Frequency-locking of a CW dye laser to the center of the sodium D lines by a Faraday filter

Single-mode CW oscillations at the center of the sodium lines have been achieved by inserting a Faraday filter in an argon-laser-pumped dye laser cavity. The oscillations at the D1and D2lines can be selected by choosing adequate values of the sodium temperature and the magnetic field strength. Experimentally obtained conditions to get the single-mode oscillations at the center of the lines are compared with the theoretically calculated feature of the Faraday filter, and a relatively good agreement has been found. The shifts of oscillation frequencies due to the magnetic field are also discussed.