Investigation on hig-order cascaded parametric processes in terahertz parametric oscillator with a noncollinear phas-matching scheme

Cascaded optical parametric processes in terahertz parametric oscillator with a noncollinear phas-matching scheme based on bulk lithium niobate were observed. The spectra of the first-, second-, and thir-order Stokes waves were observed. By analyze the spectra of the first-, second-, and thir- order Stokes waves it is found that the frequency difference between adjacen-order Stokes waves is approximately equivalent, which means that the hig-order cascaded parametric processes have realized. With hig-order cascaded terahertz parametric processes one pump photon can generate several THz photons, which means that the quantum conversion efficiency can be enhanced.