Numerical investigation of relative intensity noise in frequency-doubled multimode fiber lasers

In this paper, we study the intensity noise performance of frequency-doubled lasers. particular, investigate how relative (RIN) multimode fiber lasers is affected by second harmonic generation process. We first develop an analytical approach and show that, in contrast with a single-mode laser, low frequency RIN (or excess noise) two-mode laser can increase more than 6 dB after frequency-doubling operation. This occurs when intensities both modes are different explained nonlinear coupling between modes. To deal commonly-used lasers, have extended our to any number For purpose, developed model numerically simulate dynamics laser. includes sources mode competition due spatial hole burning. It gives access complex amplitude electric field Using model, confirmed that be higher before frequency-doubling.