Gut, Kazimierz. “Broadband Differential Interference in a Waveguide With a Gradient Refractive Index Distribution”. Photonics Letters of Poland 14, no. 3 (September 30, 2022): 53–55. Accessed April 13, 2024. https://www.photonics.pl/PLP/index.php/letters/article/view/14-18.