REX-Optics › Coating Designer

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Free Optical Coating Designer for X-Ray, EUV and Thin-Film Multilayers

Build a layer stack, pick your materials, and see reflectance, transmittance and absorptance in real time — from hard X-rays and EUV through the visible to the infrared. Transfer-matrix physics, curated optical constants, and 50 ready-made example designs.

Open the Coating Designer See worked examples

Made by REX-Optics, a University of Twente spin-off building X-ray and EUV multilayer optics.

REX-Optics Coating Designer showing an EUV Mo/Si multilayer mirror Screenshot-style preview of the coating designer interface: a periodic silicon and molybdenum multilayer stack of 40 periods on the left, and its computed reflectance spectrum on the right, peaking at 72.8 percent at 13.42 nanometres. REX-Optics · Coating Designer BETA Datasheet ⤓ Copy link Request → STACK SCHEMATIC ambient · vacuum Si 4.14 nm Mo 2.76 ⋮ ×40 periods Si substrate · σ 0.3 nm ×40 Si / Mo multilayer period Λ = 6.90 nm · total 276 nm Edit layers ▾ R / T / A 020 406080 12.513.013.5 14.014.5 wavelength (nm) R (%) R = 72.8 % @ 13.42 nm Reflectance Transmittance Absorptance AOI 5° · unpolarised
The designer showing a Mo/Si EUV multilayer mirror — 40 periods, Λ = 6.9 nm, σ = 0.3 nm on superpolished silicon. The curve is real output from the tool: peak reflectance 72.8 % at 13.42 nm.
0.01 nm – 2 mmX-ray, EUV, VUV, visible, IR
67 / 122materials / n,k datasets
50ready-made example designs
Freeno account, no install
What it does

A thin-film reflectivity calculator that works across the whole spectrum

Most online coating calculators stop at the visible and near-infrared. This one is built by an X-ray and EUV optics group, so the same transfer-matrix engine handles a 6.9 nm Mo/Si multilayer period and a 2 µm anti-reflection coating with equal rigour.

Build any layer stack

Add, reorder and edit layers directly, or define a periodic multilayer as a single group with a period count — so a 40-period Mo/Si mirror stays four numbers instead of eighty rows.

  • Per-layer thickness and RMS interface roughness
  • Pick a specific dataset per material, or let it choose
  • Substrates: thick incoherent slab, semi-infinite, free-standing membrane, or none

Three ways to scan

Sweep wavelength at fixed angle, sweep incidence angle at fixed wavelength, or compute a full wavelength × angle map to see how a design behaves over an entire cone of illumination.

  • s, p or unpolarised light
  • Angles from normal, or grazing for X-ray work
  • Axis units in nm, µm, Å or eV

Take the result with you

Export a branded datasheet with the full layer table and simulated spectrum, or copy a link that encodes the entire design so a colleague opens exactly the stack you built.

  • Datasheet export for reports and reviews
  • Shareable design links — no account needed
  • One click to ask REX-Optics to quote the coating
Spectral coverage

From hard X-rays to the far infrared

Coverage is set by the optical-constant datasets behind each material. The app flags the limiting dataset whenever your requested range runs past the data, so you always know when you are extrapolating.

BandWavelengthTypical designs you can model
Hard X-ray0.01 – 0.5 nmGrazing-incidence mirrors, W/Si and Mo/Si X-ray multilayers, Kiessig-fringe stacks
Soft X-ray / EUV0.5 – 50 nmMo/Si 13.5 nm lithography mirrors, Sc/Si 46.9 nm mirrors, Al-coated SiN filter membranes
VUV & UV50 – 400 nmExcimer laser mirrors at 248 nm, UV broadband AR, fluoride multilayers
Visible400 – 700 nmBroadband AR coatings, 532 nm laser mirrors, beamsplitters, dichroics, notch filters
Near IR0.7 – 2.5 µm1064 nm laser mirrors, telecom-band filters, hot mirrors, NIR AR
Mid & far IR2.5 µm – 2 mmGe and Si windows, ZnSe and ZnS AR coatings, MWIR/LWIR optics
Worked examples

Two designs you can open right now

Both are among the 50 example designs bundled with the tool. The numbers below are computed by the same engine that runs in your browser — open either one and change a thickness to see the spectrum move.

EUV multilayer mirror at 13.5 nm

Si 4.14 nm / Mo 2.76 nm × 40 periods · σ = 0.3 nm · Si substrate · 5° incidence

The workhorse of EUV lithography. Neither metal nor dielectric reflects usefully at 13.5 nm, so reflectivity is built up by resonant interference across dozens of periods — and interface roughness of a few ångström is the difference between a good mirror and a useless one. Change σ from 0.3 to 0.8 nm in the tool and watch the peak collapse.

