arXiv subjects

Matteo Ciabattoni

Publications and source records attributed to Matteo Ciabattoni.

5 recordsLinked to original sources

arXiv2026

Maximum Q-factor of planar inductors

On-chip inductor design plays a critical role in the advancement of radio-frequency integrated circuits (RFICs). Inductors typically occupy a substantial portion of the chip area as their performance metrics, namely, inductance density and Quality factor ($Q$-factor), are fundamentally tied to the available footprint, thereby limiting miniaturization. To better understand and quantify these limitations, we employ rigorous electromagnetic analysis together with convex optimization techniques to derive a fundamental bound on the maximum achievable $Q$-factor of electrically-small planar inductors as a function of the available design area. The analysis yields analytical expressions for the bound and, via modal analysis techniques, identifies and interprets operational regimes and scaling trends with respect to design area and material conductivity. The analysis accounts for both ohmic and radiation losses, with the latter becoming significant as the inductor size increases. A broad set of state-of-the-art inductor designs from the literature is evaluated against the established $Q$-factor upper bound, identifying designs that approach the theoretical limit as well as those with potential for further improvement. The study is extended to include the effect of kinetic inductance, which offers a promising avenue toward next-generation inductors with higher inductance densities and $Q$-factors. By establishing this benchmark, this work aims to guide and inspire the design of more efficient and compact planar inductors for high-performance RF systems.

physics.optics↗

arXiv2026

Nonlocal photonic time crystals: Infinite momentum bandgaps with minimal modulation speed and strength

For over a decade, photonic time crystals have promised access to novel and exotic optical phenomena, offering fundamentally new ways to manipulate classical and quantum light. Central to these capabilities is the emergence of momentum bandgaps -- the counterpart of the more familiar frequency bandgaps in spatial crystals -- which have proven difficult to observe experimentally due to the combined need for high modulation speed and strength. To date, these requirements have all but hindered the development of time crystals at optical frequencies. Here, we show that the stringent modulation-speed requirement is a direct consequence of the Manley-Rowe relations governing conventional modulation schemes. We further demonstrate that modulating the plasma frequency of a Lorentz-dispersive material overcomes this limitation. Incorporating a specific form of spatial nonlocality (spatial dispersion) into this already temporally nonlocal (frequency dispersive) framework removes all remaining constraints, enabling momentum bandgaps of infinite extent -- in both frequency and momentum -- with arbitrarily small modulation speeds and strengths.

physics.optics↗

arXiv2026

Nonlocal Microwave Engineering: Shaping Dispersion Relations and Enabling Frequency-Momentum Transformations via Time-Switched Long-Range Interactions

Nonlocal metamaterials (MTMs) have recently attracted significant attention across different areas of wave physics, owing to their ability to translate long-range interactions among meta-atoms into a wide array of wavevector-dependent responses and functionalities. In this work, we introduce nonlocal transmission line metamaterials (TL MTMs) as a versatile platform to investigate and engineer nonlocality in the microwave frequency regime. We first establish a concise theoretical framework for nonlocal TL MTMs based on circuit and network theory, from which we derive the general dispersion relation for TL MTMs with arbitrarily complex nonlocal coupling configurations. Building upon this foundation, we demonstrate how such structures can be used to synthesize nearly arbitrary even-symmetric dispersion relations, effectively linking nonlocal circuit parameters to prescribed dispersion profiles. We then introduce time-switched nonlocal TL MTMs, a new class of metamaterials with time-varying nonlocality in which the nonlocal branches are dynamically activated as an electromagnetic pulse propagates through the structure. This platform enables complex, nearly arbitrary frequency-momentum transformations on a propagating pulse, as well as the excitation of modes with positive, negative, and zero group velocity. Finally, we experimentally validate our theoretical and numerical predictions with a proof-of-concept demonstration of a time-switched nonlocal TL MTM, observing a vertical transition in the dispersion diagram induced by abrupt time-switching. Our results provide new physical insights into the behavior of nonlocal MTMs, establish a versatile platform to investigate the interplay of frequency dispersion, spatial dispersion and time modulation, and, more broadly, lay a general foundation for the design of more advanced nonlocal and time-varying electromagnetic and photonic systems.

physics.optics↗

arXiv2024

Time-periodic (Floquet) systems in classical wave physics and engineering: Opinion

The study of classical waves in time-periodic systems is experiencing a resurgence of interest, motivated by their rich physics and the new engineering opportunities they enable, with several analogies to parallel efforts in other branches of physics, e.g., Floquet-engineered quantum materials and time crystals. Here, we first briefly review some of the most prominent features enabled by time-periodic modulations, and we then focus on two specific areas, namely, time-varying systems to break reciprocity and to overcome various theoretical limitations and performance bounds, discussing their current status, challenges, and opportunities.

physics.optics↗

arXiv2024

Observation of broadband super-absorption of electromagnetic waves through space-time symmetry breaking

Using time as an additional design parameter in electromagnetism, photonics, and wave physics is attracting considerable research interest, motivated by the possibility to explore physical phenomena and engineering opportunities beyond the physical limits of time-invariant systems. However, despite substantial theoretical promise, the practical realization and observation of many new effects and capabilities leveraging such temporal degrees of freedom have remained elusive. Here, we report the first experimental demonstration of enhanced broadband absorption of electromagnetic waves in a continuously modulated time-varying system, exceeding one of the key theoretical limits of linear time-invariant absorbers. This is achieved by harnessing the frequency-wavevector transitions and enhanced interference effects enabled by breaking both continuous space- and time-translation symmetries in a periodically time-modulated absorbing structure operating at radio-frequencies. Furthermore, we demonstrate broadband coherent wave absorption using a secondary control wave, observing a nearly perfect, reconfigurable, anti-reflection effect over a broad continuous bandwidth. Our findings provide new insights to challenge existing paradigms on the limits of wave absorption and may pave the way to the development of devices that operate in a regime fundamentally beyond the reach of any linear time-invariant system.

physics.optics↗