Structured thin films made of loss-free dielectric materials are widely used as efficient, ultracompact optical components or in complex integrated photonic systems. Suspended and highly pretensioned silicon nitride membranes in particular benefit from excellent mechanical and optical properties which allows them to be coupled by radiation pressure to the optical field of high finesse optical resonators or to be used as sensitive optomechanical devices.
In this work, we first investigate the structural and mechanical properties of suspended silicon nitride membranes patterned with one-dimensional subwavelength gratings. We introduced noninvasive methods to extract the profile and key material properties of these fragile nanostructured films that prepare the basis for accurate numerical and finite element analyses (FEA) of both their mechanical and optical properties.
The profilometry results are used as input to the numerical simulations to predict the transmission spectrum of these membranes when illuminated with linearly polarized monochromatic light at different incidence angles and an analytical coupled-mode model is developed to assess the effects of the collimation and finite size of the incoming beam.
Finally, these characterization and simulation methods are used to tailor the optical properties of various patterned membranes in order to realize ultra compact optical spatial differentiators and high spectral resolution microcavities, as components for practical applications in photonics and sensing, respectively.