Liyang Yue

Photonic nanojet of cylindrical metalens assembled by hexagonally arranged nanofibers for breaking the diffraction limit

We designed a novel cylindrical metalens assembled by hexagonally arranged close-contact nanofibers. A near-field focusing nanojet with a full-width at half-maximum (FWHM) waist, 26.7% smaller than the Abbe diffraction limit for 532 nm wavelength light, is observed at the bottom of a 1600 nm diameter cylindrical metalens assembled by 160 nm diameter nanofibers irradiated by a plane wave from the top. Using differently sized nanofibers as building blocks to assemble the metalens, the waist size of the produced photonic nanojet in the near-field zone and the lateral resolution of the focus can be flexibly adjusted, simultaneously breaking the diffraction limit.

Superlensing microscope objective lens

Conventional microscope objective lenses are diffraction limited; they cannot resolve subdiffraction features of a size smaller than 250-300 nm under white lighting condition. New innovations are required to overcome this limitation. In this paper, we propose and demonstrate a new superlensing objective lens that possesses a resolution of 100 nm, which is a two-times resolution improvement over conventional objectives. This is accomplished by integrating a conventional microscope objective lens with a superlensing microsphere lens using a customized lens adaptor. The new objective lens was successfully demonstrated for label-free super-resolution imaging of 100 nm features in engineering and biological samples, including a Blu-ray disk sample and adenoviruses. Our work opens a new door to develop a generic optical superlens, which may transform the field of optical microscopy and imaging.

Nanoparticle-derived all-dielectric metamaterial superlens

We propose and demonstrate a new class of all-dielectric metamaterial superlens constructed from 3D assembly of high-index nanoparticles (TiO2, ZrO2, Si). The fundamental physics lies in the unusual high efficiency of direct conversion of evanescent waves into propagation waves by the composite media. In Figure 1(a) 3D full wave FDTD simulation was presented for a conventional homogenous material slab and a composite metamaterial slab made from the proposed concept. The simulation reveals that evanescent wave decays quickly from source in homogenous media (Fig. 1(c)) but can be effectively converted into propagating wave in nanoparticle-formed slab. The underlying science originates from evanescent wave scattering by nanoparticles, which behaves quite differently from the case of propagating (e.g., plane) wave scattering by nanoparticles. Many interesting physics awaits discovery in such dense scattering media. We performed simulation for super-resolution imaging and discovered the nanoparticle slab and perform as a super-resolution lens (superlens) which can resolve point sources separated by 45nm (See Figs. (c)-(f)), i.e., 45nm resolution. The resolution limit can be further pushed by using other nanoparticles, with higher index and engineered shapes.

A wide-angle metamaterial narrow-band-stop filter for 532nm wavelength green light

Traditional optical interference narrow-band-stop filters do not possess wide-angle property, because peaks and troughs of filter spectrum move to short wavelength at non-normal angle of incidence (AOI), which could result in functional failure in particular cases, e.g., blocking of laser for pilot in cockpit during premeditated laser pointer direct. For this reason, we designed a wide-angle metamaterial band-stop filter assembled by cross shaped units to block 532nm green light that can maintain filter spectra at ±35° non-normal AOIs. Unnecessary shift of spectrum caused by AOI change is effectively inhibited, and corresponding mechanism is analysed via accurate near-field calculations.