Demonstration of vacuum strain effects on a light-collection lens used in optical polarimetry

Abstract

The precision by which an electron spin polarization measurement can be made using a noble-gas polarimeter depends directly on the accuracy of a light-polarization measurement. Since the electron–noble gas collisions occur in a vacuum chamber and the optical polarimeter is generally outside the chamber, this work examines the effect the vacuum window has on the perceived optical polarization. A model light source, lens system, and optical polarimeter are used that approximate the situation found in a typical atomic physics experiment. It was demonstrated that a pressure difference of 1 atm on a lens will alter the perceived polarization by as much as 0.05% with typical borosilicate (BK) lenses. This effect was demonstrated to scale with the thickness of the lens used and changes signs when the direction of the stress is reversed.

Collection of dim light for accurate optical polarimetry by a plano-convex spherical lens

“…Concurrent work with the AESOP high-accuracy polarimeter shown in figure 1 reveals that the uncertainty in the optical characteristics of the analyzing retarder is one of the largest contributors to overall uncertainty in a polarimetric measurement [7]. Additionally, Trantham et al have recently shown that imperfections in the lens can also contribute to errors in polarimetric measurements [9].…”

“…Accurate optical polarimetry plays an important role in, for example, astronomical observations [1,2], magneto-optical Kerr studies of magnetized surfaces [3,4], and atomic parity violation experiments [5,6]. Recently, it has been proposed that a calibration standard for highly precise Mott electron polarimetry could be based on measuring the fluorescence polarization of atoms excited by spin-polarized electrons to better than 0.1% of the Stokes parameters being measured (Accurate Electron Spin Optical Polarimetry-AESOP) [7][8][9]. Indeed, the precise measurement of atomic fluorescence polarization has served as an invaluable tool for the study of many aspects of electron-atom collisions [10,11].…”