The invention relates to a
quantum cascade device of
detector type comprising two electrodes for applying a control electrical field, and a
waveguide positioned between the two electrodes, said device comprising a
gain region made up of a plurality of
layers and comprising alternating strata of a first type each defining a
quantum barrier and strata of a second type each defining a
quantum well, each layer of the
gain region comprising an injection barrier exhibiting an injection subband of charge carriers with a lower
energy level called
injector level (i) and an active area, said active area being made of a set of pairs of strata made from semiconductive materials so that each of the wells has at least one upper subband called third subband (3), a middle subband called second subband (2) and a bottom subband called first subband (1), the
potential difference between the third and second subbands being such that the transition of an
electron from the third subband to the second subband emits an energy corresponding to that needed for the emission of a
photon, characterized in that:the active area also has a fourth subband (4) situated above the third subband;said fourth subband being such that, in the absence of any electrical field applied to the electrodes, the
injector level of the injection barrier is less than the level of said fourth subband and greater than the level of the third subband and that, in the presence of a field applied to the electrodes, the
charge carrier injector level (i) becomes greater than or equal to the level of the fourth subband, so as to generate a rapid relaxation phenomenon between the injector level and the fourth subband, the fourth subband being at a distance energy-wise from the third subband allowing an optical
phonon relaxation.