The optical design of the Einstein Telescope (ET) is based on a dual-recycled Michelson interferometer with Fabry-Perot cavities in the arms. ET will be constructed in a new infrastructure, allowing us to consider different technical implementations beyond the constraints of the current facilities. In this paper we investigate the feasibility of using beam-expander telescopes in the interferometer arms. We provide an example implementation that matches the optical layout as presented in the ET design update 2020. We further show that the beam-expander telescopes can be tuned to compensate for mode mismatches between the arm cavities and the rest of the interferometer.
@article{arxiv.2011.02983,
title = {Feasibility study of beam-expanding telescopes in the interferometer arms for the Einstein Telescope},
author = {Samuel Rowlinson and Artemiy Dmitriev and Aaron Jones and Teng Zhang and Andreas Freise},
journal= {arXiv preprint arXiv:2011.02983},
year = {2021}
}