Experimental investigation of a multi-wavelength Erbium-doped photonic crystal fiber laser

A multi-wavelength Erbium-doped photonic crystal fiber ring laser utilizing nonlinear polarization rotation was demonstrated by experiment. A polarization-dependent isolator with a 9m Er-doped photonic crystal fiber was used to form an equivalent fiber filter. The fiber laser without specific wavelength selection device could operate at single-wavelength, dual-wavelength, triple-wavelength and quadruple-wavelength depending on the polarization. The intensity-dependent inhomogeneous loss induced by nonlinear polarization rotation was applied to reduce the mode competition. Therefore, stable multi-wavelength output with the power fluctuation of 0.27dB was generated at room temperature. In the meantime, the tuning of wavelength could be achieved through adjusting the polarization controller. The quadruple-wavelength with a spacing of 2.2 nm was achieved, and the uniformity of multi-wavelength spectra was improved by increasing pump power. The proposed fiber laser with an extinction ratio of higher than 40 dB achieved a low threshold power of about 30 mW to realize simultaneously multi-wavelength outputs.