Development of optical sensors for measuring acoustic pressure and acoustic particle velocity

Dr. Rob Adamson is a biomedical engineering professor whose research program involves the development ofminiaturized, high-sensitivity optical underwater pressure sensors (hydrophones) for use in studying thecochlea. Ultra Electronics is a Halifax-based company specializing in civilian and military underwateracoustics. Ultra currently manufactures a number of products, among them piezoelectric hydrophones fordetection of low-frequency (100-10,000 Hz) sounds, low-frequency piezoelectric acoustic source locators usedfor detecting the direction of incoming sound waves and sonar devices for underwater imaging and ranging.Ultra has an interest in reducing the size and increasing the sensitivity of their sensors and believes that opticaltechnologies under development in Dr. Adamson's lab may help them to do so.This Engage grant proposal will develop and test two devices in Dr. Adamson's laboratory. The first is a scaledup version of the cochlear hydrophone. This device would be an all-fiber interferometric hydrophonemeasuring 2mm in outer diameter. Based on calculations laid out in this proposal it is expected to achievecomparable sensitivity to the piezoelectric hydrophone currently manufactured by Ultra, but in a form factorwith a ten times smaller outer diameter. The second is a system for measuring the fluid particle velocity due toan incoming sound wave by suspending neutrally buoyant and optically retroreflecting particles in water andmeasuring the Doppler shift from the particles using a 3D fiber optic heterodyne Doppler interferometer. Thedevice will be able to measure the 3D particle velocity of the the fluid and thereby identify the direction to asound source.