PGL diffraction gratings are manufactured using a variety of substrate sizes, shapes, and materials, determined by optical and mechanical performance requirements of the final product.
Generally rectangular shapes are preferred for end-use and production reasons. For reflection gratings with good diffracted wavefront performance, the thickness should be nominally about 1/6 of the transverse dimensions, with a maximum thickness of 100 mm.
Fused silica is an ideal material choice for most applications due to its excellent stiffness and thermal expansion coefficient combined with its availability, manufacturability, and reasonable cost. For the most demanding wavefront error requirements, especially in thermally sensitive applications, ultralow-expansion glass like Corning ULE® is a good choice. In some cases low-expansion glass ceramics like CLEARCERAM-Z® and ZERODUR® may also be used. Other materials are possible but typically require compromise on some aspects of performance, or cost, or both.
PGL utilizes grooves on the sides of its rectangular substrates to facilitate handling during manufacturing as well as final mounting of the gratings. The following groove profiles are standard for PGL. Other groove profiles are possible but generally add cost and lead time to the grating manufacturing process.
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