Origin of terminal voltage variations due to self-mixing in terahertz frequency quantum cascade lasers

Andrew Grier*, Paul Dean, Alexander Valavanis, James Keeley, Iman Kundu, Jonathan D. Cooper, Gary Agnew, Thomas Taimre, Yah Leng Lim, Karl Bertling, Aleksandar D. Rakic, Lianhe H. Li, Paul Harrison, Edmund H. Linfield, Zoran Ikonic, A. Giles Davies, Dragan Indjin

*Corresponding author for this work

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Abstract

We explain the origin of voltage variations due to self-mixing in a terahertz (THz) frequency quantum cascade laser (QCL) using an extended density matrix (DM) approach. Our DM model allows calculation of both the current-voltage (I-V) and optical power characteristics of the QCL under optical feedback by changing the cavity loss, to which the gain of the active region is clamped. The variation of intra-cavity field strength necessary to achieve gain clamping, and the corresponding change in bias required to maintain a constant current density through the heterostructure is then calculated. Strong enhancement of the self-mixing voltage signal due to non-linearity of the (I-V) characteristics is predicted and confirmed experimentally in an exemplar 2.6 THz bound-to-continuum QCL. 

Original languageEnglish
Pages (from-to)21948-21956
Number of pages9
JournalOptics Express
Volume24
Issue number19
DOIs
Publication statusPublished - 19 Sep 2016
Externally publishedYes

Keywords

  • Feedback Interferometry
  • Terahertz imaging
  • Interferometry
  • Semiconductor lasers, quantum cascade

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