title: Corrugated Waveguide Mode Content Analysis Using Irradiance Moments.
abstract: We present a novel, relatively simple method for determining the mode content of the linearly polarized modes of a corrugated waveguide using the moments of the intensity pattern of the field radiated from the end of the waveguide. This irradiance moment method is based on calculating the low-order irradiance moments, using measured intensity profiles only, of the radiated field from the waveguide aperture. Unlike the phase retrieval method, this method does not use or determine the phase distribution at the waveguide aperture. The new method was benchmarked numerically by comparison with sample mode mixtures. The results predict less than ±0.7% error bar in the retrieval of the mode content. The method was also tested using high-resolution experimental data from beams radiated from 63.5 mm and 19 mm corrugated waveguides at 170 and 250 GHz, respectively. The results showed a very good agreement of the mode content retrieved using the irradiance moment method versus the phase retrieval technique. The irradiance moment method is most suitable for cases where the modal power is primarily in the fundamental HE11mode, with <8% of the power in high-order modes.
authors.affiliation: Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Sudheer K
authors.initials: SK
authors.lastname: Jawla
authors.affiliation: Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Shapiro
authors.affiliation: Advanced Fusion Research Center, Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Idei
authors.affiliation: Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Temkin
keywords: Corrugated waveguide; irradiance moments and phase retrieval; quasi-optical beam; waveguide modes
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