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. UV lasers are sought after for applications in sterilization, UV curing of materials and sensing, but have so far been difficult to realize. 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?
Åsa Haglund is a Professor at Chalmers University of Technology in Sweden and her research group focuses on visible and ultraviolet (UV) vertical-cavity surface-emitting lasers (VCSELs) and thin-film UV light-emitting diodes. Prof. Haglund has been a visiting scientist at Ulm University in Germany and Lund University in Sweden and has published more than 150 papers. She is a mentor for researchers in physics and a technical program committee member of the International Workshop on Nitride semiconductors and the International Conference on Nitride Semiconductors. Prof. Haglund recently received two prestigious research grants from the European Research Council and the Swedish Research council to consolidate her research on blue and ultraviolet VCSELs.