Optical characterization of subwavelength objects is important for biology, nanotechnology, chemistry, and materials science. Unfortunately, the information about interaction of an isolated subwavelength object with light is contained in evanescent waves that exponentially decay away from the source. Numerous techniques have been proposed to access or restore this information. In interscale mixing microscopy (IMM), a diffraction grating positioned in the near field proximity of the object is used to convert the originally-evanescent waves into propagating modes that can be detected with far-field measurements. However, far-field signal needs to be post-processed to un-couple the diffraction-limited and subwavelength responses. Several techniques, based on multiple measurements, have been previously proposed. Here, we show that with simple Fourier-transform based post processing can be used to characterize position, and optical size of the object based on a single measurement. To verify the proposed formalism, three finite diffraction gratings were fabricated. Two of these gratings contained pre-engineered “defects” that played the role of “unknown objects”, while the remaining grating was used as a reference. We demonstrate that we can identify the position and size of ~wavelength/10 object with far-field characterization. The same measurement provides a platform to analyze optical spectrum of the object. Although demonstrated in this work on example of 1D grating, IMM can be extended to 2D subwavelength imaging
Viktor A. Podolskiy, Christopher M. Roberts, Nicolas Olivier, William P. Wardley, Bo Fan, Sandeep Inampudi, Wayne Dickson, and Anatoly V. Zayats, "Interscale mixing microscopy: far field imaging beyond the diffraction limit (Conference Presentation)," Proc. SPIE 10343, Metamaterials, Metadevices, and Metasystems 2017, 1034322 (Presented at SPIE Nanoscience + Engineering: August 10, 2017; Published: 18 October 2017); https://doi.org/10.1117/12.2274934.5616410925001.
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