Active offset-frequency control of optical frequency comb via sum-frequency mixing of passively mode-locked laser and continuous-wave laser.

We propose a method for actively controlling the frequency of an optical frequency comb (OFC) using sum-frequency generation (SFG) with a nonlinear crystal. For the first time, OFC generation was experimentally demonstrated via sum-frequency mixing of a narrowband continuous wave (CW) laser and a passively mode-locked fiber laser. By adjusting the optical frequency of the CW laser, we successfully controlled the offset-frequency of the SFG-OFC, which was mapped from the OFC of the pulse pump laser. Furthermore, by comparing the spectral widths of the SFG-OFC modes generated from two CW lasers with different spectral widths, we confirmed that the spectral characteristics of the SFG-OFC modes depended on the spectral features of the CW laser.