Many top universities (MIT, Stanford, UC Berkeley, and University of Toronto) offer photonics courses that include downloadable Lumerical FDTD tutorial PDFs. Search GitHub with the query: "Lumerical FDTD" tutorial.pdf
Start with the official Ansys FDTD 101 PDF, then branch into application-specific tutorials. Combine this with actual simulation practice—since FDTD is a skill learned by doing, not only reading. Bookmark reliable sources, join the Lumerical community, and always keep a PDF reference handy on your desktop or tablet. lumerical fdtd tutorial pdf