Abstract-Coherent three-dimensional terahertz imaging through self-mixing in a quantum cascade laser

Paul Dean^1,a), Alex Valavanis¹, James Keeley¹, Karl Bertling², Yah Leng Lim²,Raed Alhathlool¹, Siddhant Chowdhury¹, Thomas Taimre³, Lianhe H. Li¹,Dragan Indjin¹, Stephen J. Wilson², Aleksandar D. Rakić², Edmund H. Linfield¹ and A. Giles Davies¹
^{http://scitation.aip.org/content/aip/journal/apl/103/18/10.1063/1.4827886}

1 School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
2 School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Queensland 4072, Australia
3 School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia

We demonstrate coherent terahertz (THz) frequency imaging using the self-mixing effect in aquantum cascade laser (QCL). Self-mixing voltage waveforms are acquired at each pixel of a two-dimensional image of etched GaAs structures and fitted to a three-mirror laser model, enabling extraction of the amplitude and phase parameters of the reflected field. From the phase, wereconstruct the depth of the sample surface, and we show that the amplitude can be related to the sample reflectance. Our approach is experimentally simple and compact, and does not require frequency stabilization of the THz QCL.