Abstract-Terahertz inverse synthetic aperture radar imaging using self-mixing interferometry with a quantum cascade laser

H. S. Lui, T. Taimre, K. Bertling, Y. L. Lim, P. Dean, S. P. Khanna, M. Lachab, A. Valavanis, D. Indjin, E. H. Linfield, A. G. Davies, and A. D. Rakić  »View Author Affiliations
http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-9-2629

We propose a terahertz (THz)-frequency synthetic aperture radar imaging technique based on self-mixing (SM) interferometry, using a quantum cascade laser. A signal processing method is employed which extracts and exploits the radar-related information contained in the SM signals, enabling the creation of THz images with improved spatial resolution. We demonstrate this by imaging a standard resolution test target, achieving resolution beyond the diffraction limit.

© 2014 Optical Society of America

Abstract-Terahertz inverse synthetic aperture radar imaging using self-mixing interferometry with a quantum cascade laser

H. S. Lui, T. Taimre, K. Bertling, Y. L. Lim, P. Dean, S. P. Khanna, M. Lachab, A. Valavanis, D. Indjin, E. H. Linfield, A. G. Davies, and A. D. Rakić  »View Author Affiliations

http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-39-9-2629

Optics Letters, Vol. 39, Issue 9, pp. 2629-2632 (2014)
http://dx.doi.org/10.1364/OL.39.002629

We propose a terahertz (THz)-frequency synthetic aperture radar imaging technique based on self-mixing (SM) interferometry, using a quantum cascade laser. A signal processing method is employed which extracts and exploits the radar-related information contained in the SM signals, enabling the creation of THz images with improved spatial resolution. We demonstrate this by imaging a standard resolution test target, achieving resolution beyond the diffraction limit.

© 2014 Optical Society of America

Abstract-Terahertz quantum cascade lasers with thin resonant-phonon depopulation active regions and surface-plasmon waveguides

M. Salih, P. Dean, A. Valavanis, S. P. Khanna, L. H. Li, J. E. Cunningham, A. G. Davies, E. H. Linfield
http://arxiv.org/abs/1303.3205
We report three-well, resonant-phonon depopulation terahertz quantum cascade lasers with semi-insulating surface-plasmon waveguides and reduced active region (AR) thicknesses. Devices with thicknesses of 10, 7.5, 6, and 5 {\mu}m are compared in terms of threshold current density, maximum operating temperature, output power and AR temperature. Thinner ARs are technologically less demanding for epitaxial growth and result in reduced electrical heating of devices. However, it is found that 7.5-{\mu}m-thick devices give the lowest electrical power densities at threshold, as they represent the optimal trade-off between low electrical resistance and low threshold gain.

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.