Far-Subwavelength Spatial Resolution Using Relative Motion and Structured Illumination

We describe an approach for achieving far-subwavelength resolution that uses relative motion between an object and a structured coherent background field. Simulations for intensity data from a stationary object with two incident plane waves, one orthogonal to the other and the phase of one scanned to modify the structured incident field, show sensitivity to a change of λ/100 in separation between two objects, despite the addition of significant detector noise. Experimental data for motion of an object in a speckled field demonstrate the utility in applications with random background scatter and laser illumination. Correlations of measured speckle intensity patterns from heavily scattered light, obtained as a function of spatial translation of a hidden object, indicate access to far-subwavelength features in the moving object. In this experiment, acrylic rods embedded with 50-nm TiO₂ scatterers and a ground glass slide with a rough surface profile were translated between heavily scattering slabs, and transmitted laser light was measured. Use of relative motion between an object and a structured field provides high-resolution sensing and imaging opportunities for material inspection and biophysics applications.