Broadband Mid-IR Light Sources From Difference Frequency Generators Based on a 2-mm-Long Aperiodically-Poled Lithium-Niobate Crystal

We present a difference frequency generator (DFG) based on 2-mm-long MgO-doped aperiodically-poled lithium-niobate (APPLN) crystal with linearly-varying poling-period. The DFG was pumped by femtosecond fiber-laser system repetition-rate of 53.4 MHz. It produced broadband mid-infrared light source having an instantaneous-bandwidth covering 1.9–4.6 μm, average power 30 mW. Moreover, numerical simulations, we revealed that due to the relatively high intensity incident signal wave, APPLN length few milli-meters sufficient produce efficient and nonlinear conversion in high-repetition-rate, ultra-short-pulsed system.