Analysis on Reducing the Bandwidth of Kelly Sidebands in Mode-Locking Fiber Laser for Narrow Terahertz Signal Generation

The bandwidth of the ±1-order Kelly sidebands of mode-locking fiber lasers is investigated for narrow terahertz (THz) signal generation. Four key factors influencing the bandwidth of Kelly sidebands are found and analyzed in detail. Then, a numerical model is presented for manipulating the parameters of the mode-locking fiber laser. Two mode-locking fiber lasers are designed for generating narrow sidebands. The bandwidth of the ±1-order Kelly sidebands is reduced to 0.041 nm and 0.021 nm for the sidebands with different spacings. Using the data obtained from the optical spectra with narrow bandwidth Kelly sidebands, the frequency spectra of the generated THz signals are obtained. Finally, the bandwidth of the generated THz signals is reduced to 7.16 GHz and 3.4 GHz, respectively.