Slot-slot waveguide with negative large and flat dispersion covering C+L+U waveband for on-chip photonic networks

A novel, to the best of our knowledge, dual-core slot-slot waveguide with extreme high dispersion is proposed. The high dispersion value at the desired wavelength is obtained based on strong resonance coupling between two slot-waveguide modes. The properties of dispersion magnitude and bandwidth are numerically analyzed by using the finite-difference time-domain method with a perfectly matched layer boundary. All numerical simulation results reveal that for the optimized geometrical parameters of H₁=350  nm, L₁=569  nm, S₁=31.3  nm, L_a=1062.39  nm, H₂=427  nm, L₂=137.4  nm, and S₂=63.5  nm, the maximum dispersion of negative 3.645×10⁵  ps·nm^-1·km^-1 and dispersion full width at half-maximum of 6.3 nm at 1550 nm have been obtained. By cascading the slot-slot waveguides with varying width and height, a large and flattened dispersion of -3.5×10⁵  ps·nm^-1·km^-1 covering the C+L+U waveband is obtained. Dispersion compensation of a 100 Gbit/s return-to-zero on-off-keying optical time-division multiplexing signal after 50 km full spectrum single-mode optical fiber transmission with five different central wavelengths is demonstrated through simulation for the first time. In addition, fabrication tolerance of the proposed slot-slot waveguide is analyzed. Such a waveguide is compatible with complementary metal-oxide-semiconductor technology and has potential applications in next-generation large-scale photonic integrated circuits.