# How does a laser beam expander work?

## How does a laser beam expander work?

A beam expander will increase the input laser beam by a specific expansion power while decreasing the divergence by the same expansion power, resulting in a smaller collimated beam at a large distance.

## How do you increase the diameter of a laser beam?

Beam expanders are optical systems for increasing or decreasing the diameter of a laser beam. A beam expander can enlarge an input beam by the factor M, but it can also reduce it by the factor 1/M with a reversed optical beam path. Usually beam expanders are used to increase the diameter of laser beams.

How do you reduce the diameter of a beam?

The only way to make the spot size smaller is to use a lens of shorter focal length or expand the beam. If this is not possible because of a limitation in the geometry of the optical system, then this spot size is the smallest that could be achieved.

Which property of light is used for amplification of laser?

The physical properties of materials A laser (Light Amplification by Stimulated Emission of Radiation) is a powerful source of coherent light (i.e. monochromatic and all in phase).

### Why do we need beam expanders?

A laser beam expander is often a crucial element in the success of individual systems. For high-powered sources, the addition of a beam expander can provide a controlled reduction of power density. Reducing divergence can assist in alignment and reduce the spot size at the final focus at the beam.

### How do you calculate divergence of a beam?

One may also simply measure the beam intensity profile at a location far away from the beam waist, where the beam radius is much larger than its value at the beam waist. The beam divergence angle may then be approximated by the measured beam radius divided by the distance from the beam waist.

Are laser beams collimated?

Laser light from gas or crystal lasers is highly collimated because it is formed in an optical cavity between two parallel mirrors which constrain the light to a path perpendicular to the surfaces of the mirrors. In practice, gas lasers can use concave mirrors, flat mirrors, or a combination of both.

What are the 3 types of lasers?

Types of lasers

• Solid-state laser.
• Gas laser.
• Liquid laser.
• Semiconductor laser.

## How does laser amplification take place?

In other words, the two photons are coherent. Some of these photons are absorbed by the atoms in the ground state and the photons are lost to the laser process. However, some photons cause stimulated emission in excited-state atoms, releasing another coherent photon. In effect, this results in optical amplification.

## Why does the cost of a laser expander increase?

As laser energy increases, the necessity of higher quality and precision optics and coatings causes the cost of the beam expander to increase (a). Increasing the input aperture size increases the cost of the beam expander rapidly at larger input apertures because of the nonlinear dependence of aberrations on input beam diameter (b).

How does the size of the beam expander affect performance?

Increasing the input aperture size increases the cost of the beam expander rapidly at larger input apertures because of the nonlinear dependence of aberrations on input beam diameter (b). With a fixed design, increasing the input aperture leads to a decrease in performance as aberrations start to dominate the wavefront (c).

Why is a Keplerian beam expander not recommended?

Because there is a high power density due to the focused spot size at the focal point between the lenses, Keplerian beam expanders are not recommended for use with lasers with high pulse energies. This is because the high pulse energy density at the focal point can cause the air to arc.

### What’s the difference between reflective and transmissive beam expanders?

Reflective beam expanders do not suffer from chromatic aberration, whereas the magnification and output beam collimation of transmissive beam expanders is wavelength dependent. While this is not relevant for many laser applications because lasers tend to lase at a single wavelength, it may be critical in broadband applications.