High-accuracy thermal expansion measurement by laser beam diffraction off a patterned surface

Laser beam diffraction on a patterned surface is investigated theoretically and experimentally as a powerful tool to measure thermal expansion in various materials. By tracking the deviation of high-order diffraction modes from surface-patterned polymers and glasses, expansion coefficients as small as 10^-8 can be measured for temperature rises of only tens of degrees Celsius. Results are presented for PMMA, chitosan and glasses. In some materials, a grating is successfully transferred from a polymer by simple mechanical compression. The technique is applicable to relatively small volumes (mm in size).