Mode selection in a spectrally homogeneously broadened CW laser due to spatially inhomogeneously saturable absorption

A novel method is proposed for selecting a single longitudinal mode in lasers with homogeneously broadened gain medium. Mode selection is achieved by the interaction of the standing cavity wave between the gain medium and a spatially saturated absorber. The theory is treated in detail for various geometric configurations including examples of important laser systems under continuous-wave operation, such as dye lasers.