Room temperature lasing of single-mode arched-cavity quantum-cascade lasers

Single-mode lasing at room temperature in quantum-cascade lasers (QCLs) with arched cavity design has been demonstrated. The output optical power in single-mode lasing regime at $\sim$7.7-$\mu$m lasing wavelength was above 6 mW with a side-mode suppression ratio of up to 25 dB. The QCL heterostructure for the arched cavities was grown by molecular-beam epitaxy (MBE) based on a heterojunction of In$_{0.53}$Ga$_{0.47}$As/Al$_{0.48}$In$_{0.52}$As solid alloys, lattice-matched with InP substrate, and InP layers performing the function of waveguide claddings.