Design and characterisation of a ferroelectric liquid crystal over silicon spatial light modulator

摘要

Many optical processing systems rely critically on the availability of highudperformance, electrically-addressed spatial light modulators. Ferroelectric liquidudcrystal over silicon is an attractive spatial light modulator technology because itudcombines two well matched technologies. Ferroelectric liquid crystal modulatingudmaterials exhibit fast switching times with low operating voltages, while veryudlarge scale silicon integrated circuits offer high-frequency, low power operation,udand versatile functionality.udThis thesis describes the design and characterisation of the SBS256 - a generaludpurpose 256 x 256 pixel ferroelectric liquid crystal over silicon spatial light modulatorudthat incorporates a static-RAM latch and an exclusive-OR gate at eachudpixel. The static-RAM latch provides robust data storage under high read-beamudintensities, while the exclusive-OR gate permits the liquid crystal layer to be fullyudand efficiently charge balanced.udThe SBS256 spatial light modulator operates in a binary mode. However,udmany applications, including helmet-mounted displays and optoelectronic implementationsudof artificial neural networks, require devices with some level ofudgrey-scale capability. The 2 kHz frame rate of the device, permits temporal multiplexingudto be used as a means of generating discrete grey-scale in real-time.udA second integrated circuit design is also presented. This prototype neuraldetectorudbackplane consists of a 4 x 4 array of optical-in, electronic-out processingudunits. These can sample the temporally multiplexed grey-scale generated by theudSBS256. The neurons implement the post-synaptic summing and thresholdingudfunction, and can respond to both positive and negative activations - a requirementudof many artificial neural network models.