Abstract

Mode-Locked (ML) fiber lasers can produce short and ultrashort pulses. In most of micromachining applications short pulses and low repetition rates are often required. ML fiber lasers usually operate between 10 MHz and 100 MHz, therefore an external pulse-picker is needed. A laser operating at low repetition rate with picosecond pulses would then be optimal. The configuration we present operates at 3.2 MHz and is based on the same ML principle detailed in previous works [1, 2] where sub-MHz regime has even been demonstrated [2]. Aguergaray et al [3] studied the impact of a second active section in a figure eight laser cavity. Here we added a second active section in a source based on nonlinear polarization evolution in polarization maintaining fibers, and study the conditions for obtaining a stable ML regime. The experimental setup is described in figure 1. The laser has two spans of Ytterbium doped fiber (YDF). The additional span is placed between the polarizer and the Faraday Mirror. This allows controlling this section that acts as a saturable absorber in the cavity.

© 2015 IEEE