Abstract
The variation of focusing distance in a parabolic graded-index slab with the width of a one-dimensional Gaussian input fed at its waist, both axially and misaligned, into the waveguide is studied in paraxial and beyond-paraxial regimes. We obtain analytical expressions, scalable in terms of material parameters, for input coupling coefficients for such a Gaussian input. The focusing distance shows remarkable stability for an axially fed input for beam width exceeding the fundamental mode width of the waveguide. There is a smooth variation for the other regime of beam width. In the paraxial domain, we identify a unique beam width of ${\sim}0.76$ times the fundamental mode width for which the self-imaging distance is nearly independent of misalignment. The stability, a well-known sharp shift of the focusing point for an axially fed beam of width around that of the fundamental mode, and remarkable stability of self-imaging distance with misalignment at the unique beam width should be useful for efficiency enhancement of device interconnects, sensing, and lensing applications.
© 2022 Optica Publishing Group
Full Article | PDF ArticleMore Like This
Kaiyun Zhan, Xinyue Kang, Lichao Dou, Dingyuan Xue, and Bing Liu
J. Opt. Soc. Am. B 39(3) 751-755 (2022)
Mesay Addisu Jima, Alessandro Tonello, Alioune Niang, Tigran Mansuryan, Katarzyna Krupa, Daniele Modotto, Annamaria Cucinotta, Vincent Couderc, and Stefan Wabnitz
J. Opt. Soc. Am. B 39(8) 2172-2180 (2022)
Giuseppe Della Valle, Davide Gatti, and Stefano Longhi
J. Opt. Soc. Am. B 32(9) 1834-1842 (2015)