Temporal Modes and Spatiotemporal Modes

Temporal modes and spatiotemporal modes. The chapter extends the theory of spatial beam propagation to the temporal domain, and the concept of temporal waveguides and temporal Fractional Fourier transform are proposed. Afterwards, a temporal signal processing tool, i.e., a temporal diffractive deep neural network is proposed. The concept is extended beyond the spatial domain or the temporal domain, but the 4-dimensional space-time. A new class of spatial-temporal beam is discussed and a spatial-temporal diffractive deep neural network is proposed in the end.