V-shaped external cavity diode pump for 100 nm continuous tuning of a difference-frequency generation

•We have rearranged a V-shaped external cavity around a commercial diode laser.•The V-shaped diode laser is used as pump source in a difference-frequency generation setup.•By this configuration continuous tuning of idler wave up to ~100 nm between 4.76 µm to 4.86 µm is obtained.•The performance of the extended MIR-DFG radiation is shown as trace detection of P(16) and P(18) CO lines.

We report the generation of a mid-infrared (MIR) difference-frequency radiation between 4.76 µm and 4.86 µm rang inside AgGaS2 nonlinear crystal using a V-shaped external cavity configuration fabricated around pump source. The effect of using such V-shaped scheme on tuning characteristics of a commercial diode laser have been studied and experimentally presented. More than ~11 nm continuous tuning is obtained for the emerging original beam through rotating a blazed grating over a certain angular range with a measured accuracy of 1.4 µm/degree. Such characterized V-shaped external cavity is used as pump source in a DFG experimental setup. An appreciable extension in generated MIR-DFG bandwidth is observed when the intracavity grating is rotated over ~600 μm in opposite directions. The performance of such extended V-shaped external cavity base MIR-DFG radiation is demonstrated as trace detection of P(16) and P(18) rovibrational lines of 1-0 fundamental band of carbon monoxide (12C16O) molecule with and without using V-shaped cavity.