Improving the optical properties of switchable mirrors based on Mg–Y alloy using antireflection coatings

• Switchable mirrors coated with TiO2 thin films were prepared.
• The TiO2 thin film worked as antireflection layer.
• The mirror had a high visible transmittance of over 70% in the transparent state.
• The mirror had a large dynamic range between two states of over 60%.

To improve the transmittance of Mg–Y based switchable mirrors in the transparent state the surface was coated with a TiO2 thin film using e-beam evaporation and the optical properties were studied. The TiO2 films had a refractive index of ~2.1. As a result of the TiO2 coating with a thickness of ~65 nm, the transmittance in the visible range was considerably improved and consequently the visible transmittance in the transparent state reached 68%. This result was consistent with simulation results calculated using complex refractive indices for hydrides of Pd, Mg–Y alloy, and Ta. Thus, it is concluded that TiO2 is one of the best candidates for an antireflection layer to improve the optical properties of switchable mirrors.

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