Novel view on conical refraction, phenomenon, and applications

In 1832, Hamilton predicted conical refraction (CR), where light propagating along an optic axis of a biaxial crystal emerges as a hollow cone, forming a CR ring. Each point on the ring has a distinct linear polarisation state, with opposite points orthogonally polarised. Nearly two centuries later, we have revisited this unique yet underexplored phenomenon. In this presentation, we review the physics of CR and highlight its practical potential in laser physics and biophotonics. We show that CR enables novel approaches to structured light generation, polarisation control, and light–matter interaction. Traditionally dismissed as a curious optical effect with no application, CR is now proving to be a powerful tool in modern photonics. Our findings reopen this classical phenomenon to contemporary relevance and suggest exciting new directions for research and technology.