Single-nanoparticle detection using quasi-bound states in the continuum supported by silicon metasurfaces
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
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2026
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| _version_ | 1866911509247950848 |
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| author | Watanabe, Keisuke Crowther, Samuel Iwanaga, Masanobu Vollmer, Frank Nagao, Tadaaki |
| author_facet | Watanabe, Keisuke Crowther, Samuel Iwanaga, Masanobu Vollmer, Frank Nagao, Tadaaki |
| contents | The detection of single particles or molecules represents a critical milestone in the development of biosensing technologies. Recently developed optical sensors based on quasi-bound states in the continuum (qBICs) have primarily focused on detecting global refractive index changes, aiming to simultaneously enhance both refractive index sensitivity and quality ($Q$) factors. However, sensors capable of resolving local refractive index perturbations, such as the binding of a nanometer-sized molecule on a surface, remain elusive and have not yet been demonstrated in BIC geometries due to the limited $Q$ factors and relatively large mode volumes. Here, we demonstrate low-contrast BIC metasurfaces that can perform sensing with a virus-sized single-nanoparticle resolution. The qBIC resonance operating at the critical coupling condition exhibits an experimental $Q$ factor of 4.5 x 10$^4$ in heavy water. The strong interaction between the localized electric field and polystyrene nanoparticles with a diameter of 100 nm enable the experimental observation of step-like resonance wavelength shifts, serving as signatures of individual particle binding events. Furthermore, binding-induced modifications to the qBIC resonance alter the optical confinement and asymmetry factor, inducing changes not only in the resonance wavelength but also in the linewidth and amplitude with single-particle sensitivity. Combined with position-insensitive response and free-space accessible features, low-contrast BIC metasurfaces provide a user-friendly platform for next-generation single-molecule sensing integrated with microfluidic systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_12135 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Single-nanoparticle detection using quasi-bound states in the continuum supported by silicon metasurfaces Watanabe, Keisuke Crowther, Samuel Iwanaga, Masanobu Vollmer, Frank Nagao, Tadaaki Optics Applied Physics The detection of single particles or molecules represents a critical milestone in the development of biosensing technologies. Recently developed optical sensors based on quasi-bound states in the continuum (qBICs) have primarily focused on detecting global refractive index changes, aiming to simultaneously enhance both refractive index sensitivity and quality ($Q$) factors. However, sensors capable of resolving local refractive index perturbations, such as the binding of a nanometer-sized molecule on a surface, remain elusive and have not yet been demonstrated in BIC geometries due to the limited $Q$ factors and relatively large mode volumes. Here, we demonstrate low-contrast BIC metasurfaces that can perform sensing with a virus-sized single-nanoparticle resolution. The qBIC resonance operating at the critical coupling condition exhibits an experimental $Q$ factor of 4.5 x 10$^4$ in heavy water. The strong interaction between the localized electric field and polystyrene nanoparticles with a diameter of 100 nm enable the experimental observation of step-like resonance wavelength shifts, serving as signatures of individual particle binding events. Furthermore, binding-induced modifications to the qBIC resonance alter the optical confinement and asymmetry factor, inducing changes not only in the resonance wavelength but also in the linewidth and amplitude with single-particle sensitivity. Combined with position-insensitive response and free-space accessible features, low-contrast BIC metasurfaces provide a user-friendly platform for next-generation single-molecule sensing integrated with microfluidic systems. |
| title | Single-nanoparticle detection using quasi-bound states in the continuum supported by silicon metasurfaces |
| topic | Optics Applied Physics |
| url | https://arxiv.org/abs/2603.12135 |