Search

In this study, an axicon metalens comprising a large central disc surrounded by nanoposts for energy harvesting in composite metal-oxide semiconductor sensors was designed, fabricated, and experimentally characterized. The main role of the central disc is focusing light; the nanoposts of various diameters deflect light to form a Bessel-like beam. The spatial distribution of the optical transmission was measured using micro-hyperspectral imaging. The axicon metalens concentrates the light to the sensitive area of the sensor and also harvests light from adjacent pixels. After adding an axicon metalens, the normalized peak transmission is up to 250% at λ = 700 nm as compared to a blank TiO2 film. The experimental results had fair agreement with the finite-difference-time-domain simulation. The ultra-broadband energy-harvesting performance of the sensor suggests that it could be applied in surveillance and Internet of Things applications.

We propose the design and working principle of a plasmonic concentric compound lens (CCL) comprising inner circular nanoslits and outer circular nanogrooves. Dual-wavelength operations have been achieved for 650 and 750 nm at nanoscale and microscale focal lengths along with their depth of focus (DOF). By tuning the arrangement of nanogrooves, the axial resolution can be modulated and the narrowest DOF is achieved by a design of gradually decreasing groove width. For the ultrahigh tunability of axial resolution, DOF over 400 nm for both working wavelengths is also achieved. We not only developed an approximate-perturbed-focus model for explaining the performance of DOF but also found an extraordinary way to improve the resolution. The enhanced resonance of central disk as nannoantenna in CCL also has great influence on nanofocusing with different deigns of outer nanogrooves. This work provides new sight of focusing ability governed by the general optical nanogrooves. The optimized CCL shows excellent focu...

Subwavelength focusing is crucial for many applications in photonics including super-resolution micro/nanoscopy, nanolithography, and optical trapping. However, most nanostructures exhibit poor ability to modulate focusing spot, which makes them hard to achieve ultra-small resolution. Here, we propose three kinds of plasmonic lens (PL) by utilizing different meta-aperture designs for efficient subwavelength focusing modulation. The shape of nanoaperture strongly influences the diffraction properties. Spatial modulation of focusing spot by employing a circular array of proposed nanoapertures is explored. The best focusing performance among these PLs is the design of T-shape nanoaperture, which has great resolution achieving ultra-small focusing spot of 0.14 λ2 and 0.20 λ2 (λ = 633 nm) for simulation and experiment respectively, better than lots of focusing devices especially by using linear polarization. Multiple-object trapping can be realized by using T-shape nanoaperture-based PL. Our designed PLs with different nanoapertures demonstrate the capability to broaden and integrate different functionalities for on-chip nanotechnologies development.

We demonstrate an elliptical gold nanodisk array (GNA) for engineering the spectral profile of surface lattice resonance (SLR). The nanodisk's shape has a great impact on SLR. Small linewidth of 20 nm at an aspect ratio of 1.17, as well as large wavelength tuning of 64 nm within 4% strain via different orientations and polarizations, are achieved experimentally. The enhanced wavelength response of 6.93 nm per 1% strain variation for elliptical GNA is 2.4 times better than that for general circular GNA. Furthermore, the strain sensing for elliptical GNA approaches is 5.7 times greater than that for circular GNA.

We design the hybrid Ag-Au double-layered structure as plasmonic lens. The subwavelength focusing can be achieved with focal length within 500 nm. Furthermore, the focusing properties can be tuned by the thickness ratio of Ag/Au. Finally, we find the best of focusing effect as the thickness ratio is 1.

We investigate both numerically and experimentally the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. The gold ENR exhibits a strong localized surface plasmon bonding mode in near-infrared region, whose peak wavelength is red-shifted as increasing the aspect ratio under longitudinal and transverse polarizations. Furthermore, the disk- and hole-like optical properties for longitudinal and transverse modes are observed, which cause different behaviors in field intensity enhancement. For biomolecule sensing, we find that both modes show increased surface sensitivities when enlarging the aspect ratio of gold ENR.

We investigate the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. Gold ENRs with 1.58 high aspect ratio show a total wavelength shift of 35 nm for molecule sensing.

Abnormal temperature dependence of peak energy and bandwidth of photoluminescence spectra was observed for InN nanorods with a diameter