Designing surfaces that precisely control how light behaves at the nanoscale is tricky. Optical Fourier surfaces, which are nanostructured gratings that redistribute light into specific directions and wavelengths, hold enormous potential for compact spectrometers, augmented-reality displays, and advanced sensors. However, their standard design process relies on computer simulations that assume idealized conditions such as single-angle illumination and the absence of fabrication imperfections—a far cry from reality.
The gap between what simulations predict and what fabricated devices actually do has long frustrated researchers. It widens further when designers try to exploit one of the most powerful but underused design parameters: the angle of incoming light. Changing the incident angle can activate or suppress optical modes without any physical modification to the structure, effectively enabling multiple functions on a single device.
“This effectively introduces an additional degree of freedom beyond geometry, expanding the design space significantly,” said Associate Professor Dong Zhaogang from the Singapore University of Technology and Design (SUTD). “But its practical use has been limited because simulations at oblique incidence are often computationally unstable and costly, while real experimental systems involve angular distributions rather than single-incident angles.”
