In this seminar, I will present results from two recent, distinct research projects.

The first project concerns the prediction of third-order spontaneous parametric down-conversion (TOSPDC) in resonant silicon metasurfaces [1]. We developed a quantum-classical correspondence framework between TOSPDC and its reverse classical process, three-wave sum-frequency generation (TSFG), to efficiently estimate the photon-triplet generation rate. By leveraging quasi-BIC resonances in asymmetric Si metasurfaces in the near-infrared range, we demonstrated an enhanced TSFG efficiency and predicted a photon-triplet generation rate of approximately 1 Hz—within reach of current low-noise single-photon detectors. 

The second project explores the time-domain scattering properties of dielectric Mie nanoresonators by analysing their transient response under short, sub-picosecond pulsed excitation [2]. We constructed an analytical framework that decomposes both scattering and internal Mie coefficients into exact contributions from quasi-normal modes of the resonant structure. This approach revealed unconventional scattering dynamics in resonant and anapole regimes, which we validated in a practical CMOS-compatible metastructure design.

[1] M. Bacaoco, K. Koshelev, A. Solntsev, arXiv:2504.02267 (2025).

[2] K. Koshelev, H. Wu, A. Miroshnichenko, in preparation.

Dr Kirill Koshelev is an ARC DECRA Fellow at EME, working on theoretical and numerical models for a broad range of cross-disciplinary nanophotonic applications, spanning from nonlinear optics to chiral photonics. Kirill received his PhD from the ANU in 2022, followed by a Postdoctoral Fellowship at ANU until mid-2024, and then at UNSW Canberra from mid-2024 to early 2025.