EO polymer-based integrated-optical acoustic spectrum analyzer

An acoustic spectrum analyzer based on electrooptic (EO) polymer integrated optics is presented. The device is used in a scanning heterodyne geometry by zero biasing a Michelson interferometer, It is capable of detecting vibrations from DC to GHz range. The novelty of this work is applying EO polymers to high frequency acoustic sensing applications. EO polymers have been extensively used for communication devices. However, their use in high frequency sensing applications remains unexplored. The sensor presented here is designed to analyze thin film structure by utilizing high frequency capabilities of EO polymers. The advantage of this approach over existing methods is in its potential to detect vibrations over 100 GHz with low drive voltages (V-pi less than 1 V), using a device that is completely electrically controlled with no mechanical moving parts. Low frequency tests indicate good agreement between experimental results and theoretical predictions. Acoustic vibrations excited by pulsed Nd-YAG laser are detected to frequencies up to 200 MHz using the device presented.