Experimental investigation of nonlinear process based on cSHG/DFG in PPLN waveguide

Effects of second harmonic generation (SHG) and cascaded second harmonic generation/difference frequency generation(cSHG/DFG) based on the quasi-phase-matching (QPM) condition in periodically poled lithium niobate (PPLN) waveguide were investigated experimentally. SHG conversion efficiency of-13.6 dB and QPM bandwidth of 0.45 nm were achieved using a 16.1 dBm power of fundamental wave at 1550.4 nm. Using pulsed all-fiber passive mode locked laser and tunable continuous wave laser,cSHG/DFG effect utilized for optical sampling was observed. Conversion efficiencies were calculated, and 11.88 nm-wide QPM bandwidth was achieved through changing the wavelength of input signal. Conversion efficiency of cSHG/DFG effect increased linearly with the total injected power.