Dr. Attilio Zilli Profile

Dr. Attilio Zilli

Research Associate at Politecnico di Milano

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Author

Area of Expertise:

Nanophotonics , Nonlinear optics , Nanoparticles , Metamaterials

Attilio Zilli is a Physics graduate from Sapienza University of Rome, Italy. He earned his PhD in 2018 from Cardiff University, UK, where he studied the optical properties of colloidal nanoparticles under the supervision of Prof. Paola Borri and Wolfgang Langbein. In 2019 he joined as a post-doc the Nano-Optics Lab led by Prof. Michele Celebrano in Politecnico di Milano, Italy. He is currently a Research Associate affiliated with the same group, where he performs experimental research in the field of nonlinear nano- and meta-photonics.

Proceedings Article | 4 October 2023 Presentation

Interferometric all-optical routing of upconverted light by dielectric metasurfaces

Attilio Zilli, Agostino Di Francescantonio, Davide Rocco, Fabrizio Conti, Vincent Vinel, Adrien Borne, Aristide Lemaître, Paolo Biagioni, Lamberto Duò, Costantino De Angelis, Giuseppe Leo, Marco Finazzi, Michele Celebrano

Proceedings Volume PC12646, PC126460Q (2023) https://doi.org/10.1117/12.2677509

KEYWORDS: Interferometry, Dielectrics, Sum frequency generation, Diffraction, Windows, Visibility, Tunable filters, Third harmonic generation, Silicon, Photons

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Proceedings Article | 24 May 2022 Presentation

Coherent modulation of the nonlinear emission of a plasmonic nanoantenna by dual-beam pumping

Attilio Zilli, Andrea Locatelli, Agostino Di Francescantonio, Xiaofei Wu, Thorsten Feichtner, Paolo Biagioni, Costantino De Angelis, Bert Hecht, Marco Finazzi, Michele Celebrano

Proceedings Volume PC12131, PC1213107 (2022) https://doi.org/10.1117/12.2621333

KEYWORDS: Modulation, Plasmonics, Nanoantennas, Nonlinear optics, Gold, Electromagnetism, Dielectrics, Complex systems, Visibility, Ultrafast phenomena

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The ongoing drive towards the miniaturization of nonlinear optics is motivated by the number of functionalities it could bring about in integrated devices, such as frequency conversion, information processing, and holography. The main hindrance to the technological deployment of nonlinear optics is the perturbative character of nonlinear interactions, whose intrinsic weakness is compounded at the nanoscale by the small volume of matter involved. The exploitation of the resonant electromagnetic modes supported by nanostructures in order to increase the strength of light–matter coupling is therefore a thriving area of research. In this work, we investigate gold dimers, where a V-antenna tuned to resonate at a telecom frequency ω (corresponding to a 1550 nm wavelength) is electromagnetically coupled to a rod resonating at 2ω. The structures were patterned lithographically out of a 40 nm-thick monocrystalline gold flake with a focused-ion (Ga) beam. In our experiment, a pump pulse at ω is mixed with its frequency-doubled replica, resulting in SFG at frequency ω+2ω = 3ω. A thorough experimental characterization discloses a rich phenomenology as the SFG is ruled by the resonant response. Such sensitive dependence on the geometry of the system and the excitation is unraveled through a systematic comparison to full-vectorial numerical simulations. In our dimers, on the one hand the doubly resonant design boosts both pumps of the SFG; on the other hand, the non-centrosymmetric shape allows interference of SFG with third-harmonic generation (THG), which also occurs at ω+ω+ω = 3ω. Delay traces of the signal at 3ω exhibit strong interference fringes (power modulation above 400%) with a 2ω periodicity. The small dephasing between pumps required to achieve such sizable modulation can be imparted by either mechanical or electro-optic means; along with the instantaneous (electronic) character of the materials response, this suggests enticing perspectives for ultrafast modulation and coherent control.

