We demonstrated a compact. widely tunable. and monochromatic high-repetition-rate terahertz (THz) source based on difference frequency generation in a GaSe crystal. The dual-wavelength pump laser was a doubly resonant near-degenerate type-II periodically poled LiNbO3 (PPLN) optical parametric oscillator (OPO). https://www.ngetikin.com/limited-buy-NHL-Dallas-Stars-Lineup-iPhone-13-Skin-p119122-great-pick/