Multi-stage Er-doped fiber amplifier for gain-switched laser diodes

Abstract

We present a compact laser source delivering picosecond pulses at 1 MHz repetition rate based on the fiber amplification of a gain-switched laser diode at 1550 nm, with a FWHM spectral bandwidth of 0.06 nm and 116 mW average output power. Gain-switched semiconductor laser diodes are very attractive sources [1] of picosecond pulses because they are compact, stable and provide tunable repetition rates from pulse-on-demand up to hundreds of megahertz. They are a good alternative to picosecond mode-locked lasers, which are more expensive, less robust and require complex long-cavity designs or pulse pickers to reach repetition rates below 10 MHz. The pulse energy of gain-switched laser diodes, however, is typically only in the order of a few tens of picojoules. As a consequence, the pulses need to be amplified by several tens of dBs, in order to reach energy levels in the microjoule range nowadays available from mode-locked lasers.