Ultra violet radiation controlled non-linear dielectrics

The term beam steering means the focussing of a beam of light in order to improve the amount of light reaching a specific target, rather like a searchlight. But to increase the coverage the bean is rapidly modulated - the searchlight is very rapidly swept back and forth. The same principle applies to radio waves and microwaves. This proposal aims to make an array of antennas that can be electronically steered in order to improve this focussing. To achieve this we need phase shifters which are devices that can alter the output signal phase on the application of a voltage. In comparison with current communication systems, in which transmitter/receiver antennas operate without beam steering, this will improve their performance hugely. Transmitter power is reduced, saving energy and reducing electromagnetic radiation, and inter-channel interference is reduced due to the space resolution of radiation directions.The main barrier preventing the development of phased-array antennas is the high cost of the antenna control systems containing banks of phase-shifters. The cost of ferrite or semiconductor based phase-shifters in these banks depends on frequency band and costs from $50 (L-band) up to $250 (Ka-band) and more for one unit. Taking into account the need to use between 20-1000 similar devices for each antenna to provide the required antenna parameters it becomes clear that 60 - 90% of the price of steerable beam antennas is connected with their control system. Phase-shifters and other control devices based on ferroelectric films can reduce the cost of a single element down to a few dollars due to their technological simplicity. However, ferroelectric devices exhibit residual polarization (a hysteresis phenomenon that is observed after decreasing the bias voltage down to zero) and slow relaxation at pulsed control voltage. This disadvantage is the main barrier for their implementation, as it causes a decrease of tunability and an ambiguous time response to the pulsed control voltage. The aim of this proposal is to develop new tuneable [ferroelectric] devices based on a new phenomenon. We and our collaborators have made an interesting observation: a reduction in the hysteresis of ferroelectric materials upon the application of ultra violet light. This discovery requires further experimentation. The effect could be used in an entirely new generation of electronic devices.