A comparative investigation into planarized liquid crystal over silicon spatial light modulators

Spatial light modulators (SLMs) are arguably the critical elements in coherent optical processing systems. Planarization techniques have been identified as crucial to increasing the performance of ferroelectric liquid crystal over very large scale integration SLMs when used in such systems. Planarization techniques allow enlarged and phase-flat pixel mirrors and improved liquid crystal alignment. This type of SLM is electrically addressed, i.e. transfers electrically represented information into an optical representation via binary phase modulation of the liquid crystal layer by the enlarged pixel modulation mirrors. The backplane design available for use in the study was a 176 × 176 pixel array dynamic random access memory. Investigations show an improvement in the device performance due to the planarization. This improvement was particularly evident when the SLMs were studied operating in a coherent optical system, where the diffraction efficiency was increased. The results compare favourably with transmissive SLMs, although further improvement in the liquid crystal quality is required.