Retracing behaviors of the phase-matching angle in noncollinear phase-matched optical parametric oscillators

We theoretically studied the retracing behaviors of the phase-matching angle in β-BaB2O4 optical parametric oscillators with noncollinear phase matching when they were pumped with the harmonic of a Nd:YAG laser. The results imply that two or more sets of signal–idler outputs can be observed at certain phase-matching angles. Meanwhile, we observed that over a quite broad signal wavelength range the phase-matching condition can be reached simultaneously, leading to an optical parametric oscillator of broad signal and idler spectral widths. Experimentally, with the pump at 532 nm, we observed a two-band signal spectrum, indicating the simultaneous phase matching of two center phase-matching angles, or retracing behavior. Also, broad signal and idler spectra were obtained with a well-chosen set of phase-matching conditions. The signal and idler spectral widths were 145 nm (745–890 nm) and 540 nm (1.32–1.86 μm), respectively.