a, Cavity transmission for the spectral translation device in visible, pump, and telecom bands, with device parameters prescribed in Fig. 2(c). b, Zoom-in transmission traces for TE1 modes at 665.8 nm (red), 939.5 nm (green), and 1572.7 nm (blue) from left to right with loaded factors of ≈ (1 – 3) × 105 estimated by Lorentzian fitting (red lines). c-d, Visible-telecom photon-pair spectra by spontaneous four-wave mixing, with a degenerate pump at 939.5 nm. Inset of ¸ shows the visible spectrum in log scale. The 669.8 nm/1572.7 nm photon-pair spectra are free from broadband noise and are > 16 dB larger than adjacent mode sets, which indicates good frequency- and phase-matching for the dFWM process.