  We demonstrate a tunable, narrow-band filter based on optical-pumping-induced
circular dichroism in rubidium vapor. The filter achieves a peak transmission
of 14.6%, a linewidth of 80 MHz, and an out-of-band extinction >35 dB. The
transmission peak can be tuned within the range of the Doppler linewidth of the
D1 line of atomic rubidium at 795 nm. While other atomic filters work at
frequencies far from absorption, the presented technique provides light
resonant with atomic media, useful for atom-photon interaction experiments. The
technique could readily be extended to other alkali atoms.
