Widely tunable CW optical parametric oscillators: mastering the challenges posed in quantum technology research

Widely tunable continuous wave optical parametric oscillators (cw OPOs) are gaining popularity as novel sources of tunable laser light, not least due to the unprecedented wavelength coverage in the visible and the near infrared spectral range. While the potential and the advantages of tunable cw OPOs are becoming increasingly recognized, in particular within the quantum research community, the experimental requirements are often challenging. In this context, we discuss the characteristics of state-of-the-art tunable cw OPO designs and describe several tuning schemes tailored to meet various experimental needs. In an illustrative fashion, we compare several recently published experimental datasets from photoluminescence excitation experiments, which have been carried out on ensembles as well as on individual quantum emitters under different experimental conditions.