Thermal behavior and production capabilities of photopolymer-based VPHGs

Volume Phase Holographic Gratings (VPHGs) are dispersing elements employed in astronomical spectrographs thanks to their high diffraction efficiency. The possibilities of optimizing VPHGs in the Vis-NIR are reported showing the diffraction efficiency and the effect of residual absorption. As holographic materials, photopolymers are chosen especially thanks to the self-developing. The stability of the VPHGs at different temperatures is evaluated and no variations are apparent up to 80°C for weeks. At 100°C, a drop in diffraction efficiency occurs and the reasons are under investigation. Finally, the results in the transmitted wavefront are reported in terms of RMS value, providing useful data for the design of VPHGs in situations that need a control of the wavefront error.