Spectral multiplexed VPHG based on photopolymers: the first application on a spectrograph

Many of the current spectrographs available at state-of-the-art telescopes facilities, possess specifications that are strongly limited by the dispersing elements that are used. Therefore, a refurbishment of these devices would potentially increase the performances if innovative designs are considered. We propose a solution for designing stacked VPHG that is able to secure efficiently different spectra in a single shot. This could be possible considering parameters that are specific for a particular class of holographic material, the photopolymers, that are well known for bringing reliability and precise throughput. We demonstrate the applicability of our solution, through the example of the new spectrograph designed for the 1m telescope at SAO RAS. The spectrograph will cover a spectral range 444-706 nm with the spectral resolving power of R=4273-5176 and the throughput maximum of 64%. The working ranges of the gratings are selected to provide more diffraction efficiency around the main important lines used in astrophysics.