Analysis of the effect of stress-induced waviness in airgap-based optical filters

The preliminary results of a study on the effect of the membrane deformation on the optical response of the distributed Bragg reflector, that is based on a stack of such membranes, are presented. The analysis is applied to airgap-based optical filters, which offer an enhanced refractive index contrast and hence are highly promising for optical MEMS devices. The available methods and materials in MEMS technology would make fabrication of such devices feasible, but the optical requirements impose strict geometrical implications on the membrane structure. Although (an overall) tensile stress in membrane is expected to result in a flat structure after the release, a stress gradient results in a deformed structure. A combined finite element and finite-difference time- domain method has been utilized in this work to study the effects of a stress gradient in a distributed Bragg reflector. The results on the effects of both a linear and a non-linear stress gradient are presented. It is shown that a non-linear stress profile results in twice the deformation and a further reduction of optical performance. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.