Nonlinear Processes Associated With The Amplification Of Mhz-Linewidth Laser Pulses In Single-Mode Tm:Fiber

This work studies the accumulated nonlinearities when amplifying a narrow linewidth 2053 nm seed in a single mode Tm:fiber amplifier. A \u3c2 MHz linewidth CW diode seed is externally modulated using a fiberized acousto-optic modulator. This enables independent control of repetition rate and pulse duration (\u3e30 ns). The pulses are subsequently amplified and the repetition rate is further reduced using a second acousto-optic modulator. It is well known that spectral degradation occurs in such fibers for peak powers over 100\u27s of watts due to self-phase modulation, four-wave mixing, and stimulated Raman scattering. In addition to enabling a thorough test bed to study such spectral broadening, this system will also enable the investigation of stimulated Brillouin scattering thresholds in the same system. This detailed study of the nonlinearities encountered in 2 μm fiber amplifiers is important in a range of applications from telecommunications to the amplification of ultrashort laser pulses