Thin-Film Optical Coating Calculator
Find the ideal thin-film thickness for constructive interference at a chosen wavelength.
Thin-Film Interference Coatings
Thin-film coatings (like anti-reflective camera lens coatings or soap bubbles) work by interference: light reflecting off the top and bottom of the film either reinforces or cancels depending on the film’s thickness. For normal incidence, constructive interference occurs when 2nt = mλ, where n is the film’s refractive index, t is thickness, m is a whole-number order, and λ is the wavelength in air.
Solving for thickness gives t = mλ ÷ (2n) — the calculator here shows the thickness needed for constructive reflection at your chosen order. In practice, single-layer anti-reflective coatings usually target m corresponding to destructive interference instead (a quarter-wave layer), so check which effect you want to design for.