra-compact and mobile laser projection systems), sponsored by the German Ministry for Education and Research and involving technologies for ultra-compact and mobile laser projection systems. In 2010, researchers at the firm received the Karl-Heinz-Beckurts Award for development work on the green laser.  

See related items:

Osram develops 50mW direct-emitting green InGaN laser

Osram Opto team receives Beckurts Prize for developing direct green-emitting laser

Tags: Osram Green laser


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