Abstract: The present invention relates to a laser amplification system (1). The system (1) is constituted by a laser light source (2) for providing a main laser beam (LB); a laser light amplifier (3) for amplifying the main laser beam (LB) and apparatus for supplying a bleed laser beam (BO) to the laser radiation amplifier (3). The bleed laser beam (BO) is amplified by the laser radiation amplifier (3) at least when the main laser beam (LB) has a low or zero power valve substantially to prevent super-radiance.

Abstract: A laser optical cavity extends between two end reflectors (11, 12) and is defined by at least three sections. A number of folding reflectors (14) are provided for directing radiation emerging from one section into the next. An active medium is contained in the sections and excitation means are provided to produce laser action. A rigid support member (10) supports the end reflectors (11, 12) and the folding reflectors (14) around a generally cylindrical surface such that a continuous optical path extends between the end reflectors (11, 12) by way of each folding reflector (14) in turn. At least three of the laser sections extend across a substantial part of the area with the cylinder (10) and each section crosses at least one other section at or near to the axis of said cylinder as viewed along that axis.