Sub-micron elastic properties measurement of single laser-affected volume in fused silica

Non-ablative femtosecond laser exposure of transparent substrates leads to bulk volumetric changes, and consequently, localized structural changes resulting in micron-scale variation of elastic properties in the material. Here, we demonstrate the use of grid nano-indentation to characterize the elastic stiffness field across the laser-modified volume. Sub-micron spatial resolution is achieved by adapting a deconvolution procedure to the laser-affected zone (LAZ) geometry that minimizes a projection residual out of which an elastic description of the modified glass is sequentially constructed. Thanks to this method, a bimodal stiffness-distribution across the laser-affected zones is revealed, highlighting the complex nature of the interaction.