A Martin–Puplett interferometer (MPI) optical polarimeter: Design and laboratory tests

Abstract

Spontaneous and external magnetic fields interacting with plasmas are essential in high-energy-density and magnetic confinement fusion physics. Measuring these magnetic fields, especially their topologies, is crucial. This paper develops a new type of optical polarimeter based on the Martin–Puplett interferometer (MPI), which can probe magnetic fields with the Faraday rotation method. We introduce the design and working principle of an MPI polarimeter. With the laboratory tests, we demonstrate the measurement process and compare the results with the measurement result of a Gauss meter. These very close results verify the polarization detection capability of the MPI polarimeter and show the potential for its application in magnetic field measurement.

Probing the peripheral self-generated magnetic field distribution in laser-plasma magnetic reconnection with Martin–Puplett interferometer polarimeter

“…From Eq. 2.5 in Zhang et al (2023), [16] we can find that the intensity of interference fringes obtained after the MPI polarimeter depends on (i) the polarization direction of the input probe light θ and (ii) the phase difference at each CCD pixel ∆ϕ. For the polarized light at a specific angle, i.e., θ is fixed, the intensity at a specific pixel is fixed.…”

“…This results in fringes of equal inclination interference, which is described by Eq. 2.5 in Zhang et al (2023) [16]…”

“…. [16] The intensity is normalized in this plot. The intensity changes periodically with both polarization angle θ and phase difference ∆ϕ.…”

“…[12,13] In laser-plasma experiments, the commonly used mag-netic field detection methods are proton photography [14] and magnetic probe [15] methods, while the cases of optical diagnostic methods for probing magnetic fields are relatively limited. Here we use the new type of optical polarimeter based on the Martin-Puplett interferometer (MPI) [16] to probe the peripheral self-generated magnetic field distribution in laserplasma MR. MPI polarimeter is developed for probing magnetic fields with the Faraday rotation method. [17] Utilizing the polarization characteristics of MPI can overcome the depolarization problem of the probe light and the response difference problem of separated images in traditional diagnostic methods.…”

“…According to Eqs. 2.3-2.5 in Zhang et al (2023), [16] the resulting intensity after interference is determined by the phase difference and the polarization angle. For each pixel at a fixed position, the intensity varies as a sinusoidal function of the polarization angle.…”