Effects of non-lasing band in two-dimensional photonic-crystal lasers clarified using omnidirectional band structure.

We investigated the effects of non-lasing bands on the beam patterns in photonic-crystal lasers by evaluating the omnidirectional band structure both experimentally and theoretically. We found that a new, weak dual-streak pattern is occasionally generated around the main lobe of the output beam because of scattering of the lasing beam in the non-lasing bands despite a wavenumber mismatch. This result indicates that we can design the high-quality devices without such a noise pattern. In addition, this evaluation method is expected to be useful for developing various high-functionality PC lasers.