Weijing Kong

Bloch Surface Waves have emerged as a promising alternative to Surface Plasmon Resonance for high-sensitivity sensing applications, owing to their low optical losses, sharp resonance dips, and tunable polarization properties. This paper explores a high-performance Bloch surface wave sensor based on an optimized one-dimensional photonic crystal structure for ultra-sensitive refractive index detection. The sensor architecture consists of a periodic stack of TiO₂ and SiO₂ layers with a TiO₂ cap layer, designed using the transfer matrix method to operate in aqueous environments. Through numerical simulations and theoretical analyses, we systematically engineer the photonic bandgap structure to achieve enhanced field localization and low transmission loss. A Kretschmann-Raether prism coupling setup with precision angular control is employed to experimentally validate the device’s exceptional performance. The narrow resonance feature (FWHM = 0.036°) and high quality factor (Q > 1480) confirm excellent sensing capabilities, demonstrating high sensing sensitivity and an intensity-based detection resolution of 4.51 × 10⁻⁷ RIU. This work establishes BSW sensors as a next-generation platform for label-free biochemical sensing with low detection limit in the near-infrared regime.

In aims to enhance the electric-field confinement capability of Bloch surface wave (BSW) with low propagation loss, here, we develop a high-performance hybrid BSW waveguide that incorporates a high-index nano-ridge loaded photonic crystal slab with a silicon dielectric nanowire. Leveraging the mode hybridization, a subwavelength mode confinement in conjunction with long-range waveguiding is achievable. Its robust properties against the possible fabrication imperfection for practical implementations and comparisons with similar hybrid waveguide configurations are also discussed to indicate the improved guiding performance of our proposed waveguide. These remarkable optical properties render such waveguide to hold the promise of building numerous high-performance nanophotonic devices.

We report the realization of strongly confined low-loss optical waveguiding at telecommunication wavelength by exploiting the hybridization of photonic modes guided by coupled dielectric mode and Bloch surface polaritons on the interface between one-dimensional photonic crystal and dielectric nanowire. Owing to the combined effects induced by the coupling between two types of guided modes, tight field localization in conjunction with significantly lower propagation loss can be achieved simultaneously. The characteristics of the hybrid modes are comprehensively numerically investigated through tuning key structural parameters of the coupled dielectric nanowire and its distance to the photonic crystal surface. The hybrid mode could effectively balance the compromise between the mode confinement and propagation loss for a wide geometrical parameter range. It reveals the hybrid mode is capable of enabling larger propagation distance (centimeter level) with subwavelength mode confinement, leading to a high figure of merit nearly one order of magnitude larger as compared to the conventional hybrid waves in dielectric-metal-based surface plasmon waveguides over the range of dimensions considered. The outstanding properties of the proposed guiding scheme could open up possibilities for a variety of high-performance intriguing nanophotonic components.

Surface plasmon polaritons (SPPs) have been thoroughly studied in the past decades for not only sensing but also waveguiding applications. Various plasmonic device structures have been explored due to their ability to confine their optical mode to the subwavelength level. However, with the existence of metal, the large ohmic loss limits the propagation distance of the SPP and thus the scalability of such devices. Therefore, different hybrid waveguides have been proposed to overcome this shortcoming. Through fine tuning of the coupling between the SPP and a conventional waveguide mode, a hybrid mode could be excited with decent mode confinement and extended propagation distance. As an effective alternative of SPP, Bloch surface waves have been re-investigated more recently for their unique advantages. As is supported in all-dielectric structures, the optical loss for the Bloch surface wave is much lower, which stands for a much longer propagating distance. Yet, the confinement of the Bloch surface wave due to the reflections and refractions in the multilayer structure is not as tight as that of the SPP. In this work, by integrating a periodic multilayer structure that supports the Bloch surface wave with a metallic nanowire structure, a hybrid Bloch surface wave polariton could be excited. With the proposed hybrid nanowire structure, a hybrid mode is demonstrated with the deep subwavelength mode confinement and a propagation distance of tens of microns.

For enhancing the sensitivity of the Bloch surface wave-based sensing applications, the dependency of the Bloch surface wave (BSW) resonance dip and the associated phase change on the loss of a truncated one-dimensional photonic crystal structure is numerically analyzed and studied. Furthermore, through evaluating the sensitivity of a BSW sensor based on the intensity interrogation scheme and the phase detection method, a comparison is carried out to optimize the sensing performance. The results demonstrate that the sensing sensitivity of the BSW sensor is significantly affected by the applied sensing schemes. It is shown that the optimized device loss is not the same for different sensing schemes. Relatively high phase-detection sensing sensitivity can be maintained for low-loss BSW devices, while that of the intensity interrogation scheme may drop sharply. On the other hand, the performance of intensity interrogation scheme is less affected by the higher device loss. Our result could be useful for improving the performance of the BSW sensors and selecting the appropriate sensing scheme for such devices.