Abstract-Patch antenna microcavity terahertz sources with enhanced emission

J. Madéo1,2,a), Y. Todorov2, A. Gilman1, G. Frucci2, L. H. Li3, A. G. Davies3, E. H. Linfield3, C. Sirtori2 and K. M. Dani1
http://scitation.aip.org/content/aip/journal/apl/109/14/10.1063/1.4963891
a) Author to whom correspondence should be addressed. Electronic mail: julien.madeo@oist.jp
Appl. Phys. Lett. 109, 141103 (2016); http://dx.doi.org/10.1063/1.4963891

We study the emission properties of an electroluminescent THz frequency quantum cascade structure embedded in an array of patch antenna double-metal microcavities. We show that high photon extraction efficiencies can be obtained by adjusting the active region thickness and array periodicity as well as high Purcell factors (up to 65), leading to an enhanced overall emitted power. Up to a 44-fold increase in power is experimentally observed in comparison with a reference device processed in conventional mesa geometry. Estimation of the Purcell factors using electromagnetic simulations and the theoretical extraction efficiency are in agreement with the observed power enhancement and show that, in these microcavities, the overall enhancement solely depends on the square of the total quality factor.

Abstract-Continuous-wave coherent imaging with terahertz quantum cascade lasers using electro-optic harmonic sampling

M. Ravaro¹, V. Jagtap¹, G. Santarelli², C. Sirtori¹, L. H. Li³, S. P. Khanna³, E. H. Linfield³, and S. Barbieri¹

^{http://apl.aip.org/resource/1/applab/v102/i9/p091107_s1?isAuthorized=no}

¹Laboratoire Matériaux et Phénomènes Quantiques (MPQ) and CNRS, UMR 7162, Université Paris-Diderot, 10, rue A. Domont et L. Duquet, 75205 Paris, France
²Laboratoire Photonique, Numérique et Nanosciences (LP2N) and CNRS, UMR 5298, Université de Bordeaux 1, Institut d'Optique, 351 cours de la Libération, 33405 Talence, France
³School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom                        

We demonstrate a coherent imaging system based on a terahertz (THz) frequency quantum cascade laser (QCL) phase-locked to a near-infrared fs-laser comb. The phase locking enables coherent electro-optic sampling of the continuous-wave radiation emitted by the QCL through the generation of a heterodyne beat-note signal. We use this beat-note signal to demonstrate raster scan coherent imaging using a QCL emitting at 2.5 THz. At this frequency the detection noise floor of our system is of 3 pW/Hz and the long-term phase stability is <3°/h, limited by the mechanical stability of the apparatus.