Anti-reflection coating design for metallic terahertz meta-materials

Pancaldi, Matteo; Freeman, Ryan; Heinrich, Matthias; Hoffmann, Matthias C.; Urazhdin, Sergei; Vavassori, P.; Bonetti, Stefano

doi:10.1364/oe.26.002917

Cited by 8 publications

(4 citation statements)

References 35 publications

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“…This is not surprising considering the narrow resonance of the structure plotted in figure 1(b). It is however worth highlighting that the broadband characteristics of the pulse can be preserved in other types of MM structures, when the resonance frequency is far off the bandwidth of the impinging radiation [36,55].…”

Section: Field Enhancementmentioning

confidence: 99%

Terahertz magnetic field enhancement in an asymmetric spiral metamaterial

Polley

Hagström

Schmising

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

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We use finite element simulations in both the frequency and the timedomain to study the terahertz resonance characteristics of a metamaterial (MM) comprising a spiral connected to a straight arm. The MM acts as a RLC circuit whose resonance frequency can be precisely tuned by varying the characteristic geometrical parameters of the spiral: inner and outer radius, width and number of turns. We provide a simple analytical model that uses these geometrical parameters as input to give accurate estimates of the resonance frequency. Finite element simulations show that linearly polarized terahertz radiation efficiently couples to the MM thanks to the straight arm, inducing a current in the spiral, which in turn induces a resonant magnetic field enhancement at the center of the spiral. We observe a large (approximately 20 times) and uniform (over an area of ∼ 10 µm 2 ) enhancement of the magnetic field for narrowband terahertz radiation with frequency matching the resonance frequency of the MM. When a broadband, single-cycle terahertz pulse propagates towards the metamaterial, the peak magnetic field of the resulting band-passed waveform still maintains a 6-fold enhancement compared to the peak impinging field. Using existing laser-based terahertz sources, our metamaterial design allows to generate magnetic fields of the order of 2 T over a time scale of several picoseconds, enabling the investigation of non-linear ultrafast spin dynamics in table-top experiments. Furthermore, our MM can be implemented to generate intense near-field narrowband, multi-cycle electromagnetic fields to study generic ultrafast resonant terahertz dynamics in condensed matter.

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Section: Field Enhancementmentioning

confidence: 99%

Terahertz magnetic field enhancement in an asymmetric spiral metamaterial

Polley

Hagström

Schmising

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

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“…Wide-range tunable broadband THz conductivity means active impedance matching control [5], and it possibly enables powerful new technologies for active THz devices. However, metal films are limited by nonadjustable THz conductivity [6]; traditional semiconductor films with controllable carrier concentration always have poor response [7]; patterned metamaterials can be good in designed performances but have high cost for large scale applications and limited bandwidth [8]. Therefore, new impedance matching conductors are still in urgent need.…”

Section: Introductionmentioning

confidence: 99%

Active broadband terahertz wave impedance matching based on optically doped graphene–silicon heterojunction

Zhou

Yao

et al. 2019

Nanotechnology

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Broadband terahertz (THz) impedance matching is important for both spectral resolution improvement and THz anti-radar technology. Herein, graphene-silicon hybrid structure has been proposed for active broadband THz wave impedance matching with optical tunability. The main transmission pulse measured in the time domain indicates a modulation depth as high as 92.7% totally from the graphene-silicon interface. The interface reflection from the graphene-silicon junction implies that an impedance matching condition can be actively achieved by optical doping. To reveal the mechanism, we propose a graphene-silicon heterojunction model, which gives a full consideration of both the THz conductivity of graphene and the loss in doped junction layer. The theory fits well with the experimental results. This work proves active THz wave manipulation by junction effect and paves the way for active anti-reflection coating for THz components.

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“…In many cases, silicon is preferable in terahertz frequency range. For instance, in condensed matter physics investigations, a silicon anti-reflection coating has been involved and designed for planar metamaterials enhancing an electromagnetic terahertz field of pumping to prevent a probing light reflection by metallic elements of the metamaterial [7]. Results of experimental research on nonlinear properties of silicon wafer with metallic periodical structure placed on one of its surfaces are presented in [8].…”

Section: Introductionmentioning

confidence: 99%