On‐Chip Metamaterial Enabled Wavelength (De)Multiplexer

Wavelength‐division multiplexing (WDM) technology can offer considerable parallelism for large‐capacity data communications. While several configurations have been demonstrated to realize on‐chip WDM systems, their practical applications might be hindered by large footprints or compromised performances. Recently, metamaterial‐assisted silicon photonics is emerging for on‐chip light manipulation by subwavelength‐scale control of optical wavefronts. They can reach more compact footprints and broadband functionalities beyond the classical waveguide‐based architectures. Herein, wavelength (de)multiplexers are experimentally demonstrated in the subwavelength‐structured metamaterials regime with highly compact footprints. Two‐dimensional metamaterials composed of quasi‐periodic dielectric perturbation arrays patterned on a multimode waveguide are proposed to stimulate multiple high‐order waveguide modes at different wavelengths, which are then coupled to different WDM channels by cascading mode (de)multiplexers. The four‐channel wavelength (de)multiplexer is demonstrated in a box‐like spectrum with a compact footprint of 2.5 × 250 µm2, with the measured losses less than 2 dB and channel crosstalk less than –14.3 dB. By varying the patterned metamaterial structures, the proposed devices also have the merits of flexible operating wavelengths and bandwidths. The concept features large scalability, compactness, and competitive performance, which can offer versatile on‐chip light manipulation and significantly improve the integration density for various on‐chip WDM optical systems. The metamaterial is designed to stimulate multiple high‐order modes at different wavelengths, then coupled into different waveguides by cascaded mode (de)multiplexers, thus serving as a compact wavelength (de)multiplexer with a footprint of 2.5 × 250 µm2. The metamaterial design is scalable and provides a viable route for versatile on‐chip spatial mode and wavelength manipulation.