The laser beam spot size calculator determines the beam diameter at focus and the depth of focus using the following formulas:

$$w_0 = \frac{4 \lambda f M^2}{\pi w_L}$$

$$\text{DOF} = \frac{2 \lambda f^2 M^2}{\pi w_L^2}$$

Where:

• \(w_0\) is the beam diameter at focus.
• \(\text{DOF}\) is the depth of focus.
• \(\lambda\) is the wavelength of the laser.
• \(f\) is the focal length of the lens.
• \(M^2\) is the beam quality factor.
• \(w_L\) is the beam diameter at the lens (1/e).

The beam diameter at focus (\(w_0\)) is calculated by taking into account the wavelength, focal length, beam quality, and beam diameter at the lens. Similarly, the depth of focus (DOF) is determined by the same parameters, giving insight into the distance over which the beam remains focused.