Single-mode narrow beam divergence surface-emitting concentric-circular- grating terahertz quantum cascade lasers

Guozhen Liang, Houkun Liang, Ying Zhang, Suraj P. Khanna, Lianhe Li, A. Giles Davies, Edmund Linfield, Dau Fatt Lim, Chuan Seng Tan, Siu Fung Yu, Hui Chun Liu, Qi Jie Wang

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


Single-mode surface-emitting terahertz quantum cascade lasers with second-order concentric-circular-gratings are firstly demonstrated. The gratings are designed for single-mode operation and surface emission for efficient and directional optical power out-coupling. The first structure exhibits single-mode operation over the entire dynamic range with a side-mode-suppression-ratio of around 30 dB, and a six-fold rotationally symmetric far-field pattern, while a modified structure demonstrates single-mode operation with an improved beam divergence, whose far-field patteren consists of two lobes, each of which has a beam divergence within 13.5°×7° (full-width at half-maximum, FWHM). In addition, the devices show a peak output power approximately three times higher than in conventional ridge-waveguide lasers of similar size, whilst maintaining similar threshold current densities and maximum operating temperatures.
Original languageEnglish
Title of host publication2012 Photonics Global Conference, PGC 2012
Publication statusPublished - 1 Dec 2012
Event2012 Photonics Global Conference, PGC 2012 - Singapore, Singapore
Duration: 13 Dec 201216 Dec 2012


Conference2012 Photonics Global Conference, PGC 2012

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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