The apparatus has an optical medium (6-1) placed in the light from the laser diode (1) and with an emission aperture or an outlet aperture smaller than the inlet aperture. A laser medium (7-1) is arranged in contact with the emission aperture of the optical medium and is pumped by the light emitted by the optical medium. The laser diode is a linear array type laser diode and the optical medium can be a conical rod. One side of the conical rod, which is made of an inflexible element or material, is polished to a mirror finish
