A very simple scheme for spectrally resolved imaging by means of curved polymeric gratings

We report the fabrication of a simple and inexpensive device based on diffractive optics for spectrally resolved imaging. A brass surface manufactured on a metal lathe and a deformable, reflecting diffraction grating guarantee spatially and spectrally resolved images without the need for other optical elements. The grating is a metal-polymer nanocomposite replica of a plastic grating: reflectivity of the transparent dielectric substrate is obtained by the implantation of gold clusters, hence preserving deformability. The brass surface is a portion of a rotation ellipsoid, on which the deformable grating adheres to gain optical power. According to the optical tests performed on the system, the achieved spatial resolution of the system is ~80 μm, whereas limiting spectral resolution of about 3 nm is observed. Reflectivity of the zero-order reflection and the first order diffraction approaches 45% and 5% respectively. We detail the results for the reconstruction of an on-axis and off-axis pointlike source, and a vertically extended slit-like source with a 110 μm obstruction.