A laser beam is not a perfect straight ray. It pinches to a minimum waist, then inevitably spreads — the diffraction limit written into every beam of light.
Gaussian BeamLive
how a laser beam spreads
Controls
Presets
A real laser beam is not a perfect ray — it narrows to a minimum waist then spreads. Within one Rayleigh range of the waist it stays roughly collimated; beyond, it diverges at an angle set by wavelength over waist size. Tighter focus means faster spreading — the fundamental diffraction trade-off behind every laser and telescope.
Reading this result: Divergence is set by λ/(π·w₀): shrinking the waist or lengthening the wavelength both make the beam spread faster — the core diffraction trade-off.
Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.
★ Sign in to save this setupSave your tuned setup, or drop this simulation into your own site, docs, or course page.
How it works
A Gaussian beam narrows to a waist and expands as a hyperbola. Within one Rayleigh range of the waist it stays nearly collimated; beyond that it diverges at an angle set by wavelength divided by waist size. Focusing tighter forces faster spreading — the unavoidable trade-off that shapes laser cutting, microscopy, and free-space optical links.
✦
Ask the AI about this model
The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.
Is this Gaussian beam Rayleigh range tool really free?▾
Yes. Gaussian Beam runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?▾
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
Can I save or share my simulation?▾
Create a free account to save projects, and use a shareable embed or minted DOI to publish a live, interactive version anywhere.
How accurate are the results?▾
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.