In this chapter, we describe how to simulate nonstationary, or pulsed, random fields. These fields can be simulated in the frequency or time domains; however, here we focus on the latter. Simulating the time evolution of thermal (or pseudo-thermal) sources provides insights into how random fields actually behave and can therefore be a valuable pedagogical tool. These insights are generally not available from ω-domain simulations.

We begin with a brief summary of the pertinent theory, which primarily concerns the beam coherence-polarization matrix (BCPM) Γ from Chapter 3. Continuing to follow the general outline of Chapter 3, we then present coherent-modes and bimodal expansions of Γ before concluding with the superposition rule. Like for WSS fields in Chapters 2 and 4, all of these theoretical concepts can be adapted to simulate nonstationary sources. Nonetheless, only simulation techniques derived from the superposition rule are widely applicable, and of those, only the “superposition-rule method” produces thermal (physically representative) field realizations. Consequently, we focus on simulating pulsed random fields using that method. We conclude this chapter by generating three nonstationary sources: a pulsed Schell-model (SM) beam, a non-uniformly correlated (NUC) beam, and a space-time coupled beam.