  In the quest for applicable quantum information technology miniaturised,
compact and scalable sources are of paramount importance. Here, we present the
concept for the generation of 2-photon N00N states without further
post-processing in a single non-linear optical element. Based upon a
periodically poled waveguide coupler, we present the principle of state
generation via type-0 parametric down-conversion inside this type of devices.
With the eigenmode description of the linear optical element, we utilise the
delocalised photon pair generation to generate a N00N state in the measurement
basis. We show, that we are able to eliminate the need for narrow-band spectral
filtering, as well as for phase-stabilisation of the pump light, making this
approach an elegant way to produce 2-photon N00N states.
