title: Tunable terahertz quantum cascade lasers with external gratings.
abstract: We demonstrate a frequency tunable external cavity terahertz quantum cascade laser using an abutted antireflection-coated silicon lens to reduce facet reflection and as a beam-forming element, with an external grating providing frequency selective optical feedback. Angle tuning of the grating allows a single longitudinal mode of the laser ridge to be selected, resulting in discontinuous tuning over a 165 GHz range around a center frequency of 4.4 THz. Another device exhibited 145 GHz of total tuning with 9 GHz of continuous tuning near the longitudinal modes of the laser.
authors.affiliation: Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. awmlee@mit.edu
authors.forename: Alan Wei Min
authors.initials: AW
authors.lastname: Lee
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Williams
authors.forename: Sushil
authors.initials: S
authors.lastname: Kumar
authors.forename: Qing
authors.initials: Q
authors.lastname: Hu
authors.forename: John L
authors.initials: JL
authors.lastname: Reno