title: Surface-emitting distributed feedback terahertz quantum-cascade lasers in metal-metal waveguides.
abstract: Single-mode surface-emitting distributed feedback terahertz quantum-cascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and use of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19.7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 mW of cw power at 5 K. In general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers.
authors.forename: Sushil
authors.initials: S
authors.lastname: Kumar
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Williams
authors.forename: Qi
authors.initials: Q
authors.lastname: Qin
authors.forename: Alan W
authors.initials: AW
authors.lastname: Lee
authors.forename: Qing
authors.initials: Q
authors.lastname: Hu
authors.forename: John L
authors.initials: JL
authors.lastname: Reno