Aim

To advance the physics and the technology of the ‘optical ruler’ concept towards the realization of practical – compact, robust, etc. – implementations for real-world metrology applications.

Details

By analogy with a physical ruler, an ‘optical ruler’ is a complex electromagnetic field in which singularities serve as deeply subwavelength marks on the scale: The field is generated by the diffraction of light on a metasurface, and the scale is revealed by high-magnification interferometric observation. It can resolve deeply subwavelength lateral displacements between two macroscopic platforms but, in its original form, required sequential recording of diffraction patterns for four different polarization states of light for each positional measurement.

We have developed a single-shot implementation of the optical ruler, using a polarization-sensitive camera, which simplifies instrumentation, reduces measurement time (repetition rate), and eliminates uncertainties associated repeated (re)setting of waveplate positions.

This configuration of the instrument is enabled by the fundamental finding that, while the polarization state of light generally cannot be fully characterized without knowledge of circular components, under the constraint of 2D symmetry, knowledge of four linear polarization states is sufficient to localize phase singularities.