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Photonics and Terahertz Group

Equipe Photonique et Terahertz

The research group, led by Dr. Alexandre Locquet and Prof. David. S. Citrin, is part of the lab "Unité Mixte Internationale (UMI) 2958 Georgia Tech-CNRS", an international collaboration between the Centre National de la Recherche Scientifique and the Georgia Institute of Technology. The lab is located at Georgia Tech Lorraine,Metz, France, which is the European campus of the Georgia Institute of Technology. The research activities encompass photonic information processing (from fundamentals of laser nonlinear dynamics to applications) as well as, terahertz imaging and spectroscopy for non-destructive evaluation.
Video presentation of the lab: click HERE.

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February 2019:Demonstration of a simple displacement sensor with 10 nanometer resolution based on optical feedback into a laser diode:
D. Choi, M. Wishon, E.A. Viktorov, D.S. Citrin, and A. Locquet, Nanometric sensing with laser feedback interferometry, Opt. Lett. 44, 903 (2019). Collaboration with E.A. Viktorov, ITMO University, Saint Petersburg, Russia.

August 2018:Demonstration of a multi-GHz frequency tunable microwave oscillator with a phase noise level of -107 dBc/Hz at 10 kHz:
M.J. Wishon, D. Choi, T. Niebur, N. Webster, Y. K. Chembo, E.A. Viktotov, D.S. Citrin, and A. Locquet, Low-noise X-band tunable microwave generator based on a semiconductor laser with feedback , IEEE Photon. Technol. Lett. 30, 1597-1600 (2018). Collaboration with E.A. Viktorov, ITMO University, Saint Petersburg, Russia, and Y.K. Chembo, UMI 2958 Georgia Tech-CNRS Mirror lab, Atlanta, US.

July 2018: Subsurface damage can be seen in carbon fiber-reinforced composites thanks to terahertz imaging:
J. Dong, P. Pomarède, L. Chemami, A. Locquet, F. Meraghni, N.F. Declercq, and D.S. Citrin, Visualization of subsurface damage in woven carbon fiber-reinforced composites using polarization-sensitive terahertz imaging , NDT&E International 99, 72-79 (2018).

June 2018: We demonstrate that the voltage across a laser diode subjected to optical feedback can be used to generate random bits with rates of several Gbit/s. Further, it appears that the statistics of the voltage is better suited than the optical intensity for extracting random bits as less or no post-processing is needed.
M.J. Wishon, N. Li, D. Choi, D.S. Citrin, and A. Locquet, Chaotic laser voltage: An electronic entropy source, Appl. Phys. Lett. 112, 261101 (2018).

March 2018: We reinterpret the instabilities arising in semiconductor lasers subjected to optical feedback using simultaneous measurements of the optical phase, intensity and carriers:
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.033849

December 2017: We reveal, using terahertz imaging and sparse deconvolution, the various paint layers of a XVIIth century oil painting on canvas "Madonna in Preghiera" by the workshop of Sassoferrato : Global mapping of stratigraphy of an old-master painting using sparsity-based terahertz reflectometry. Work in collaboration with Marcello Melis, from Profilocolore (Rome, Italy) and Musée de La Cour d'Or (Metz, France).

November 2017: Spontaneous mode-locking can occur in an external-cavity laser due to a resonance between the relaxation oscillation period and the external-cavity round-trip time: Delay induced high order locking effects in semiconductor lasers. Work in collaboration with University College Cork, Cork Institute of Technology, Institut de Physique de Nice, ITMO university, and Université Libre de Bruxelles.

September 2017: We read data on a commercial CD/DVD without making use of a photodiode but by sending the light reflected from the CD/DVD back into the laser and monitoring the resulting changes in the laser voltage:Reading bits on a CD-ROM without a photodiode (IET Optoelectronics 11, 10 (2017))

June 2017: We improve significantly the depth resolution of terahertz pulsed imaging through spectral extrapolation: Depth-resolution enhancement of terahertz deconvolution by autoregressive spectral extrapolation (Optics Letters 42, 1828 (2017))

April 2017: We show that a laser diode subjected to optical feedback can be used to generate a tunable, multi-GHz, periodic signal. The setup is remarkably simple and does not require the use of a fast photodetector.
https://doi.org/10.1109/JQE.2017.2682702 (IEEE J. Quantum Electron 53, 2000406 (2017)).

March 2017: Our latest paper on a new signal processing method for Terahertz nondestructive evaluation, based on the sparse deconvolution concept. It decreases the number of measurements needed (superresolution) and can increase axial resolution and dynamic range: https://doi.org/10.1109/TTHZ.2017.2673542 (IEEE Transactions on THz Science and Technology, 8 March 2017, early access).

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PHOTONICS AND TERAHERTZ GROUP
@ UMI 2958 Georgia Tech-CNRS

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