Laser Beam Expander Calculator

Find the output beam size and divergence after a beam expander.

Input lens focal length

Output lens focal length

Input beam diameter

Magnification (×) 4

Output beam diameter 8

Formula: M = f₂ ÷ f₁

Step-by-step with your numbers:

1. Values used:

2. Input lens focal length = 25

3. Output lens focal length = 100

4. Input beam diameter = 2

6. Magnification = Output lens focal length / Input lens focal length = 100 / 25 = 4×

7. Output beam diameter = 8

Did we solve your problem today?

A beam expander widens a laser beam, which also reduces its divergence.

The math behind it

Magnification M = f₂ ÷ f₁. The beam widens by M and its divergence shrinks by the same factor.

f₁ = 25 mm, f₂ = 100 mm → 4× expansion (2 mm → 8 mm).

Why expand a beam?

A wider beam stays collimated over longer distances.