ELT-HIRES the High Resolution Spectrograph for the ELT: simulation results of polarimetric aberrations for the Polarimetric module

摘要

ELT-HIRES (High Resolution Spectrograph for the Extremely Large Telescope) is a multifold fiber-fed spectrographplanned for the Nasmyth B focal station on ELT, with a large spectral coverage, ranging from 0.4 to 1.8 μ. It’s our intentionto equip it with a full Stokes polarimetric facility, feeding the UBVRI and the zYJH bands. Among the most relevantscientific targets there is the detection of life signature in the extrasolar atmospheres for Earth-like planets. The polarimetricinstrument will consist of two subunits: the main one intended to be installed in the intermediate focus where the opticalbeam is split into the two polarized components via a double Wollaston calcite prism; the other one installed in one of thefour arms of the Front End on the Nasmyth platform, in charge of the atmospheric dispersion correction, field stabilizationand selection of the operating modes before the fiber injection.This has been presented for the Phase A as the only possible design solution fulfilling the top level requirement of reachinga sensitivity of 10~(-5) S/I (with S equivalent to one of the Stokes vectors), condition achievable only if the polarizers areinstalled in a rotationally symmetric focus.In the present work we illustrate novel simulations of the polarized aberrations based on an integration of the structuraland thermal FEM analysis within a Zemax design with the help of Matlab and Python tools.