Besides their potential for high brightness sources, coupled laser networks reveal intriguing physics. First, very large arrays of >1000 lasers with nearest-neighbor coupling are shown to rapidly “dissipate” into long-range phase ordering, identical to the ground state of a corresponding XY spin Hamiltonian . For negative coupling "anti-ferromagnetic" phase order is observed, which reveals "geometric frustration" in a Kagome lattice  and odd-numbered rings . Second, arrays of coupled lasers with fluctuating lengths reveal phase and power fluctuations that agree with extreme value distributions of random matrices [3,4]. Thirdly, long range dissipative coupling is used for real-time wave-front shaping through scattering media , for controlling spatial coherence , and for observing “quantum” phase transitions for spin-like systems with quenched disorder . Fourthly, complex laser networks with homogenous time delayed coupling are shown to divide into phase-synchronized or chaos-synchronized clusters where the number of clusters is the greatest common divider of the number of lasers in simply connected loops [8-10]. Finally, complex light fields stored in warm atomic media are shown to reveal identical dissipative dynamics into a ground state of a corresponding continuous Hamiltonian .
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