E L Ginzton Laboratory, Stanford University, Stanford, California 94305, USA.
Opt Lett. 2011 Mar 15;36(6):864-6. doi: 10.1364/OL.36.000864.
It is shown that random duty-cycle errors in quasi-phase-matching (QPM) nonlinear optical devices enhance the efficiency of processes far from the QPM peak. An analytical theory is shown to agree well with numerical solutions of second-harmonic generation (SHG) in disordered QPM gratings. The measured efficiency of 1550 nm band SHG in a periodically poled lithium niobate (PPLN) waveguide away from the QPM peak agrees with observations of domain disorder in a PPLN wafer by Zygo interferometry. If suppression of parasitic nonlinear interactions is important in a specific application of QPM devices, control of random duty-cycle errors is critical.
研究表明，准相位匹配（QPM）非线性光学器件中的随机占空比误差会提高远离 QPM 峰值的过程效率。本文提出的分析理论与非晶 QPM 光栅中二次谐波产生（SHG）的数值解吻合较好。在远离 QPM 峰值的周期性极化铌酸锂（PPLN）波导中，对 1550nm 波段 SHG 的测量效率与 Zygo 干涉仪对 PPLN 晶片畴失配的观测结果一致。如果在 QPM 器件的特定应用中抑制寄生非线性相互作用很重要，那么控制随机占空比误差则至关重要。
