Fully Illuminated Modes in a Penrose Unilluminable Room Microcavity

Roger Penrose proposed an interesting cavity geometry, known as the Penrose unilluminable room, which always has unilluminable regions unreachable by optical rays wherever a point light source is set in the cavity. I studied resonance modes in microcavities having a Penrose unilluminable room using the finite element method. Contrary to expectations, I obtained fully illuminated resonance modes that spread widely in the entire cavity. My numerical calculation results revealed that the fully illuminated modes are formed by interactions between resonance modes confined in different limited regions in the cavity.