THRESHOLD CURRENT-DENSITY CALCULATIONS FOR FAR-INFRARED SEMICONDUCTOR-LASERS

We study theoretically the conditions for achieving lasing action at infrared and far-infrared wavelengths based on intersubband transitions in semiconductor quantum well structures, taking into account resonant tunnelling and intersubband absorption-emission processes. Analysis of optical losses in the semiconductor quantum well structures reveals that a reasonably low threshold current density in the range of 1-5 kA cm-2 is achievable for room temperature lasing at emission wavelength of lambda = 60 mum. A significantly higher threshold current density of 40-50 kA cm-2 is required for lasing at lambda = 10 mum.