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

Step-chirped gratings is utilized to broaden the bandwidth of wavelength conversion based on single-pass/ double-pass cascaded second harmonic generation and difference frequency generation. By adding the step-chirped gratings number and optimizing the poling period, broad conversion bandwidth and flat response can be obtained simultaneously. The bandwidth of 4-cm-long waveguide with 6-section chirped gratings are 169 nm for single-pass scheme and 164 nm for the double-pass one, which are 98 nm and 101 nm larger than those of uniform gratings, respectively. Furthermore, comparison between step-chirped gratings and equal-segmented gratings is carried out.