Hi Akhil,

Those are not coatings, those are materials. Hence the keyword MATE. These are material definitions according to the syntax below (extracted from the Help File):

! Sample material definitions
! Format:
! MATE <material name>
! wavelength real_index imaginary_index

You can make a coating out of a material, and the syntax is described below (also from Help File):

! Sample coating definitions
! Metallic coatings typically used for mirror substrate; thickness is irrelevant in this case
! Format:
! COAT <coating name>
! material thickness is_absolute loop_index tapername

For example, in the default coating file, you have the following for copper:

! Copper based on fit of experimental data from Brendel-Bormann Model per refractiveindex.info (Rakic et al, 1998)
MATE CU
0.4861 1.1512 -2.3025
0.5876 0.46090 -2.9736
0.6563 0.26010 -3.6726
1.0640 0.37861 -7.0658
10.600 9.4305 -67.7600

COAT COPPER
CU 0.0001 1

The first part is the definition of the copper CU in terms of wavelength and refractive index. This is the material definition. The second part is an actual coating COPPER, which is a single layer of CU with a thickness of 0.0001, and the absolute flag is true (1) meaning the thickness is in micrometers, so in this case 0.1 nm of copper.

You’ll find the COPPER coating in the drop-down menu of your non-sequential object, but you will not find CU.

Does that make sense?

Take care,

David