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Designer spoof surface plasmon structures collimate terahertz laser beams

LL-1: Terahertz quantum cascade lasers typically have poor output emission profiles, deleterious to their exploitation. Here we demonstrated that patterning appropriate ‘spoof’ surface plasmon structures onto the laser facets reduced the beam divergence from ~180˚ to ~10˚, improved the directivity by >10 decibels, and increased the power collection efficiency six-fold, without compromising the threshold current or operating temperature. This research consolidated an internationally-leading collaboration between Leeds and Harvard (and subsequently Nanyang Technical University, Singapore), and underpinned several successful grant applications, including a 2012 European Space Agency programme (Ref:4000105304, PI:Davies, €250k) to develop terahertz local oscillators for astronomy and atmospheric sensing.