# What is the beam waist?

## What is the beam waist?

The beam waist (or beam focus) of a laser beam is the location along the propagation direction where the beam radius has a minimum. The waist radius is the beam radius at that location.

## How is a Gaussian beam defined?

In optics, a Gaussian beam is a beam of electromagnetic radiation with high monochromaticity whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile.

**How do you calculate the divergence of a beam?**

Answer from the author: Provided that the beam focus is outside these two points, and that the beam diameter at the focus is much smaller than at those points, you can calculate the beam divergence angle as the difference of the beam radius divided by the distance of 50 cm.

**What is the equation for Gaussian beam?**

The Thin Lens Equation for Gaussian Beams The behavior of an ideal thin lens can be described using the following equation 2: (7)1 s′ = 1 s + 1 f 1 s ′ = 1 s + 1 f In Equation 7, s’ is the distance from the lens to the image, s is the distance from the lens to the object, and f is the focal length of the lens.

### What is the formula for waist radius of a beam?

w0 = w(0) is the waist radius, R(z) is the radius of curvature of the beam’s wavefronts at z, and ψ(z) is the Gouy phase at z, an extra phase term beyond that attributable to the phase velocity of light.

### How accurate is the Gaussian beam model?

Since the Gaussian beam model uses the paraxial approximation, it fails when wavefronts are tilted by more than about 30° from the axis of the beam. From the above expression for divergence, this means the Gaussian beam model is only accurate for beams with waists larger than about 2λ/π .

**What is the beam diameter of the mixed mode Gaussian beam?**

Consequently the beam diameter of the mixed-mode beam will always be Mtimes the beam diameter of the embedded Gaussian, but it will have the same radius of curvature and the same Rayleigh range (z=R). M w w 2 0 0 =RR v v (2.25) 2ch_GuassianBeamOptics_Final.qxd 6/15/2009 2:54 PM Page 2.11