Phase-mismatched optical parametric oscillators based on aperiodic quasi-phase-matched crystals.

We present that femtosecond optical parametric oscillators (OPOs) based on aperiodic quasi-phase-matched (AQPM) crystals can be configured to operate in the "phase-mismatched" region. The phase-mismatch-induced frequency chirp is mainly introduced by the subcrystal that first interacts with pump pulses. By optimizing the intracavity group velocity dispersion and by selecting the direction of crystals, OPOs based on AQPM crystals could support the generation of wavelength-tunable, transform-limited pulses in an all-normal-dispersion cavity. In a preliminary experiment, transform-limited optical pulses with a tuning range over 1520-1660 nm were obtained by simply altering the cavity length. This scheme represents a unique and concise scheme of producing widely tunable, chirp-free femtosecond optical pulses.

Tunable femtosecond optical parametric oscillators resonating at 0.65-1.02†µm and 1.07-2.3†µm.

We present a singly resonant femtosecond optical parametric oscillator (OPO) cavity architecture supporting ultra-broadband wavelength tuning and efficient outcoupling of the generated optical pulses. Experimentally, we demonstrate an OPO with its oscillating wavelength tuned over 652-1017 nm and 1075-2289 nm, spanning nearly 1.8 octaves. This is, as far as we know, the widest resonant-wave tuning range obtained from a green-pumped OPO. We show that intracavity dispersion management is crucial for the stationary and single-band operation of such a broadband wavelength tuning system. This architecture is universal, and therefore can be extended to allow the oscillation and ultra-broadband tuning of OPOs at various spectral regions.