Singly resonant continuous-wave optical parametric oscillator with tunable output above 4 µm and low oscillation threshold

In this work, we have built an OPO system that shows significantly decreased oscillation threshold with respect to the earlier design. Therefore, our new OPO system demonstrates that a tunable pump laser with much lower output power and better affordability can be used to pump it while maintaining SR operation and wide tuning range of the output idler beam wavelength near and above 4 μm.