Acoustic Micro Lens
An optoacoustic lens which is able to concentrate the ultrasound to a lateral spot size of about 50 nm is the key component in the scanning probe version of the SOAM instrument. For optimal materials (sound velocity), this requires a curved acoustic objective microlens with about 0.5 μm diameter.
In our approach for the fabrication of the micro-lens, we first place a glass microsphere onto an Al film (2 micron thickness) at designated location with precise control. We then use a high precision nanoindenter to exert force on the microsphere, which is then removed by sonication, leave only the curved surface.
The figure below is the SEM image of one of our earlier microlens.