Intersubband light source with separate electron injector and reflector/extractor

An intersubband semiconductor laser comprising:

• a core region including a unipolar, undoped radiative transition (RT) region, an injector-only (I) region disposed on one side of said RT region and a reflector-only (R/E) region disposed on the other side of said RT region,
• said RT region comprising a plurality of GaInAs quantum well (QW) layers interleaved with a AlInAs barrier layers, said QW layers being sufficiently coupled to one another to produce an upper energy level and a lower energy level between which a single lasing transition takes place,
• said I region having a first miniband of energy levels aligned so as to inject electrons into said upper energy level, and said R/E region having a second miniband of energy levels aligned so as to extract electrons from said lower energy level and also having a minigap aligned so as to inhibit the extraction of electrons from said upper level, said upper energy level being centrally aligned with respect to said minigap,
• upper and lower cladding regions bounding said core region,
• an optical cavity resonator, said core region being disposed in said resonator, and
• electrodes for applying a voltage of less than about 3 V, and for applying current above the lasing threshold, to said laser effective to cause electrons in said RT region to undergo said transition and to generate stimulated emission of light at a wavelength determined by the energy difference between said upper and lower energy levels.