F. Wang, I. Kundu, L. Chen, L. Li, E. H. Linfield, A. G. Davies, S. Moumdji, R. Colombelli, J. Mangeney, J. Tignon, and S. S. Dhillon
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-3-2174
The far-field emission profile of terahertz quantum cascade lasers (QCLs) in metal-metal waveguides is controlled in directionality and form through planar horn-type shape structures, whilst conserving a broad spectral response. The structures produce a gradual change in the high modal confinement of the waveguides and permit an improved far-field emission profile and resulting in a four-fold increase in the emitted output power. The two-dimensional far-field patterns are measured at 77 K and are agreement in with 3D modal simulations. The influence of parasitic high-order transverse modes is shown to be controlled by engineering the horn structure (ridge and horn widths), allowing only the fundamental mode to be coupled out.
© 2016 Optical Society of America
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