Quantum cascade lasers with electrically tunable emission wavelengths

A tunable quantum cascade laser comprising:

• an optically active region including at least one cascaded stage comprising an injection section and an active section, wherein the injection and active sections are separated by a barrier layer and comprise multiple quantum well layers and barrier layers, and each active section supports electronic states that provide for a lasing optical transition whose energy separation is controlled by the application of an applied electric field;
• means for pumping electrons through the active region by applying a bias voltage to the optically active region with a pair of conducting layers disposed on opposite sides of the optically active region;
• means for modulating a transverse electric field in the optically active section of each cascaded stage after a lasing threshold is reached by changing the bias voltage that is applied to the optically active region by the pair of conducting layers thereby modulating wavelengths of laser light emitted in the lasing optical transition between electronic states in the active section of each cascaded stage;
• a region located proximal to one side of the optically active region comprising a grating structure that provides for wavelength selective reflections of optical waves propagating through the optically active region;
• and
• means for confining optical waves to the active section.