A laser mirror assembly is disclosed with improved pointing stability. An
elongated mirror includes a concave reflecting portion. A pair of
elongated planar portions extend parallel to the concave reflecting
portion on either side thereof. The planar portions are stepped down from
the reflecting portion. The mirror is formed from copper. A pair of
stainless steel strips are connected to planar portions. The bimetallic
effect between the copper mirror and the stainless steel strips operates
to counteract the warping of the mirror due to differential heating
effects which arise during operation. In an alternate embodiment, a pair
of aluminum strips are mounted on the rear surface of the mirror.