Swept-frequency feedback interferometry using terahertz frequency QCLs: A method for imaging and materials analysis

Aleksandar D. Rakić, Thomas Taimre, Karl Bertling, Yah Leng Lim, Paul Dean, Dragan Indjin, Zoran Ikonić, Paul Harrison, Alexander Valavanis, Suraj P. Khanna, Mohammad Lachab, Stephen J. Wilson, Edmund H. Linfield, A. Giles Davies

Research output: Contribution to journalArticlepeer-review

91 Citations (Scopus)


The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of high-power radiation with a narrow intrinsic linewidth. As such, THz QCLs are extremely promising sources for applications including high-resolution spectroscopy, heterodyne detection, and coherent imaging. We exploit the remarkable phase-stability of THz QCLs to create a coherent swept-frequency delayed self-homodyning method for both imaging and materials analysis, using laser feedback interferometry. Using our scheme we obtain amplitude-like and phase-like images with minimal signal processing. We determine the physical relationship between the operating parameters of the laser under feedback and the complex refractive index of the target and demonstrate that this coherent detection method enables extraction of complex refractive indices with high accuracy. This establishes an ultimately compact and easy-to-implement THz imaging and materials analysis system, in which the local oscillator, mixer, and detector are all combined into a single laser.

Original languageEnglish
Pages (from-to)22194-22205
Number of pages12
JournalOptics Express
Issue number19
Early online date12 Sep 2013
Publication statusPublished - 23 Sep 2013
Externally publishedYes


Dive into the research topics of 'Swept-frequency feedback interferometry using terahertz frequency QCLs: A method for imaging and materials analysis'. Together they form a unique fingerprint.

Cite this