NCTU Nanophotonics

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Photonic crystal surface emitting lasers

Photonic crystals (PCs) with photonic band gaps for photons have many advantages in arbitrarily controlling the light emission and propagation and can be utilized to realize various new optical devices. For example, semiconductor PC lasers have emerged as a versatile building block to construct photonic circuitry. Two kinds of semiconductor PC lasers have been developed. One is the photonic crystal nanocavity laser with a high Q value within a small modal volume resulting in strong Purcell effect and low-threshold lasing. The other is the two-dimensional (2D) surface emitting photonic crystal laser based on multidirectionally distributed feedback effect near the band edges in a 2D PC structure, which has potential for high-power and single mode surface-emitting lasers. Many works have been done mainly using organic, GaAs and InP material systems. However, few GaN-based PC lasers have been reported yet. Nitride-based materials have attracted a great attention in the early 1990s due to the large direct band gap and the promising potential for the optoelectronic devices, such as light emitter diodes and laser diodes. We recently demonstrated the fabrication and the room temperature lasing action of GaN-based 2D surface-emitting PC structures with bottom AlN/GaN distributed Bragg reflectors. We also developed multiple scattering method and two dimensional coupled wave method to calculate the threshold gain, mode frequency and mode patterns for PCSELs. GaN-based PCSELs with honeycomb lattice show great laser characteristics and could be potential for high power applications such as laser display, projection and solid state illumination systems in the near future.