Weak absorption of light by two-dimensional systems, including monolayer materials and some quantum wells, is one of the critical challenges for contemporary optoelectronics. The problem becomes even more pronounced in 2d systems with back gates used to control the carrier density, where the destructive interference of incident and reflected waves enforces ultralow absorbance. We show that both challenges are resolved in the metal-contacted 2d systems, with the metal sections being much wider than 2d sections. Absorption coefficient is raised to 50% in such structures without a back reflector, and up to 100% in the presence of the back reflector. Surprisingly, the distance to the back reflector can be well below the quarter of incident wavelength, contrasting the conventional matching condition in wave optics. The reason for perfect absorption with ultra-proximate reflector lies in large light phase shift acquired upon passage through metal-based grating.

Kirill Kapralov, Vladislav Atlasov, Alina Khisameeva, Viacheslav Muravev, Dmitry Svintsov,
JETP Letters 124, issue 4 (2026)