Dielectric optical coatings

These are based on constructive and/or destructive interference effects of incident and reflected light. These antireflection coatings have bandwidths of a few nanometers for optimal operation. With appropriate material selection, their absorption can be minimized, and excellent durability can be achieved. They are, however, more complicated to deposit, requiring precise knowledge of the optical constants of the films, endpoint monitoring for determining the correct thickness of the film, and optimization of deposition conditions for denser defect-free films. For these reasons, they cost more than aluminum mirrors. 

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The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

The ability to apply a planarizing, optically transparent, thermally stable polymer system that cures under relatively mild conditions has recently been demonstrated to have utility in the fabrication of multilayer devices such as advanced color liquid-crystal display31,32 The ability to apply this material as a dielectric or optical coating for thin-film electronics devices has also recently been demonstrated with the fabrication of an optical wave guiding device.33... 

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... 

Tantalum oxide Gate insulators in metal-oxide-semiconductor devices, dielectrics for capacitors, optical coatings. 

Let us next consider a metal hoUow-optical fiber with dielectric inner coating. When the coating thickness is properly designed, the dielectric layer enhances reflection in a specific wavelength range owing to the interference effect. Let us consider a metal surface coated with a dielectric film of thickness d as shown in Fig. 2. From Fresnel s formula, the reflection coefficient of the electric field on boundary I is expressed as... 

Optical consideration, metal-dielectric antireflection coating... 

Macleod, H.A. (1978). A new approach in the design of metal-dielectric thin-film optical coatings. Optica Acta. Vol. 25, No. 2, pp. 93—106. 

A. Duparre, Light Scattering of Thin Dielectric Films, in Thin Films for Optical Coatings, R. Hummel, K.H. Guenther (Eds.), CRC Press, Boca Raton, 1995. 

TajOs, TiOj, ZrOa, HfOa, MgO Dielectric films for multilayer optical coatings... 

The proposed appUcatirms of aerogel are numerous and vary a great deal yet most remain uiu ealized. Commercial applications such as thermal window insulatirHi, acoustic insulation, optical coatings, capacitor electrodes, low dielectric constant layers in integrated circuits, piezoelectric transducers, and catalytic supports have all been proposed, but little in the way of actual use has resulted [1, 5-11]. However, sihca aerogel monohths have been used extensively in Cerenkov radiation detectors in high-energy physics experiments [12-16]. 

Dielectric used in film supercapacitors. Tantalum oxide is a high-refractive index, low-absorption material usable for making optical coatings from the near-UV (350 nm) to the IR (8 p.m). Insoluble in most chemicals except HF, HF—HNO3 mixtures, oleum, fused alkaU metal hydroxides (e.g. NaOH and KOH) and molten pyrosulfates. Tantalum pentoxide (tantalite, tantala)... 

Carbon film, which is chemically inert, can be applied as protective coating and antireflection layers for optical components for the infrared range and laser devices, wear protection, dielectric materials, coatings on fusion reactor walls, etc. Superlattices of a-C H and a-Si H have been obtained, and compound layers of a mixture of carbon and silicon have been grown. 

A line filter is essentially a Fabry-Perot etalon with a very small optical path nd between the two reflecting surfaces. The technical realization uses two highly reflecting coatings (either silver coatings or dielectric multilayer coatings) that are separated by a nonabsorbing layer with a low refractive index (Fig. 4.60). For instance, for nd = 0.5 p,m the transmission maxima for vertical incidence are obtained from (4.62a) at Ai = 1 xm, A2 = 0.5 p,m, A3 = 0.33 p,m, etc. In the... 

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