Patent ID: 6922427

Claim:
A quantum cascade laser comprising: a gain region ( 14 ) formed: from several layers ( 20 ) each including alternating strata of a first type ( 26 ) each defining a quantum barrier and strata of a second type ( 28 ) each defining a quantum well, said strata consisting of a first and of a second semiconductor material, respectively constituting said barriers and said wells, and from several injection barriers ( 22 ), each one being formed from a stratum of the first type and interposed between two of said layers ( 20 ), two optical confinement layers ( 12 , 16 ) placed on each side of the gain region ( 14 ), and two electrodes ( 10 ), each one adjoining one of the confinement layers ( 12 , 16 ) in order to apply an electric field thereto, characterized in that the layers ( 20 ) of the gain region ( 14 ) each constitute an active region extending from one to the other of the injection barriers ( 22 ) which are adjacent to it and in which said strata ( 26 , 28 ) are dimensioned such that: each of the wells ( 28 ) comprises, in the presence of an electric field, at least a first upper subband, a second middle subband and a third lower subband, the probability of an electron being present: in the first subband, is highest in the vicinity of one of the adjacent barriers, in the second subband, is highest in the middle part of the active region, and in the third subband, is highest in the vicinity of the other of the adjacent barriers, and the transition of an electron from the upper subband to the middle subband forms the basis for the optical gain.