Analysis of grating-coupled surface-emitting lasers

Grating-coupled surface-emitting diodes are modeled and analyzed in terms of radiation power, threshold gain, and saturation effects. We find that the dominant (i.e., the lowest-loss) mode radiates poorly, while a weaker mode has a much higher radiation power and appears dominant if only the radiated power is measured. The weakly radiating mode effectively lowers the device efficiency and broadens the far-field radiation pattern. We also show that an increase in the length of the distributed Bragg reflector sections at the end can double the radiated power and reduce the threshold gain.