Modern experiments for the investigation of cold atom ensembles require an ultra-high vacuum apparatus with a very large optical access and an accurate preservation of the state of polarization of laser beams. Typical ultrahigh vacuum cells suffer from residual stress-induced birefringence, which deteriorates the polarisation's purity. In addition, birefringence gradients prevent the full compensation of birefringence. This effect effectively limits the extinction ratio to > 10-5. We recently filed a patent application regarding an ultralow birefringence ultra-high vacuum cell, which exhibits an extinction two orders of magntitude smaller.