Cascade frequency generation regime in an optical parametric oscillator

In a parametric oscillator of a special two-sectional design based on a lithium niobate periodic structure, a cascade frequency generation regime was observed in which a signal wave pumped a secondary parametric oscillator, producing secondary signal and idler waves. The secondary parametric oscillator can be tuned in a broad range of ~200 nm with respect to a fixed wavelength of the primary idler wave.