Abstract. An actively mode-locked dye laser is experimentally investigated. Coupling the laser resonator to an empty external cavity (passive feedback control) is found to dramatically influence the mode-locking performances. Under certain feedback conditions a large improvement of the known capabilities of the actively mode-locked dye lasers is obtained. Operation on the femtosecond time scale is demonstrated at considerably increased output powers and with the tunability preserved. Further, the laser is insensitive to unusually large cavity length variations.

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