Sensing micrometer-scale deformations via stretching of a photonic crystal

This paper reports micrometer-scale strain measurements that are enabled through the observed wavelength shift in a stretched surface photonic crystal narrow bandwidth optical reflectance filter. The photonic crystal optical filter is comprised of a 550 nm period, dielectric-coated linear grating structure, which was fabricated on the surface of a thin sheet of silicone rubber. When stretched, the change in grating period induced a change in the wavelength of light coupled into the photonic crystal, which could be measured using a spectrometer. The observed wavelength change was 4.53 nm per 1% strain and was linear up to 3.75% strain. The measurement was affected by temperature fluctuations, which could be compensated. The resolution of the measurement was 78 με.