Single-mode surface-emitting concentric-circular-grating terahertz quantum cascade lasers
Khanna, Suraj P.
Davies, A. Giles
Lim, Dau Fatt
Tan, Chuan Seng
Yu, Siu Fung
Liu, Hui Chun
Wang, Qi Jie
Date of Issue2013
School of Electrical and Electronic Engineering
We demonstrate single-mode surface-emitting terahertz frequency quantum cascade lasers utilising non-uniform second-order distributed feedback concentric-circular-gratings. The grating is designed for single-mode operation and surface emission for efficient and directional optical power out-coupling. The devices exhibit single-mode operation over the entire dynamic range with a sidemode- suppression-ratio of around 30 dB at 78 K, and a six-fold rotationally symmetric far-field pattern. In addition, the devices show a peak output power approximately three times higher than in ridge-waveguide lasers of similar size, whilst maintaining similar threshold current densities for the 3.8 THz emission and without remarkably sacrificing the maximum temperature operation performance. Owing to the high symmetry of the structure and the broad area light emission from surface, the devices are potentially very suitable for use as single-mode, high power emitters for integration into two-dimensional laser arrays.
DRNTU::Engineering::Electrical and electronic engineering::Electronic systems::Signal processing
Applied physics letters
© 2013 American Institute of Physics. This paper was published in Applied Physics Letters and is made available as an electronic reprint (preprint) with permission of American Institute of Physics. The paper can be found at the following official DOI: http://dx.doi.org/10.1063/1.4789535. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.