Reviewed by Lexie CornerAug 28 2024
A recent study published in Advanced Photonics Nexus by researchers from SPIE introduces a novel type of sensor that utilizes exceptional points (EPs) to achieve unprecedented levels of sensitivity.
The tunable and reconfigurable EP sensing system operates on a single plasmonic resonator. This schematic illustration shows a conventional sensor (left, standing wave mode) in the absence of perturbations and the second-order EP sensor (right, traveling wave mode) with two dynamically movable Rayleigh scatterers. Image Credit: Y. Zhang, H. Hu, et al.
Recent breakthroughs in sensor technology, thanks to improvements in photonics and materials science, have pushed the limits of what can be detected and recorded. Among these developments, non-Hermitian physics has become a key field of study, providing novel approaches to controlling light and improving sensor sensitivity.
This study presents a single-spoof localized surface plasmon (LSP) resonator-based highly sensitive and customizable sensor. Exceptional points are distinct spectral singularities that greatly increase the sensitivity of optical sensors by converging eigenvalues and their related eigenvectors.
Conventional EP-based sensors have shown improved sensitivity over conventional sensors, such as whispering gallery mode (WGM) microtoroids. However, these sensors have some drawbacks: their excitation efficiency and perturbation strength are limited, making it difficult to precisely modify their EPs after construction.
Additionally, these sensors typically only function within a narrow frequency range, making it difficult for them to detect very minute particles.
To overcome these limitations, the new sensor design incorporates spoof LSP resonators, which provide more flexibility and mimic the behavior of localized surface plasmons. This arrangement, which consists of two movable Rayleigh scatterers paired with a suspended microstrip line, enables dynamic reconfiguration of EP states over a broad frequency range.
This flexibility increases the sensor's resistance to manufacturing flaws and improves its capacity to detect minuscule particles.
Key features of the new sensor include:
- Reconfigurability: Adjustable Rayleigh scatterers allow for dynamic formation and reconfiguration of EPs, enhancing the sensor’s precision and flexibility.
- Increased Perturbation Strength: Electromagnetic fields are confined to the resonator's surface, greatly amplifying the sensor's sensitivity to perturbations from nearby particles.
- Multipolar Mode Excitation: The design accommodates multiple plasmonic resonance modes, broadening the sensor's operational bandwidth and detection capabilities.
This advancement marks a major breakthrough in sensor technology. It delivers unparalleled sensitivity for detecting particles as small as 0.001 times the wavelength of light and paves the way for innovative applications in scientific research and industry.
Journal Reference:
Zhang, Y., et al. (2024) Reconfigurable exceptional point-based sensing with 0.001λ sensitivity using spoof localized surface plasmons. Advanced Photonics Nexus. doi.org/10.1117/1.apn.3.5.056004.