Acoustic resonator based on periodically poled transducers: Fabrication and characterization

Abstract

Passive radiofrequency filters and resonators exploited for telecommunication applications are generally based on surface or bulk acoustic wave (SAW or BAW) devices. However, these devices present some technological limits as short-circuits between the electrodes of the interdigital transducers (for SAW devices) or an accurate control of the resonator dimension (plate or film thickness for BAW devices). An alternative concept based on periodically poled transducers (PPT) implemented on ferroelectric substrates (LiNbO3 or LiTaO3) embedded between two guiding substrates yielding advanced packaging opportunities has been developed. An oscillator stabilized by such a PPT-based resonator operating at 131 MHz has been successfully fabricated. A phase noise of −165 dBc/Hz at 60 kHz from the carrier has been measured with an input power of 2 mW and a relative short term frequency stability of 10−9 per second. Other resonators built on waveguides exploiting thinned PPTs (around thirty microns) have allowed the excitation of only one contribution with a thermal sensibility equal to the one of the guiding materials (−30 ppm/K for silicon).

Experimental evidence of Bloch surface waves on photonic crystals with thin-film LiNbO_3 as a top layer

“…A second configuration has been also fabricated using a single-crystal TFLN bonded to a Cr and Au layer on an Si substrate [22], which is thereafter bonded to the 1DPhC. For this geometry, the multilayer used was composed of Si/Au/Cr/Au/ TFLN.…”

“…The layer's thicknesses were 500 μm for Si, 20 nm for both layers of Cr, 400 nm for the Au layer, and about 2 μm for the TFLN, respectively. In this case, the TFLN was manufactured by polishing of bulk LiNbO 3 bonded to an Si wafer by Au and Cr [22]. The thickness profile of the TFLN is shown in Fig.…”

Hybrid wafers based on a “Silicon/PPLN thin film” stack for optical and Radio-Frequency applications

“…Gold electrode A dedicated poling bench allows to invert the ferroelectric domains of thick (500μm) optical quality Z-cut LiNbO 3 plates. The poling mainly consists of a high voltage amplifier used to submit the wafer to an electric field strong enough to invert the negative poling of the material [4]. The bonding of the PPLN plate on a silicon substrate is done by metallic diffusion.…”

“…Figure 8 presents the process steps for the fabrication of a SHG device based on a PPLN-ridge. To start, commercial LiNbO 3 wafers are periodically poled electrically [4]. A silica layer (about 300nm-thick) is sputtered by ICPECVD equipment on one face of the PPLN substrate.…”

Static/dynamic trade-off performance of PZT thick film micro-actuators

“…In order to limit the generation of mechanical stress inside the structure, we propose here to keep the bonding step at room temperature. This is inspired from a process for bonding materials with different thermal expansion coefficients [29]. Thanks to that process, an additional repolarization step is not required, and residual mechanical stress in the designed structure is prevented.…”