Extending the spectral operation of multimode and polarization-independent power splitters through subwavelength nanotechnology

Abstract: Power splitters play a crucial role in virtually all photonic circuits, enabling precise control of on-chip signal distribution. However, state-of-the-art solutions typically present trade-offs in terms of loss, bandwidth, and fabrication robustness, especially when targeting multimode operation. Here, we present a novel multimode 3-dB power splitter based on a symmetric Y-junction assisted by subwavelength grating metamaterials. The inclusion of the metamaterial structure circumvents the practical limitations of conventional Y-junction tips and realizes smooth modal transitions. Simulations for a standard 220-nm-thick silicon-on-insulator platform predict minimal excess loss (< 0.2 dB) for the fundamental and the first-order transverse-electric modes over an ultra-broad 700 nm bandwidth (1300-2000 nm). For the fundamental transverse-magnetic mode, losses are less than 0.3 dB in the 1300-1800 nm range. Experimental measurements validate these predictions in the 1430-1630 nm wavelength range, demonstrating losses < 0.4 dB for all three modes, even in the presence of fabrication deviations of up to \pm 10 nm. We believe that this device is suitable for the implementation of advanced photonic systems requiring high-performance distribution of optical signals.