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Holography represents a very elegant and versatile method for the manufacturing of high-performance diffraction gratings. This is particularly true within the frame of space applications, e.g., for utilization in customized, high end optical spectrometers. Holography enables both symmetrical (sinusoidal or binary) and blazed groove profiles on arbitrarily shaped substrates, ranging from plane over spherical to freeform surfaces. In addition, holographic recording of grating lines is not restricted to straight lines of constant density (either on a plane surface or on a plane projection plane above a curved substrate figure) but can rather be deterministically controlled to yield defined groove distortions and locally varying groove densities. Being able to control not only the groove density but also grooves local curvature represents a major advantage for the optical design of spectrometers, since it adds another degree of freedom to the design – enabling improved focusing and / or aberration correction features within the grating surface. In contrast to frequently encountered misbeliefs, it is shown that holography can also address very low groove density gratings with periods well above 10 µm (i.e. g < 100 lines/mm). Furthermore, two strategies are presented that allow for flattening a grating’s spectral diffraction efficiency (which is often of particular importance for gratings with low groove density): (1) multi-zone gratings with zone-wise varying blaze wavelength and (2) “kinked” groove profiles with more than just one effective blaze facet within the grating period.
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