Principal Investigator Jeffrey Shapiro
Co-investigator Franco Wong
Since the introduction of octave-spanning femtosecond comb technology, optical frequency measurements can now be routinely performed using the regularly-spaced comb lines as frequency markers. The comb-based measurement capability can be further enhanced by a 3-to-1 optical frequency divider that provides three strong frequency markers at f, 2f, and 3f, where 3f is the pump frequency for a 3-to-1 optical parametric oscillator (OPO) with outputs at f and 2f. The f and 2f frequency markers can be used to lock two optical frequency combs centered at different spectral regions, thus creating a phase-locked multi-octave-spanning comb. We have utilized a double-grating PPLN crystal to implement the 3-to-1 OPO, and preliminary results show self-phase locking at the f-2f-3f operating point. In the same apparatus we have discovered a novel cascaded parametric oscillation process in which the signal field of the primary parametric oscillator pumps the secondary parametric oscillator. Above the secondary threshold, the primary signal power is clamped and all the other output powers increase linearly with the input pump power, unlike the square-root dependence in a conventional OPO, thus providing a convenient and efficient way to generate multiple tunable outputs.