Spatial hole burning and oligo-mode distance control in CW dye lasers

Spatial hole burning at the position of the dye cell is identified to be responsible for stable double-, triple-, and higher oligo-mode action in a narrow-band CW dye laser. This may be exploited systematically to control the mode distances by arranging the positions of both resonator end mirrors. A total output power up to over 100 mW is obtainable for double- or triple-mode action. Special conditions are described to obtain stable double-mode action with 1772-MHz mode spacing, as needed for simultaneous optical pumping of the two sodium hyperfine ground states.