Laser Beam Divergence Calculator
Find a laser's divergence angle from beam growth over distance.
Even laser beams spread out a little; divergence measures how fast.
How the Math Works
The Laser Beam Divergence Calculator uses the formula θ = (d₂ - d₁) ÷ distance to determine how quickly a laser beam spreads as it travels. Here, d₂ and d₁ represent the beam diameters measured at two different points along its path, and 'distance' is the separation between these measurement points. The result, θ (theta), is the divergence angle typically expressed in milliradians (mrad), showing how much the beam expands per unit of travel distance.
Practical Applications
To use this calculator practically, measure the laser beam diameter at two known distances from the source using a beam profiler or calibrated detector. Enter these diameter values (ensuring consistent units) and the distance between measurement points into the calculator. This determines the beam's divergence characteristics, which is critical for applications like laser cutting, optical alignment, or assessing beam quality in industrial and research settings where beam spread affects performance.
Day-to-Day Use
Understanding laser beam divergence helps explain why laser pointers appear brightest when shone directly at you and dimmer as they travel farther. It also guides safe laser usage, as highly divergent beams spread their power over larger areas, reducing intensity and potential eye damage at distance. This knowledge is useful when selecting laser pointers for presentations or aligning optical systems in hobby projects, ensuring you choose appropriate lasers for your needs.
Worked example
2 mm to 20 mm over 100 m → 0.18 mrad.
FAQ
Why does it spread at all?
Diffraction limits how parallel any real beam can be.