Fig. 1. Significance, principle and design of our work.

a General block diagram of photonic neural network integrated activation function devices, where different types of reported on-chip AF devices are compared. b Principle of choosing the AF with phase activation based on the fact that the coherent ONN is complex-valued and linear operation matrix is phase-sensitive. c Simplified flow-chart of our proposed complex-valued optical neural network. Det detector, Mod modulator, ONN optical neural network, AF activation function, Real real part, Imag imaginary part.