Gated blue cesium Faraday atomic line filter

We developed and tested a 2 inch aperture, wide field-of-view transmission gated cesium Faraday atomic line filter with ultranarrow passbands at 455 and 852 nm. By modulating the magnetic field of this magneto-optic filter, we were able to obtain a gate of variable duration, typically 1 microsec, with a 20 ns risetime. To minimize the rise time, we operated the filter at a cesium vapor temperature that minimized the magnetic field requirement. To rapidly generate the field over the sizable vapor volume, we minimized the coil inductance at the expense of a high current requirement. The pulsed magnetic field was provided by a pair of single turn `Helmholtz' coils, driven by a square current pulse produced by a spark gap switched pulse forming network.