Reconstructing the full modal structure of photonic states by stimulated-emission tomography in the low-gain regime

Stimulated emission tomography (SET) is a powerful and successful technique to both improve the resolution and experimentally simplify the task of determining the modal properties of biphotons. In the present paper we provide a theoretical description of SET valid for any quadratic coupling regime between a nonlinear medium and pump fields generating photons by pairs in the low-gain regime. We use our results to obtain not only information about the associated modal function modulus but also its phase, for any mode, and we discuss the specific case of time-frequency variables as well as the quantities and limitations involved in the measurement resolution.