## Beam parameter product | previous | next | feedback |

Equipment for measuring the beam parameter product can be purchased from:

- (currently no entries)

Ask RP Photonics for advice on beam quality and related aspects of lasers.

Definition: product of beam radius in a focus and far-field beam divergence

Acronym: BPP

The beam parameter product (BPP) of a laser beam is defined as the product of beam radius (measured at the beam waist) and the beam divergence half-angle (measured in the far field). The usual units are mm mrad (millimeters times milliradians). The BPP is often used to specify the beam quality of a laser beam: the higher the beam parameter product, the lower the beam quality.

The BPP can also be defined for non-Gaussian beams. In that case, standard deviations should be used for the definitions of beam radius and divergence. The smallest possible beam parameter product is then achieved with a diffraction-limited Gaussian beam; it is λ/π. For example, the minimum beam parameter product of a 1064-nm beam is about 0.339 mm mrad.

A related, less frequently used quantity is the diameter-divergence product.

See also: beam radius, beam divergence, beam quality, *M*^{2} factor, beam profilers