Design and characterization of a low-optical-loss UV-C laser diode

We present an optical modeling and characterization study of prototype ultraviolet laser diode (LD) structures grown on single-crystal AlN substrates, with focus on the reduction of modal loss caused by optical mode coupling to the absorptive layers on the p-side (i.e. p-contact and p-metal layers). The transparent AlN substrates enabled optical pumping for measuring modal loss without requiring functioning LDs. The modal loss measured in this way was in good agreement with electrically evaluated results of processed LDs, and both results were consistent with optical modeling predictions. By using 0.32 m thick p-side cladding, we were able to suppress the modal loss of the designed LD structure to 8.4 cm−1, where the contribution from the absorptive p-contact layers was less than 3 cm−1.