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By using the transfer matrix method, the theoretical investigation has been carried out in the near- and mid-infrared bandgaps for a periodic multilayered structure that was composed of superconductor (SC) and semiconductor-metamaterial. It was found that two bandgaps appeared within the computational regions which are effectively optimized by manipulating the thickness of the SC film, fill factor of the semiconductor-metamaterial and the incidence angle of the incident electromagnetic wave. However, the thickness of the SC film and fill factor of the semiconductor-metamaterial are responsible for the red-shift of bandgaps, while the blue-shift is accounted for by the angle of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. It is notable, for the TM wave, that the bandgaps disappeared at the incident angles of approximately 60${}^{\circ }$. Such properties are quite useful in designing any new types of edge filters and other optical devices in the near- and mid-infrared frequencies.

In this work, we demonstrate the sensing principle to simultaneously detect the salinity and temperature of seawater using a 1D-defective photonic crystal structure. We designed a one-dimensional defective mode photonic crystal based on the well-known transfer matrix method (TMM) for detecting the seawater salinity and temperature. Our proposed optical sensor is based on the following concept. Since the concentration of the salinity in the seawater changes the refractive index of the seawater, the sensitivity can be calculated by a peak wavelength shift happening in the output transmission spectrum for its variation of different concentration of samples. By adjusting the design parameters of our proposed structure such as the thickness of the defect layer, the temperature and the salinity, we investigated the corresponding optical properties response where the resulted transmittance peak can be turned over the considered range.

Amorphous hydrogenated silicon carbide (a-SiC:H) thin films have been prepared by the RF reactive magnetron sputtering technique. The optical properties of the films have been studied by optical spectroscopy with an incoherent light source. The material is commonly regarded as a dielectric. We have discovered however that some films that were prepared under certain deposition conditions and on certain substrates may respond to external light as a metallic thin film, i.e. there are strongly enhanced reflection peaks in the optical spectrum. We have further discovered that some films may have a strong and broadened absorption peak at about 590 nm, which is an apparent photonic bandgap in the visible spectrum. The appearance of the photonic bandgap is very sensitive to two parameters: the substrate and the deposition gas. By changing the two parameters, one shifts the status of the film from with and without the photonic bandgap.

The opal photonic crystals made of polystyrene microspheres with 155, 230, 270 or 410 nm in diameter were used to enhance upconversion (UC) emission of YF₃:Yb³⁺, Er³⁺ nanoparticles, respectively. The red or green UC emission of YF₃:Yb³⁺, Er³⁺ nanoparticles can be selectively enhanced when the red or green UC emission wavelength overlapped with the photonic bandgaps of opals, which is attributed to Bragg reflection of photonic bandgap. In addition, when the 980 nm excitation light wavelength was in the region of the photonic bandgap, red and green UC emissions of YF₃:Yb³⁺, Er³⁺ nanoparticles were enhanced due to the enhancement of excitation field.

This paper presents a review on the selected highlights of highly-functional devices in two-dimensional photonic crystals slab structure. By introducing artificial defects in the photonic crystals (that is, defect engineering), novel photonic devices of line-defect waveguides and point-defect nanocavity are demonstrated. For more efficient manipulation of photons, the fundamentals of heterostructure photonic crystals are also reviewed. Heterostructures consist of multiple photonic crystals with different lattice-constants and they provide further high-functionalities such as multiple wavelength operation while maintaining optimized performance and the enhancement of photon manipulation efficiency. Because of the importance of high quality (Q) nanocavity for realization of nanophotonic devices, we also review the design rule of high Q nanocavities and present recent experiments on nanocavities with Q factors in excess of one million (~ 1.2 × 10⁶). The progress of defect engineering and heterostructure in two-dimensional photonic crystals slab structure will accelerate development in ultrasmall photonic chips, cavity quantum electrodynamics, optical sensors, etc.

We consider an optical pulse propagation in a one-dimensional nonlinear periodic structure doped uniformly with inhomogeneously broadening two-level atoms wherein the pulse propagation is governed by the nonlinear coupled mode-Maxwell Bloch equations. We investigate the pulse-train like periodic waves as well as bright and dark solitons near the photonic bandgap structure under the influence of self-induced transparency (SIT) effect. Further, we demonstrate that the resulting bright and dark SIT Bragg solitons may be realized both in anomalous and normal dispersion regimes, and this novel concept is ultimately the crux of this paper.

A computational study of the bandgap structure in two-dimensional (2D) photonic crystals (PhCs) with both square lattice and triangular lattice has been investigated in this paper. By studying in-plane light propagation in 2D PhCs, we solve the partial differential equations (PDEs) with periodic boundary conditions by using the finite element method (FEM) in frequency domain. The numerical results show that the numerical method is efficient and convergent. Moreover, based on the finite element procedure, a new numerical design scheme has been presented to obtain a desired photonic bandgap structure, which demonstrated by a design experiment in triangular lattice.