Yb Fiber Laser Pumped Mid-IR Source Based on Difference Frequency Generation and Its Application to Ammonia Detection

Abstract

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 µm with a power of ∼2.5 µW 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 µm) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm·m was estimated.