Résonateurs de Perot-Fabry accordables en fréquence par cristal liquide

National audienc

A liquid crystal tunable ultra-thin Fabry-Perot resonator in Ka-band

International audienceA tunable, liquid-crystal (LC)-based, subwavelength Fabry-Perot (FP) resonator has been designed and fabricated in the 27-GHz band. The grid mirrors are identical and consist of metallic capacitive meshes characterized by a high filling ratio. This ensures simultaneously a high reflectivity and a strong negative phase of the reflection coefficient on the mirror so as to reduce the resonator thickness as much as possible. The resonator has been filled with a 110-$mu$ m thick E3 nematic LC. A frequency shift of 6% has been obtained numerically (finite-difference time-domain (FDTD) simulations) using permittivity values measured under 1-T driving magnetic field $(epsilon _{//}= 2.91, epsilon_{perp}= 2.52)$ . An experimental tunability of 2% has been obtained by applying a 10-kHz ac bias voltage of 10 V. This lower value is due to the low driving field $({sim 0.1}~{hbox{V}}/ mu {hbox{m}})$, the nonperfect polyvinylalcohol (PVA) layer, and the relatively high thickness of the E3 mixture