The invention disclosed here teaches methods and apparatus for altering the temporal and spatial shape of an optical pulse. The methods correct for the spatial beam deformation caused by the intrinsic DC index gradient in a volume holographic chirped reflective grating (VHCRG). The first set of methods involves a mechanical mean of pre-deforming the VHCRG so that the combination of the deflection caused by the DC index gradient is compensated by the mechanical deformation of the VHCRG. The second set of methods involves compensating the angular deflection caused by the DC index gradient by retracing the diffracted beam back onto itself and by re-diffracting from the same VHCRG. Apparatus for temporally stretching, amplifying and temporally compressing light pulses are disclosed that rely on the methods above.
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