Effects of spontaneous surface buckling on the diffraction performance of an Au-coated elastomeric grating

Stretchable silicone gratings show promise as dynamic beam scanners but are usually limited to transmission applications because of the low reflectivity of the material. We modify an elastomeric replicated grating for use in reflection geometries by adding a 100 nm surface layer of Au. Diffraction efficiency in the sample increases by a factor of 50. Scanning of the first-order diffraction is performed by stretching the grating in one direction, with Δθ = 2.34° for normal incidence at a maximum applied strain of 7.6%. Distortion of the deflected beam is minimal. Buckles on the Au surface perpendicular to the grating grooves spontaneously appear in response to compressive stress resulting from elongation. Diffraction efficiency decreases with increasing strain. This is attributed to reflectivity loss and secondary diffraction from the buckling structures. The initial efficiency and its variation with strain are dependent on the specific area of the grating being used. We are able to describe the observed behavior of efficiency vs. strain in terms of an inverse relationship between efficiency and compressive stress.