Structuring of 2D photonic crystal on InP membranes as polarizing element for optical MEMS based sensor systems

Narrow band Fabry-Pérot MEMS filters are investigated for the integration in optical fiber sensor networks. We present a technological process to implement a 2D photonic crystal (PhC) structure on an InP membrane, in order to provide an InP/air-gap Fabry-Pérot filter with polarization selectivity. The capabilities and limitations of Focused Ion Beam (FIB) lithography combined with Reactive Ion Etching (RIE) are investigated to fabricate the PhC structure. Special focus is given to the etching rate of the required hard mask, utilized in the FIB lithography, to determine the optimal thickness to produce high quality structures. Additionally, the mechanical properties of the PhC membrane and the influence on the basic filter structure are investigated.