基于级联和频+差频效应的平坦带宽波长转换器

针对改善波长转换器转换特性的问题，研究了周期极化铌酸锂晶体中采用分段准相位匹配光栅结构对基于级联和频+差频效应的波长转换器特性的影响.对于单通和双通构型，增加段数，并优化设计每段的极化周期，可以同时获得高转换效率、大转换带宽和较好的平坦性.在相同条件下，双通构型波长转换器的转换效率和平坦性较好，但转换带宽比单通构型稍差.与采用位移泵浦光的波长提高平坦性的方法相比，利用分段准相位匹配光栅结构能够获得几乎相同的平坦性，但转换效率和转换带宽却比泵浦光波长位移法好.此外，研究了晶体长度对基于分段准相位匹配光栅结构波长转换器特性的影响.

Flattop Broadband Wavelength Converters Based on Cascaded Sum+Difference Frequency Generation

In order to improve the conversion characteristics of wavelength converters,the effect of the segmented quasi-phase matched grating structure in the periodically poled lithium niobate crystal on the characteristics of wavelength converters based on cascaded sum + difference frequency generation is studied. For both of single-pass and double-pass configurations, high conversion efficiency, large conversion bandwidth, and good flatness can be achieved simultaneously by increasing the number of segments and optimizing the poling period of each segment. Under the same conditions, the conversion efficiency and flatness of the double-pass configuration are better, but the conversion bandwidth is slightly worse than that of the single-pass configuration. Compared with the method of shifting the wavelength of one of the pump light, the use of segmented quasi-phase matched grating structure in wavelength converter can obtain almost the same flatness but better conversion efficiency and conversion bandwidth. Moreover, the effect of crystal length on the characteristics of a wavelength converter based on the segmented quasi-phase matched grating structure is also investigated.