title: Generation of backward terahertz waves in GaSe crystals.
abstract: We have observed a backward-propagating terahertz wave by mixing two coherent infrared beams in two GaSe crystals. For the 47 mm long crystal, the output wavelength can be tuned in the wide range of 167.6 to 2060 microm (0.146 to 1.79 THz), whereas the output peak power reaches 217 W. The corresponding power conversion efficiency is approximately 0.03%.
authors.affiliation: Department of Electrical and Computer Engineering, Lehigh University, 19 Memorial Drive West, Bethlehem, PA 18015, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.forename: Yujie J
authors.initials: YJ
authors.lastname: Ding