ONLINE Halbleiter zum Frühstück - Out of the Blue: Ultraviolet Lasers

In recent years, there has been tremendous improvement in the performance of blue-emitting vertical-cavity surface-emitting lasers (VCSELs), and they are now on the cusp of commercialization. Here we will summarize state-of-the-art results and outline the main challenges in what comes next, namely extending the emission wavelength into the ultraviolet (UV) region. Our method, involving simultaneously achieving high-reflectivity mirrors and good cavity length control by selective electrochemical etching, has been essential in demonstrating the world’s first UV-B VCSEL at 310 nm. But what are the challenges to going even shorter in wavelength, and is there a limit?