Difference-frequency generation of 4.8 μm mid-infrared light was performed using a waveguide periodically poled LiNbO3 (PPLN) crystal. 871 and 1064 nm external-cavity diode lasers followed by tapered amplifiers were used as pump sources. A conversion efficiency of ̃2%/W with the output power of 2 mW was achieved even under considerable absorption of the crystal at this wavelength. Lamb-dip spectroscopy of carbonyl sulfide was demonstrated showing the satisfactory performance of this device for saturation spectroscopy. The observed dip width shows that the laser linewidth is ̃2 MHz, which corresponds to those of the pump lasers. © 2013 Optical Society of America.