A device for magnetic-field angle control in magneto-optical filters using a solenoid-permanent magnet pair

TL;DR

This paper introduces a novel device combining a solenoid and permanent magnets to precisely control the magnetic-field angle in atomic bandpass filters, improving accuracy and ease of adjustment over previous methods.

Contribution

A new method using a solenoid-permanent magnet pair for arbitrary magnetic-field angle control in magneto-optical filters is proposed and experimentally validated.

Findings

The new device produces magnetic fields similar to traditional methods.

Filter transmission profiles are consistent across different magnetic field generation methods.

The device allows precise and adjustable control of the magnetic-field angle.

Abstract

Atomic bandpass filters are used in a variety of applications due to their narrow bandwidths and high transmission at specific frequencies. Predominantly these filters in the Faraday (Voigt) geometry, using an applied axial(transverse) magnetic field with respect to the laser propagation direction. Recently, there has been interest in filters realized with arbitrary-angle magnetic fields, which have been made by rotating permanent magnets with respect to the $k$-vector of the interrogating laser beam. However, the magnetic-field angle achievable with this method is limited as field uniformity across the cell decreases as the rotation angle increases. In this work, we propose and demonstrate a new method of generating an arbitrary-angle magnetic field, using a solenoid to produce a small, and easily alterable, axial field, in conjunction with fixed permanent magnets to produce a large transverse field. We directly measure the fields produced by both methods, finding them to be very similar over the length of the vapor cell. We then compare the transmission profiles of filters produced using both methods, again finding excellent agreement. Finally, we demonstrate the sensitivity of filter profile to changing magnetic-field angle (solenoid current), which becomes easier to exploit with the much improved angle control and precision offered by our new design.