  To improve the optical coupling in Microwave Kinetic Inductance Detectors
(MKIDs), we investigate the use of a reflective plate beneath the meandered
absorber. We designed, fabricated and characterized high-Q factors TiN-based
MKIDs on sapphire operating at optical wavelengths with a Au/Nb reflective thin
bilayer below the meander. The reflector is set at a quarter-wave distance from
the meander using a transparent Al$_2$O$_3$ dielectric layer to reach the peak
photon absorption. We expect the plate to recover undetected photons by
reflecting them back onto the absorber.
