Patent ID: 7944959

Claim:
A quantum cascade laser amplifier which is capable of emitting infrared laser radiation, and which includes: a lower horizontal layer of a substrate in indium phosphide (InP); an active area which is formed by a vertical stack or horizontal layers of semiconducting materials grown epitaxially on the substrate; an anti-reflection vertical coating which covers a laser radiation output end vertical face and which has a refractive index (n D ) determined so as to let a totality of the laser radiation pass through the output face, the anti-reflection coating including: at least one layer having a first refractive index (n 1 ) smaller than the determined refractive index (n D ); and at least one second layer having a second refractive index (n 2 ) larger than the determined refractive index (n D ); wherein a first layer of the anti-reflection coating is made in yttrium fluoride (YF 3 ).