ABSTRACT
We demonstrate highly efficient pulse stretching in Er(3+)-doped femtosecond mode-locked fiber lasers by tailoring cavity dispersion using an intracavity short-pass edge filter. The cavity dispersion is preset at around zero to obtain the shortest pulsewidth. When the cutoff wavelength of the short-pass edge filter is thermo-optically tuned to overlap the constituting spectral components of mode-locked pulses, large negative waveguide dispersion is introduced by the steep cutoff slope and the total cavity dispersion is moved to normal dispersion regime to broaden the pulsewidth. The time-bandwidth product of the mode-locked pulse increases with the decreasing temperature at the optical liquid surrounding the short-pass edge filter. Pulse stretch ratio of 3.53 (623.8 fs/176.8 fs) can be efficiently achieved under a temperature variation of 4 °C.
ABSTRACT
A new design for a Fabry-Perot-based array filter for wavelength-division multiplexing (WDM) applications is proposed. The device is composed of two partially reflective mirrors; the surface of one of the mirrors is stepwise. Not only does the configuration of multiple air-gap cavities into a single unit provide wavelength tunability but the channel numbers can be expanded. A four-channel multiplexer has been demonstrated. The results revealed that a compact and cost-effective WDM device should be easily attainable.
