Week 1: Chapters 1–4, basic rate equations and level systems; problems on threshold and gain. Week 2: Resonators, Gaussian beams, ABCD matrices; compute w0, zR for examples. Week 3: Q-switching, mode-locking, nonlinear optics basics; simulate simple rate equations. Week 4: Laser types, applications, safety, review problems and design exercises.

An atom absorbs an incoming photon, jumping from a lower to a higher energy state.