Low threshold 2-D photonic crystal lasers

Several feasible forms of low threshold 2-D slab photonic crystal lasers such as nondegenerate unit-cell lasers and band edge lasers are discussed. Through the existence of very small, very high-Q resonant modes in the square lattice, we argue the effectiveness of the photonic bandgap in photon confinement. However, the issues still needing to be solved are those of electrical pumping and surface recombination. We believe the photonic crystal will help us to find the route to the ultimate thresholdless lasers that have extremely small mode volume and high-Q values. In addition, the demonstration of the cavity-less small volume band edge laser can lead us to a new form of very small practical lasers.