OSRAM Opto Semiconductors has introduced InGaN-based direct emission green laser diodes, wavelengths from 510-530 nm, for pico projection and other RGB or green-laser applications.
Mounted in a tiny TO38icut or TO56 package with integrated photodiode, they combine an unbeatable form factor with excellent beam quality which makes them particularly suitable as light sources for projectors and showlasers as well as point and line lasers.
Two models in particular, PL 520B & PL 520, offer slightly different wavelength ranges at power levels of 30mW or 50mW from a 3.8 mm diameter package (at 25 degrees Celsius), with high colour rendering and excellent contrast.
Direct emission green laser diodes are an important step toward powerful embedded projectors and signal the end of the laborious method of producing green light by doubling the frequency of infrared lasers. Direct emission green laser diodes mean that frequency doubling of infrared lasers is redundant.
The wavelength of the new single-mode PL 520 laser diode is 515-530 nm - the precise green for laser projection applications. Its optical output is 50 mW and its efficiency is typically 5-6 % at present. With a package diameter of only 3.8 mm these laser diodes enable projection units to be reduced considerably in size.
Osram says the lasers have a very high beam quality - an extremely narrow beam that spreads out only slightly due to its small divergence angle. This is an important property for micro-electro-mechanical systems (MEMS) based projectors in which the colour 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. The image is always sharp, even on curved surfaces. With their excellent beam quality, the lasers are well suited to optical imaging of light.
The single-mode green lasers open up new possibilities as light sources for laser shows. Their high beam quality enables extremely fine structures to be displayed at a considerable distance. The projectors also benefit from the high thermal stability and small size of the lasers.
Thanks to their efficiency, the temperature increase of the lasers during operation is minimised and a long lifetime and high reliability at continuous operation is guaranteed.
Green light is perceived more easily by the eye than red light; therefore, for the same laser output and, crucially, the same laser safety class, green laser diodes have the advantage, especially outdoors as point or line lasers. This means that distance meters, such as those used by builders, can be used with greater safety over larger distances, says Osram.
Another benefit of using direct emission green lasers rather than frequency-doubled lasers for outdoor applications is that they have a high operating temperature range of up to 85 °C without active cooling.
Osram green laser diodes are available from the Optoelectronics Company Ltd.