A Random Optical Parametric Oscillator

Abstract Optical parametric oscillators provide short coherent light pulses at widely tunable wavelengths. Their primary drawback is the requirement of precise cavity control, making such devices specially challenging to develop in long cavities, and with oscillation limited to a fixed repetition rate. Herein, exploiting the inherent disorder of the refractive index in single-mode fibres we developed the first random optical parametric oscillator - the parametric analogous of random lasers. Parametric amplification is provided by modulation instability through the Χ(3) non-linearity and feedback is given by Rayleigh scattering. The system is realised in a pulsed configuration, with extremely small (<0.001%) feedback. To enhance the weak feedback, a novel piecewise distributed random cavity is demonstrated. In contrast to conventional parametric oscillators, the emission is sustained at arbitrary rates and dispensing any kind of cavity control loop, resulting in a far more versatile device, representing an important step toward the development of stable and tunable - both in wavelength and repetition rate - parametric oscillators. The ultra-long cavity used in experiments (~5km) enabled the generation of four-wave mixing products between the pump and the singly-resonant oscillator, giving rise to a train of picosecond-pulses, which would find applications in ultra-fast optics.