EXPERIMENTAL INVESTIGATION INTO FEMTOSECOND FIBER RING LASER WITH PASSIVE MODE LOCKING

A passively mode-locked Er(3+)-doped fiber ring laser is experimentaly investigated, with the emphasis on its practical design by considering the effects of ring cavity length, pumping light power, and optical amplification on the femtosecond optical pulses obtained. It is shown that the designed fiber ring laser can operate at the center wavelength of 1550 nm to produce a train of periodic optical pulses with full width at half maximum (FWHM) of 270 fs, repetition,frequency of 20 MHz, and average output optical power of 146 mu W. The resulting femtosecond optical pulses are then amplified by using three kinds of Er(3+)-doped optical fibers with different lengths and Er(3+)-doped concentrations, respectively, while employing the same planning laser. In the experiments, both the FWHM of amplified optical pulses and the amplifier gain are measured under different conditions. The optimization of optical pulse width is also carried out in terms of pumping light power. (C) 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 63-67, 2009; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.2398