Kerr-lens mode-locked lasers for optical frequency measurements

The frequency of the intercombination line P-3(1) - S-1(0) Of Calcium at 657 nm is phase-coherently measured in terms of the output of a primary cesium frequency standard using an optical frequency comb generator comprising a < 10 fs Kerr-lens mode-locked Ti:Sapphire laser and an external microstructure fiber for self-phase-modulation. The measured frequency value of v(Ca) = 455 986 240 494 276 Hz agrees within its relative uncertainty of 4x10(-13) with die values previously measured with a traditional harmonic frequency chain and the value recommended for the realization of the SI unit of length. Furthermore, we investigate the coherence properties of the broadened frequency comb and find no indications for incoherent scattering processes in the microstructure fiber.