Mid-IR Faraday optical filter with an ultra-narrow single transmission peak at 5.33 μm

Abstract

We present a theoretical and experimental study of a mid-infrared Faraday optical filter (MIFOF) with an ultra-narrow single transmission peak. The typical representative of paramagnetic molecules, gas-phase nitric oxide (NO), is selected as the working material. We focus on the transmission of such a filter operating on a Q(3/2) transition, and its dependence on the strength of the magnetic field. This MIFOF simultaneously achieves a peak transmission of 52%, an equivalent noise bandwidth (ENBW) of 444 MHz, and an out-of-band rejection ratio of 2 × 104, for a magnetic field of 17 mT and a NO pressure of 10 mbar.