Double-layered silicon-nitride photonic crystal slab guided-mode-resonance high-sensitivity sensor application for refractive index sensing and nanoparticle detection

In this work, the silicon-nitride-based double-layered photonic crystal slab (DPCS) operating on guided-mode resonance (GMR) is demonstrated to realize a high-sensitivity sensor. By applying the three-dimensional finite-difference time-domain (3D-FDTD) analysis method, the relationships between Q -factor and slab thickness, hole radius, and space distance are extensively explored. The highest Q -factor of 7605 has been obtained for the optimized structure. Through detecting the resonant peak shifts when the DPCS sensor is immersed in different liquids, we realize an ultrahigh sensitivity up to 937.64 nm/refractive index unit (RIU). On the other hand, particle detection is simulated by the above-mentioned sensor, and the explanations of different resonant shifts versus different trapped positions are sophisticatedly elucidated. Furthermore, the effect of the vertical alignment deviation (lattice displacement) of the two photonic crystal slabs (PCSs) on the Q -factor and transmittance is discussed in detail. The investigations show that the DPCS sensor allows an alignment deviation of ∼ 40 n m , which exhibits excellent fabrication error robustness.