Faraday Rotation Measurements in High-Energy-Density Plasmas Using Shaped Laser Beams

Abstract

Magnetic fields play an important role in plasma dynamics, yet it is a quantity difficult to measure accurately with physical probes, whose presence disturbs the very field they measure. The Faraday rotation (FR) of a polarized beam of light provides a mechanism to measure the magnetic field without disturbing the dynamics and has been used with great success in astrophysics and high-energy-density plasma science, where physical probes cannot be used. However, the rotation is typically small, which degrades the accuracy of the measurement. Since polarization cannot be measured directly, detectors rely on a polarizer to measure a small change in beam intensity instead. In this work, we show how beam shaping can improve FR measurements using an optical derivative setup. Since the rotation measurement is now strictly proportional to the beam shape and intensity, the system allows to improve the measurement accuracy simply by increasing the laser beam power.