INDEX layers

Figure 12.3b shows the widths of the Bragg layers as a function of the layer number of the CBNL depicted in Fig. 12.3a. There are two notable properties of the Bragg layers (1) the width of the high-index layers is smaller than the width of the low-index layers, and (2) the width of the layers decreases exponentially as a function of the radius, converging asymptotically to a constant value. The first property exists in conventional DBRs as well and stems from the dependence of the spatial oscillation period, or the wavelength, on the index of refraction. The second property is unique to the cylindrical geometry and arises from the nonperiodic nature of the solutions of the wave equation (Bessel or Hankel functions) in this geometry.

An optical waveguide is a high refractive index layer situated between two materials of lower refractive index, as it is shown in Fig. 5.1. 

Fig. 5.13. The resonant mirror device. The light from the soiuce is coupled through a prism Emd is totally reflected at the interface with the low refractive index layer, generating an evanescent field which couples light into the high refractive index waveguide layer The light transmitted through the waveguide also generates a evanescent field which interacts with the receptor layer.

Fig. 2 Various types of hollow-core photonic bandgap fibers, (a) Photonic crystal fiber featuring small hollow core surrounded by a periodic array of large air holes, (b) Microstructured fiber featuring medium-sized hollow core surrounded by several rings of small air holes separated by nano-size bridges, (c) Bragg fiber featuring large hollow core surrounded by a periodic sequence of high and low refractive index layers...

A very promising electrically conductive omnidirectional reflector suitable for use in LEDs is shown in Fig. 1.17 [62, 63], The reflector comprises the LED semiconductor material with a refractive index ns, a low-refractive index layer (nu), and a metal with a complex refractive index Nm = nm + i km, where km is the extinction coefficient. 

The low-index layer is perforated by many small ohmic contacts that cover only a small fraction of the entire area. The array of microcontacts allows the electrical current to pass through the dielectric layer. Assuming that the ohmic contacts have an area of 1 % of the reflector, and that the alloyed ohmic contact metal is 50% reflective, the reflectivity of the ODR is reduced by only 0.5%. The ODR described here can be used with low-cost Si substrates or metal substrates using conductive epoxy or a metal-to-metal bonding process. These bonding processes have much less stringent requirements than direct semiconductor-to-semi-conductor wafer bonding processes. 

The index layer is composed of the evaluation factors capable of reflecting the characteristics of water resources allocation system. They are measured by quantification, analysis and comparison of the index, which could obtain the degree of the harmoniousness of water resources allocation more scientifically. The corresponding evaluation indexes for each system of the criterion layers are set up, which is widely ranged thanks to the complexity of these systems. Therefore, in order to seize the key to determine the mode of water resources development and facilitate the calculation of the evaluation, the most representative and key indicators will be selected, and the indicators which have little to do with the research purpose should be abandoned. 

Here we focus on the capabilities of a porous silicon waveguide biosensor for the detection of small molecules. The porous silicon waveguide, shown schematically in Figure 3a, consists of two porous silicon layers. Light is trapped in the top, high refractive index layer, based on total internal reflection at the interfaces with air and the bottom, low refractive index porous silicon... 

The newest form of pearlescent pigment is a coated mica. The mica provides a transparent platelet shape with its two parallel faces. These faces are coated with a high-refractive-index layer of titanium dioxide or iron oxide. An absorption color layer can be overlaid on the oxide layer, giving additional reflective surfaces. These coated micas have high operating temperatures and are nontoxic. They are supplied in a range of particle sizes, usually from 10 to 50 xm. Loadings of coated mica pearlescents usually run about 1.5-3 percent. 

Similarly, a multilevel stair-step grating can be modeled as a stack of homogeneous layers with different effective indices. A grating with a continuously-varying dielectric constant profile s(x,z), such as a sinusoidal shape for example, can be approximated as a graded-index layer along the thickness direction as... 

The results shown in Table 1 and Fig. 7 prove the applicability of our model - a gradient refractive index layer, where the local refractive index is determined from the volume fraction of the constituents by the Lorentz-Lorenz formula, as the fitted layer thickness corresponded to the particle diameter (Table 1) - and the other results were also consistent with the expectations both about the behavior of the particles and the structure of the interfacial layer. 

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