Physics of Wave Processes and Radio SystemsPhysics of Wave Processes and Radio Systems1810-31892782-294XPovolzhskiy State University of Telecommunications and Informatics869210.18469/1810-3189.2021.24.1.15-21Research ArticlePoint spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearityVorob’evaElena V.<p>was born in 1977, Candidate of Physical and Mathematical Sciences, associate professor of the Department of Optics and Spectroscopy, Samara National Research University, Samara, Russia.</p>
<p><em>Research interests</em>: nonlinear optics, dynamic holography.</p>loginovaely@mail.ruIvakhnikValery V.<p>was born in 1951, Doctor of Physical and Mathematical Sciences, professor, head of the Department of Optics and Spectroscopy, Samara National Research University, Samara, Russia.</p>
<p><em>Research interests</em>: nonlinear optics, dynamic holography.</p>ivakhnik@ssau.ruKapizovDarkhan R.<p>was born in 1996, 1st year postgraduate student of the Department of Optics and Spectroscopy, Samara National Research University, Samara, Russia.</p>
<p><em>Research interests</em>: nonlinear optics, dynamic holography.</p>darkhankapizov@gmail.comNikonovVladimir I.<p>was born in 1959, Candidate of Physical and Mathematical Sciences, associate professor of the Department of Optics and Spectroscopy, Samara National Research University, Samara, Russia.</p>
<p><em>Research interests</em>: nonlinear optics, dynamic holography.</p>nikon5919@mail.ruSamara National Research University06052021241152106052021Copyright © 2021, Vorob’eva E., Ivakhnik V., Kapizov D., Nikonov V.2021<p>An expression is obtained for the point spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearity, taking into account the transfer of energy from the object wave to the signal wave and vice versa. For single-mode pump waves, the presence of «generation» points is shown and conditions are found on the waveguide parameters, characteristics of the interacting waves, under which the «generation» condition is realized. In the vicinity of the «generation» points, the shape of the point spread function is determined by one of the waveguide modes, the number of which coincides with the number of the pump wave mode. For a four-wave radiation converter in a waveguide with infinitely conducting surfaces, the quality of the wavefront conjugation near the second «generation» point coincides with the quality of the wavefront conjugation at a low reflection coefficient. For a four-wave radiation converter in a parabolic waveguide near the second and next «generation» points, the shape of the point spread function is determined by one of the waveguide modes.</p>four-wave radiation converterpoint spread functionKerr nonlinearityчетырехволновой преобразователь излученияфункция размытия точкикерровская нелинейность[Turitsyn S.K. et al. Inverse four-wave mixing and self-parametric amplification in optical fibre. Nature Photonics, 2015, vol. 9, no. 9, pp. 608–615. DOI: https://doi.org/10.1038/nphoton.2015.150][Weng Y. et al. All-optical ultrafast wavelength and mode converter based on intermodal four-wave mixing in few-mode fibers. Optics Communications, 2015, vol. 348, pp. 7–12. 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