Phase transitions in Wick-rotated PT-symmetric optics

PT-symmetric models with a Wick rotation of time (t→±it) show spectral phase transitions that are similar to those of dissipative systems driven out of equilibrium. Optics can provide an accessible test bed to explore spectral phase transitions of Wick-rotated PT-symmetric models. This is shown by considering the transverse dynamics of laser light in optical cavities with variable reflectivity and tilted mirrors. Two specific examples are discussed: the optical analogue of the hydrodynamic Squire model of vorticity, and the Wick-rotated PT-symmetric nonlinear dimer model. In the latter case the spectral phase transition is associated with the universal phase locking-unlocking transition in Adler's theory of coupled oscillators.