tech briefs: Violet Lasers Hit Their Stride by Michael Cook, Coherent Inc., Auburn, Calif., USA GaN-based lasers have overcome initial design problems to prepare for diverse applications, including optical storage, bio-instrumentation, graphic arts and semiconductors. Violette Laser überwinden ìhre Macken GaN-basierende Laser sind den Kinderschuhen entwachsen und stehen bereit für zahlreiche Anwendungen wie optischen Speichern, biologischen Instrumenten, grafischen Kunsten und Les laser violet règlent les problèmes Les lasers GaN éliminent les problèmes initiaux de conception et sont prêts pour diverses applications, que ce soit pour le stockage optique, la bio-instrumentation, les arts graphiques et I laser operanti nel violetto si aprono la strada I laser basati su materiali GaN hanno superato le iniziali diffi- colta' di progetto, ed ora sono pronti per varie applicazioni, tra cui l'immagazzinamento ottico di dati, la biostrumen- tazione, le arti grafiche e l'industria dei semiconduttori. When GaN-based violet diode lasers were intro- duced in 1998, they caused quite a stir in the pho- tonics industry. Their potential as relatively in- expensive, ~400-nm direct diode sources was seen as very ex- citing. Initially, they were targeted mainly for the optical storage marketplace. As the lasers have evolved, the lures of longer lifetime, very low power consumption and improved heat dis- sipation have made them even more attractive, and researchers in bio-instrumentation, microscopy, graphic arts and the semi- conductor industry are looking at ways to incorporate this For the bio-instrumentation and microscopy markets, the use of 400-nm laser light reduces the need for expensive, bulky and high-maintenance ultraviolet sources and expands the wavelength choices for dye enhancements. Pharmaceutical companies are using the violet light in high-throughput screen- ing for research ranging from new drug therapies to cancer detection. The graphic arts marketplace is developing prod- ucts in computer-to-plate instruments (and photo finishing) to enhance higher throughput with smaller footprints at re- duced prices and with lower utility requirements. The course of violet laser implementation, however, has not been without obstacles; the first users discovered that these diode lasers had certain troublesome peculiarities. Early diode laser lifetimes were quite short and subject to many environ- mental dependencies; temperature and humidity played a strong role. Electrostatic discharge to extremely low volt- ages would commonly cause fatal damage. In addition, out- put beam parameters varied radically from diode to diode, making the devices difficult to adapt in some high-volume GaN lasers emitting at 400 nm are replacing bulky, expensive ultraviolet sources in many applications. Reprinted from the January/February 2003 issue of EuroPhotonics © Laurin Publishing Co. Inc.

Updated violet lasers are robust, with extended lifetimes applications. Other frustrating parameters included low power, long- and short-term output power noise issues, elliptical beam shapes and expensive per-unit diode costs — in the thousands-of-dollars' range. Thus, many early implementers became discouraged. As customers tried to adapt GaN technology into their ap- plications, diode laser module manufacturers looked at ways of making this technology more manageable and robust. For many years, Coherent Inc. has been adapting off-the-shelf diode lasers in the visible and near-IR to make easy-to-use...