On-Chip Cascaded Metasurfaces for Visible Wavelength Division Multiplexing and Color-Routing Meta-Display.

Integrating metasurfaces on-chip offers a promising strategy for modulating and extracting guided waves, suggesting tremendous applications in compact wearable devices. However, despite the full acquisition of on-chip manipulation of optical parameters, including phase, amplitude, and polarization, the functionality of on-chip metasurfaces remains limited by the lack of wavelength selectivity. Here, an on-chip approach to differentiate wavelength components is proposed in the visible regime for wavelength division multiplexing (WDM). Through horizontally cascading on-chip meta-atoms with structural dimension variation and optimization, different wavelength components propagating along the waveguide would be selectively extracted, realizing meta-demultiplexing functionality. More intriguingly, color nanoprinting images or holographic displays can be correspondingly enabled. This approach surpasses conventional free-space meta-devices in terms of exhibiting improved wavelength-selective allocation and eliminating the energy waste caused by spatial multiplexing. We envision that such an on-chip cascading strategy paves the way for next-generation WDM devices in photonic integrated circuits and wearable miniature meta-displays.