I am sharing the lecture notes for an undergraduate course PC4246 Quantum Optics that I will be teaching at NUS next semester:
https://www.ece.nus.edu.sg/stfpage/tmk/Quantum_Optics_v0.2.pdf
Still very rough; use at your own risk. Comments welcome. I include only topics that are essential in my humble and very biased opinion and I have to omit many other important topics; apologies if I omit your favorites. The course will cover Chapter 1-12. Chapter 13 is the beginning of an attempt to bridge between the basics and my own research; hope to add more chapters in the future.