Scalar Product in the Space of Waveguide Modes of an Open Planar WaveguideA.L. Sevastianov, L.A. Sevastianov, A.A. Tiutiunnik and N.E. NikolaevEPJ Web of Conferences, 108 (2016) 02041DOI: https://doi.org/10.1051/epjconf/201610802041