Characterization of the Vacuum Birefringence Polarimeter at BMV: Dynamical Cavity Mirror Birefringence

We present the current status and outlook of the optical characterization of the polarimeter at the biréfringence magnétique du vide (BMV) experiment. BMV is a polarimetric search for the quantum electrodynamics predicted anisotropy of vacuum in the presence of external electromagnetic fields. The main challenge faced in this fundamental test is the measurement of polarization ellipticity on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> induced in linearly polarized laser field per pass through a magnetic field having an amplitude and length B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> L = 100 T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> m. This challenge is addressed by understanding the noise sources in precision cavity-enhanced polarimetry. In this paper, we discuss the first investigation of dynamical birefringence in the signal-enhancing cavity as a result of cavity mirror motion.