Fig. 2: Characterization of the nonlinear process.

a The experimental setup for 5WM. Telecom pump and probe lasers are coupled into the chip through a fiber lens and the output signals are collected by another fiber lens. The visible and telecom signal photons are separated by a wavelength division multiplexer (WDM), and then filtrated from background via a series of band-pass filters and dense wavelength division multiplexing (DWDM), respectively. The coincidence of generated photon pairs is characterized by single photon detectors (SPCM and SNSPD) and a correlator. b Transmission spectrum of telecom modes and the corresponding second-harmonic generation. The dips in dashed frames correspond to the modes characterized for synthetic five-wave mixing. The on-chip pump power is 1.8 mW. c–e The input-output relation of χ⁽²⁾, χ⁽³⁾ and χ⁽⁴⁾ processes. In c and d, we add a probe light at a₋₂ mode to construct stimulated χ⁽²⁾ and χ⁽³⁾ process and collect the output photon at b₋₂ and a₂ separately. The on-chip probe power in c is 22 mW and in d is 1.1 mW. Error bars denote standard deviations.