Abstract

Ytterbium-doped fiber lasers are attractive sources of femtosecond pulses due to their compactness, excellent beam quality and high efficiency. Typically, the studied mode-locked fiber lasers have repetition frequencies from 20 to 200 MHz [1] providing pulse energies up to several nanojoule, while a number of applications such as imaging and cutting of biological tissue and micro-machining require short and high energy pulses with low average power. Therefore a low repetition rate femtosecond oscillator could serve as a seed source for a chirped pulse amplifier (CPA) for the generation of high-energy pulses. With this approach a complex and costly pulse picking device would become unnecessary. Recently, some efforts were made to develop low repetition rate fiber lasers resulting in pulse durations not shorter than 200 fs at 1550 nm and 400 fs at 1030 nm [2,3].

© 2009 IEEE