Photonic-crystal surface-emitting laser

Recently, there has been growing interest in photonic-crystal surface-emitting lasers (PC-SELs) (1-4). The lasing principle exploited by the lasers is based on the band-edge effect in a two-dimensional (2D) PC, where the group velocity of light becomes zero and a 2D cavity mode is formed. The output power is coupled to the vertical direction by the PC itself, which gives rise to the surface-emitting function. Based upon this novel lasing mechanism, PC-SELs possess the following important features: first, perfect, single longitudinal, and lateral mode oscillation can be achieved even when the lasing area becomes very large (for example, devices >300 μm in diameter) (1, 2, 4); and second, the polarization mode (2) and the beam pattern (4) can be controlled by appropriate design of the unit cell and/or lattice phase in the 2D PC (as a result, a range of vector beams (5, 6) can be directly generated); third, the on-chip controllability of the beam direction (7) can be realized using a composite photonic crystal composed of square and rectangular lattices. In this report, we will overview the lasing principle, the device structures and these important features of PC-SELs. The lasing oscillation in blue-violet regime based on GaN PC-SELs (8) will also be discussed.