Shaoyun Yin

Three-dimensional nanoscale Far-field Focusing of Radially Polarized Light by Scattering the SPPs with an Annular Groove

Three-dimensional (3D) nanoscale focusing of radially polarized light in far field by a simple plasmonic lens composed of an annular slit and a single concentric groove is reported. The numerical calculations reveal that the incident light is coupled to surface plasmon polaritons (SPP) by the annular slit and a focal spot with a size less than a half of the illumination wavelength is formed in the far field due to the constructive interference of the scattered light by the groove. More importantly, the focal length can be modulated by changing the groove diameter. This structure provides an admirable choice for the nano-optical devices.

Imaging by a sub-wavelength metallic lens with large field of view.

The characteristics of the phase retardations and the invariability against the incident angles are investigated when light enters the rectangular holes with different sizes perforated on metallic film. A kind of metallic structure with a great potential in imaging is brought forward. The finite difference time domain (FDTD) method and the Rayleigh-Sommerfeld diffraction integrals are used to testify the imaging ability at different incident angles by examining the electric field on focal plane. The calculation results indicate that a quite large view of field lens can be achieved by increasing the number of the holes per unit area with the mentioned structure. A metallic structured lens with a 280 microm aperture and 240 microm focal length is designed and the view angle range of +/-15 degrees can be achieved.

Hybrid metallic nanoparticles for excitation of surface plasmon resonance

A Ag nanostructure was put forward in this paper. There are two types of Ag nanoparticles, spherical and pyramidal particles. Both of them have the same period, but different height and shapes. The hybrid nanoparticles can produce the localized surface plasmon resonance (LSPR), which couples each other and leads to an extra peak transmission. Our UV-visible-IR spectrophotometer measurement results show that some extra small and sharp peaks appear besides the normal LSPR wave peaks in the transmittance spectrum. The hybrid Ag nanoparticles being used as nanosensors will be more sensitive and selective than the conventional LSPR-based nanosensors.

Surface enhanced Raman scattering substrate with metallic nanogap array fabricated by etching the assembled polystyrene spheres array

A sensitive surface enhanced Raman scattering (SERS) substrate with metallic nanogap array (MNGA) is fabricated by etching of an assembled polystyrene (PS) spheres array, followed by the coating of a metal film. The substrate is reproducible in fabrication and sensitive due to the nanogap coupling resonance (NGCR) enhancement. The NGCR is analyzed with the finite difference time domain (FDTD) method, and the relationship between the gap parameter and the field enhancement is obtained. Experimental measurements of R6G on demonstrate that the enhancement factor (EF) of the MNGA SERS substrate is increased by more than two fold compared with the control sample.

Specific Protein Detection in Multiprotein Coexisting Environment by Using LSPR Biosensor

Specific protein detection in multiprotein coexisting environment by localized surface plasmon resonance (LSPR) biosensor is studied. After the surfaces of self-assembly fabricated triangular Ag nanoparticles on the chip are activated, a specific biological molecule layer with δ-toxic protein identifying function is linked to the chip. Based on the LSPR spectrometer measurement system in our laboratory, δ-toxic protein in sonicated Bacillus thuringiensis cell fractions (which consists of many kinds of proteins) is detected successfully by measuring the extinction spectrum of the chip.

The coupled electric field effects on localized surface plasmon resonance in nanoparticle arrays

When a metal nanoparticle exhibits its unique dipole plasmon resonance, optical properties can be treated by considering a point dipole. Here we established a strong correlation between the surface-plasmon-induced coupled electric field in nanoparticle arrays and the extinction peak shifts. The model provides an effective way to explain the peak shifts caused by variation of the array structures. The extinction peak shifts of a one-dimensional silver cylinder array with different interparticle distances were predicted, and the results are in good agreement with those obtained by the discrete dipole approximation.

Method of realizing compact Fourier transform spectrometer without moving parts based on birefringent liquid crystal

Abstract. A method of realizing a compact Fourier transform spectrometer is proposed in this work, which is based on the polarization interference in a single layer of birefringent liquid crystal (BLC). The continuous interference between the ordinary light and the extraordinary light is driven by a continuously adjusted electric field. Benefiting from the single-layer configuration with no moving parts, the spectrometer is easily miniaturized. The method to realize the spectrometer is theoretically analyzed and experimentally demonstrated by a layer of nematic BLC with a 100-μm thickness.

Multi-focus plasmonic lens design based on holography

Multi-focus plasmonic lens with metallic nanoslits of variant widths have great potential applications in optical interconnection, integrated optics and nanophotonics. But the design method with simulated annealing algorithm or Yang-Gu algorithm requires complex calculation and multi focuses are limited to be set on the same output plane. In this paper, we propose a design method based on holography. The desired light field distribution and the incident plane wave can be treated as object wave and reference wave, respectively. So the calculation is relative simple and multi focuses can be located in different output plane. Numerical simulation of multi-focus lens design is performed through finite-difference time-domain (FDTD) method and the result confirms the feasibility of our method.

Nanochannel fabrication by imprinting-induced cracks

A simple and low-cost process of imprinting-induced cracks is proposed to fabricate controllable nanochannel structures with high depth-to-width ratio, in ultraviolet (UV) curable photoresist. The nanochannels are formed by the cracks of UV-curable photoresist due to its volume reduction as a result of solidification, with imprinting induced predesigned crack patterns. The proposed process is demonstrated with a nanochannel structure consisting of a periodically distributed hexagonal 30 nm-width and 100 nm-depth channels, which is fabricated by anodic aluminum oxide template imprinting induced cracks on a thiolene UV-curable photoresist. A finite element analysis provided theoretical foundation for the process, shedding lights on the parameters influencing the process.

Experimental study on polarization lens formed by asymmetrical metallic hole array

A polarization bifocal lens based on the polarization effect caused by asymmetrical hole arrays had been designed, fabricated, and characterized experimentally. By considering the fact that the skin depth of an infrared electromagnetic field inside metal is much shorter than the incident wavelength, a polarization bifocal lens composed of high deep-width ratio metallic holes was realized by using a gold-coated silicon structure to replace the one directly formed on a thick metal film. An infrared optical experiment setup is built based on the secondary imagery method for characterizing the focal length of the designed bifocal lens. The measured focal lengths of the fabricated bifocal lens coincide well with the designed values, which proves the validity for realizing the polarization elements with the proposed structure and the feasibility of the fabrication process.