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Abstract

A system for generating pulses of laser radiation which vary in frequency with time to achieve a chirp or frequency sweep in which single or multiple laser spectra in the form of mode lines are displaced or shifted in frequency during the generation of the laser pulse. The system provides for the mode line shift through the use of an optical wedge which moves tranversely through one of the optical paths utilized in the optical loop to generate the laser pulse. This provides a linear increase with time in the optical path length so as to perturb the wavelength of oscillation of the laser output, which results in a linear chirp. In a preferred embodiment a number of prisms of optically dense material with a wedge-like profile are mounted on a rotating disc. When the disc with the prisms is interposed in the optical loop of an injection locked laser oscillator, successive prisms traverse the laser's optical loop. In a further embodiment, pairs of identically configured optical elements are located on diametrically opposite sides of the rotating disc so as to remove any beam position jitter introduced by shaft wobble, prism misalignment or refraction angle changes due to input beam angle deviation, with the second prism of the pair cancelling errors introduced by the first prism of the pair. To further reduce errors, all prisms are positioned at the point of minimum deviation.

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First Claim