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.
© 2010 Optical Society of America
Lasers and Laser Optics
Original Manuscript: October 29, 2009
Revised Manuscript: January 12, 2010
Manuscript Accepted: January 15, 2010
Published: March 18, 2010
Alan Wei Min Lee, Benjamin S. Williams, Sushil Kumar, Qing Hu, and John L. Reno, "Tunable terahertz quantum cascade lasers with external gratings," Opt. Lett. 35, 910-912 (2010)