Micro-optical Processing LCI
Microfabrication is used in SMARTIEHS to produce the probing wafers, responsible to execute the optical operation of the system, i.e. the generation of the interference signal. The LCI fabrication combines thin-film deposition, replication and multi-wafer assembly techniques to arrange the elements in the Mirau configuration, shown in the figure below.
Following the sequence of fabrication, the micromirrors for the reference beam have been created by aluminum evaporation over an absorbent layer of amorphous silicon. The latter is created to reduce the undesired back-reflected light. Microlenses and their diffractive optical element for aberrations compensation are created by UV-molding replication. The planar beam-splitter is conceived by a multi-layer stack of dielectric materials to achieve the 50/50 ratio of reflected/transmitted light. A spacer wafer is created by ultrasonic drilling of a glass stack, and it allows adjusting the distances to equalize the optical path. The whole system is brought together by UV gluing of the separate parts to get the final probing wafer, as shown in the images below.