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

Summary form only given. A cw narrow-linewidth tunable mid-IR coherent source has become a useful tool for trace gas detection since almost all gases exhibit fundamental rovibrational absorption lines with high absorption strength in the mid-IR. This particular source is obtained by a difference frequency generation technique which is that two near IR laser pump sources (/spl lambda//sub 1/, /spl lambda//sub 2/) are mixed to generate mid-IR (/spl lambda//sub 3/=(1//spl lambda//sub 1/-1//spl lambda//sub 2/)/sup -1/) in a quasi-phase-matched nonlinear optical crystal such as a periodically poled LiNbO/sub 3/ in single-pass geometry. Such a spectroscopic source can operate at room temperature with single spatial mode, single frequency and tunable in wide frequency region without mode hop. This paper reports an experimental study of a fiber laser (1063.8 nm) based mid-IR generation to detect methane.