Ultra-low threshold gallium nitride photonic crystal nanobeam laser

GaN-based materials are well-recognized for their exceptional optical qualities, particularly in the blue and UV parts of the spectrum. In addition, their wide bandgaps allow efficient operation at room temperature and higher. This work will describe the room-temperature performance of optically-pumped GaN photonic crystal (PC) nanobeam lasers, with thresholds as low as 9.1 μJ/cm2, the lowest recorded in this material system. The low thresholds result from the high Q/V value of the cavity structure and the high spontaneous emission factor, β = 0.94. A key factor in achieving the low threshold is the rather unusual active layer, comprising Indium Gallium Nitride (InGaN) fragmented quantum well (fQWs). Lasers with fQW active layers have thresholds an order of magnitude lower than those with uniform QW active layers. We believe that the extra confinement of photogenerated carriers for fQWs compared to QWs is responsible for the excellent performance: