High Fidelity Picosecond Pulse Fiber Amplification With Inter-Stage Notch Filter

We propose and demonstrate a high fidelity narrowband picosecond pulse two-stage fiber amplification scheme with inter-stage filtering technique using fiber Bragg grating. This technique can not only narrow the bandwidth of the pulses broadened by self phase modulation in the first-stage fiber amplifier, but also reshape the pulse temporal profile to near Gaussian shape, which reduces the spectral broadening slope of the pulses in the second-stage fiber amplifier and improves the narrowband fiber amplification ability. Using this technique, pulse energy of 10 nJ is achieved from a 0.2-nJ initial pulse by only using standard single mode fiber amplifiers while retaining 10 ps pulse width and 0.4 nm root mean square bandwidth. This technique may provide a simple and effective solution for high fidelity fiber amplification of low-energy ps seed pulse from fiber oscillators.