  Silicon immersion gratings and grisms enable compact, near-infrared
spectrographs with high throughput. These instruments find use in ground-based
efforts to characterize stellar and exoplanet atmospheres, and in space-based
observatories. Our grating fabrication technique uses x-ray crystallography to
orient silicon parts prior to cutting, followed by lithography and wet chemical
etching to produce the blaze. This process takes advantage of the crystal
structure and relative difference in etching rates between the (100) and (111)
planes such that we can produce parts that have surface errors < {\lambda}/4.
Previous measurements indicate that chemical etching can yield a final etched
blaze that slightly differs from the orientation of the (111) plane. This
difference can be corrected by the mechanical mount in the case of the
immersion gratings, but doing so may compromise grating throughput due to
shadowing. In the case of the grisms, failure to take the actual blaze into
account will reduce the brightness of the undeviated ray. We report on multiple
techniques to precisely measure the blaze of our in-house fabricated immersion
gratings. The first method uses a scanning electron microscope to image the
blaze profile, which yields a measurement precision of 0.5 degrees. The second
method is an optical method of measuring the angle between blaze faces using a
rotation stage, which yields a measurement precision of 0.2 degrees. Finally,
we describe a theoretical blaze function modeling method, which we expect to
yield a measurement precision of 0.1 degrees. With these methods, we can
quantify the accuracy with which the wet etching produces the required blaze
and further optimize grating and grism efficiencies.
