High-efficiency Doubly Resonant Optical Parametric Oscillator Based On PPKTP

Continuous-wave optical parametric oscillators (cw OPOs) are attractive sources of widely tunable and narrow linewidth single-frequency coherent radiation in spectral regions inaccessible to lasers. Because of these remarked features, cw OPOs have been getting people’s attention. Recently, improvements in the coherence of pump sources and in the quality of nonlinear-optical materials lead cw OPOs to practical devices. They can used for high-resolution spectroscopy, quantum communication and remote sensing.Still, many desirable OPO applications are limited by defects in the conventional birefringent phase-matching techniques in available materials, such as Poynting-vector walk-off, low effective nonlinear coefficient, and discommodious phase-matching temperatures and angles. Quasi phase matching (QPM) crystal is a new nonlinear crystal. A significant advantage of quasi-phase matching is that the interacting waves can be chosen so that coupling occurs through the largest element of the x(2) tensor. Another benefit is that any interaction within the transparency range of the material can be noncritically phase matched at a specific temperature, even interaction for which birefringent phase matching is impossible and quasi-phase matching is a useful technique for extending the range of available nonlinear optical materials. QMP cw OPOs have become efficient and coherent workhorses for spectroscopy in the near and mid infrared.This thesis is devoted to various studies involving quasi-phase matched doubly resonant optical parametric oscillator based on periodically poled KTiOPO4(PPKTP). It is formed by four parts:1) Briefly introduce the developments of OPOs.2) The cavity equations of motion of OPOs and the selection of PPKTP are briefly introduced.3) The classical characteristics of quasi-phase-matched doubly resonant optical parametric oscillator (DROPO) are theoretically analyzed. The tuning characteristics of DROPO output by changing crystal’s temperature, OPO’s cavity length and pump frequency respectively are theoretically analyzed. Then coarse and continuous frequency tuning characteristics are investigated experimentally. The wavelength of signal can be tuned from791.29to807.53nm by the crystal’s temperature changed from10to90℃, the corresponding idler wavelength tuning is from1573.37to1512.87nm. The wavelength tuning of0.2nm is achieved by tuning of263.25nm for cavity length, the corresponding idler wavelength tuning is0.71nm. Continuous frequency tuning of4.3GHz for signal is also achieved by smooth tuning of6.6GHz for pump, the idler continuous tuning is2.3GHz. When the cavity length is varied by2.9nm, then a mode hop will occur. When the cavity length is varied by half of the pump wavelength, then a cluster jump will occur. In addition, the oscillation threshold and input-output relations are also theoretically analyzed. In our work, the OPO has a low threshold of30mW and can deliver245mW single-frequency output at0.8and1.5μ.m with pump power of390mW, and the total down-conversion efficiency is63%.4) Conclusion and prospect.