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The paper shows the determination of the transmission of one dimensional metal-dielectric photonic band gap materials (1D-MD PBG) theoretically and experimentally. It has been found that the location and bandwidth of transmission can be tailored by initiatively adopting a suitable structure. We proposed a special 1D-MD PBG obtained by magnetron sputtering, in which each layer of metal film is not continuous. These structures have a number of advantages such as high transmittance (55% or better), broad bandwidth (the full width at half of maximum ranges from 400 nm to 780 nm) and high electrical conductivity (the sheet resistance can be lower than 0.98 Ω /square). Meanwhile, it has been also theoretically and experimental indicated that both the light transmittance and electrical conductivity could be improved effectively by using the (pqp)N structure.

An optical refractive index (RI) sensor, possessing excellent sensing characteristics in sensitivity, resolution and SNR, is proposed by using a composite subwavelength grating (CSG). The CSG has a sandwich structure: the interlayer is a low-RI grating layer (LRGL), and the two sides are arranged with a high-RI grating layer. The light-coupling condition of the CSG is sensitive to RI changes of the liquid sample. The calculated results indicate that the sensitivity mainly depends on the CSG period, and the resolution and SNR can be improved by regulating the thickness and position of the LRGL. By optimizing these parameters, finally, an averaged sensitivity of ∼273°/RIU and resolution ranging from 0.1° to 0.15° are given by this CSG, and there is a minimal reflectance of ∼1% adjacent to the resonant peak.

This work reports the gold-coated self-organized silicon nanopyramidal array prepared by a wet etching and magnetron sputtering process at room temperature. Scanning electron microscopy was used to detect the morphology of gold films. The surface-enhanced Raman scattering (SERS) spectra of the rhodamine 6G (R6G) molecules adsorbed on a nanoscale gold film were recorded. Experimental results show the relationships between gold film thickness and SERS intensity. A full three-dimensional finite difference time domain calculations were carried out, which compare the experimental results and show agreement with ratios of the SERS enhancement for the different thicknesses of gold films. Furthermore, numerical simulations of the array were conducted for both a real gold metal coating and a perfect electrical conductor to determine whether the SERS enhancement was due to diffraction or plasmonic effects. The sample with the fast fabrication process used in this work could provide a new way to obtain a uniform enhancement and low cost SERS substrate.

This study examines nanomeshed Pt and Pt(Au) thin films formed by a dewetting process on a p-GaN surface. With prolonged annealing, the Pt(Au) layer shows more stable contact resistance to p-GaN and lower sheet resistance than the Pt layer. L–I curves show that the GaN light-emitting diode (LED) with the Pt(Au) transparent conducting layer (TCL) produces more light output power than the GaN LED with the Pt TCL. The higher light output of the LED with the Pt(Au) TCL is attributed to the lower sheet resistance, which improves current spreading in the active region.

In this paper, we report a characteristic transmission control property of a nano-optical system by introducing an antenna over the input opening of a bowtie aperture. The transmission process through the system is investigated quantitatively by the coupling and transmission efficiencies, and an optical switch effect is found as the antenna length varies. To understand the physical mechanism, we then investigate the electrical field distribution of the antenna over a rectangle aperture as a simplified model. It is discovered that the "on" state of the system is due to Fabry–Perot resonances in the horizontal cavity formed by antenna, dielectric layer, and metal film. On the other hand, a cutoff occurs for the characteristic rectangle length shorter than the diffraction limit to turn the device to the "off" state. Such a phenomenon can thus provide a promising candidate for application in manipulating light in large-scale optoelectronic device integration.

Local field surface plasmon excitation of pair arrays of silver nanospheres was studied using three-dimensional finite-difference time-domain method. The near-field enhancement was associated with the radius of nanosphere and the incident wavelength, the highest of which always appeared in the penultimate gaps, regardless of the number of the pairs. The surface plasmon resonance could be controlled and tuned by radius of nanosphere and incident wavelength.

In this paper, a subwavelength metal-grating assisted sensor of Kretschmann style that is capable of detecting the sample with a refractive index higher than that of the substrate is proposed. The sensor configuration is similar to the traditional Kretschmann structure, but the metal film is pattered into a grating. As a TM-polarized laser beam impinges from the substrate, a resonant dip point in reflectance curve is produced at a certain incident angle. Our studies indicate that the sensing sensitivity and resolution are affected by the grating's gap and period, and after these parameters have been optimized, a sensing sensitivity of 51.484°/RIU is obtained with a slightly changing resolution.

