Low threshold quantum-cascade lasers of room temperature continuous-wave operation grown by metal-organic chemical-vapor deposition

Very low threshold current densities are reported from buried heterojunction quantum-cascade laser (QCL) grown by metal-organic chemical-vapor deposition at an emission wavelength of 5.07μm. Continuous-wave operation threshold current densities as low as 0.75 and 0.83kA∕cm2, efficiencies of 1079 and 879mW∕A, and total output powers of 116 and 74mW have been achieved for temperatures of 288 and 298K. These cw threshold current densities are lower than all previously reported values for Fabry-Pérot QCLs. Internal loss as low as 1.84cm−1 has been extracted; also the lowest value thus far reported in the literature.