Resonance energy transfer (RET) is a near-field mechanism for propagating optical energy between particles with suitably matching frequency response. The process communicates electronic excitation between suitably disposed (donor and acceptor) dipoles in close proximity, activated on excitation of the donor. In a multi-component system the transfer of excitation between any given donor and acceptor is usually passive, and it competes with loss mechanisms such as radiative decay and the possibility of transfer to one or more other acceptors. It thus appears that any potential exploitation of RET for optical switching is compromised by the innate passivity of the process. Now it emerges that there is a direct, all-optical route to introduce the necessary control. In a system constructed to satisfy frequency-matching conditions, but designedly to inhibit RET by geometric configuration, the throughput of laser pulses can facilitate energy transfer processes that would otherwise be forbidden, by laser-assisted resonant energy transfer. Suitably configuring an arrangement of transition dipoles, it proves possible to design parallel planar arrays of optical donor and acceptor particles such that the transfer of energy from any single donor, to its counterpart in the opposing plane, can be switched by appropriate laser radiation. As the energy transfer is itself mediated electromagnetically, the device operates as an optical transistor. For simplicity, a pair of two-dimensional arrays is envisaged, each consisting of equally spaced, identical particles arranged on a square lattice. A detailed appraisal of the system, including a consideration of competing processes, suggests that this configuration offers a new basis for the design of optically activated nanoscale transistor arrays.