Widely Tunable Difference Frequency Generation in Periodically-Poled LiNbO3 Using an All-Solid-State Cr3+:LiSrAlF6 Laser

An all-solid-state tunable mid-infrared coherent source based on a quasi-phase-matched (QPM) difference frequency generation (DFG) is reported. The QPM-DFG was carried out by mixing a spectrally narrowed Cr3+:LiSrAlF6 laser with a diode laser (1020 nm) in a bulk periodically-poled LiNbO3 (PPLN) crystal with single grating period of 22.2 µm. Wide tuning range around 4.0 and 4.6 µm was obtained by tuning the laser and altering the PPLN temperature between 20 and 40°C. Even wider tuning range is expected by optimizing the PPLN grating period and expanding the tuning range of the Cr3+:LiSrAlF6 laser.