The invention relates to an optical wavelength conversion device adapted to receive at least one first pump beam (λ1) as an input and emitting a different wavelength output beam (λS), which includes: an optical cavity (CE); an optically non-linear medium (CNL) placed inside the optical cavity; and a control system (BA1) for controlling said optical cavity having the wavelength of the first pump beam; said control system being adapted to receive, as an input, a first signal (S1) representing the power stored in the cavity having said first wavelength and a second signal (S2) representing the power of the output beam. The invention also relates to a coherent light source comprising such a device and one or two pump laser sources (L1, L2).