基于级联倍频+差频效应的宽带波长转换过程

Broadband Wavelength Conversion Based on Cascaded Second Harmonic Generation and Difference Frequency Generation

利用阶梯分段准相位匹配结构实现了基于级联倍频+差频效应的单通/双通宽带波长转换。对于固定的晶体长度,通过增加阶梯段数并合理设计准相位匹配结构参数,可以同时获得高转换效率、大转换带宽和高平坦性。当晶体长度为3cm时,在保证平坦度低于0.2dB的前提下,单通构型波长转换器的转换带宽和最大转换效率可分别达到177nm和-9.94dB,而双通构型的分别为170nm和-4.15dB。最后对基于阶梯分段准相位匹配结构的波长转换器与基于正弦啁啾光学超晶格和分段光栅结构的波长转换器的特性进行了对比分析,结果显示阶梯分段结构具有良好的综合特性。

Bandwidth enhancement and response flattening of wavelength conversion based on single-pass and double-pass cascaded second harmonic generation and difference frequency generation in step-segmented quasi-phase matched gratings are investigated.For the same waveguide length,high conversion efficiency,broad signal bandwidth and flat response can be obtained simultaneously by adding the segment number of quasi-phase matched gratings and optimizing the poling period of the step-segmented quasi-phase matched structure.The conversion bandwidth and the maximum conversion effeciency in a 3-cm-long waveguide are 177 nm and-9.94 dB for single-pass scheme,and 170 nm and-4.15 dB for the double-pass one,respectively,meanwhile the peak-to-peak ripple less than 0.2dB.Moreover,the comparison among step-segmented gratings,sinusoidally chirped optical superlattices（SCOS）and segmented gratings is carried out,and higher conversion efficiency and flatter response than the other two gratings are found on the step-segmented gratings,which is easier to fabricate in practice than SCOS.