References of "Isoniemi, Tommi"
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See detailElectron Energy Loss Spectroscopy of Bright and Dark Modes in Hyperbolic Metamaterial Nanostructures
Isoniemi, Tommi; Maccaferri, Nicolò UL; Ramasse, Quentin M. et al

in Advanced Optical Materials (2020), 8(13), 2000277

Layered metal/dielectric hyperbolic metamaterials (HMMs) support a wide landscape of plasmon polariton excitations. In addition to surface plasmon polaritons, coupled Bloch-like gap-plasmon polaritons ... [more ▼]

Layered metal/dielectric hyperbolic metamaterials (HMMs) support a wide landscape of plasmon polariton excitations. In addition to surface plasmon polaritons, coupled Bloch-like gap-plasmon polaritons with high modal confinement inside the multilayer are supported. Photons can excite only a subset of these polaritonic modes, typically with a limited energy and momentum range in respect to the wide set of high-K modes supported by hyperbolic dispersion media, and coupling with gratings or local excitation is necessary. Strikingly, electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope allows nm-scale local excitation and mapping of the spatial field distribution of all the modes supported by a photonic or plasmonic structure, both bright and dark, and also all other inelastic interactions of the beam, including phonons and interband transitions. Herein, experimental evidence of the spatial distribution of plasmon polaritons in multilayered type II HMM nanostructures is acquired with an aloof electron beam adjacent to structures of current interest. HMM pillars are useful for their separation and adjustability of optical scattering and absorption, while HMM slot cavities can be used as waveguides with high field confinement. The nature of the modes is confirmed with corresponding simulations of EEL and optical spectra and near-field intensities. [less ▲]

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See detailDesigner Bloch plasmon polariton dispersion in grating-coupled hyperbolic metamaterials
Maccaferri, Nicolò UL; Isoniemi, Tommi; Hinczewski, Michael et al

in APL Photonics (2020), 5

Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. How- ever, it is challenging to tailor and excite these modes at optical ... [more ▼]

Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. How- ever, it is challenging to tailor and excite these modes at optical frequencies by prism coupling because of the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we report on the mechanism of excitation of high-index Bloch plasmon polariton modes with sub-diffraction spatial confinement using a meta-grating, which is a combined structure of a metallic diffraction grating and a type II HMM. We show how a one-dimensional plasmonic grating without any mode in the infrared spectral range, if coupled to an HMM supporting high-index modes, can efficiently enable the excitation of these modes via coupling to far- field radiation. Our theoretical predictions are confirmed by experimental reflection measurements as a function of angle of incidence and excitation wavelength. We introduce design principles to achieve a full control of high-index modes in meta-gratings, thus enabling a better understanding of light–matter interaction in this type of hybrid structure. The exploitation of the spectral response of these modes can find applications in bio-chemical sensing, integrated optics, and optical sub-wavelength imaging. [less ▲]

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See detailFabrication and Optical Characterization of Hyperbolic Nanoparticles on a Transparent Substrate
Iarossi, Marzia; Darvill, Daniel; Isoniemi, Tommi et al

in Proceedings of SPIE : The International Society for Optical Engineering (2019), 10927

We report on the fabrication and optical characterization of hyperbolic nanoparticles on a transparent substrate. These nanoparticles enable a separation of ohmic and radiative channels in the visible and ... [more ▼]

We report on the fabrication and optical characterization of hyperbolic nanoparticles on a transparent substrate. These nanoparticles enable a separation of ohmic and radiative channels in the visible and near-infrared frequency ranges. The presented architecture opens the pathway towards novel routes to exploit the light to energy conversion channels beyond what is offered by current plasmon-based nanostructures, possibly enabling applications spanning from thermal emission manipulation, theragnostic nano-devices, optical trapping and nano-manipulation, non-linear optical properties, plasmonenhanced molecular spectroscopy, photovoltaics and solar-water treatments, as well as heat-assisted ultra-dense and ultrafast magnetic recording. [less ▲]

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See detailHyperbolic Meta-Antennas Enable Full Control of Scattering and Absorption of Light
Maccaferri, Nicolò UL; Zhao, Yingqi; Isoniemi, Tommi et al

in Nano Letters (2019), 19(3), 1851-1859

We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables full control of absorption and scattering of light in the visible/near-infrared ... [more ▼]

We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables full control of absorption and scattering of light in the visible/near-infrared spectral range. This ability lies in the different nature of the localized hyperbolic Bloch-like modes excited within the meta-antenna. The experimental evidence is corroborated by a comprehensive theoretical study. In particular, we demonstrate that two main modes, one radiative and one non-radiative, can be excited by direct coupling with the free-space radiation. We show that the scattering is the dominating electromagnetic decay channel, when an electric dipolar mode is induced in the system, whereas a strong absorption process occurs when a magnetic dipole is excited. Also, by varying the geometry of the system, the relative ratio of scattering and absorption, as well as their relative enhancement and/or quenching, can be tuned at will over a broad spectral range, thus enabling full control of the two channels. Importantly, both radiative and nonradiative modes supported by our architecture can be excited directly with far-field radiation. This is observed to occur even when the radiative channels (scattering) are almost totally suppressed, thereby making the proposed architecture suitable for practical applications. Finally, the hyperbolic meta-antennas possess both angular and polarization independent structural integrity, unlocking promising applications as hybrid meta-surfaces or as solvable nanostructures. [less ▲]

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