Defining and Evaluating Multilayer Coatings in FRED Marko Swoboda.
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Transcript of Defining and Evaluating Multilayer Coatings in FRED Marko Swoboda.
What are Multilayer Coatings?
• Anti-Reflection Coatings consist of one or more layers
• Dielectric Mirrors use constructive/destructive interference
• interferometric filters select narrow lines by clever layer sequence
• required: precise control of optical layer thickness homogeneous deposition of dielectric/optical media
What is their role in FRED?
• most raytraced objects act by their refractive indices, a coating is only a few micron thick still major influence
• multilayer coatings act on the phase of the light, in reflection and transmission and achieve the highest possible reflectivities for single wavelengths
• all that makes it important to include such coatings in exact simulations of any system
How to make a coating?
simple as that:
two ways:-by clicking and
typing
-by script and data(also typing)
Coatings by Clicking
• 3-pair DBR • don’t forget to include the materials into your database
from the standard or self-defined materials! later
Plotting Coating Properties
• once defined, coatings can be added to any surface in FRED
• their properties are evaluated with the plot function
Plot Function Options
• great number of settings
• wavelength region always the maximum of present rays
• polarization sensitive
• amplitude AND phase of reflected light
Plot Function Results: 3-pair DBR
• plot function results @ 0 degree incidence• saveable as text file
Evaluation still has to be done by hand...
• click on plot coating the filter just defined
narrowbandtransmissionpeak!
Finally: New Materials
• Thin-Film layers so far are only limited by the availability of materials in the FRED-database
• defining a new material from external parameters helps:
Best way: Scripts generated by Matlab
• get lambda, n , k values from CXRO or your favourite website
Conclusion
• Coatings can greatly alter the behaviour of any surface in FRED
• they are defined a bit on the side, and can be evaluated independently from rays (mostly)
• they are defined from either standard materials in the optical region
• or from imported data (preferably with matlab) for any other wavelength region