LECTURER : Andrea Bianco

AFFILIATION: INAF-Osservatorio Astronomico di Brera

TITLE: High efficiency diffraction gratings for astronomy: the case of VPHGs

ABSTRACT: Modern astronomical spectrographs working in the optical and
infrared require tailored dispersing elements to provide the desired
resolution and dispersion. In order to maximize the instrument throughput,
the dispersing elements must show a high efficiency since they have an
important impact on the final performances. Volume Phase Holographic Gratings
(VPHGs) are dispersing elements suited for the application in such instruments,
since they can be tailored according to the requirements, they are robust
and can show diffraction efficiency often larger than 90%. For these reasons,
they are considered the baseline in the field of optical spectrographs. At the
INAF-Osservatorio Astronomico di Brera, we design and manufacture high performance
VPHGs based on innovative technologies. More than 10 elements are now mounted
on observing facilities around the world and a new facility to produce large
size VPHGs (up to 450 mm in diameter) is is being built. In this talk, the
performances of these elements will be presented through some examples.