Page 214 - High Power Laser Handbook
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182 So l i d - S t at e La s e r s Intr oduction to h igh-Power Solid-State Lasers 183
Deformable
mirror Aberrated
wavefront in
Clean
Piezoelectric wavefront out
actuators
Wavefront
sensor
Figure 7.11 Closed-loop adaptive optics (AO) system for laser wavefront
correction.
loops and actuators. An AO system involves actively, or adaptively,
controlling the shape or orientation of optics in the beam path so as to
reduce or eliminate OPD on the high-power output beam. Most often,
the actuated optics are integrated with active sensing of the output
beam wavefront as part of a continuous feedback loop. However, AO
systems can also be configured as feed-forward devices based on
such laser operating parameters as pump power levels.
A simple example of a closed-loop AO system is shown in Fig. 7.11.
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An aberrated, high-power beam is incident on a deformable mirror
(DM). The DM’s optical surface consists of a thin, polished face sheet
with a low-absorption high-reflectivity (HR) coating. The face sheet
changes its shape in response to stress imposed by individually
addressable piezoelectric actuators attached to its rear surface (Fig. 7.12).
The beam reflected from the DM is sampled and its wavefront mea-
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sured using a Shack-Hartmann sensor. This wavefront information
Figure 7.12 Deformable mirror for high-power SSL beam correction
(Xinetics, Inc.). Individual actuators can be seen through the 1064-nm high-
reflection coated face sheet, which is transparent at visible wavelengths.