This calculator will help you to compute the Spatial distribution of Gaussian beams

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$\theta = \frac{2\lambda}{\pi w_0} $
$ R_z = z [1+ (\frac{Z_R}{z})^2]$

$Z_R = \frac{\pi w_0^2}{\lambda} $
$ w_z = w_0\sqrt{1+(\frac{z}{Z_R})^2}$

$w_0$ is the laser waist spot radius, $\theta$ is the far-field divergence angle, $\lambda$ is the light wavelength, $Z_R$ is the Rayleigh length, $w_z$ is the spot radius at z from the waist spot, and $R_z$ is the radius of curvature of the wave surface.


Input
Laser wavelength , $\lambda$:
nm

Beam waist radius, $w_0$:
mm
Distance from waist, $z$
mm



Output
Far-field divergence angle:
mrad
Rayleigh length:
mm
Spot radius at z:
mm
Radius at z:
mm