Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection.

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generates mid-IR at 3 mum with a power of similar to2.5 muW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm(-1)) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm(-1) (3.0345 mum) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm.m was estimated.