Stress and compensation of stress in nano-engineered optical coatings

We consider anisotropic stress in substrates coated with vacuum-deposited optically-anisotropic thin films. Birefringent films with tilted-columnar and normal-columnar nanostructures and thin film helicoidal bianisotropic mediums are considered. In the case of tilted-columnar nanostructures, the sign and relative magnitude of the stresses parallel to the deposition plane and perpendicular to the deposition plane depend on deposition angle. We show that an ion-assisted overcoat, applied with the primary purpose of protecting optical properties, can be designed to provide effective compensation of stress.