分段小信号近似方法研究准相位匹配倍频效率

从PPLN波导微结构出发分析准相位匹配倍频过程中的相位补偿机理，以极化畴为单元，通过耦合波方程计算极化畴内产生的二次谐波电场，通过电场相干叠加计算倍频效率。分别在小信号近似和基频光高消耗情况下计算准相位匹配倍频效率，结果显示：倍频效率小于5％时，两种情况下的计算结果吻合得很好；随着转换效率增大，小信号近似不再适用，需要在基频光高消耗情形下计算倍频效率。研究了基频光功率密度与准相位匹配倍频效率的关系，定性分析了极化周期存在误差时，误差对倍频效率的影响。

Research on QPM Frequency Doubling Efficiency Using Subsection Small Signal Approximation

Based on PPLN waveguide micro-structure, phase-compensation-mechanism in the process of quasi-phase-matching （QPM） frequency doubling （FD） is analyzed. With polarization domain as a unit, through the superposition of the second harmonic electric field within this polarization domain, the FD efficiency is calculated with the help of the coupled-wave equation. In the conditions of the small signal approximation （SSA） and the fundamental frequency of high consumption （FFHC）, the QPM FD efficiency are researched, respectively. The results show that if the FD efficiency is less than 5%, the calculation results in the SSA correspond to the case of the FFHC. And with the conversion efficiency increasing, the calculation of the FD efficiency must be in the condition of the FFHC instead of that of the SSA. At last, by using of the subsection SSA, the relationship between the power of the fundamental frequency and the QPM FD efficiency is explored. While the polarization periods have length errors, the effect of this errors on the FD efficiency are qualitatively analyzed.