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17 Jun 2002
US scientists at Brown University, Rhode Island and Sandia National Laboratories, New Mexico, have developed what they say is the first vertical-cavity surface-emitting laser (VCSEL) that operates in the near-ultraviolet region.
Based on InGaN/GaN multiple quantum wells, the device emits up to 3 mW at 383 nm when optically pumped with a 355 nm Nd:YAG laser source. The VCSEL, which functions in a quasicontinuous-wave mode at room temperature, was grown using organometallic vapour-phase epitaxy on a sapphire substrate.
Sandia's lead scientist, Jung Han, said that his team's achievement was "a dream". He added: "No-one before this has had the technology to create a compact laser source for ultraviolet excitation. It is important for security work, because many molecular bonds of interest do not respond to longer wavelengths of light."
Applications of the novel source include chemical and biochemical sensing, such as detecting weapons-grade nuclear material, and dangerous bacteria, such as E-coli. Current detection of these materials requires the addition of a chemical tag that responds to longer-wavelength excitation - a time-consuming and expensive process.
Another application could be the efficient generation of white light for indoor lighting, although this would require electrical rather than the current optical pumping of the devices.
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