Characterization of V-shaped plasmon polariton waveguides using a differential heterodyne microscope at single polarization

The possibility of using a scanning differential heterodyne microscope for characterization of V-shaped plasmon waveguides is demonstrated. To characterize a waveguide profile, a specific algorithm based on solution of the inverse problem is proposed. The microscope response library at various waveguide parameters is calculated using the image formation theory and rigorous couple wave analysis for matching with experimentally measured responses. The investigation of stability of the inverse problem solution has revealed unstable zones within specified ranges of waveguide parameters. Further analysis shows that these zones can be shifted with variation of the probing beam wavelength. (paper)