Midinfrared Tunable Laser with Noncritical Frequency Matching in Box Resonator Geometry

Monolithic optical parametric oscillators extend laser frequencies in compact architectures, but normally guide and circulate all pump, signal, and idler beams. Critical frequency matching is raised among these resonances, limiting operation stability and continuous tuning. Here, we develop a box resonator geometry that guides all beams but only resonates for signal. Such noncritical frequency matching enables 227 GHz continuous tuning, with sub-10 kHz linewidth and 0.43 W power at 3310 nm. Our results confirm that monolithic resonator can be effectively used as a tunable laser including midinfrared wavelength, as further harnessed with methane fine spectral measurement at MHz accuracy.