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

Abstract

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.