Optical reflector coating

Commercial MMW components are precisely machined to tight specifications and can be bought on their specification with assured performance. Machining the cavities and interfacing the pumping and sampling systems does not require particularly sophisticated tools, and the mirrors can even be built around surface coated optical reflectors where suitable sizes are available. Experimentation is nonetheless an expensive business for the MMW components alone, particularly at higher frequencies. 

In dry methods - the metal is deposited from the vapour phase to produce generally thin coats such as those found in laminates associated with the Packaging industry, electromagnetic shielding of electrical equipment, capacitors, recording tape, CDs and optical reflectors as well as decorative trim panels, to mention just a few of the applications. The coating metal is evaporated under vacuum by one of several methods such as resistance... 

Optical Properties. Rhodium has the highest optical reflectivity of all platinum-group metals (Fig. 3.1-274), ranging about 20% below the reflectivity of Ag. It is used as hard and corrosion-resistant coating on silver jewelry and for optical reflectors. Data of the spectral emissivity are given in Table 3.1-216. 

For molded-plastic patls, vacuum coating techniques are increasingly replacing conventional coating methods, such as electroplating. For example, using vacuum coaling methods, automobile reflectors obtain a mirror-like surface, plastic articles in the furniture, decoration, clock and vratch as ell as electronics industry are metal-coated and optical effects are created on articles in the decoration industry. 

From a theoretical point-of view, significantly higher current densities are feasible, but require further improved front TCO films and perfect mirrors as back reflectors. This is illustrated by the dotted curve in Fig. 8.28, which shows simulations of quantum efficiency for a 1 pm thick pc-Si H solar cell. These simulations reveal a current potential of 29.2 mA cm-2 by improved optical components like reduced parasitic absorption in the front TCO, ideal Lambertian light scattering, dielectric back reflectors, and antireflection coatings on the front side [147]. However, this still has to be achieved experimentally. 

The metal layers frequently consist of chromium (semitransparent absorber metal) or aluminum (opaque reflector metal). Silicon dioxide or magnesium fluoride are the materials mostly used for the dielectric layers. In the case of pigment particles, there is a symmetrical arrangement of the layers, as shown in Figure 5.28, whereas optical coatings can also consist of a system of unsymmetrical layers. All these arrangements are the basis for an optical phenomenon called the Fabry-Perot effect... 

The most important applications are as follows retardation plates, cholesteric reflectors and filters, storage materials for optical informations, agents for preventing unauthorized copying of documents, and pigments for iridescent and polarizing coatings. 

Use Alloy with platinum for high temperature thermocouples, furnace windings, laboratory crucibles, spinnerettes in rayon industry electrical contacts, jewelry, catalyst, optical instrument mirrors, elec-trodeposited coatings for metals, vacuum-deposited glass coatings, headlight reflectors. 

The structures that have evolved for ablative-mode optical discs make use of interference effects to minimize the reflectance (R) of the disc in the absence of a hole. A typical ablative-mode optical disc has the structure shown in Figure 5.51. The substrate is an optically transparent material such as polycarbonate, poly(methyl methacrylate), poly(ethylene terephthalate), or poly(vinyl chloride), topped by a subbing layer to provide an optically smooth (to within a fi-action of a nanometer) surface for the recording layer. A metal reflector (typically aluminum) is then incorporated next to a transparent dielectric medium such as spin-coated poly(a-methyl styrene) or plasma-polymerized fluoropolymers. This dielectric spacing layer serves both to satisfy the quarter-wave (2/4) antireflection conditions and to insulate thermally the A1 reflector from the top absorbing layer where the information pits are created. 

Marshall, G. F. 1984, A unified geometrical insight for the design of toroidal reflectors with multilayered optical coatings , Proc. SPIE 563, 114. 

PEI resins have been used in a variety of applications such as electrical connectors, internal computer parts, printed-circuit boards, flexible circuits, optical fiber connectors, fire helmets, large appliances, aircraft interiors, trays, microwave cookware, reflectors, motor parts, gears, pumps, lubrication systems, wire coating, industrial applications, bearings, small appliances, films, and fibers. Polyetherimides are used in a wide range of applications. A few of the key markets for PEI resins and some of the benefits they bring to the application are summarized below. 

---