Yang Hongyan

The effect of array periodicity on the filtering characteristics of metal/dielectric photonic crystals

We present a both theoretical and experimental investigation into the effect of array periodicity on the filtering characteristics of metal/dielectric photonic crystals (MDPhCs) with hexagonal arrays of subwavelength holes in gold/silicon dioxide films, varying the array periodicity from 6 to 8 ?m every 1 ?m while the ratio of hole radius to array periodicity is kept constant (1/4). The results indicate that the reflectance spectrum is highly dependent on the array periodicity. When the array periodicity increases, the reflectance spectrum exhibits a large redshift regularly. The finite difference time domain (FDTD) simulations agree well with the experimental results. By analyzing the relationship between the position of the reflectance minimum and the array periodicity, we find that the filtering characteristics of MDPhCs have an almost linear relationship with the array periodicity under the conditions of keeping the same ratio of hole radius to array periodicity (1/4). This finding provides an effective way to control the filtering characteristics of MDPhCs, which have potential applications in optical filters, plasmonic thermal emitters and so on.

A low noise multi-channel readout IC for X-ray cargo inspection

A low noise multi-channel readout integrated circuit (IC) which converts a detector current to analog voltage for X-ray cargo inspection is described. The readout IC provides 32 channels of a circuit having a maximum dynamic range of 15 bit and is comprised of integrator gain selection, timing generator, shift register chain, integrator array, sample/hold (S/H) stage amplifier etc. It was fabricated using 0.6 μm standard CMOS process, and occupies a die area of 2.7 × 13.9 mm2. It operates at 1 MHz, consumes 100 mW from a 5 V supply and 4.096 V as reference, and has a measured output noise of 85 μ Vrms on 63 pF of integrator gain capacitance and 440 pF of photodiode terminal capacitance so that steel plate penetration thickness can reach more than 400 mm.

Significantly enhanced transmission achieved with double-layered metallic aperture arrays with sub-skin-depth Ag film

We present both theoretical and experimental investigation on significantly enhanced transmission through (Ag/Au) double-layered metallic aperture arrays with sub-skin-depth Ag film due to the coupling role of a surface plasmon polariton at the Ag/Au interface by evanescent waves. The results indicate that the enhanced transmittance is highly dependent on the Ag film thickness. When the Ag film thickness increases, the peak transmittance firstly increases and then decreases. Moreover, other metal material properties are also discussed. The highest peak transmittance is obtained when the Ag film thickness is 4 nm. The finite-difference time-domain simulations agree well with the experimental results. This finding provides an effective way to control the enhanced transmission for double-layered metallic aperture arrays, which has potential applications in designing a high-performance plasmonic thermal emitter.

Enhanced Light Narrow Transmission through Cascaded Metallic Structure with Periodic Aperture Arrays

We present experimental and numerical studies on the enhanced light narrow transmission through cascaded Au/SiOxNy/Au aperture arrays by varying the refractive index and thickness of SiOxNy. It is found that the enhancement as well as narrowing of the optical transmission originates from the coupling role of surface plasmon polaritons. The results indicate that the transmission enhancement is highly dependent on the refractive index and thickness of SiOxNy. A higher transmission efficiency and narrower peak are obtained in Au/SiO2.1N0.3/Au structure with a small refractive index (1.6) and thin thickness (0.2 μm).