SIMPLE ANALYTIC EXPRESSIONS FOR AM AND FM MODE-LOCKED PULSES IN HOMOGENEOUS LASERS

Abstract

Simple expressions for the mode‐locked pulses induced by either intracavity phase or amplitude (FM or AM) modulation in a homogeneous laser are developed by following a Gaussian pulse through one pass around the laser cavity. The predicted pulsewidth in either case is τ_p ∼ (g₀/δ)^1/4 × (Δf_axialΔf_atomic)^−1/2, where g₀ = saturated single‐pass excess laser gain, δ = single‐pass modulation index, Δf_axial = axial mode spacing, and Δf_atomic = atomic linewidth. The FM case also shows a frequency `chirp' equal to the pulsewidth. Experiments with the FM case in a Nd:YAG laser show excellent agreement with the analysis.