Breaking the Intrinsic Absorption Limit for Arbitrarily Thin Conductive Films at Grazing Incidence

The absorption properties of ultrathin conductive films are of fundamental significance in electromagnetics and photonics, impacting applications from radar stealth to two-dimensional material optoelectronics. For decades, a 50% absorption limit has been considered intrinsic to such films in symmetric environments, regardless of frequency or incident angle. Here, we demonstrate the breaking of this long-standing limit under grazing incidence, where the absorption was regarded as negligible due to extreme impedance mismatch. We reveal a previously unknown absorption limit of 2sqrt[2]-2≈82.8% for grazing transverse-magnetic waves on arbitrarily thin, highly conductive films. This exceptional absorption arises from a pseudo-Brewster effect with minimal reflection 3-2sqrt[2]≈17.2% and vanishing skin depth of grazing waves. Remarkably, the enhanced absorption is sustained across an ultrabroad frequency range. Terahertz experiments using deep-subwavelength doped silicon wafers validate our theoretical predictions. These findings fundamentally advance our understanding of wave-matter interactions at deep-subwavelength scales and pave the way for extreme-angle photonic and electromagnetic devices.