## Selection of coupling focal length for an elliptical beam

### Determination of the effective coupling diameter

In order to find the best coupling focal length in case of an elliptical beam use the effective beam diameter Ø

_{eff}which is calculated from the small and the large diameters Ø_{||}and Ø_{⊥}of the collimated elliptical laser beam:{!{!{\emptyset_{eff}=\sqrt{\emptyset_{||}\cdot\emptyset_\bot}}!}!}

Definition of the effective beam diameter Ø_{eff}.

### Selection of focal length

After determining the effective beam diameter Ø_{eff. }The best focal length can be determined. This is done by replacing the diameter Ø_{beam }with Øeff in the corresponding formula.

5AN-2.5

### Measures to increase the coupling efficiency for elliptical beams

Coupling efficiency can be increased by converting the elliptical laser beam to a circular beam using anamorphic beam-shaping optics.