An optronic porthole comprises a substrate with two faces. It comprises on one of the faces of the substrate or on both faces, a stack of several hetero-structures, each hetero-structure being composed of at least two semi-conducting layers SC1, SC2, the layer SC1 being doped, the layer SC2 itself comprising a two-dimensional electron gas layer formed at the interface with the layer SC1. It furthermore comprises an electrode in contact with all the electron gas layers, a bi-periodic metallic grid buried in the stack, in contact with the electrode. The substrate and the layers are transparent in the 0.4 μm-5 μm band.