CW-OPO referenced to an optical frequency comb: precise frequencies in the mid-IR

The central concept of a frequency comb is that the pulse train generated by a mode-locked laser corresponds to a frequency spectrum consisting of discrete, regularly spaced comb lines which provide precise frequency measurements. On short time-scales (tens of μs), the emission linewidths of continuous-wave optical parametric oscillators (cw-OPOs) can be very small and the frequency can be set freely inside the emission band. This makes them very promising candidates for high power precision frequency sources in the mid-IR. This paper describes how to combine both systems for accurate frequency measurements and ultra-stable laser light generation in the mid-infrared.