Loss reduction technique in ferroelectric tunable devices by laser micro-etching. Application to a CPW stub resonator in X-band

Ferroelectric materials are known to be lossy at microwaves. A local microetching technique based on laser ablation is implemented here to reduce the insertion loss of highly tunable devices fabricated on KTa1−xNbxO3 (KTN) ferroelectric thin films. The relevance of this approach is studied in X-band by comparing numerically and experimentally the performance of a frequency-tunable coplanar waveguide stub resonator before and after KTN microetching. The experimental data demonstrate a large loss reduction (by a factor 3.3), while keeping a high-frequency tunability (47%) under a moderate biasing static electric field (80 kV/cm). This approach paves the way for the design of ferroelectric reconfigurable devices with attractive performance in X-band and even beyond.