We report improved surface sensing capabilities of photonic crystal biosensors through the inclusion of a subwavelength dielectric feature inside the photonic crystal unit cell. Incorporation of a 50 nm silicon bar (i.e., anti-slot) spanning a traditional silicon photonic crystal unit cell increases the local energy density and consequently increases the resonance shift when molecules are captured on the sensor surface. Simulations and corroborating proof-of-concept experimental results based on a layer-by-layer polymer deposition are demonstrated. A perturbation theory approach for more computationally efficient predictions of photonic crystal biosensor performance is also reported, along with a discussion of the biosensor performance as a function of the spatial position of molecule attachment on the different sensor surfaces.

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Yanrong Zhang, Rabeb Layouni, Christopher S. Whittington, Sami I. Halimi, and Sharon M. Weiss, "Improved molecular detection sensitivity through photonic crystal unit cell design," Proc. SPIE 12397, Frontiers in Biological Detection: From Nanosensors to Systems XV, 1239703 (Presented at SPIE BiOS: January 29, 2023; Published: 17 March 2023); https://doi.org/10.1117/12.2659243.