Electrically powered semiconductor laser diodes, like those found in CD and DVD players, are a highly convenient source of laser light, but their wavelength of operation is yet to reach deep into the ultraviolet (UV). This week online in Nature Photonics, Harumasa Yoshida and his colleagues report an AlGaN laser diode that operates at a wavelength of 342 nm — the shortest wavelength of operation reported so far.
The achievement is important because there are many applications in biomedicine, data-storage and materials processing that require short-wavelength UV laser diodes. The next-generation of optical data-storage systems following today’s blu-ray disks may need short-wavelength UV laser diodes. In addition, semiconductor lithography for the manufacture of microchips also requires UV lasers and fluorescence in biological systems is excited by UV light.
Importantly, the laser developed by Yoshida and colleagues contains no indium. Indium is usually added to improve the efficiency of a UV laser diode, but it limits device operation to longer wavelengths. The demonstration proves that it is possible to create a practical and efficient indium-free UV laser diode that operates at room temperature. The device emits powers in the milliwatt range when driven by a pulsed electrical current.