INVESTIGATION OF PYROELECTRIC EFFECT GENERATED BY LITHIUM NIOBATE CRYSTALS INDUCED BY INTEGRATED MICROHEATERS

This thesis work focuses on the investigation of the pyroelectric effect from the ࢠZ surface of Lithium (LiNbO3) crystal using different microheater (à,µH) designs fabricated on the +Z surface of the crystal. Thermal analyses of the microheater designs were performed both theoretically and experimentally using COMSOLࢠ¢ Multiphysics and FLIR SC7000 thermocamera respectively. The pyroelectric effect was investigated analysing the current impulses detected using a metallic probe detector connected to an oscilloscope. The temperature variation induced by the microheater causes a spontaneous polarization in the crystal resulting in the formation surface bound charges. The electric field generated between the probe and the crystal surface causes the charge emission that appears as a voltage impulse on the oscilloscope. In an ambient condition, the air layer act as a dielectric thin film layer at few hundreds of microns between the detector probe and crystal surface gap spacing. It was demonstrated and validated that the threshold field strength require to generate the PE was near the dielectric breakdown of air. The pyroelectric emission shows a higher dependency on the rate of thermalization of the microheater and also the electric field generated between the probes to surface gap spacingࢠs of crystal. The deep characterization of à,µHs is investigated, in order to demonstrate the reliability and the effectiveness of these microdevices for all those applications where compact and low-power consuming electrical field sources are highly desirable.