Ultrafast All-Optical Control of Multiple Light Degrees of Freedom through Mode Mixing in a Graphene Nanoribbon Metamaterial for Modulation of Electromagnetic Waves

The evolution of optical technologies necessitates advanced solutions for selective and dynamic manipulation of light’s degrees of freedom, including amplitude, phase, polarization, wavelength, and angular momentum. Metamaterials can offer such control through the interplay between the intrinsic material and geometrical properties of nanostructures or extrinsically through excitation and detection of symmetry breaking, leading to customizable performance. However, achieving dynamic control over multiple light degrees of freedom remains a challenge. To address existing limitations, we present a dual-stack metamaterial design capable of broadband ultrafast control over amplitude, phase, polarization, spin angular momentum, and handedness of light mediated by two independently controlled nanoribbon layers that enable flexible and selective mode mixing in both reflection and transmission. Through a combination of a thermal response model and finite-difference time-domain simulations, we investigate graphene as a suitable material for the metamaterial design, leveraging the intrinsic optical properties of graphene and its tunable conductivity through electrostatic gating and ultrafast optical excitation, achieving selective control over multiple light degrees of freedom at ultrafast time scales. This selective ultrafast mode mixing significantly advances the capabilities of high-speed photonic systems, paving the way for compact, high-data-rate optical technologies essential for future applications by offering a flexible method for multifunctional light modulation.