Expanders vs Collimators

[monika]

Hi guys

As far as I can see beam expanders change the size and divergence of a laser. Collimators collimate the light.

One article I read claims "Beam expanders improve a beam’s collimation" so my question is why do we have both items if beam expanders can collimate beams?????

What are the practical uses of these?

 

[hwang21]

Beam expanders recollimate collimated light. If you have a collimated laser that has a divergence of ~1.5mRad (arbitrary number), a 10x beam expander will reduce the divergence to 0.15 mRad. A collimating lens is used to collimate the laser light that is being emitted from the laser diode, a beam expander is used to collimate a laser's already-collimated beam. This gives the laser a nice and straight (albeit thicker) beam

 

[steve001]

Your confusion arises because you haven't realized beam expander and collimator are one in the same.