Laser concepts

The dominating sources used for PV-related processes are solid state lasers.
This is due to the demand of simultaneously delivering high power, top beam
quality, and maximum repetition rates, all of which are needed to realize
high processing speeds together with high resolution.

Regarding solid state lasers, there are four concepts competing with each
other. Up to now, the laser equipment of research institutes as well as of solar
cell producers mainly consists of diode-sidepumped and diode-endpumped
solid state lasers, containing a neodymium-doped rod made of YAG or
Vanadate. Recently, two other geometries of the laser active medium have
been challenging the established concepts: fiber and disc. But none of them
is capable of occupying the solar market alone. The diversity of various
processes leads to the necessity to constantly develop tailored laser solutions.

Due to its exceptional material processing properties, especially the disc
laser concept is gaining more and more acceptance in solar cell production. As
a result of the comparatively low volume of the active laser medium, diode
pumping takes place via a parabolic mirror, leading to a multi-pass reflection.
The laser crystal is water-cooled from the rear side, causing only a onedimensional
temperature gradient. Therefore, compared to a rod, a disc
laser offers significant higher beam quality or, in other words, much higher
average power of best beam quality.