Fundamental limits in photonics and electromagnetics: a tutorial

Theoretical limits and physical bounds across many areas of science, mathematics, and technology -- including Shannon's information-capacity limits, Bennett and Landauer's thermodynamic limits on computation, and G\"odel's incompleteness theorem in formal logic -- serve as defining pillars of their fields. In photonics and electromagnetism, numerous physical bounds and constraints have likewise been uncovered over the past several decades. In this Tutorial, we first review the fundamental principles that constrain light-matter interactions, and then discuss limits at different hierarchical scales, from optical material responses to wave propagation, scattering, and related optical phenomena and functions, relevant to a wide range of applications. By providing a more unified treatment of these results and highlighting the many open questions that remain, our goal is to help readers rapidly get up to speed with the frontier of this research area and contribute to advancing the broader vision of a universal framework for fundamental limits of light interactions with matter.