Quantum optics of a cavity and Input output theory

This lecture covers the quantum optics description of a cavity, defining quantum input and outputs. Topics include cavity mode as a harmonic oscillator, Heisenberg-Langevin equation, input-output relation, one-sided cavity, two-sided cavity, and fiber taper. It delves into quantized optical cavity mode, cavity mode as an open system, quantum Langevin equations, time-reversed quantum Langevin equation, and quantum causality. The lecture also explores examples of empty one-sided and two-sided cavities, input-output ports, and scattering matrices. In summary, it provides a quantum picture of optical cavity field dynamics through Quantum Langevin equations, defining input and output fields and their relationships.