Abstract: Volume-Phase Holographic (VPH) gratings provide uniquecapabilities over classical surface gratings which canbe exploited in modern astronomical spectrographs. Thepeak diffraction efficiency of a VPH grating is tunabledue to the nature of Bragg diffraction. This allows asingle dispersing element to serve the function ofseveral classical gratings. Additionally, VPH gratingstructures can be stacked to produce complex gratingscapable of directing the diffracted light in ways thatclassical gratings can not.!3
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