Low-cost and simple fabrication of hierarchical Al nanopit arrays for deep ultraviolet refractive index sensing.

Herein, we proposed a simple non-lithographic way to fabricate hierarchical Al nanopit arrays performed as deep ultraviolet (DUV, 200-300 nm) refractive index sensing. Only by adjusting the Al deposition thickness on the Al nanopit array, the hierarchical Al nanopit arrays with tunable plasmonic properties in the DUV region were obtained. The prepared hierarchical Al nanopit arrays are of very good time stability and its RI sensitivity and concentration detection limit of adenine ethanol solution reach 311 nm/RIU and5×10-6M,respectively, as the Al deposition thickness is 60 nm. Furthermore, the electric field distribution simulation results show that high RI sensing characteristic are mainly attributed to the local surface plasmon resonance. This investigation provides a facile way to develop low cost, high efficient and easily fabricated Al-based RI sensor in the DUV region.

Exact optical path difference and complete performance analysis of a spectral zooming imaging spectrometer.

The optical path difference (OPD) equations of the dual Wollaston prisms (DWP) with an adjustable air gap (AG) are derived by the wave normal tracing method, which is suitable for arbitrary incidence plane and angle. The spatial distribution of the OPD for various AG is presented. The validity of the OPD equation is verified by comparing the calculated interferograms with experimentally observed one. The performance of a novel static birefringent Fourier transform imaging spectrometer (SBFTIS) based on the DWP is investigated. The spectral resolution can be adjusted by changing the AG and the field of view can reach 10.0°, which is much larger than that predicted by our previous work. The results obtained in this article provide a theoretical basis for completely describing the optical transmission characteristic of the DWP and developing the high-performance birefringent spectral zooming imaging spectrometer.

Facile fabrication of 2D hetero core-satellites patterned Ag nanoparticle arrays with tunable plasmonic bands for SERS detection.

A core-satellites metal nanostructure with high local electromagnetic (EM) intensity and density has shown great potential in ultrasensitive detection technologies, but complexity and uncontrollability of fabrication is a major obstacle for further application. Here, only by controlling the deposited Ag thickness, we facilely achieved 2D hetero core-satellites patterned Ag nanoparticle (NP) arrays for surface-enhanced Raman scattering (SERS) detection. The Ag nanoparticles were assembled by electron beam evaporation of Ag onto the anodized patterned aluminum template (APAlT) at a temperature above 0.24 times the melting point of Ag. The plasmonic bands can be continuously tuned from the visible to near-infrared region. The SERS enhancement factor (EF) and relative standard deviation (RSD) of as-prepared SERS active substrates for R6G molecules reached 107 and about 5%, respectively, and a SERS detection limit down to 10-9 M was obtained. Finite-difference time-domain (FDTD) simulations revealed that the high SERS activity originates mainly from the local electromagnetic (EM) enhancement in the gaps between the core and satellites. The simple and controllable fabrication strategy and superior SERS performance make the 2D hetero core-satellites patterned Ag NPs arrays promising candidates for SERS-based sensor applications and provide a new approach for developing an inexpensive, efficient, and mass-produced SERS active substrate.