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Multilayer Dielectric Internal Reflectance Enhancement

IP.com Disclosure Number: IPCOM000051314D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Armitage, JD: AUTHOR [+2]

Abstract

Multilayer dielectrics between a dielectric substrate and a reflecting metal film enhance internal substrate-to-metal reflectance. The most common application is for an aluminum film on a glass substrate.

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Multilayer Dielectric Internal Reflectance Enhancement

Multilayer dielectrics between a dielectric substrate and a reflecting metal film enhance internal substrate-to-metal reflectance. The most common application is for an aluminum film on a glass substrate.

Multiple dielectric layers over aluminum on a front-surfaced mirror enhance the air-aluminum interface reflectance from about 90% to about 99%. Mirrors back-surfaced with aluminum, by itself, exhibit a glass-aluminum reflectance of about 86.5%. Several configurations for multiple dielectric layers sandwiched between glass and aluminum provide a range of enhanced reflectance selectably based on a trade-off of improvement against cost. For example, the following table illustrates reflectance for several possible interface layer configurations between glass, having a refractive index of 1.6, and aluminum: See Original.

These are specific embodiments of the general configurations:

1) Glass - (HL)/M/ - Aluminum

2) Glass - (LHL)/M/ - Aluminum. where H is a high index material, L a low index material, and M indicates repetitions. As M increases, the peak reflectance increases, but the spectral width around Lambda c becomes narrower, as shown in Fig. 1, where R is the relative magnitude of reflectance.

Some numeric data for typical coatings for Lambda of 5900 Angstroms where the layer thicknesses are Lambda/4 optical thickness (e.g., MgF(2) = 1000 A and TiO(2) = 600 Angstroms) are shown in the following table:
See Original. where n and k are the real and imaginary parts o...