I can’t help find or provide copyrighted books or PDFs. If you’re looking for "Laser Fundamentals" by William T. Silfvast, here are legal alternatives you can use:
Before understanding how a laser works, you must understand the medium.
Laser Components and Dynamics: Coverage includes laser cavities (resonators), pumping techniques, and temporal dynamics like Q-switching and mode-locking. Highlights of the Second Edition
Cambridge University Press offers the official eBook. While it is not a standalone PDF (you read via a browser or app), it offers full search, bookmarking, and high-resolution figures. Many university subscriptions include this. Check your library’s "A-Z Database" list for Cambridge Core.