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

Dean, Paul; Valavanis, Alexander; Keeley, James; Bertling, Karl; Lim, Yah Leng; Alhathlool, R.; Chowdhury, Siddhant; Taimre, Thomas; Li, Lianhe; Indjin, D.; Wilson, Stephen J.; Rakić, Aleksandar D.; Linfield, E. H.; Davies, A. G.

doi:10.1063/1.4827886

Cited by 53 publications

(42 citation statements)

References 24 publications

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“…Optical feedback occurs to a greater or lesser extent in all laser applications, regardless of whether it is intentional, thereby necessitating its inclusion in operating models of many laser systems. Intentional optical feedback can be used in interferometric sensing applications [8,14], for example, to infer the properties of a target from the measured self-mixing voltage [15][16][17], and has been applied recently to applications including THz biomedical imaging, explosives detection, and THz radar imaging [18][19][20][21][22][23][24]. Conversely, optical feedback in communication applications is usually undesirable and has the potential to cause problems such as unwanted self-mixing fringes, coherence collapse, chaotic behavior, or unwanted transitions between laser operating regimes [25,26].…”

Section: Introductionmentioning

confidence: 99%

Model for a pulsed terahertz quantum cascade laser under optical feedback

Agnew¹,

Grier²,

Taimre³

et al. 2016

Opt. Express

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Abstract:Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation.Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. 4, 631-633 (2014). 11. G. Giuliani, M. Norgia, S. Donati, and T. Bosch, "Laser diode self-mixing technique for sensing applications," J. Opt.A 1937-1942 (2016

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Section: Introductionmentioning

confidence: 99%

Model for a pulsed terahertz quantum cascade laser under optical feedback

Agnew¹,

Grier²,

Taimre³

et al. 2016

Opt. Express

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“…The amplitude as well as the phase of the scattered field therefore can be monitored through the QCL terminal voltage. [6] To isolate the signal scattered by the tip apex from that due to the wave scattered by the entire needle, a modulation scheme was employed in which the needle tip was dithered sinusoidally at 90 Hz in the z-direction with amplitude of 1 μm, using a piezoelectric transducer. The synchronized inphase component of the self-mixing signal was then recovered using a lock-in amplifier referenced to the needle modulation.…”

Section: Resultsmentioning

confidence: 99%

“…They serve as a high-power source of THz waves and at the same time can be used as a sensitive detector due to the effect of self-mixing, which has already enabled coherent THz imaging applications [6].…”

Section: Introductionmentioning

confidence: 99%

Terahertz near-field microscopy using the self-mixing effect in a quantum cascade laser

Dean

Mitrofanov

Keeley

et al. 2016

2016 41st International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

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Abstract-We demonstrate terahertz (THz) apertureless nearfield microscopy exploiting the self-mixing effect in a quantum cascade laser (QCL). A THz wave is scattered by a sharp needle positioned above an object and coupled back into the QCL cavity resulting in detection of the THz near-field signal through the self-mixing effect. Using this technique we demonstrate twodimensional imaging at 2.53 THz with a spatial resolution of 1 μm -the highest image resolution achieved with a THz frequency QCL to date. This method offers an experimentally simple approach to coherent, high-resolution THz imaging.

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“…Each fringe is a line of constant height on the target, with height difference between two adjacent fringes corresponding to k=2 ðk=2 ¼ 1:785 lmÞ, giving an indication of the surface depth gradient, and suggesting the potential application of the SM technique to three-dimensional imaging. 28 In summary, we have demonstrated the SM effect in an ICL. We have shown that a SM signal in an MIR ICL can be acquired through the variation in voltage across the laser terminals, removing the need for an external detector.…”

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confidence: 99%