Eva Pogna

Politecnico di Milano, Department of Physics, Graduate Student

Followers

Following

Public Views

Address: Spain

less

Interests

Uploads

Papers by Eva Pogna

Near-field THz detection of phonon-polariton modes in thin flakes of topological insulator materials: Bi2Se3 and Bi(Te1-x Sex)3

We report on the study of phonon polaritons modes in thin crystalline flakes of Bi<inf>2&lt... more We report on the study of phonon polaritons modes in thin crystalline flakes of Bi<inf>2</inf>Se<inf>3</inf> and Bi<inf>2</inf>(Te<inf>1-x</inf> Se<inf>x</inf>)3 as a function of the flake thickness, by means of two near-field THz techniques: phase resolved self-detection and THz time domain spectroscopy (TDS-SNOM). Background-free near-field imaging with nanoscale spatial resolution is demonstrated.

Near-Field Mapping of THz Polaritons Propagation in Quantum Materials

CLEO 2023

Near-field imaging is applied to investigate the terahertz collective excitations of thin films o... more

All in One‐Chip, Electrolyte‐Gated Graphene Amplitude Modulator, Saturable Absorber Mirror and Metrological Frequency‐Tuner in the 2–5 THz Range

Advanced Optical Materials

Near-field study of THz collective excitations in topological insulators

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)

Self‐Induced Phase Locking of Terahertz Frequency Combs in a Phase‐Sensitive Hyperspectral Near‐Field Nanoscope

Advanced Science

Chip-scale, electrically-pumped terahertz (THz) frequency-combs (FCs) rely on nonlinear four-wave... more Chip-scale, electrically-pumped terahertz (THz) frequency-combs (FCs) rely on nonlinear four-wave-mixing processes, and have a nontrivial phase relationship between the evenly spaced set of emitted modes. Simultaneous monitoring and manipulation of the intermode phase coherence, without any external seeding or active modulation, is a very demanding task for which there has hitherto been no technological solution. Here, a self-mixing intermode-beatnote spectroscopy system is demonstrated, based on THz quantum cascade laser FCs, in which light is back-scattered from the tip of a scanning near-field optical-microscope (SNOM) and the intracavity reinjection monitored. This enables to exploit the sensitivity of FC phase-coherence to optical feedback and, for the first time, manipulate the amplitude, linewidth and frequency of the intermode THz FC beatnote using the feedback itself. Stable phase-locked regimes are used to construct a FC-based hyperspectral, THz s-SNOM nanoscope. This nanoscope provides 160 nm spatial resolution, coherent detection of multiple phase-locked modes, and mapping of the THz optical response of nanoscale materials up to 3.5 THz, with noise-equivalent-power (NEP) ≈400 pW √Hz −1. This technique can be applied to the entire infrared range, opening up a new approach to hyper-spectral near-field imaging with wide-scale applications in the study of plasmonics and quantum science, inter alia.

Download

Lattice dynamics and elastic properties of black phosphorus

Physical Review B

We experimentally determine the lattice dynamics of black phosphorus layered crystals through a c... more We experimentally determine the lattice dynamics of black phosphorus layered crystals through a combination of x-ray diffuse scattering and inelastic x-ray scattering, and we rationalize our experimental findings using ab initio calculations. From the phonon dispersions, at terahertz frequencies, we derive the full single-crystal elastic tensor and relate it to the macroscopic elastic response of black phosphorus, described by the elastic moduli. The elastic stiffness coefficients obtained here, provide an important benchmark for models of black phosphorus and related materials, such as phosphorene and black phosphorus nanotubes, recently emerged quantum materials, disclosing a huge potential for nanophotonics, optoelectronics and quantum sensing.