The optical properties of silver spherical nanoparticle dimer arrays with various incident wavelength are investigated by using the finite difference time domain method. Due to surface plasmon resonance, in the arrays of strongly coupled Ag nanoparticles, the energy of incident light is effectively confined in the gap of penultimate dimer under the influence of surface plasmonic reflection at the end of array structure. Furthermore, the suitable radius of the nanoparticles can be chosen to obtain the resonant peak at the optional position in the range of visible-nearinfrared wavelength. The above effects can be utilized to design effective functional end-structures in integrated optics.

Metal nanostrip array for light transmission enhancement in the nanoslit is studied using a finite-difference time-domain method (FDTD). The strips with uniform shape are placed on upper side of a metal film with the nanoslit fabricated in it. It is found that the transmission efficiency can be promoted with an optimization of the strip. Effects of the single strip on the promotion are discussed in detail, a Fabry-Perot resonance model is competent for well understanding the phenomena.

Optical properties of bowtie antennas are investigated using a numerical method of finite-difference time-domain (FDTD). The optical response in the antenna feed gap is simulated as functions of its geometry parameters (flare angle, arm length, apex width, thickness, gap dimension, as well as the index of substrate), which provide a clear guideline to exploit such antenna structures in practice.

A surface plasmon resonant cavity capable of enhancing ultradeep subwavelength photolithography in a large area is proposed. The cavity consists of two metal films: one is etched with periodic grooves for exciting surface plasmon resonance at the metal/dielectric interface; the other below is separated by a photoresist layer. Numerical simulations show that the properties of photolithographic patterns in the cavity can be modulated by the depth of the cavity; the physical image behind the modulation is confirmed by the phase regulation of gap surface plasmons in such a system.

The bowtie aperture surrounded by concentric gratings (the bull's eye structure) integrated on the near-field scanning optical microscopy (NSOM) probe (aluminum coated fiber tip) for nanolithography has been investigated using the finite-difference time domain (FDTD) method. By modifying the parameters of the bowtie aperture and the concentric gratings, a maximal field enhancement factor of 391.69 has been achieved, which is 18 times larger than that obtained from the single bowtie aperture. Additionally, the light spot depends on the gap size of the bowtie aperture and can be confined to sub-wavelength. The superiority of the combination of the bowtie aperture and the bull's eye structure is confirmed, and the mechanism for the electric field enhancement in this derived structure is analyzed.

Indentations etched on the output surface of a metallic mask are proposed to produce fine lithographic patterns with a resolution of 500 nm using the finite-difference time domain (FDTD) method. Such a designed mask is capable of enhancing near field lithography (NFL) resolution more than three times compared with the structure without indentations. The simulation results show that the interference disturbance between the adjacent lithographic channels can be eliminated efficiently by employing the indentations. As a straightforward consequence, the channel-to-channel interspaces can be shortened significantly, maintaining a uniform field distribution and high contrast.

We investigate optical properties of a bowtie-shaped aperture using the finite difference time domain method to optimize its geometric parameters for specific incident lights. The influence of the parameters on local field enhancement and resonant wavelength in the visible frequency range is numerically analysed. It is found that the major resonance of the spectrum is exponentially depended on the bowtie angle but independent of the whole aperture size. The simulation also demonstrates that increasing the aperture size raises the local field intensity on the exit plane due to an enlarged interaction area between the light and the metal medium. And the near-field spot size is closely related to the gap. Based on these results, the design rules of the bowtie structure can be optimized for specific wavelengths excited.

A way of improving near field lithography is proposed, using metallic nanostrips arranged right above the lithographic channels, between which a dielectric film is used, designed to support the strips and modulate the surface plasmon resonance at the metal/dielectric interface. The dependence of the light transmission in the channels on the properties of the strip array and dielectric film are studied numerically. The results show that the transmission is associated with the width of the strip, the permittivity of the film and the thicknesses of both. With the optimized structure, not only is transmission efficiency promoted, but also a uniform field distribution of good contrast at the channel exports can be obtained, which is beneficial to the lithography.