Leyi Chen

Generation of polarization-entangled photon pairs via concurrent spontaneous parametric downconversions in a single χ (2) nonlinear photonic crystal

We propose a scheme for generating polarization-entangled photon pairs using a χ((2)) nonlinear photonic crystal, which is designed for enabling two concurrent quasi-phase-matched spontaneous parametric downconversion processes. Beamlike photon pairs produced from each process are collinear but noncollinear with the pump. Moreover, the source we design works in a postselection-free way and applies to both degenerate and nondegenerate cases. Combining possible waveguide technologies, our scheme may provide an integrated polarization entanglement source.

Quantum effects in the optical activity of α-quartz

An experiment was proposed to probe quantum effects on optical activity. The helical structures in optically active media act as natural microsolenoids for the electromagnetic waves passing through them, which produces a longitudinal magnetic field in the axis of helices. Magnetic flux through a helical crystal structure is quantized. A high number of quanta in the rotatory power was probed in the optical activity of α-quartz.

Plasmon-enhanced magneto-optical activity in a nanostructure with circle annular arrays

The optical properties and magneto-optical (MO) activity in a bilayer nanostructure consisting of a ferromagnetic dielectric film and a noble metal film perforated with circle annular arrays are investigated. Enhanced Faraday rotation peaks with opposite signs are found. Meanwhile, enhanced polar Kerr rotation with large reflectance is also obtained at the same wavelength. The peak positions of the MO rotations accompanied by large transmittance and reflectance can be efficiently tailored by changing the geometrical parameters and the filling medium. These findings are important for applications in highly integrated optoelectronics and multiple channel magneto-optical devices.

Waveguide plasmon resonance induced enhancement of the magneto-optics in a Ag/Bi:YIG bilayer structure

The optical transmission and magneto-optical (MO) activity in the bilayer systems of a silver film perforated with nanohole arrays and a uniform dielectric film magnetized perpendicular to its plane are investigated. A new peak corresponding to magneto-optic enhancement in the visible region is found, which mainly originates from the interplay of surface plasmon polaritons, localized surface plasmon resonance, and the waveguide resonance. The peak positions of the MO rotations accompanied with large transmittance can be efficiently tailored by changing the geometrical parameters and the filling medium. These findings have significant impacts and applications in highly integrated optoelectronic and MO devices.

Enhancement of magneto-optical Faraday effects and extraordinary optical transmission in a tri-layer structure with rectangular annular arrays.

The properties of optics and magneto-optical Faraday effects in a metal-dielectric tri-layer structure with subwavelength rectangular annular arrays are investigated. It is noteworthy that we obtained the strongly enhanced Faraday rotation of the desired sign along with high transmittance by optimizing the parameters of the nanostructure in the visible spectral ranges. In this system, we obtained two extraordinary optical transmission (EOT) resonant peaks with enhanced Faraday rotations, whose signs are opposite, which may provide the possibility of designing multi-channel magneto-optical devices. Study results show that the maximum of the figure of merit (FOM) of the structure can be obtained between two EOT resonant peaks accompanied by an enhanced Faraday rotation. The positions of the maximum value of the FOM and resonant peaks of transmission along with a large Faraday rotation can be tailored by simply adjusting the geometric parameters of our models. These research findings are of great importance for future applications of magneto-optical devices.

Effect of NH3 and N2 annealing on the interfacial and electrical characteristics of La2O3 films grown on fully depleted SiGe-on-insulator substrates

The interfacial structure and the electrical properties of pulsed laser deposition derived La2O3 ultra-thin films on fully depleted SiGe-on-insulator (FD SGOI) substrates before and after post-annealing in NH3 and N2, respectively, have been investigated comparatively. The results from high-resolution transmission electron microscopy and x-ray photoelectron spectroscopic revealed that interface reactions take place after the NH3 and N2 annealing process, but, as compared with the N2 annealing process, the NH3 annealing process can effectively decrease the thickness of the interfacial layer and incorporate more nitrogen at the dielectric/SiGe interface, resulting in smaller equivalent oxide thickness. The La2O3 capacitors annealed in NH3 show good capacitance–voltage characteristics with negligible hysteresis, smaller interface trap density and lower gate-leakage current density in comparison with those of capacitors annealed in N2. It is demonstrated that the NH3 annealing process can be a promising technology in improving the quality of high-k dielectric on FD SGOI substrates.

Fano resonance and magneto-optical Kerr rotaion in periodic Co/Ni complex plasmonic nanostructure

We report a pure ferromagnetic metallic magnetoplasmonic structure consisting of two-dimensional ordered Ni nanodisks array on Co film. With a sufficient height of the nanodisks, a steep and asymmetric Fano resonance can be excited in this structure. We attribute the fascinating spectral lineshape to the strong coupling between the excitation of surface plasmon polaritons at the interface and the localized surface plasmon resonance of nanodisks. The conclusion is fully confirmed by spectrum measurements in nanostructures with different heights. Furthermore, the enhancement and sign of the magneto-optical Kerr rotation in this structure are significantly modified by the Fano resonance.

Plasmonics Resonance Enhance Magneto-Optical Effects Through Metallic Sub-wavelength Grating with Bismuth Iron Garnet Slab

We theoretically investigated an enhancement of the magneto-optical Faraday rotations along with large transmittance in two multilayer structures. The shifts of the Faraday rotation peaks are more obvious than the transmittance peaks when the grating period is changed, which is beneficial to acquire the large Faraday rotation and transmittance. The Faraday rotation of tri-layer system is five times larger than the bilayer system, and the Faraday resonance peak can be mediated by changing the refractive index or thickness of the additional nonmagnetic dielectric layer (NDL) layer. These results are important for applications in highly integrated optoelectronic and magneto-optical devices.

Surface Plasmon Resonance Enhanced the Transverse Magneto-optical Kerr Effect in One-dimensional Magnetoplasmonic Nanostructure

The properties of the optics and transverse magneto-optical Kerr effect (TMOKE) of one-dimensional magnetoplasmonic nanostructures are experimentally investigated. It shows that the resonant dips of the reflectance spectra and the enhancement of the TMOKE of the designed structures are attributed to the excitation and the coupling of the localized surface plasmon (LSP) and surface plasmon polariton (SPP) modes. Moreover, the insertion of the nonmagnetic dielectric SnO2 layer into the quadrilayer structure of Ag/Co/SnO2/Ag can not only pronouncedly enhance the TMOKE signals of the sample but also prompt their resonant positions to generate a blueshift. It has been demonstrated that the enhancement of the TMOKE signal and the blueshift of the resonant wavelength of the TMOKE stems from the coupling of SPP of the two different interfaces of the silver film.

In situ synthesis of chemically ordered primitive cubic Pt 3 Co nanoparticles by a spray paint drying method for hydrogen evolution reaction

A facile two-step method is developed for large-scale synthesis of chemically ordered Pt3Co nanoparticles (NPs) as a high-performance catalyst for hydrogen evolution reaction. Due to the NaCl-matrix as dispersing media avoids the severe aggregation during the high-temperature annealing process, the resulting Pt3Co NPs are pure and well crystallized with narrow size distribution. Furthermore, the chemically ordered Pt3Co NPs exhibit excellent HER property in acidic solution. Our methodology can be also applied to synthesis of other Pt-based NPs.