Switchable Fresnel zone lenses for optical interconnections

Various on-axis and off-axis Fresnel zone lenses with different focal lengths and apertures were fabricated in quartz glass by means of microstructuring techniques. The kinoform profile of the diffractive optical elements was approximated by a staircase-like profile with a number of discrete phase levels. Dynamic, i.e. electrically switchable, lenses have been realized by filling the structured surface with liquid crystal. By applying an AC voltage, the elements can be switched from the state of a "focusing lens" to that of a "transparent glass-plate". The optical properties of the lenses and the switching behaviour were studied. Experimental measurements are compared with theoretical results.