About multilayer.app
The pitch
A free, browser-based transfer matrix method calculator for thin-film optics. Predict reflectance, transmittance, absorptance, layer-resolved absorption, electric-field intensity, and perceived color of arbitrary multilayer stacks — no install, no licence fee, every stack travels by URL.
What you can compute
- Coherent, incoherent, and mixed-regime stacks.
- R, T, A spectra in s, p, or unpolarized.
- Wavelength, angle, and thickness sweeps.
- Layer-by-layer absorption and |E(z)|2 profiles.
- Reflected / transmitted color (CIE / sRGB / D65).
- refractiveindex.info catalog, custom n/k tables, oscillator and roughness models.
- Permanent shareable links for any stack configuration.
Foundations
multilayer.app is built on two open resources from the optics community, with explicit attribution:
sbyrnes321/tmm
The numerical core extends Steven Byrnes' open-source tmm Python package (MIT). Transfer-matrix equations follow the review in arXiv:1603.02720; layer-resolved absorption for incoherent films follows the phase-integrated formulation in Coatings 9, 536 (2019).
refractiveindex.info
Optical constants come directly from refractiveindex.info material pages — the same database the optics community already trusts — or from your own n/k tables, oscillator models, and roughness layers.
Tutorials & validation
Five interactive tutorials walk through canonical thin-film effects, plus one validation case reproducing a published paper.
How it compares
A best-effort feature snapshot against widely used thin-film optics tools. Symbols: ✓ supported, ~ partial / limited, — not supported.
| Tool | Free | Browser | Open source |
Coherent + incoherent |
Field profile |
Layer- resolved A |
Color output |
Shareable link |
|---|---|---|---|---|---|---|---|---|
| multilayer.app | ✓ | ✓ | ✓1 | ✓ | ✓ | ✓ | ✓ | ✓ |
| Essential Macleod | — | — | — | ✓ | ✓ | ✓ | ✓ | — |
| OptiLayer | — | — | — | ✓ | ✓ | ✓ | ✓ | — |
| TFCalc | — | — | — | ✓ | ✓ | ✓ | ✓ | — |
| FilmStar | — | — | — | ✓ | ✓ | ✓ | ✓ | — |
| OpenFilters | ✓ | — | ✓ | ~ | ✓ | ~ | ~ | — |
| PV Lighthouse OPAL 2 | ✓ | ✓ | — | ✓ | ~ | ✓ | — | ~ |
1 The TMM core is built on the MIT-licensed sbyrnes321/tmm Python package. Feature data is best-effort from each tool's public documentation and may be incomplete or out of date — corrections welcome via the feedback button on the calculator. sbyrnes321/tmm and refractiveindex.info are listed under Foundations rather than as competitors, since multilayer.app builds on both.
Method scope
The transfer matrix method assumes plane-parallel layers, isotropic and locally homogeneous materials, and linear optical response. It does not directly model lateral structures such as diffraction gratings, photonic-crystal lattices, particulate scattering, or roughness-induced diffuse scattering. Within those assumptions it remains one of the standard tools for optical-coating design and thin-film stack analysis. Color rendering uses CIE standard-observer functions, reference illuminants, chromatic adaptation, and sRGB transforms following Bruce Lindbloom and Kruschwitz, Field Guide to Colorimetry and Fundamental Color Modeling.
Project & credits
multilayer.app is designed and maintained by Ilia Rasskazov as a free, dependable optical-coating calculator for researchers, engineers, and students. Feedback and corrections are welcome through the feedback button on the calculator.