17 Jun 2002
German researchers claim to have made Europe's first continuous-wave, room-temperature blue laser diode.
Exclusive from Opto & Laser Europe (OLE) magazine
Osram Opto Semiconductors and academic collaborators at the Fraunhofer Institute for Applied Solid-State Physics and the universities of Stuttgart, Ulm and Braunschweig have shown continuous-wave output at 420 nm from a laser diode operating at room temperature.
The breakthrough was made as part of a government-funded project that aims to counter the de facto Asian monopoly in blue and violet laser diodes.
The diode, which is based on indium gallium nitride (InGaN), showed an output power of more than 20 mW and a threshold current of 110 mA.
Its lifetime, however, is no more than "several minutes", according to Osram's marketing manager Marion Brand. While she admits that such a lifetime is far too short for commercial applications, she said: "Nobody else in Europe has achieved as much as we have. The product is still in its research phase."
By changing the composition of the InGaN gain material, the researchers hope to be able to develop diodes at different wavelengths within the blue/violet region of the spectrum, as well as enhancing the performance of the initial 420 nm diode.
Osram fabricated the diode in March this year, but it has kept quiet about its achievement. "We did not want any publicity, but a press release was issued by the Fraunhofer Institute without our knowledge," Brand told OLE. She denies that market uncertainty owing to the ongoing patent dispute between Nichia and Cree is the cause of Osram's silence.