Abstract-Optomechanical response with nanometer resolution in the self-mixing signal of a terahertz quantum cascade laser

Andrea Ottomaniello, James Keeley, Pierluigi Rubino, Lianhe Li, Marco Cecchini, Edmund H. Linfield, A. Giles Davies, Paul Dean, Alessandro Pitanti, Alessandro Tredicucci,

(a) Sketch of the two configurations of the SM apparatus. (b) Calculated Δ𝑁$\mathrm{\Delta }N$ (blue curve), and measured 𝑉SM$V_{\mathrm{S}\mathrm{M}}$ (red points) as a function of Δ𝐿$\mathrm{\Delta }L$ using configuration 1

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-23-5663

Owing to their intrinsic stability against optical feedback (OF), quantum cascade lasers (QCLs) represent a uniquely versatile source to further improve self-mixing interferometry at mid-infrared and terahertz (THz) frequencies. Here, we show the feasibility of detecting with nanometer precision, the deeply subwavelength (<𝜆/6000$<\lambda /6000$) mechanical vibrations of a suspended Si3N4${\mathrm{S}\mathrm{i}}_3{\mathrm{N}}_4$ membrane used as the external element of a THz QCL feedback interferometer. Besides representing an extension of the applicability of vibrometric characterization at THz frequencies, our system can be exploited for the realization of optomechanical applications, such as dynamical switching between different OF regimes and a still-lacking THz master-slave configuration.

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.

Abstract-Symmetry enhanced non-reciprocal polarization rotation in a terahertz metal-graphene metasurface

Andrea Ottomaniello, Simone Zanotto, Lorenzo Baldacci, Alessandro Pitanti, Federica Bianco, and Alessandro Tredicucci

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-3-3328&origin=search

In the present article we numerically investigated the magneto-optical behaviour of a sub-wavelength structure composed by a monolayer graphene and a metallic metasurface of optical resonators. Using this hybrid graphene-metal structure, a large increase of the non-reciprocal polarization rotation of graphene can be achieved over a broad range of terahertz frequencies. We demonstrate that the symmetry of the resonator geometry plays a key role for the performance of the system: in particular, increasing the symmetry of the resonator the non-reciprocal properties can be progressively enhanced. Moreover, the possibility to exploit the metallic metasurface as a voltage gate to vary the graphene Fermi energy allows the system working point to be tuned to the desired frequency range. Another peculiar result is the achievement of a structure able to operate both in transmission and reflection with almost the same performance, but in a different frequency range of operation. The described system is hence a sub-wavelength, tunable, multifunctional, effective non-reciprocal element in the terahertz region.

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