Pierpasquale Tortora, Abashin, Maxim , Märki, Iwan , Nakagawa, Wataru , Vaccaro, Luciana , Salt, Martin , Herzig, Hans Peter , Levy, Uriel , and Fainman, Yeshaiahu . 7/9/2005. “Observation Of Amplitude And Phase In Ridge And Photonic Crystal Waveguides Operating At 1.55&Thinsp;Μm By Use Of Heterodyne Scanning Near-Field Optical Microscopy”. Optics Letters, 30, 21, Pp. 2885-2887. https://www.osapublishing.org/ol/abstract.cfm?URI=ol-30-21-2885.