  Polaritons, arising from the strong coupling between excitons and photons
within microcavities, hold promise for optoelectronic and all-optical devices.
They have found applications in various domains, including low-threshold lasers
and quantum information processing. To realize complex functionalities,
non-intuitive designs for polaritonic devices are required. In this
contribution, we use finite-difference time-domain simulations of the
dissipative Gross-Pitaevskii equation, written in a differentiable manner, and
combine it with an adjoint formulation. Such a method allows us to use topology
optimization to engineer the potential landscape experienced by polariton
condensates to tailor its characteristics on demand. The potential directly
translates to a blueprint for a functional device, and various fabrication and
optical control techniques can experimentally realize it. We inverse-design a
selection of polaritonic devices, i.e., a structure that spatially shapes the
polaritons into a flat-top distribution, a metalens that focuses a polariton,
and a nonlinearly activated isolator. The functionalities are preserved when
employing realistic fabrication constraints such as minimum feature size and
discretization of the potential. Our results demonstrate the utility of inverse
design techniques for polaritonic devices, providing a stepping stone toward
future research in optimizing systems with complex light-matter interactions.
