Grier, A, Dean, P, Valavanis, A orcid.org/0000-0001-5565-0463 et al. (14 more authors) Origin of terminal voltage variations due to self-mixing in a terahertz frequency quantum cascade laser. In: International Quantum Cascade Lasers School and Workshop, 04-09 Sep 2016, Cambridge, UK.
Abstract
The use of quantum cascade lasers (QCLs) for laser feedback interferometry (LFI) has received significant attention since it enables a wide range of sensing applications without requiring a separate detector, and hence simplifies experimental apparatus [1]. LFA (based on the self-mixing effect) refers to the partial reinjection of the radiation emitted from a laser after reflection from a target; the injected radiation field then interacts with the intra-cavity field causing measurable variations of the QCL terminal voltage. The theory of LFI with conventional laser sources is well studied and explained by the Lang–Kobayashi model [2, 3]. However, while this enables the dynamic state populations and light interaction to be modelled, a linear relationship between the change in cavity light power, ∆P, and terminal voltage variation is commonly assumed, i.e. VSM ∝ ∆P [4, 5]. This is not strictly applicable to QCL structures since carrier transport is dominated by the mechanisms of electron subband alignment, intersubband scattering and photon driven transport between subbands with energy separations that change with applied bias (terminal voltage). We present experimental results of a QCL which departs significantly from this assumed linear behavior. We observe strong enhancement of the self-mixing signal in regions where the local gradient of the current-voltage (I–V) curve increases. We explain the origin of this signal using an extended density matrix (DM) approach [6] which accounts for coherent transport and interaction of the optical light field with the active region. The model is used to calculate the I–V characteristics of a bound-to-continuum (BTC) terahertz (THz) QCL and predict the effect of light variation on terminal voltage at a fixed drive current. This approach is shown to predict the experimental signal with good agreement.
Metadata
Item Type: | Conference or Workshop Item |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This is an author produced version of a paper presented at the International Quantum Cascade Lasers School and Workshop, 4th-9th September 2016, Cambridge, UK. |
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Electronic & Electrical Engineering (Leeds) > Pollard Institute (Leeds) |
Funding Information: | Funder Grant number EPSRC EP/J002356/1 EPSRC EP/J017671/1 Royal Society WM150029 EU - European Union 633054 |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Jan 2017 10:59 |
Last Modified: | 28 Jan 2018 02:38 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:110112 |