Proceedings Article | 24 May 2022 Presentation

Second-harmonic generation of visible light by a monolithic lithium niobate metasurface

Attilio Zilli, Luca Carletti, Fabio Moia, Andrea Toma, Marco Finazzi, Costantino De Angelis, Dragomir Neshev, Michele Celebrano

Proceedings Volume PC12130, PC1213007 (2022) https://doi.org/10.1117/12.2621067

KEYWORDS: Lithium niobate, Visible radiation, Second-harmonic generation, Polarization, Nonlinear optics, Magnetism, Integrated optics, Computer programming, Transparency, Refractive index

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Metasurfaces hold promise to miniaturize many bulk (~mm) optical elements and concurrently enable the implementation of multiple optical functionalities in individual integrated optical devices. Nonlinear optics is a fast-rising area of application, albeit the sub-wavelength thickness of metasurfaces means that their nonlinear conversion efficiency is often very low. In this framework, lithium niobate (LN) is a ferroelectric material widely employed for optoelectronics and nonlinear optics thanks to its high refractive index, broad transparency window, and large electro-optical response and second-order nonlinearity. Over the last few years, much effort has thus been directed towards the realization of LN nanoparticles and nanostructures [1,2]. Here, we report highly directional second-harmonic (SH) generation of visible light by a monolithic LN metasurface [3]. The metasurface was milled on a commercially available z-cut LiNbO3 substrate via dual-beam focused ion beam lithography. Using an 80 MHz train of 140 fs laser pulses with 500 MW/cm2 peak intensity as a pump, we measured SH conversion efficiencies (SH power /exciting power) up to 2.5E-8. The numerically-assisted design of the metasurface [4] exploits the resonant modes of the single pillar: a magnetic dipole at the exciting wavelength of 820 nm, along with an electric dipole and a magnetic quadrupole at the SH wavelength. The interplay between the single-pillar emission and the grating mode of the metasurface brings about an efficient (~20 dB) rerouting of the SH emission from the zeroth into the first diffraction orders, which exhibit a unconventional polarization behavior. The studied system exemplifies a design concept of NL diffractive metasurface and is suitable for applications such as NL holography with polarization encoding. [1] A. Fedotova, et al., Nano Letters 20, 8608–8614 (2020) [2] T. Santiago-Cruz, et al. arXiv 2103.08524 (2021) [3] L. Carletti, et al. ACS Photonics 8, 731–737 (2021) [4] L. Carletti, et al. Optics Express 27, 33391–33398 (2019)

Proceedings Article | 18 April 2021 Presentation + Paper

Enhanced second-harmonic generation by single metal–insulator multilayered nanocavities with axial symmetry resonating in the near-infrared

Attilio Zilli, Tommi Isoniemi, Marzia Iarossi, Marco Finazzi, Francesco De Angelis, Michele Celebrano, Nicolò Maccaferri

Proceedings Volume 11770, 117700Y (2021) https://doi.org/10.1117/12.2589836

KEYWORDS: Nonlinear optics, Nanostructures, Complex systems, Visible radiation, Second-harmonic generation, Optoelectronics, Nonlinear crystals, Gold, Composites, Absorption

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Proceedings Article | 1 April 2020 Presentation

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

Lavinia Ghirardini, Eva Aurelia Arianna Pogna, Attilio Zilli, Paolo Biagioni, Lamberto Duò, Giovanni Pellegrini, Francesco Rusconi, Andrea Locatelli, Luca Carletti, Davide Rocco, Carlo Gigli, Giuseppe Marino, Aristide Lemaître, Andrea Mazzanti, Giuseppe Della Valle, Xiaofei Wu, Bert Hecht, Giulio Cerullo, Giuseppe Leo, Costantino De Angelis, Marco Finazzi, Michele Celebrano

Proceedings Volume 11344, 113440J (2020) https://doi.org/10.1117/12.2554643

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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.

Proceedings Article | 7 March 2019 Paper

Quantitative high-throughput optical sizing of individual colloidal nanoparticles by wide-field imaging extinction microscopy

Lukas Payne, Attilio Zilli, Yisu Wang, Wolfgang Langbein, Paola Borri

Proceedings Volume 10892, 108920J (2019) https://doi.org/10.1117/12.2507632

KEYWORDS: Particles, Nanoparticles, Spatial coherence, Microscopy, Scattering, Gold, Microscopes, Point spread functions

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