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Breaking the Intrinsic Absorption Limit for Arbitrarily Thin Conductive Films at Grazing Incidence
Yuxuan Liu1, Ren-Hao Fan2,3, Dong-Xiang Qi2
1Soochow University, School of Physical Science and Technology, Jiangsu Key Laboratory of Frontier Material Physics and Devices, and Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Suzhou 215006, China.
Physical Review Letters
|February 16, 2026
Summary
Researchers broke the 50% absorption limit for ultrathin conductive films. At grazing incidence, they achieved ~82.8% absorption for transverse-magnetic waves, advancing electromagnetics and photonics.
Area of Science:
- Electromagnetics and Photonics
- Wave-Matter Interactions
- Materials Science
Background:
- Ultrathin conductive films are crucial for applications like radar stealth and optoelectronics.
- A 50% absorption limit was historically considered intrinsic for these films.
- Absorption was previously thought negligible at grazing incidence due to impedance mismatch.
Purpose of the Study:
- To challenge the established 50% absorption limit in ultrathin conductive films.
- To investigate absorption properties under grazing incidence conditions.
- To explore new possibilities for photonic and electromagnetic devices.
Main Methods:
- Theoretical analysis of wave propagation and absorption in ultrathin films.
- Investigation of pseudo-Brewster effect and impedance matching at grazing angles.
- Experimental validation using terahertz spectroscopy on doped silicon wafers.
Main Results:
- Demonstrated a novel absorption limit of approximately 82.8% for grazing transverse-magnetic waves.
- Identified a pseudo-Brewster effect contributing to high absorption and low reflection (~17.2%).
- Observed sustained enhanced absorption across an ultrabroad frequency range.
Conclusions:
- The long-standing 50% absorption limit for ultrathin films is not universal.
- Grazing incidence enables significantly enhanced absorption via a pseudo-Brewster effect.
- Findings open avenues for advanced deep-subwavelength photonic and electromagnetic devices.
