A team from the University of Michigan and IMRA America, both of Ann Arbor, has generated narrowband coherent terahertz radiation, or T-rays, with periodically poled LiNbO3 (PPLN). T-rays have potential applications in spectroscopy, imaging and sensing. The researchers, who published their results in the Aug. 28 issue of Applied Physics Letters, illuminated 1.2- and 7.2-mm PPLN crystals at 18 to 298 K with 200-fs, 800-nm pulses from a Ti:sapphire regenerative amplifier. They measured bandwidth as low as 18 GHz with a spectral center of 1.8 THz and found little broadening to 120 K. Output power decreased with increasing temperature from a maximum observed power of 5 µW.