This book serves as a supplement to the classic texts by Angus Macleod and Philip Baumeister, taking an intuitive approach to the enhancement of optical coating (or filter) performance. Drawing from 40 years of experience in thin film design, Cushing introduces the basics of thin films, the commonly used materials and their deposition, the major coatings and their applications, and improvement methods for each.
This book started as a short supplement to demonstrate how to improve the performance of coatings beyond the techniques described in the standard texts by Macleod and Baumeister. The coatings are designed with TFCalc®, but any of the available programs provide similar answers. The approach to designing is not mathematical in nature, but intuitive. I have more than 40 years experience building coatings and filters, and I mostly used an optical monitor as the primary control because the desired results were optical coatings, and other available methods of monitoring were unreliable. Early work used thermal sources without ion assistance, and the results for crystal monitoring were inconsistent. The stability of crystal monitoring has vastly improved with the energetic sources now available. This allows for nonquarterwave layers that can be counted on to be within a reasonable tolerance. I have made edge filters with 30 layers that follow the theoretical curves within a few nanometers of cutoff tolerance.
I have not manufactured many of the films described in this book; the concepts were originally depicted for papers presented at conferences. One can only present what is allowed by the employer(s). Typically, one cannot talk about the work that is currently being pursued, and the equipment for producing the described coatings may not be available when moving on to a new job. I anticipate that the designs are fairly easy to accomplish based on the work that I was able to do.
The designs were produced using TFCalc; copies of the designs, materials, and targets are supplied in the TFCalc format. I have also copied the designs into a new freeware program called OpenFilters. This program is available from École Polytechnique de Montréal, described in Applied Optics (Vol. 13, May 2008, p. c219). It is freely available on the website http://www.polymtl.ca/larfis.
The materials I used are also provided and need to be added to those given in the program. For the most part I have not supplied targets for these designs.