Unidirectional operation of the Er:YAG monolithic nonplanar ring oscillators

We experimentally quantify loss difference requirements in an Er:YAG monolithic nonplanar ring oscillator (NPRO) during power scaling. A linear correlation (<i>R</i>²=0.98) between the pump power and the required loss difference threshold was demonstrated for the first time, to the best of our knowledge. The slope of the fitting line is 0.0016%/W, indicating that at high pump powers (>6.5<i>W</i>), the required loss difference exceeds the empirical threshold of 0.01%. Our work provides a reference for the design of future NPRO, particularly those requiring higher power or lower magnetic field strengths.