Bridging the green gap
The announcements earlier this year by Sumitomo (Kyushu, Japan) and Osram Opto Semiconductors (Regensburg, Germany) that they each have developed green-emitting laser diodes (at 531 and 515 nm respectively) raises the specter of a “true green” semiconductor laser light source competing in the laser marketplace very soon.
The announcements earlier this year by Sumitomo (Kyushu, Japan) and Osram Opto Semiconductors (Regensburg, Germany) that they each have developed green-emitting laser diodes (at 531 and 515 nm respectively) raises the specter of a “true green” semiconductor laser light source competing in the laser marketplace very soon. Small second-harmonic-generation-based external-cavity green lasers are readily available and widely applied, but the advantages of direct-emitting laser diodes make them better candidates for some applications, especially displays. Blue- and red-emitting laser diodes already exist; a green counterpart would make red-green-blue (RGB) displays less complex and easier to build. Interest is high: besides Sumitomo and Osram other groups working on bridging the green gap include Rohm (Kyoto, Japan) and Nichia (Tokyo, Japan), as well as researchers at Rensselaer Polytechnic Institute (Troy, NY) among others.
Meanwhile, another green laser technology, the optically pumped semiconductor laser (OPSL), continues to make inroads into new markets, most recently attracting the interest of ultrafast researchers for pumping Ti:sapphire systems. Part of its appeal is based on low-noise delivery of 5 W output at 532 nm. The advent of green laser diodes and new versions of the OPSL underscores the broader technology development centered on commercial green-emitting sources. Other green lasers include the fiber laser, the disk laser, and diode-pumped solid-state systems. With so many choices the market should be interesting to watch over the next couple of years. With this in mind, the 2010 Lasers & Photonics Marketplace Seminar will feature a “Technology Forum” focused on green-emitting laser technologies, their markets, and applications. The seminar is held in conjunction with Photonics West next January in San Francisco, CA. Find out more at www.marketplaceseminar.com.
Silicon technology revolutionized electronics so a significant body of research is now aimed at applying the lessons learned to photonics. Engineers at Intel (Santa Clara, CA) have “reinvented” avalanche photodetectors, producing monolithically grown CMOS-compatible devices with world-record gain-bandwidth product that can be used at common optical communications wavelengths.
Stephen G. Anderson
Editor in Chief