Feedback suppression in 405 nm superluminescent diodes via engineered scattering

Superluminescent diodes are promising devices for applications in which low coherence, high efficiency, small foot-print and good optoelectronic integration are required. Blue emitting superluminescent diodes with good performances and easy fabrication process are sought for next generation solid state lighting devices, micro-projectors and displays. These devices are laser diodes in which the optical feedback is inhibited, and lasing action avoided. Conventional fabrication processes minimize optical feedback by ad-hoc designs, e.g. anti-reflection coating, tilted waveguide or absorber sections, requiring specific fabrication steps. In this work, we propose and demonstrate the introduction of scattering defects in the device waveguide as a method for feedback inhibition. By performing pulsed laser ablation on a commercial 405 nm GaN laser diode we demonstrate a superluminescent diode, featuring a maximum output power of 2 mW and a spectral width of 5.7 nm.