Integrated continuous-wave aluminum nitride Raman laser

Wurtzite aluminum nitride (AlN) is known to exhibit six Raman-active optic phonons, making it appealing for Raman lasing. Here, we demonstrate continuous-wave Raman lasers with a low threshold and a high slope efficiency in high quality factor AlN-on-sapphire microrings. Stokes radiations around 1.7–1.8 μm and cascaded operation into 1.9–2.0 μm are identified with a telecom pump. Two types of Stokes lights with distinct Raman shifts and polarizations are recorded via selective excitation of corresponding optic phonons, in accordance with the Raman selection rules in AlN. The observed lasing behavior is satisfactorily accounted for by a theoretical analysis. Our results indicate that AlN-on-sapphire should be promising for integrated nonlinear optics.