Spatial light modulators (SLM) are utilized in systems which compensate for distortion of a laser beam caused by transmission through a distorting medium. The Northrop Grumman linear beam cleanup system [1] uses an SLM to modify the phase front of the input beam to cancel the phase changes produced along the transmission path. At longer wavelengths these phase changes may not be achievable with current liquid crystal or lead lanthanum zirconate titanate (PLZT) modulators. High laser power levels may also produce adverse effects in these materials if operated in transmission mode. The silicon SLM (Si-SLM) produces a phase change by reflection of the laser from the surface of moveable pixels. The all silicon construction of the Si-SLM reduces the effects of temperature changes on the flatness of the reflecting surface.