500 nm continuous wave tunable single-frequency mid-IR light source for C-H spectroscopy

A computer controlled tunable mid-IR light source, based on single resonant difference frequency generation (DFG), is experimentally investigated. The DFG process is pumped by an external cavity tapered diode laser, tunable over a spectral range of 30 nm. Grating feedback to the single mode channel of the tapered diode narrows the spectrum and allows for tuning of the emitted spectrum in the range from 780 to 810 nm. The DFG process takes place intra-cavity in a high finesse diode pumped 1064 nm solid state Nd:YVO 4 laser cavity, using periodically poled LiNbO 3 as the nonlinear material. Based on this new approach, a tunable single-frequency output power exceeding 3 mW was obtained in the mid-IR tuning range from 2.9 to 3.4 μm.