No abstract

No abstract

We fabricated surface-emitting quantum cascade lasers with photonic crystal resonators whose active layers were strain-compensated InGaAs/AlInAs multiple quantum wells to operate at 4.3 μm. We tested two kinds of square-lattice photonic crystals consisting of circular and pentagonal InGaAs cylinders as a unit structure. We examined their output power and far-field pattern to find that both of them were improved by lowering the photonic-crystal symmetry to achieve a high extraction efficiency. The maximum output power was 50 mW at 77 K and the far-field pattern was a single peak with a divergence angle smaller than 1° for the pentagonal cylinder structure. In addition, we attributed the lasing mode to a B2-symmetric (quadrupole) eigen state on the Γ point for the circular cylinder structure by observing the polarization dependence of the far-field pattern and comparing it with calculations by the k·p perturbation method.

No abstract