Concave Diffraction Gratings by High-Precision Injection Moulding

As an example of the applicable process chain, a concave grating (1175 grooves/mm) with an active area of approx. 24 mm to 24 mm has been replicated by means of electroplating and further by injection moulding with polycarbonate, resulting in a surface accuracy even below 4 µm peak-to-valley (PV). The obtained moulds were further metallised with bare aluminium to obtain components for optical applications. To our knowledge, this is the first time that such a large nanostructured nonplanar surface has been manufactured by injection moulding in such an accuracy.