A scanning acoustic microscope based on picosecond ultrasonics

Abstract

We report on the development of a new type of scanning acoustic microscope. We use a femtosecond light pulse to generate a short sound pulse, and then focus this sound onto the sample by means of a specially designed and microfabricated acoustic lens of radius a few microns. The sound travels to the sample through a thin layer of water. The sound reflected from the sample is collected by the lens and then passes through a monolithically integrated optical resonant cavity. The induced change in the properties of this cavity are measured using a time-delayed probe light pulse. We describe some of the challenges involved in the construction and operation of this high-precision metrology apparatus and present some preliminary results.

Advances in applications of time-domain Brillouin scattering for nanoscale imaging

“…63, with the use of metal-coated cylindrical or spherical sub-micron hollowed regions on the end of an immersed tapered fibre in a standard near-field scanning optical microscope geometry, TDBS could follow focused GHz acoustic phonon pulses in liquids, extending the resolution of 3D acoustic imaging [49][50][51] of biological structures to the nanoscale. In addition to focusing of CAPs 63,109 other possibilities for improving the lateral resolution of TDBS imaging include photo-generation of CAPs significantly narrower than the pump laser beam dimensions as a result of nonlinear processes in opto-acoustic transformation 110 and application of near-field optical schemes 111,112 .…”

All-optical broadband ultrasonography of single cells

“…Moreover, PU takes advantages of the controlled emission of acoustic waves to amplify the light scattering, hence allowing the study of smaller volumes. Bridging acoustic microscopy and PU, an acoustic lens with a high numerical aperture 23 combined with a Fabry-Perot cavity 24 has been recently developed to create a new type of acoustic microscope offering a 100 nm lateral resolution at room temperature.…”

Label-free Brillouin endo-microscopy for the quantitative 3D imaging of sub-micrometre biology

“…PEM technology offers super-optical resolution in the axial dimension utilising sub-optical wavelength coherent acoustic phonons. In theory, these same sub-optical wavelength CAPs can be used as the lateral resolution mechanism, provided that the transducer on the fibre-tip is converted into an acoustic lens 32 , 33 , which would make possible full 3D sub-optical resolution imaging. Realising this technology would present a benign path to super-optical resolution imaging since it uses non-destructive phonons and low-energy near infrared (NIR) photons.…”