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Collimation of diode laser beams with a single holographic diffractive element

Holographic diffractive optical elements collimating highly divergent, elliptical and astigmatic edge emitted diode laser beams are analyzed. Elements are recorded using only divergent beams with spherical wavefronts while off-axis astigmatism and coma of the holographic recording arrangement are compensated in a narrow beam approximation. Because of the very asymmetrical recording setup, significant blazing properties are present. Two types of the collimators are proposed: one for obliquely and the other for perpendicularly incident laser beam. Astigmatic properties of the output beams were measured in the reverse setup, i.e. when the collimated laser beams impinge on elements from their back side. Comparison of the advantages and drawbacks of both arrangements is presented.