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Experimental demonstration and modeling of near-infrared nonlinear third-order triple-photon generation stimulated over one mode

Triple Photon Generation (TPG) is a third-order nonlinear optical interaction in which a photon of energy ℏωp splits into three photons at ℏω1, ℏω2, and ℏω3, with ℏωp = ℏω1 + ℏω2 + ℏω3. The triplets possess different quantum signatures from those of photon pairs, with strong interest in quantum information. In the present study, we report the first experimental demonstration of TPG stimulated over one mode of the triplet, at ℏω1, whereas previous work on TPG concerned stimulation over two modes, at ℏω2 and ℏxω3. The nonlinear medium is a KTiOPO4 crystal pumped in the picosecond regime (15 ps, 10 Hz) at λp = 532 nm. The stimulation beam is emitted by a tunable optical parametric generator: the phase-matching was found at a stimulation wavelength λ1 = 1491 nm, the other two modes of the triplet being at λ2 = λ3 = 1654 nm in orthogonal polarizations. Using superconducting nanowire single photon detectors, the measurements of the polarizations and wavelength signatures of the two generated modes are in full agreement with calculations. It has been possible to generate a total number of photons per pulse on modes 2 and 3 up to 2 × 104, which corresponds to the generation of 104 triplets per pulse, or 105 triplets per second since the repetition rate is equal to 10 Hz. We interpreted these results in the framework of a model we developed on the basis of the nonlinear momentum operator in the Heisenberg representation under the undepleted pump and stimulation approximation.