Abstract: An interband cascade laser amplifier medium having an amplifier region (V) comprising a hole quantum film (1) comprising a first semiconductor material and an electron quantum film (2) comprising a second semiconductor material, an electron collector region (K) comprising at least one collector quantum film (4) comprising a third semiconductor material and separated by a first barrier layer (3), and an electron injector region (I) following the latter and comprising at least one injector quantum film (5) comprising a fourth semiconductor material and separated by a second barrier layer (3). The first semiconductor material of the hole quantum film (1) is a III-V compound semiconductor comprising at least four elements, at least two of the elements selected from Ga, In and Al, and at least two of the elements selected from As, Sb, P and N. The amplifier medium exhibits an efficient laser emission at wavelengths above 2.5 ?m.