1 Kerr - lens mode - locked lasers as transfer oscillators for optical frequency measurements

We introduce a novel concept for optical frequency measurement and division which employs a Kerr-lens mode-locked laser as a transfer oscillator whose noise properties do not enter the measurement process. We experimentally demonstrate, that this method opens up the route to phase-link signals with arbitrary frequencies in the optical or microwave range while their frequency stability is preserved. 1. Introduction Continuous-wave mode-locked lasers emit a periodic train of short pulses. The spectrum of this emission corresponds to a comb of distinct lines with well-defined spacing if the mode-coupling mechanism is sufficiently strong and fast. It has been shown that the non-resonant, electronic Kerr-lens mode-locking (KLM) process can satisfy this requirement [1], making such lasers highly suited for optical frequency measurements [2], [3], [4]. The frequency of any line of the spectral comb emitted by such a KLM laser is given by an integer order number m, the pulse repetition frequency f rep and a so called carrier-envelope offset-frequency ν ceo , which accounts for the offset of the entire comb with respect to the frequency zero: