Abstract

Doubly-resonant synchronously pumped optical parametric oscillators (SPOPO) have been established as one promising method to extend wavelength range of frequency combs to the mid-infrared spectral region. Wong et al. demonstrated that in degenerate operation, when signal and idler fields are indistinguishable, that the common carrier-envelope offset (CEO) frequency f_ceo(s,i) is automatically locked to the one of the pump laser f_ceo(p) [1]. In non-degenerate operation, where signal- and idler comb are spectrally separated and clearly distinguishable, their offset frequencies f_ceo(s) and f_ceo(i) are in general different. It was shown that the constraint of the double resonance condition fixes the slope Δf_ceo(s) / Δf_ceo(p) to ν_s / ν_p, where ν_s and ν_p are the optical frequencies of signal and pump comb, respectively [2]. A “partially degenerate” regime, where signal and idler combs are distinguishable but spectrally overlapping exhibits interesting dynamic behavior and was first described in [3].

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