Problem statement

The team developed an ultrasound detector using the photonic crystal (PC). The PC-based ultrasound sensor has potentials to offer a broad bandwidth and high sensitivity. The PC structure is comprised of a sub-wavelength dielectric grating, which selectively reflects light at a particular wavelength, known as the PC resonant wavelength. Acoustic wave can result in a shift of resonant wavelength due to the compression of the superstrate material. In our experiment, this shift was estimated by measuring the reflection from the PC substrate using a laser and a photodetector. For more challenge, the team developed an optical setup to generate high-frequency ultrasound with up to 2MHz frequency using a plasmonic substrate. The plasmonic substrate consists of a two-dimensional (2D) gold nanostructure, nipped between a glass coverslip and approximately 10um thick polydimethylsiloxane (PDMS) layer. The 2D gold nanostructure serves as light absorbing layer and DPMS layer can launch acoustic wave due to its thermos-elastic effect.

SYSTEM DESCRIPTION

This senior design project aims to develop a 2D array of optoacoustic detectors. The optoacoustic detector consists of a planar plasmonic crystal sturecure, which exhibits enhanced optical transmission at a particular resonant wavelength. Acoustic displacement of the plasmonic sensor results in a measurable change of the resonant wavelength. We will build a near infrared imaging system using a CCD camera, a moduled laser diode, and a delay generator, to interrogate the ultrasound field. In order to obtain high sensitivity and high frequency detection, the team will explore the nanoscale interface between photonics and acoustics.

                                                

Project plan

Reference

2D imaging of ultrasound fields using CCD array to map output of Fabry-Perot polymer film sensor
M. Lamont and P.C. Beard