Flexible All-Optical Wavelength Shifters Using Strong Focusing in a Wideband Engineered PPLN

Wavelength shift of modified second-harmonic bandwidth in a 20-mm-long engineered chirped periodically poled lithium niobate is experimentally demonstrated by focalpoint displacement of a strongly focused pump beam of a 30-μm beam waist. Utilizing this non-confocal arrangement in a cascaded second harmonic generation and difference frequency generation process, a CW probe as a signal wavelength is variably shifted within an 8-nm span by pump tuning using a ~7-nm second-harmonic bandwidth.