Sodium-vapor dispersive Faraday filter.

Ultranarrow bandpass Na vapor dispersive Faraday filters at 589 nm are studied experimentally and theoretically. Their anticipated performance in the line-center operation is demonstrated experimentally with a thin Na cell in an axial magnetic field of 1750 G. A peak vapor transmission of 85%, a FWHM linewidth of 0.002 nm (or 1.9 GHz), and a background transmission of 2 x 10(-5) have been achieved.