Laser Oscillators Described via the Dirac Notation

Here we derive the classical linewidth cavity equation (9.1) Δ λ ≈ Δ θ ( ∂ θ ∂ λ ) − 1 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315216720/70121b16-f2c6-4331-b1ba-eecb806b93da/content/eq384.tif"/>