Highly confined surface plasmon polaritons in the ultraviolet region

Designable Poly(methacrylic Acid)/Silver Cluster Ring Arrays as Reflectance Spectroscopy-Based Biosensors for Label-Free Plague Diagnosis

A hole array was fabricated via photolithography to wet the bottoms of holes using oxygen plasma. Amide-terminated silane, a water immiscible compound before hydrolysis, was evaporated for deposition on the plasma-treated hole template surface. The silane compound was hydrolyzed along the edges of circular sides of the hole bottom to form a ring of an initiator after halogenation. Poly(methacrylic acid) (PMAA) was grafted from the ring of the initiator to attract Ag clusters (AgCs) as AgC-PMAA hybrid ring (SPHR) arrays via alternate phase transition cycles. The SPHR arrays were modified with a Yersinia pestis antibody (abY) to detect the antigen of Yersinia pestis (agY) for plague diagnosis. The binding of the agY onto the abY-anchored SPHR array resulted in a geometrical change from a ring to a two-humped structure. The reflectance spectra could be used to analyze the AgC attachment and the agY binding onto the abY-anchored SPHR array. The linear range between the wavelength shift and agY concentration from 30 to 270 pg mL^-1 was established to obtain the detection limit of ~12.3 pg mL^-1. Our proposed method provides a novel pathway to efficiently fabricate a ring array with a scale of less than 100 nm, which demonstrates excellent performance in preclinical trials.

Programmable bandstop filter based on spoof surface plasmon polaritons

Spoof surface plasmon polaritons (SSPPs) have been developed rapidly because of the advantages of strong field constraints, low inter-channel cross talk, and low loss. However, the functions of plasmonic devices made of traditional passive SSPPs are completely fixed and cannot reach reconfigurable capability once the devices are fabricated. For the current development status, it is an urgent issue to design a reconfigurable device to control SPP waves dynamically in real time. This paper proposes a dynamic reconfigurable bandstop filter by using the concept of programmable SSPPs. The filter has a significant regulation function in the wideband range from 4 GHz to 22 GHz. The center frequency, number, and bandwidth of the stop band can be reconstructed in real time by programming the bias voltage, and the transmission coefficient (S₂₁) has good transmission performance of more than -3dB. The results show that the experimental processing test is close to the theoretical simulation results, which proves the feasibility of the designed device. The study extends the functional principles of information science and digital logic to the application of physical devices.

Aluminium-Based Plasmonic Sensors in Ultraviolet

We theoretically investigate the surface plasmon polaritons (SPPs) generated on an Al film covered by an Al₂O₃ layer in the context of their application as refractive index sensors. The calculated reflection spectra indicate SPP resonance excited by ultraviolet light, which was affected by the thickness of both the metal and the oxide layers on the surface. With optimized geometry, the system can work as a tunable sensor with a wide UV wavelength range λ∼ 150–300 nm. We report a quality factor of up to 10 and a figure of merit on the order of 9, and these are comparable to the performance of more complicated UV plasmonic nanostructures and allow for the detection of a 1% change of the refraction index. The sensor can operate on the basis of either the incidence angle or wavelength changes. The effect of oxide surface roughness is also investigated with an emphasis on amplitude-based refraction index sensing.