Symmetry Breaking and Zero Modes in Photonic Crystal Cavity Arrays

Nanolasers are most appealing candidates for integrated nanosources on photonic microchips because of their ability to operate in the so-called thresholdless regime, compatible with ultra-low energy consumption operation. Remarkably, nanolaser technology has experimented a huge progress in the recent years, and today, a myriad of cavity designs and materials come to maturity [1]. Such technological advances enable the realization of coupled nanolaser arrays [Fig. 1(a), (d)] with unprecedented control over the geometrical (coupling), nonlinear (carrier-induced refractive index change) and non-Hermitian (gain/loss) parameters, and give a handle to generate and tailor laser beams with symmetry and/or topological protection.