Widely tunable femtosecond soliton generation in a fiber-feedback optical parametric oscillator

Optical parametric oscillators (OPOs) are uniquely versatile-albeit complex-platforms for the generation of tunable coherent light in difficult-to-access spectral regions. A synchronously pumped chi((2)) femtosecond OPO producing sub100-fs pulses, by means of optical soliton formation in a single-mode fiber-feedback cavity, is presented for the first time. This approach removes the requirement for active stabilization and bulk dispersion compensation elements associated with traditional OPOs, while reducing the physical footprint by a factor of 3. Transform-limited pulses of 80-120 fs are generated for both normal and anomalous dispersion, while a new type of spectral sideband formation is observed and studied. Experimental results are supported by detailed simulations based on nonlinear pulse propagation theory, which serve to enrich the understanding of femtosecond pulse evolution in OPOs perturbed by strong Kerr nonlinearity. The OPO provides a unique platform for the study of intracavity soliton phenomena across a wide wavelength range. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement