In this work, we have designed, fabricated, and tested an all-optical ultrasound transducer by integrating a photoabsorptive polyimide thin film into a Fabry¿Pérot (etalon) high-frequency receiver. A 5-ns UV pulse was used for thermoelastic ultrasound generation in the polyimide film, and the transmission had a maximum amplitude of 4.3 MPa centered at 27 MHz with a fractional bandwidth of 107%. The device attained a noise-equivalent pressure of 1.3 Pa/Hz in receive-only mode. When used in pulse¿echo mode, the ¿6-dB upper cutoff frequency of the transmit/receive response reached 47 MHz. Basic imaging capabilities were also investigated by scanning the near-infrared probe beam across the device to create a 2 × 2 mm synthetic aperture. The imaging of targets placed at depths of 1.8 and 5.2 mm yielded estimates of 71 and 145 ¿m, respectively, for the lateral resolution and 35 and 38 ¿m, respectively, for the axial resolution. Finally, a design concept for a forward-viewing intravascular imager is presented that entails the coupling of light to a rotating, linear array of optical fibers on top of which are deposited polyimide¿ etalon transducers. Such a design would allow for a flexible and compact high-resolution imager well-suited for intravascular applications, such as guidance of treatment in the case of chronic total occlusion.
|Original language||English (US)|
|Number of pages||8|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|State||Published - 2012|
Bibliographical noteFunding Information:
Manuscript received January 10, 2012; accepted June 4, 2012. This work is supported by the University of Minnesota faculty startup funding and by the University of Minnesota Institute for Engineering in Medicine.