Abstract-THz surface plasmon polariton modes coupled to complementary metasurfaces tuned by inter meta-atom distance

Janine Keller, Curdin Maissen,   Johannes Haase,  Gian Lorenzo Paravicini-Bagliani,  Federico Valmorra, José Palomo, Juliette Mangenev,  Jérôme Tignon,   Sukhdeep S. Dhillon,  Giacomo Scalari, Jérôme Faist

http://ieeexplore.ieee.org/document/8087672/

Tailoring the electro-magnetic response of materials beyond naturally occurring properties is possible with the concept of meta-materials [1]. Subwavelength elements which are usually closely spaced can influence the electro-magnetic response and form a fundamental building block of modern optics. The influence of the spacing of the meta-atoms has been investigated for direct meta-materials [2] but only little for complementary metamaterials [3], which are of interest e.g. in ultra-strong coupling experiments at THz frequencies [4]. The effective medium condition is changing due to the presence of a metal sheet in between the meta-atoms which has a very high refractive index in the THz.THz time domain spectroscopy was performed for 15 samples with a constant frequency of the complementary split ring resonator (cSRR) and varying inter meta-atom distances from 40 μm to 160 μm [6], a sample sketch is shown in Fig. 1 a). For spacings of the cSRR that are not strictly subwavelength anymore, a regime of resonant coupling to THz surface plasmon polaritons (SPPs) [5] is entered. We observe an anti-crossing (shown in Fig. 1 b)) of the cSRR LC-mode and the SPP-mode, leading to a strong coupling with a normalized coupling ratio of 3.5% at the resonance frequency of 1.07 THz. Finite element simulations with CST MWS show the characteristic field distribution of the two modes in the plane of the resonator and the intermixing of the LCmode with the SPP-mode very clearly as well as simulations of the mode extensions into the substrate (see Fig. 1 c)). Analytical modeling with a simple two oscillator model describes the coupling well and yields an effective relative permittivity of 11.6 for the coupled system. Measurements of the broader, dipole-like resonance of the cSRR in orthogonal polarization direction show a Fano-like lineshape when the SPPs tune across. Utilizing rectangular array configurations we show that the excitation direction lies along the polarization of the exciting THz pulse. Additionally, we measured the dependence of the incident angle on the frequency of the measured SPPs, where we see a splitting of the SPP. We demonstrate that the understanding of the SPP modes is fundamental for research and applications in which the metasurface has to be designed for special needs.

Abstract-Measuring intensity correlations of a THz quantum cascade laser around its threshold at sub-cycle timescales

Ileana Cristina Benea Chelmus, Christopher Bonzon, Curdin Maissen, Giacomo Scalari, Mattias Beck, Jerome Faist

(Submitted on 29 Nov 2016)

https://arxiv.org/abs/1611.09562

The quantum nature of photonic systems is reflected in the photon statistics of the light they emit. Therefore, the development of quantum optics tools with single photon sensitivity and excellent temporal resolution is paramount to the development of exotic sources, and is particularly challenging in the THz range where photon energies approach kbT at T=300 K. Here, we report on the first room temperature measurement of field g1({\tau}) and intensity correlations g2({\tau}) in the THz range with sub-cycle temporal resolution (146 fs) over the bandwidth 0.3-3 THz, based on electro-optic sampling. With this system, we are able to measure the photon statistics at threshold of a THz Quantum Cascade Laser.

Abstract-Electrically tunable graphene anti-dot array terahertz plasmonic crystals exhibiting multi-band resonances

Electrically tunable graphene anti-dot array terahertz plasmonic crystals exhibiting multi-band resonances Peter Q. Liu, Federico Valmorra, Curdin Maissen, and Jerome Faist  »View Author Affiliations

http://www.opticsinfobase.org/optica/abstract.cfm?uri=optica-2-2-135

Optica, Vol. 2, Issue 2, pp. 135-140 (2015)
http://dx.doi.org/10.1364/OPTICA.2.000135

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Graphene-based plasmonic structures feature large tunability, high spatial confinement, and potentially low loss, and are therefore an emerging technology for unconventional manipulation of light. In this paper, we demonstrate electrically tunable terahertz plasmonic crystals consisting of square-lattice graphene periodic anti-dot arrays on a SiO2/Sisubstrate. Transmission spectroscopy reveals multiple distinct resonances arising from excitations of graphene surface-plasmon–polariton (SPP) modes on different branches of the SPP dispersion curves inherent to the periodic structures. The resonance frequencies are readily tuned electrostatically with the Si back-gate and exhibit the dependency on the carrier density unique to SPP in graphene. Simulations show excellent agreement with the experiments and further illustrate the symmetry-based selection rule for the excited graphene SPP modes. Such graphene plasmonic crystals may lead to a broad range of applications including plasmonic waveguide and transformation optics. Exploiting higher-order graphene SPP modes is an effective way to further facilitate field localization and enhancement.

© 2015 Optical Society of America

Abstract-Low-Bias Active Control of Terahertz Waves by Coupling Large-Area CVD Graphene to a Terahertz Metamaterial

Federico Valmorra *†, Giacomo Scalari *†, Curdin Maissen †, Wangyang Fu ‡, Christian Schönenberger‡, Jong Won Choi §, Hyung Gyu Park §, Mattias Beck†, and Jérôme Faist †

http://pubs.acs.org/doi/abs/10.1021/nl4012547

We propose an hybrid graphene/metamaterial device based on terahertz electronic split-ring resonators directly evaporated on top of a large-area single-layer CVD graphene. Room temperature time-domain spectroscopy measurements in the frequency range from 250 GHz to 2.75 THz show that the presence of the graphene strongly changes the THz metamaterial transmittance on the whole frequency range. The graphene gating allows active control of such interaction, showing a modulation depth of 11.5% with an applied bias of 10.6 V. Analytical modeling of the device provides a very good qualitative and quantitative agreement with the measured device behavior. The presented system shows potential as a THz modulator and can be relevant for strong light–matter coupling experiments.