IEM Distinguished Lecturers Seminar: Modulation and routing of nonlinear optical signals with metasurfaces above GHz rates
***Coffee and cookies will be served at 13:00 in the hall of BM 5202***
Abstract
Optical metasurfaces are rapidly gaining traction as ultrathin multifunctional platforms for light management. Their capability to shape the wavefront of light makes them ideal for free-space optical analog computing. In this framework, the fast reconfigurability of metasurfaces constitutes an indisputable requirement to secure practical application. To date, electro-optical and all-optical modulation represent the foremost approaches for light manipulation through metasurfaces, thanks to the compatibility with CMOS technology and the modulation rates above the GHz. Yet, fast modulation often comes at the expense of optical signals modulation depths (i.e. efficiency).
The last decades witnessed major efforts in the field of nanophotonics to attain efficient nonlinear optical effects in nanoscale volumes. The main challenge in this scenario resides in the perturbative character of the nonlinear interactions in nanoscale systems. A key strategy to circumvent this limitation is to boost light–matter interaction by leveraging optical resonances in engineered nanoantennas and metasurfaces [1]. While conversion efficiencies at the nanoscale will unlikely reach those of bulk nonlinear crystals, the nonlinear character of these signals grants higher sensitivity to environmental changes compared to linear signals. This enables strong signal modulation depths at the nanoscale [2], fueling the development of nonlinear metasurfaces for electro- and all-optical light manipulation (e.g. modulation, steering and amplification).
In this seminar, I will show our latest approaches to light modulation and routing by means of optical metasurfaces based on highly nonlinear materials, namely lithium niobate (LiNbO3) and aluminum gallium arsenide (AlxGa1-xAs). First, I will present a LiNbO3 metasurface design, empowered by quasi bound states in the continuum (q-BIC) resonances, that allows realizing electro-optic modulation of optical signals at telecom wavelengths with efficiency exceeding 10% at rates above the GHz [3]. Noteworthy, this platform also achieves a record modulation of the second harmonic generated by a CW pump laser of more than one order of magnitude. Finally, by means of a periodic AlxGa1-xAs metasurfaces, I will demonstrate all-optical routing and polarization modulation of upconverted optical signals exploiting nonlinear interferometry [4,5]. These experimental realizations allow envisioning modulation rates approaching that of the light optical cycle and can be employed for the realization of enhanced sensing platforms.
References
[1] L. Bonacina, P.-F. Brevet, M. Finazzi, and M. Celebrano “Harmonic Generation at the Nanoscale” Journal of Applied Physics 127, 230901 (2020)
[2] M. Celebrano et al. “Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces” Opt. Lett. 46 2453-2456 (2021).
[3] A. Di Francescantonio et al. “Efficient GHz electro-optical modulation with a nonlocal lithium niobate metasurface in the linear and nonlinear regime” submitted. https://arxiv.org/abs/2412.03422
[4] A. Di Francescantonio et al. “All-optical free-space routing of upconverted light by metasurfaces via nonlinear interferometry”, Nat. Nanotechnology (2023). https://doi.org/10.1038/s41565-023-01549-2
[5] Y. Luan, et al. “All-optical polarization control and routing by nonlinear interferometry at the nanoscale”, submitted. https://arxiv.org/abs/2412.07714
Short Bio
Michele Celebrano (https://www.fisi.polimi.it/en/staff/michele.celebrano) is Associate Professor at the Department of Physics of Politecnico di Milano and PI at the “supra Nano-Optics Milano” sNOm Lab (https://www.fisi.polimi.it/en/research-labs/snom), currently investigating the linear and nonlinear optical properties of nanoantennas and metasurfaces with the aim of exploiting nonlinear upconversion processes for sensing, optical logic operations and THz generation.
He received his PhD in Physics in 2008 at Politecnico di Milano under the supervision of Prof. Giulio Cerullo and successively worked as Post-Doc in the Nano-Optics Group led by Prof. Vahid Sandoghdar at ETH Zurich (2008-11).
He currently Associate Editor at Optics Express and chair of the ‘Plasmonics and Metamaterial’ Committee of the CLEO-EQEC Congress. He published more than 150 among scientific papers and conference proceedings with more than 4000 citations and received the Italian habilitation to Full-Professor in 2020.
