Stable evanescent wave mode-locked laser based on a photonic-crystal-fiber-induced Mach–Zehnder filter as a gain-tilt equalizer

Abstract

In this paper, a switchable multichannel ytterbium-doped fiber laser based on a Mach–Zehnder interferometer (MZI) has been experimentally demonstrated. The MZI is fabricated by splicing a short piece of nonlinear photonic-crystal fiber (NLPCF) between two segments of a single-mode fiber. MZI-based NLPCF gathering with the intracavity birefringence polarization controller offers functions as both the selective comb filter and the mode locker. The laser can emit a single, dual, triple, or quadruple channel that can be varied in the spectral span around1030–1050 nm by only adjusting the pump power or polarization state. A stable evanescent wave, picosecond mode-locking generation with variable repetition rate (24.5 to 18.23 MHz and 34.64 MHz) has been realized via only inserting the polarization controller and adjusting its state inside the cavity. To the best of the authors’ knowledge, this the first demonstration of a passive filter based on a NLPCF-MZ interferometer to generate switchable mode-locked pulses delivered from a single laser oscillator.