Low-loss, efficient, wide-angle 1 × 4 power splitter at ∼1.55 μm wavelengths for four play applications built with a monolithic photonic crystal slab

Higher Q factor and higher extinction ratio with lower detection limit photonic crystal-parallel-integrated sensor array for on-chip optical multiplexing sensing

We introduce an alternative method to establish a nanoscale sensor array based on a photonic crystal (PhC) slab, which is referred to as a 1×4 monolithic PhC parallel-integrated sensor array (PhC-PISA). To realize this function, four lattice-shifted resonant cavities are butt-coupled to four output waveguide branches, respectively. By shifting the first to the two closest neighboring holes around the defect, a high Q factor over 1.5×10⁴ has been obtained. Owing to the slightly different cavity spacing, each PhC resonator shows an independent resonant peak shift as the refractive index changes surrounding the resonant cavity. The specific single peak with a well-defined extinction ratio exceeds 25 dB. By applying the finite-difference time-domain (FDTD) method, we demonstrate that the sensitivities of each sensor in PhC-PISA S₁=60.500  nm/RIU, S₂=59.623  nm/RIU, S₃=62.500  nm/RIU, and S₄=51.142  nm/RIU (refractive index unit) are achieved, respectively. In addition, the negligible crosstalk and detection limit as small as 1×10^-4 have been observed. The proposed sensor array as a desirable platform has great potential to realize optical multiplexing sensing and high-density monolithic integration.

Multiplexed Simultaneous High Sensitivity Sensors with High-Order Mode Based on the Integration of Photonic Crystal 1 × 3 Beam Splitter and Three Different Single-Slot PCNCs

We simulated an efficient method for the sensor array of high-sensitivity single-slot photonic crystal nanobeam cavities (PCNCs) on a silicon platform. With the combination of a well-designed photonic crystal waveguide (PhCW) filter and an elaborate single-slot PCNC, a specific high-order resonant mode was filtered for sensing. A 1 × 3 beam splitter carefully established was implemented to split channels and integrate three sensors to realize microarrays. By applying the three-dimensional finite-difference-time-domain (3D-FDTD) method, the sensitivities calculated were S₁ = 492 nm/RIU, S₂ = 244 nm/RIU, and S₃ = 552 nm/RIU, respectively. To the best of our knowledge, this is the first multiplexing design in which each sensor cite features such a high sensitivity simultaneously.