BU MEMS Hydrophone

This is a small part of the Boston University MEMS Hydrophone BUMH project in the AME department to build an ultrasound hydrophone on a silicon chip using MEMS technology. A cartoon of the device is shown to the right. An incoming sound wave is incident on a hourglass cavity carved into a silicon chip. The top half of the cavity acts as an acoustic horn which gives a broadband amplification of the acoustic signal. The bottom half is a Helmholtz resonator which gives a large amplification over a narrow bandwidth. The sound is detected by a small optically reflective membrane placed in the middle of the device. A laser beam is introduced into the lower cavity by means of a fibre optic. The moving membrane and the tip of the fibre make up the etalon of a Fabry-Perot interferometer. The optical signals reflected from the tip of the fibre and the moving membrane interfere and the combined signal is detected by a photodetector.

There is a lay paper about this project that was written for the ASA-EAA meeting in Berlin, Germany, March 1999. A local version of the manuscript is also available.

The response of a Helmholtz resonator carved into a silicon chip is shown here.

Pressure on the face of a square piston is shown here.

Fabry-Perot Interferometer analysis.

Cross-talk stuff.

Funding agency:

DARPA:ATO Sonoelectronics programme

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