基于周期极化晶体MgO:PPLN的纠缠光子对制备过程的研究

基于二阶非线性效应的自发参量转换技术制备纠缠光子对过程中,以掺5 mol%MgO:PPLN周期极化晶体为研究对象,将光参量变换过程中的动量守恒和能量守恒条件与该晶体的色散方程,以及晶体极化周期随温度变化的热膨胀方程相联系,得到了355 nm、405 nm、532 nm、780 nm和1 064 nm这5个实验室常用波长点在制备纠缠光子对时的周期调谐特性和温度调谐特性。研究过程中发现,出现了晶体极化周期过小和产生两对纠缠光子对问题,总结并归纳了各波长点在一定极化周期和温度下与非线性晶体作用所产生的纠缠光波段范围。当选用其他非线性周期极化晶体进行实验时,改变QPM动量守恒条件中的极化周期项,同时根据具体使用的晶体改变色散方程。该研究方案可直接推广到使用不同非线性晶体产生通信光波段或红外光波段的纠缠光子对研究中,在制备量子光源等领域具有重要研究价值。

Study on preparation process of entangled photon pairs based on periodically polarized crystal MgO:PPLN

In the process of preparing entangled photon pairs by spontaneous parametric conversion technology based on second-order nonlinear effects, the periodically polarized crystals doped with 5 mol%MgO:PPLN were studied. By linking the momentum conservation and energy conservation conditions in the process of optical parametric transformation with the dispersion equation of the crystal and the thermal expansion equation of the crystal polarization period with temperature, the period-tuning and temperature-tuning properties of entangled photon pairs were obtained at the five commonly used wavelength points of 355 nm, 405 nm, 532 nm, 780 nm and 1 064 nm. It was found that the crystal polarization period was too small and two pairs of entangled photon pairs were generated during the research process, and the entangled light band range generated by the interaction of each wavelength point with nonlinear crystals under a certain polarization period and temperature was summarized. When other nonlinear periodical polarized crystals were selected for experiments, the polarized periodic term in the QPM momentum conservation condition was changed, and the dispersion equation was changed according to the specific crystal used. This research scheme can be directly extended to the research of using different nonlinear crystals to generate entangled photon pairs in the communication optical band or infrared optical band, and has important research value in the field of preparing quantum light sources.