Volume phase holographic echelle grating: a theoretical study

Volume phase holographic gratings (VPHGs) are becoming fundamental dispersing elements in astronomical instrumentation. Here it will be described the efficiency behavior of such dispersing elements at high diffraction orders for understanding the possible use as echelle gratings. The efficiency is calculated based on RCWA analysis and different parameters are changed/optimized, i.e film thickness, refractive index modulation and profile. The results show that the VPHGs are not suitable for working at high orders in the classical configurations.