A novel narrow-linewidth mid-IR source based on difference frequency generation of fiber coupled diode laser seed sources at 1.08 µm and 1.56 µm mixed in periodically poled LiNbO3 is reported. Both seed pump wavelengths are amplified by a cascaded Yb and Er/Yb amplifier combination to generate coherent radiation of up to 0.1 mW at 3.5 µm. Furthermore, PPLN crystals of 0.5 mm and 1 mm thickness of 20 mm and 50 mm length have been compared in terms of their respective conversion efficiencies. Up to 1 mW at 3.5 µm of stable, tunable mid-infrared light was generated using separate Yb and Er/Yb amplifiers and a 50 mm long PPLN crystal.
© 2001 Optical Society of AmericaPDF Article