Engineered Fractal Disorder for Light Management in Silicon Optoelectronics

Maria Josè Lo Faro^a, Antonio Alessio Leonardi^b, Maurilio Galletta^c, Barbara Fazio^c, Francesco Priolo^a, Alessia Irrera^c

^aPhysics and Astronomy Department, University of Catania, S. Sofia 64, Catania I-95123, Italy

^bDepartment of Chemical, Biological, Pharmaceutical and Environmental Sciences (ChiBioFarAm), University of Messina, ERIC aisbl and CASPE/INSTM, Messina, Italy

^cCNR IMM Institute for Microelectronics and Microsystems National Research Council, Viale F. Stagno D’Alcontres 31, 98158 Messina, Italy

Proceedings of MATSUS Fall 2026 Conference (MATSUSFall26)

E3 Photonics in Energy Conversion Materials and Devices

Palma, Spain, 2026 October 26th - 30th

Organizers: Miguel Alexandre, Catarina Ferreira and Guillermo Martínez-Denegri

Invited Speaker, Maria Josè Lo Faro, presentation 065
Publication date: 22nd July 2026

Engineered disorder is emerging as a powerful paradigm in modern photonics, enabling unconventional mechanisms for light transport, localization, and enhanced light–matter interaction beyond the limits of ordered photonic architectures [1–3]. In this framework, fractal silicon nanowire networks represent an ideal platform for multifunctional silicon optoelectronics, combining scalable fabrication, large surface-to-volume ratio, and broadband optical response with silicon technological compatibility.

In this invited contribution, we discuss recent advances in the development of two-dimensional fractal arrays of ultrathin silicon nanowires fabricated by metal-assisted chemical etching. The correlated fractal morphology promotes strong multiple scattering and efficient light trapping over broad spectral ranges, leading to extremely low reflectance, enhanced Raman scattering, and room-temperature photoluminescence [4–6]. Real-space and Fourier-space optical imaging reveal coherent and weakly localized Raman transport together with directional Raman beaming phenomena, providing direct visualization of photon diffusion and localization processes in disordered photonic media [5,6].

Beyond fundamental light transport physics, fractal silicon nanowire platforms enable several emerging applications in silicon optoelectronics and energy technologies. The strong enhancement of light–matter interaction supports highly sensitive optical biosensing, including amplification-free detection of viral targets [7], while the ultrahigh nanowire density and large electrochemically active surface area make these architectures promising candidates for energy-storage devices such as high-performance supercapacitors [8]. Additional functionalities are achieved through hybrid photonic configurations, including rare-earth active coatings for enhanced optical emission and telecom photonics applications.

These results demonstrate how engineered fractal disorder can transform silicon nanostructures into multifunctional photonic platforms for advanced light management, optical sensing, and sustainable optoelectronic technologies.

References:

[1] D. S. Wiersma, “Disordered photonics,” Nature Photonics, vol. 7, pp. 188–196, 2013.

[2] K. Vynck, M. Burresi, F. Riboli, and D. S. Wiersma, “Photon management in two-dimensional disordered media,” Nature Materials, vol. 11, pp. 1017–1022, 2012.

[3] S. Yu et al., “Engineered disorder in photonics,” Nature Reviews Materials, 6, 226–243 (2021).

[4] B. Fazio et al., “Strongly enhanced light trapping in a two-dimensional silicon nanowire random fractal array,” Light: Science & Applications, vol. 5, e16062, 2016.

[5] B. Fazio et al., “Coherent backscattering of Raman light,” Nature Photonics, vol. 11, pp. 170–176, 2017.

[6] M. J. Lo Faro et al., “Visualization of directional beaming of weakly localized Raman from a random network of silicon nanowires,” Advanced Science, vol. 8, 2100139, 2021.

[7] A. A. Leonardi et al., “SARS-CoV-2 and Omicron variant detection with a high selectivity, sensitivity, and low-cost silicon bio-nanosensor,” Nano Select, vol. 4, pp. 160–169, 2023.

[8] A. A. Leonardi et al., “2D fractal arrays of ultrathin silicon nanowires as cost-effective and high-performance substrate for supercapacitors,” Advanced Energy and Sustainability Research, vol. 5, 2400080, 2024.

Acknowledgements:

MJLF acknowleges the funding from “Piano di incentivi per la ricerca di Ateneo 2024/2026 (Pia.ce.ri.), Università di Catania”. CNR-IMM of Messina acknowledges the Italian Project PNNR “I-PHOQS─Integrated Infrastructure Initiative in Photonic and Quantum Science CUP B53C22001750006.”

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