Abstract
Optical metasurfaces are rapidly gaining traction as ultrathin multifunctional platforms for light management. Their capability to shape the wavefront of light makes them ideal for free-space optical analog computing. In this framework, the fast reconfigurability of metasurfaces constitutes an indisputable requirement to secure practical application. To date, electro-optical and all-optical modulation represent the foremost approaches for light manipulation through metasurfaces, thanks to the compatibility with CMOS technology and the modulation rates above the GHz. Yet, fast modulation often comes at the expense of optical signals modulation depths (i.e. efficiency).
The last decades witnessed major efforts in the field of nanophotonics to attain efficient nonlinear optical effects in nanoscale volumes. The main challenge in this scenario resides in the perturbative character of the nonlinear interactions in nanoscale systems. A key strategy to circumvent this limitation is to boost light–matter interaction by leveraging optical resonances in engineered nanoantennas and metasurfaces [1]. While conversion efficiencies at the nanoscale will unlikely reach those of bulk nonlinear crystals, the nonlinear character of these signals grants higher sensitivity to environmental changes compared to linear signals. This enables strong signal modulation depths at the nanoscale [2], fueling the development of nonlinear metasurfaces for electro- and all-optical light manipulation (e.g. modulation, steering and amplification).
In this seminar, I will show our latest approaches to light modulation and routing by means of optical metasurfaces based on highly nonlinear materials, namely lithium niobate (LiNbO3) and aluminum gallium arsenide (AlxGa1-xAs). First, I will present a LiNbO3 metasurface design, empowered by quasi bound states in the continuum (q-BIC) resonances, that allows realizing electro-optic modulation of optical signals at telecom wavelengths with efficiency exceeding 10% at rates above the GHz [3]. Noteworthy, this platform also achieves a record modulation of the second harmonic generated by a CW pump laser of more than one order of magnitude. Finally, by means of a periodic AlxGa1-xAs metasurfaces, I will demonstrate all-optical routing and polarization modulation of upconverted optical signals exploiting nonlinear interferometry [4,5]. These experimental realizations allow envisioning modulation rates approaching that of the light optical cycle and can be employed for the realization of enhanced sensing platforms.
References
[1] L. Bonacina, P.-F. Brevet, M. Finazzi, and M. Celebrano “Harmonic Generation at the Nanoscale” Journal of Applied Physics 127, 230901 (2020)
[2] M. Celebrano et al. “Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces” Opt. Lett. 46 2453-2456 (2021).
[3] A. Di Francescantonio et al. “Efficient GHz electro-optical modulation with a nonlocal lithium niobate metasurface in the linear and nonlinear regime” submitted. https://arxiv.org/abs/2412.03422
[4] A. Di Francescantonio et al. “All-optical free-space routing of upconverted light by metasurfaces via nonlinear interferometry”, Nat. Nanotechnology (2023). https://doi.org/10.1038/s41565-023-01549-2
[5] Y. Luan, et al. “All-optical polarization control and routing by nonlinear interferometry at the nanoscale”, submitted. https://arxiv.org/abs/2412.07714
Short Bio
Michele Celebrano (https://www.fisi.polimi.it/en/staff/michele.celebrano) is Associate Professor at the Department of Physics of Politecnico di Milano and PI at the “supra Nano-Optics Milano” sNOm Lab (https://www.fisi.polimi.it/en/research-labs/snom), currently investigating the linear and nonlinear optical properties of nanoantennas and metasurfaces with the aim of exploiting nonlinear upconversion processes for sensing, optical logic operations and THz generation.
He received his PhD in Physics in 2008 at Politecnico di Milano under the supervision of Prof. Giulio Cerullo and successively worked as Post-Doc in the Nano-Optics Group led by Prof. Vahid Sandoghdar at ETH Zurich (2008-11).
He currently Associate Editor at Optics Express and chair of the ‘Plasmonics and Metamaterial’ Committee of the CLEO-EQEC Congress. He published more than 150 among scientific papers and conference proceedings with more than 4000 citations and received the Italian habilitation to Full-Professor in 2020.
Practical information
- General public
- Free