Transcript Slide 1
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 Examples of Coatings • Distributed Bragg-Reflector: 8(l/4) • Narrow-band Interferometric Filter: l/2 4(l/4) 4(l/4) 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 • tons of options: focus on the most general: Thin Film Layered Coatings Coatings by Clicking • layers can be repeated in groups (e.g. lambda/4 stacks) 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 Other Option for Coating Definition • write a script, defining the properties: Evaluation still has to be done by hand... • click on plot coating the filter just defined narrowband transmission peak! One more example: • DBR with high-index layer on top: reflectance One more example: • DBR with high-index layer on top: phase phase jump at design wavelength! One more example: • solution: low-index-layer on top: • phase-jump only in transmitted light! 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