72.8 %peak reflectance
13.42 nmpeak wavelength
80layers, edited as one group

Broadband anti-reflection coating, 400–700 nm

MgF₂ 113.3 / Ta₂O₅ 24.8 / MgF₂ 44.1 / Ta₂O₅ 18.7 nm · BK7 substrate · normal incidence

A four-layer visible AR coating on BK7 glass. Bare glass reflects about 4.25 % per surface across the visible; this stack takes the coated face down to a mean of 0.37 %, an eleven-fold reduction — the classic reason optical systems are coated at all.

0.37 %mean R, coated face
4.25 %mean R, bare BK7
11×reflection reduction
Under the hood

How the simulation works

The designer solves the transfer-matrix method (TMM) for a stratified medium: each layer contributes a 2×2 characteristic matrix built from its complex refractive index ñ = n + ik and phase thickness, the matrices multiply through the stack, and reflectance, transmittance and absorptance follow from the resulting amplitude coefficients. It is the same formalism used by commercial thin-film software, applied without approximation from X-ray to infrared wavelengths.

Interface roughness

Real interfaces are never atomically sharp. Each interface accepts an RMS roughness σ, applied through the Névot–Croce factor — the standard correction in X-ray and EUV multilayer work, where sub-nanometre roughness dominates achievable reflectivity. Because it is a real physical parameter rather than a fudge factor, you can use it to ask honest questions: how good does my polishing have to be?

Substrates handled properly

A 0.5 mm glass window is thousands of wavelengths thick, so its front and back surfaces do not interfere coherently. The tool models a thick substrate incoherently, the way a spectrophotometer actually measures it, with optional back-surface reflection — so a transmittance number means what you would measure on a bench. Semi-infinite substrates and free-standing membranes (where both faces do interfere) are separate modes.

Where the optical constants come from

67 materials and 122 datasets, compiled from curated public sources: refractiveindex.info (CC0 public domain) for the optical range, and CXRO/IMD compilations for X-ray and EUV. Every dataset carries its source, data type, valid range and licence, visible in the app next to each layer. Where several datasets exist for one material, you can pin the one you trust — because for sputtered films the difference between two literature sources is often larger than the effect you are trying to design.

Verification

The engine is checked against analytic references on every build: bare-substrate Fresnel reflectance, an incoherent glass slab, a quarter-wave AR coating, Brewster's angle for p-polarised light, energy conservation in lossless stacks, and a Mo/Si EUV multilayer against published reflectivity. Every bundled example design also carries machine-checked acceptance criteria, so the numbers quoted in each preset note are re-verified whenever the material data changes.

Who it is for

Built for people who need a number before they need a quote

Researchers & PhD students

Check whether a multilayer can reach the reflectivity your beamline needs, estimate how many periods it takes, or work out what roughness budget your experiment can tolerate — before writing the proposal.

Optical & process engineers

Sanity-check a supplier's design, explore how a stack degrades away from its design angle, or find out whether a requirement is physically reachable with materials that can actually be deposited.

Beamline & instrument builders

Compare candidate mirror coatings across the X-ray and EUV range, evaluate filter membranes, and see the full wavelength × angle behaviour of a component before it goes into a design review.

FAQ

Common questions

Is the Coating Designer really free?

Yes — free to use, no account, no licence, no installation. It runs entirely in your browser and is currently in public beta. We built it because we need this tool ourselves, and an accurate free calculator is the most useful introduction to what we do.

What wavelength range does it cover?

The dataset library spans roughly 0.012 nm (about 100 keV) to 2 mm. The usable range for any particular design is set by the materials you pick, and the app shows a coverage banner whenever your requested range runs past the available data — it will never silently extrapolate.

Which optical constants does it use?

67 materials with 122 datasets, from refractiveindex.info (CC0 public domain) and CXRO/IMD compilations for the X-ray and EUV range. Each dataset shows its source, type, valid range and licence in the app, and you can pin a specific dataset per layer rather than accepting the automatic choice.

Can it model X-ray and EUV multilayer mirrors?

Yes — that is what it was built for first. There is a grazing-angle convention for X-ray work, Névot–Croce roughness on every interface, and a periodic-multilayer group editor so a 40-period stack is four numbers rather than eighty rows.

Is my design private?

Designs are not stored on our servers or linked to you. The physics runs server-side and returns computed values only; a design exists in your browser and in the shareable link you choose to copy. This page and the app set no cookies and load no third-party scripts.

How accurate is it compared with a real measurement?

The physics is exact for the model you specify; the uncertainty lives in the inputs. Published optical constants are usually measured on bulk or evaporated material, while a sputtered film differs in density, stoichiometry and roughness. Treat a simulation as an engineering starting point — realistic for design and comparison, not a substitute for measuring the coating you actually received.

Can REX-Optics manufacture the coating I design?

Often, yes — multilayer mirrors, membranes and filters from X-ray to IR are our core business. The Request this coating button in the app sends the stack and spectral requirements straight to our engineers, who review manufacturability before quoting. Get in touch if you would rather start with a conversation.

Open the Coating Designer

Free, no sign-up, runs in your browser. Load one of the 50 example designs or start from a bare substrate.

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