Abstract: An harmonic generator system for generating at least two output beams (6a, 6b, 6c) of higher order harmonic radiation from an input beam (1) of radiation of frequency .omega. comprises at least two non linear optical crystals (3a, 3b, 3c) arranged in series. Radiation output from each crystal stage has first and higher order harmonic components. Chromatic separators (5a, 5b, 5c) separate beams of radiation output from each crystal and selected beams are then passed through a telescope (9a, 9b) to the next crystal in the series, thereby generating further radiation beams of first and higher order harmonics. Multiple beams of second, 2.omega., third 3.omega., or fourth, 4.omega., harmonic radiation may be output from the system and may be used to pump various stages of a secondary laser system or an optical parametric oscillator. Alternatively, the output beams of higher order harmonic radiation may be coherently combined to form a single output.

Abstract: A tracked vehicle with a rearwardly extending ram (13) and an energizing means (14) for the ram, for assisting the vehicle in mounting precipitous objects. A preferred vehicle configuration uses only three, track direction changing rollers (6, 7, 8) so as to locate the center of gravity (16) of the vehicle as far forward as possible.