We demonstrate what is to our knowledge the first atomic optical filter that uses velocity selection to achieve a passband width that is less than the Doppler width of the filtering transition. A narrow-linewidth pump laser is used to induce circular birefringence in a narrow velocity class of atoms in a dense potassium vapor for 694-nm light resonant with the 4<i>P</i><sub>3/2</sub>–6<i>S</i><sub>1/2</sub> transition. The filter displays a single 170-MHz passband at a peak transmittance of 9.5%. The bandwidth is an order of magnitude lower than that of previously demonstrated atomic optical filters.
© 2002 Optical Society of America
L. D. Turner, V. Karaganov, P. J. O. Teubner, and R. E. Scholten, "Sub-Doppler bandwidth atomic optical filter," Opt. Lett. 27, 500-502 (2002)