A complex network of 1600 holographically coupled opto-electronic oscillators: Network dynamics and utilisation for reservoir computing

Abstract

Networks of photonic elements are a key enabling technology for the realization of multiple next generation photonic systems. Phased beam arrays, coherent beam combining or neuromorphic computing in photonic networks: all these high-impact applications fundamentally require coupling between a large number of photonic components. Recently, a small network of ~20 semiconductor lasers based on coupling via a holographic element was reported [1]. However, the demonstration of large-scale complex photonic networks is lacking.Here, we demonstrate the scalability of holographic coupling, creating a large scale complex network of 1600 opto-electronic oscillators. The network's nonlinear nodes are implemented using a spatial light modulator (SLM) operated in intensity modulation mode. Imaging the SLM-surface through a polarizing beam splitter (PBS) onto a camera and closing the loop between camera and the SLM, we realize a nonlinear iterative map. The state of SLM pixel n is then given by I n (t + 1) = sin 2 (κI n (t) + φ 0 ). Here, I n (t)is the nth pixel intensity at time t, κ the feedback gain and φ 0 a constant phase offset. This equation corresponds to a simplified version of the Ikeda map. Figure 1 (a) schematically illustrates the experimental implementation. An exemplary bifurcation diagram for node (23, 8) is shown in Fig. 1 (b). The route to chaos shown in Fig. 1(b) exhibits the period-doubling behaviour expected from such an Ikeda system.