Piezoelectric tantalum pentoxide studied for optical tunable applications.

Piezoelectric transparent thin films are of great interest for use in tunable filters. We present experimental results on Ta2O5 single layers coated on fused-silica substrates with an electron-beam deposition process. Above 450 degrees C, coatings change from an amorphous to a polycrystallized structure. When this structure shows a preferred orientation matching the piezoelectric tensor of the Ta2O5 crystal and the external electric field, variation in the piezoelectric layer thickness is expected. We detail experimental results in terms of optical (spectrophotometric and scattering measurements) and nonoptical characterizations (x-ray diffraction and scanning electron microscopy). Then the resultant thickness variation under oscillating applied voltage is measured with an extrinsic Fabry-Perot interferometer setup.