Harnessing coupled nanolasers near exceptional points for directional emission.

Tailoring the losses of optical systems within the frame of non-Hermitian physics has appeared very fruitful in the past few years. In particular, the description of exceptional points (EPs) with coupled resonators has become widespread. The on-chip realization of these functionalities is crucial for integrated nanophotonics but requires fine control techniques of the nanodevice properties. Here, we demonstrate pump-controlled directional emission of two coupled nanolasers that distantly interact via an integrated waveguide. This coupling scheme unusually enables both frequency and loss couplings between two cavities, which can be advantageously exploited to reach EPs by either detuning the cavities or controlling the gain of nanolasers. The system can be readily reconfigured from bidirectional to unidirectional emission by adjusting the pump power.