Download

Multifunctional Ionic-Gated Graphene Salisbury Mirror Supercapacitor, with Saturable Absorption, Amplitude Modulation and Frequency-Tuning Capabilities in the 2-5 THz Range

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)

Phase-sensitive hyperspectral near-field nanoscope based on self-induced phase locking of terahertz frequency combs

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)

Ultrafast spectroscopy of two dimensional semiconductors

Italy, Mar 13, 2017

Publisher Correction: Mapping propagation of collective modes in Bi2Se3 and Bi2Te2.2Se0.8 topological insulators by nearfield terahertz nanoscopy

Nature Communications, 2021

Mapping propagation of collective modes in Bi2Se3 and Bi2Te2.2Se0.8 topological insulators by nea... more Mapping propagation of collective modes in Bi2Se3 and Bi2Te2.2Se0.8 topological insulators by near-field terahertz nanoscopy Eva Arianna Aurelia Pogna, Leonardo Viti, Antonio Politano, Massimo Brambilla, Gaetano Scamarcio, Miriam Serena Vitiello NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio 1, 67100 L’Aquila, Italy Dipartimento Interateneo di Fisica, Università degli Studi e Politecnico di Bari, via Amendola 173, 70126 Bari, Italy

Electrically Tunable Nonequilibrium Optical Response of Graphene

ACS Nano, 2022

Download

Supplementary document for Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces - 5188886.pdf

Download

Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2

Download

Enhancing and switching harmonic generation in plasmonic and dielectric nanoantennas (Conference Presentation)

Metamaterials XII, 2020

Nanoscale optical integration is nowadays a strategic technological challenge and the ability of ... more Nanoscale optical integration is nowadays a strategic technological challenge and the ability of generating and manipulating nonlinear optical processes in sub-wavelength volumes is pivotal to realize efficient sensing probes and photonic sources for the next-generation communication technologies. Yet, confining nonlinear processes below the diffraction limit remains a challenging task because phase-matching is not a viable approach at the nanoscale. The localized fields associated to the resonant modes of plasmonic and dielectric nanoantennas offer a route to enhance and control nonlinear processes in highly confined volumes. In my talk I will discuss two nonlinear platforms based on plasmonic and dielectric nanostructures. The first relies on a broken symmetry antenna design, which brings about an efficient second harmonic generation (SHG). We recently applied this concept to an extended array of non-centrosymmetric nanoantennas for sensing applications. I will also show the evidence of a cascaded second-order process in Third Harmonic Generation (THG) in these nanoantennas. Recently, dielectric nanoantennas emerged as an alternative to plasmonic nanostructures for nanophotonics applications, thanks to their sharp magnetic and electric Mie resonances along with the low ohmic losses in the visible/near-infrared region of the spectrum. I will present our most recent studies on the nonlinear properties of AlGaAs dielectric nanopillars. The strong localized modes along with the broken symmetry in the crystal structure of AlGaAs allow obtaining more than two orders of magnitude higher SHG efficiency with respect to plasmonic nanoantennas with similar spatial footprint and using the same pump power. I will also discuss a few key strategies we recently adopted to optically switch the SHG in these antennas even on the ultrafast time scale. Finally, I will show how to effectively engineer the sum frequency generation via the Mie resonances in these nanoantennas. These results draw a viable blueprint towards room-temperature all optical logic operation at the nanoscale.

All-Optical Ultrafast Control of Second Harmonic Generation in AlGaAs Nanopillars

2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2019

All-dielectric nanophotonics has recently raised an increasing interest because the optical respo... more All-dielectric nanophotonics has recently raised an increasing interest because the optical response of high-permittivity dielectric nanoparticles exhibits negligible dissipative losses and strong magnetic multipole resonances [1–4] in the visible and near-IR. We recently reported a second harmonic generation (SHG) conversion efficiency higher than 10−5 at 2 = 1554 nm (pump intensity ≈ 1.6 GW/cm2; pulse width ≈ 150 fs; repetition rate = 80 MHz) in all-dielectric Al0.18Ga0.82As-on-AlOx nanodisks [5–7]. Such a remarkable efficiency is achieved thanks to the exploitation of magnetic and electric resonances emerging at coincidence with both the pump and SHG wavelength. In addition, the choice of both the pump and, consequently, the SHG (≈ 777 nm) wavelength, set below the energy of the material bandgap, allow minimizing the two-photon absorption of the pump and the re-absorption of the SHG.

