Elastomeric diffractive gratings: Theoretical and experimental research on mechanical induced efficiency change

In this contribution the mechanical deformation of soft material (PDMS) blazed gratings is investigated. We compare a theoretical simulation based on measured grating profile data with an experimental efficiency measurement of this specific grating. The simulation consist of a finite element analysis which starts with a representation of the real optical element: a 1mm thick membrane with a 10µm periodic grating profile on top of it. This diffractive element gets virtually stretched perpendicular to the grating grooves. The emerging new profile serves as an input for a rigorous optical calculation to obtain the diffraction efficiency distribution of the stretched element. The simulation has a good accordance to our practical diffraction efficiency measurements as well as the diffraction angle changes proportionally. To get an overview for practical use of stretchable gratings we theoretically analyze several blaze grating properties as used diffraction order, periodicity and anti-blaze angle. They all show different effects under stretching. All in common is a spectral shift towards the blue region and a slightly overall efficiency loss in the desired blazing diffraction order.