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HL: Fachverband Halbleiterphysik

HL 23: Focus Session: Breakthroughs in wide-bandgap semiconductor laser diodes I

HL 23.5: Vortrag

Mittwoch, 29. März 2023, 11:45–12:00, POT 251

Single-mode lasing in optically pumped UVB VCSELs with circular relief structures — •Giulia Cardinali¹, Filip Hjort², Johannes Enslin¹, Munise Cobet¹, Michael A. Bergmann², Johan Gustavsson², Joachim Ciers², Tim Kolbe³, Felix Nippert¹, Markus R. Wagner¹, Tim Wernicke¹, Åsa Haglund², and Michael Kneissl^1,3 — ¹Institute of Solid State Physics, Technische Universität Berlin, Berlin, Germany — ²Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden — ³Ferdinand-Braun-Institut (FBH), Berlin, Germany

Extending the emission wavelength of vertical-cavity surface-emitting lasers (VCSELs) in the ultraviolet (UV) range would allow advances in many applications, e.g. in medical diagnostics, material curing, and sterilization. UV VCSELs have been demonstrated only under optical pumping and they suffer from strong filamentation (i.e. spatially inhomogeneous emission), resulting in multimode lasing. In this work, we study the emission characteristic of optically pumped UVB VCSELs with circular reliefs dry-etched on the bottom cavity. Single-mode lasing near 312 nm was achieved for VCSELs with 25 nm-deep reliefs with diameters smaller than 5 µm, when pumped up to 80 MW/cm². Here, the lateral size of the cavity was reduced below the dimension of one filament. VCSELs with 5 nm-deep reliefs did not show single mode lasing. 50 nm-deep structures did not lase for diameters below 6 µm. The higher thresholds in this sample are due to defect generation in the quantum-well by the dry etching, which was confirmed by time-resolved photoluminescence measurements of the carrier lifetimes.