Theoretical Analysis of a Cascaded Continuous-Wave Optical Parametric Oscillator

Threshold and conversion efficiency of a cascaded continuous-wave (CW) optical parametric oscillator (OPO) which can obtain CW terahertz (THz) light are analyzed by the plane wave approach. The model predicts experimental results of the first-order cascaded threshold. The theoretically predicted threshold for the backward idler parametric process agrees with the experimental data. Validation with a high-order cascaded parametric process awaits completion of experiments. At a pump wavelength of 1,030 nm and temperature of 120 A degrees C, the threshold intensity of the forward idler parametric process was 2.2-2.4 times that of the backward process when the period length of the MgO:periodically poled lithium niobate crystal was 24-30 mu m. The energy efficiency of CW THz light at a cascade order smaller than 6 is 10(-5)-10(-4). Moreover, efficiency of N cascaded processes can be increased by a factor of N compared with that of a single parametric process, which is limited by the Manley-Rowe relationship. To our knowledge, this is the first theoretical treatment of threshold and energy efficiency of a cascaded CW OPO.