### Example 2. Optimization of coating total thickness

 Using the new type of targets Thick/Stress you can optimize total thickness of the coating. Consider the same design problem of the edge filter as in Example 1. Typical total thicknesses of edge filter designs is 3.5-4.2 μm. It may be required to limit the design total thickness by 3 μm. In this case, Thick/Stress target can be specified as it is shown in Fig. 1: $\alpha_1\Sigma_{TiO_2}+\beta_1\Sigma_{SiO_2}<3000μm,$ $$\alpha_1=1, \beta_1=1$$. Target value is 3000 that corresponds to 3000 nm. Qualifier B indicates that total thickness must be less than 3000 nm. Fig. 1. Thick/Stress target specification in the case when total coating thickness is to be optimized. One of the edge filters obtained by optimizing combined merit function is shown Figs. 2 and 3. Total design thickness is less than 3000 nm. At the same time, approximation of the target reflectance in the range 583-683 nm is getting a little bit worse since the thickness is smaller. Fig. 2. Spectral performance of the 25-layer edge filter design. Total thickness is 2916 nm. Fig. 3. Refractive index profile of the 25-layer edge filter. The new option is very flexible. Obviously, with the help of this option you can not only minimize thickness of one material or/and reduce the total thickness. You can increase or limit thickness of materials or even separate layers. In order to increase thicknesses you need to specify A qualifier. To limit thicknesses of layers you need to specify not one but two targets, one with A and another one with B qualifier.  Auxiliary information for stress-targets specification