Three-colour entanglement generated by an injection-seeded nondegenerate optical parametric oscillator

► We propose a new scheme to produce three-color continuous-variable entanglement. ► We verify that pump, signal and idler beams are continuous-variable entangled. ► The injected signal can increase the nonlinear conversion efficiency. ► The injected signal can increase the stability of the NOPO. ► It is easier to realize experimentally than NOPO without injected signal.