Tracking exciton-trion interplay in the transient optical properties of WS2 inks

2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017

Transition metal dichalcogenides (TMDs) are anisotropic materials crystallizing in a graphite-lik... more Transition metal dichalcogenides (TMDs) are anisotropic materials crystallizing in a graphite-like structure, with each layer consisting of an hexagonal plane of transition metal atoms sandwiched between two hexagonal planes of chalcogen atoms. The weak interlayer Van der Waals bonds can be broken to isolate stable two-dimensional (2D) crystals. A wide variety of techniques have been developed to produce 2D-TMDs with electronic and optical properties extremely different from the bulk [1]. Among these, liquid-phase exfoliation (LPE) [2-3] has demonstrated to be a promising approach for scaling up to industrial level. The 2D versions of TMDs have attracted tremendous interest for optoelectronics applications because they offer properties that are complementary to those of graphene. They have a sizable electronic gap in the infrared and visible range and at the single-layer limit a transition from indirect to direct bandgap semiconductor occurs.

Electrically Tunable Graphene-on-Polyimide Terahertz Modulators

2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2020

We report a graphene-on-polyimide THz modulator with a tunable-by-design optical bandwidth, a 90%... more We report a graphene-on-polyimide THz modulator with a tunable-by-design optical bandwidth, a 90% modulation efficiency, a 20 KHz electrical bandwidth and tunable in the 1.9-2.7 THz range. The electrostatic tuning of the THz conductivity is achieved through a grating gate coupler on the top of the polyimide waveguide. By coupling the modulator with a THz quantum cascade laser frequency comb, we show it can fully compensate the cavity dispersion, resulting in stable frequency comb operation over a 45% dynamic range.

Near-Field THz Photocurrent Nanoscopy of InAs Nanowires FET

The increasing interest in manipulating electromagnetic waves in the terahertz (THz) spectral ran... more The increasing interest in manipulating electromagnetic waves in the terahertz (THz) spectral range has motivated, in the last decade, a great research effort in the development of miniaturized technologies for THz emission and detection. Recently, field effect transistors (FETs), exploiting semiconductor nanowires (NWs) as active element, have been proven successful in highly-sensitive room-temperature detection of THz frequency beams. The FETs act as rectifiers converting the impinging THz radiation into a DC signal between source (S) and drain (D), proportional to the absorbed power and controlled by the gate (G) bias. The THz-detection with the NW either exploits the photo-excitation of plasma waves [1], or, thermoelectric phenomena [2].

Non-equilibrium optical properties of encapsulated graphene

A multitude of existing technologies are based on the ability of converting light into electrical... more A multitude of existing technologies are based on the ability of converting light into electrical signals. Graphene has demonstrated a number of optical and transport properties [1] which are promising for this type of optoelectronic applications and great efforts have been devoted to the development of graphene-based photodetectors. Being a gapless semiconductor, graphene enables light absorption over a wide energy spectrum, spanning from the ultraviolet to the far infrared. Moreover, its absorption is wavelength-independent and its optical properties are tunable via electrostatic doping. Finally, it displays low dissipation rates and high carrier mobility and it enables electromagnetic-energy confinement to extremely small volumes [2]. However, graphene devices on standard SiO2-substrates display properties that are far inferior to that of the suspended graphene. This motivates the research for dielectrics that allow substrate-supported geometry while retaining the intrinsic quali...

Download

Tracing photodetection of THz frequency light in InAs nanowire field effect transistors via near-field THz nanoscopy

2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2020

We trace the photodetection mechanisms at THz frequencies in InAs nanowire (NW) field-effect tran... more We trace the photodetection mechanisms at THz frequencies in InAs nanowire (NW) field-effect transistors (FET) by means of a combination of two near-field techniques: photocurrent nanoscopy and detectorless scattering near-field microscopy. By mapping local THz photocurrents with nanoscale (15 nm) spatial resolution we demonstrate the activation of photo-thermoelectric and bolometric effects under THz illumination of these room temperature nanodetectors.

Eva Pogna

Uploads

Papers by Eva Pogna

Log In