  A detailed investigation of the structural and vibrational properties of
various prestressed silicon nitride membranes patterned with one-dimensional
photonic crystal structures is presented. The tensile stress-related
deformation of the structure in the vicinity of the patterned area is
determined by Atomic Force Microscopy scans, while the resonance frequencies
and quality factors of the out-of-plane membrane vibrations are measured using
optical interferometry. We show that these noninvasive measurements, combined
with results of finite element simulations, provide accurate knowledge on the
tensile stress, the elasticity modulus and the density of these nanostructured
thin films. The obtained results are interesting in two ways: first, they show
that such highly reflective thin membranes already exploited in various
photonics applications possess high-mechanical quality, which also makes them
attractive for optomechanics and sensing applications. Second, they represent a
nondestructive method to determine key material parameters which can be
applicable to a broad range of fragile nanostructured thin films.
