提出了一种新型的基于PPLN晶体的多波长中红外差频产生(DFG)光源的设计方案。针对1060 nm和1550 nm两个波段的基频光源组合，采用晶体的分段温度控制技术获得了具有多峰结构的抽运光/闲频光准相位匹配(QPM)调谐曲线。通过改变分段晶体的温度调控抽运光QPM峰的位置，实现中红外多波长DFG光源的调谐输出。理论研究结果显示当PPLN晶体分成长度相等的两个温度控制段，且信号光波长设定为1.58 \mm，分段晶体区间的温度分别设定为20 ℃和60 ℃时，抽运光波长区域存在4个QPM峰，对应的中红外闲频光QPM峰的中心波长分别位于2.95，3.03，3.75，3.83 μm处。当分段晶体区间的温度改变为50 ℃和90 ℃时，相应中红外闲频光QPM峰分别平移至3.01，3.11，3.67，3.77 μm处。该研究结果可为设计和研制多波长宽调谐中红外DFG光源提供参考。

A novel difference frequency generation (DFG) scheme for simultaneously achieving multi-wavelength mid-infrared (mid-IR) emissions based on a bulk PPLN crystal is proposed. For the combination of 1060 nm and 1550 nm wavelength band fundamental light sources, multiple pump quasi-phase-matching (QPM) peaks can be obtained by using the segmented temperature controlling techniques on a PPLN chip. Moreover, the multiple pump QPM peaks can be widely tuned by adjusting the segmented crystal temperatures and thus the tunability for the generated multiple mid-IR wavelengths is realized. Our simulated results show that when the PPLN crystal are evenly divided into two sections for temperature controlling, four pump QPM peaks are simultaneously reached, corresponding to the mid-IR idler QPM peaks at 2.95, 3.03, 3.75, 3.83 μm, as the signal wavelength setting at 1.58 μm and the segmented crystal temperatures setting at 20 ℃ and 60 ℃, respectively. When the segmented crystal temperatures are adjusted to 50 ℃ and 90 ℃, the idler QPM peak positions in the mid-IR DFG output spectrum are changed to 3.01, 3.11, 3.67, 3.77 μm. Such results may provide reference and guidance for design and development of widely tunable multi-wavelength DFG light sources.