Electrically switchable, two-color quantum cascade laser emitting at 1.39 and 2.3THz

Abstract

A quantum cascade laser emitting at 1.39 and $2.3\mathrm{THz}$ is demonstrated. The structure is based on a large single quantum well and multiwavelength operation is obtained by selectively injecting carriers by resonant tunneling in the excited states of the well. A magnetic field applied perpendicularly to the layers increases the gain enabling laser action. Extremely low values of the threshold current density (below $30\mathrm{A}∕{\mathrm{cm}}^2$ ) are observed for both wavelengths. A study of the dependence of the laser emission intensity as a function of the applied magnetic field is also presented.