Study of the Eigenmodes of Anoptical Waveguide with a Refractive Index that Varies in the Radial Direction from the Central Axis. London Journal of Engineering Research, [S. l.], v. 24, n. 5, p. 29–36, 2024. Disponível em: https://journalspress.uk/index.php/LJER/article/view/1658. Acesso em: 2 feb. 2026.