1.3 μm femtosecond pulse generation by cascaded nonlinear optical gain modulation in phosphosilicate fiber

Nonlinear optical gain modulation (NOGM) is a simple and effective approach to generate highly coherent ultrafast pulses with flexible wavelength. In this work, we demonstrate 34 nJ, 170 fs pulse generation at 1319 nm through a piece of phosphorous-doped fiber by two-stage of cascaded NOGM with 1064 nm pulsed pump. Beyond the experiment, numerical results show that 668 nJ, 391 fs pulses at 1.3 μm can be produced with up to 67% conversion efficiency by increasing pump pulse energy and optimizing the pump pulse duration. This would offer an efficient method to obtain high-energy sub-picosecond laser sources for applications such as multiphoton microscopy.