THZ QUANTUM CASCADE LASER WITH MICRO-DISC RESONATOR AND VERTICAL EMISSION BY A SECOND-ORDER GRATING

A semiconductor laser includes a laser resonator (1) having a planar active region (3), a first (2) and a second (6) wave-guide layer that define the active region (3). The resonator (1) has a shape that is defined by a perimeter, along which the first layer (2) radiation guide has a plurality of cuts (4) forming a lattice. The cuts are made as at least two adjacent slits (4a, 4b) and a zone between the slits in which an uncut portion (5a) of wave-guiding layer is present. In the case of a circular semiconductor laser, the number of cuts (4) is a prime number, or an odd number that is a multiple of a prime number, the prime number being greater than or equal to five. This way, it is avoided that resonance modes evolve outside of the zone with the cuts, or in any case with a component that is different from zero of the wave vector in a radial direction, and a pure whispering gallery operating mode is obtained, with maximum of the emitted radiation that evolves in a vertical direction, i.e. orthogonal to the plane of the laser resonator, and without the laser emitting radiation evolving in a radial direction.