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Abstract: Evolution of dual-wavelength fiber laser from continuous wave to soliton pulses is investigated experimentally by using the nonlinear polarization rotation technique. With the increase of pump power, the proposed laser successively delivers the dual-wavelength continuous wave, the single-wavelength soliton pulses, and the dual-wavelength soliton pulses. The dual-wavelength laser operates at the central wavelengths of about 1533 and 1546nm with the separation of ∼13nm. The number of soliton pulses operating in the dual-wavelength state is much larger than that of the single-wavelength state, while the pulse intensity always keeps constant. Experimental results reveal that the dual-wavelength mode locking is determined by the combination of pump strength and the cavity filtering effect. [Copyright &y& Elsevier]

Abstract: We demonstrate a tunable and switchable dual-wavelength passively mode-locked fiber ring laser in the anomalous dispersion regime that generates high-energy pulses at a sub-100kHz repetition rate. The nonlinear polarization rotation (NPR) technique is employed in this configuration to allow for passively mode-locked operation. By exploiting the intensity-dependent loss caused by NPR, the mode competition could be efficiently alleviated. Moreover, taking advantage of the intrinsic spectral filter induced by the intracavity birefringence, the dual-wavelength separations as well as the wavelength lasing locations could be flexibly tuned by properly rotating the polarization controller. With a repetition rate of 85.8kHz, the laser delivers the single pulse energy of 198nJ at a pump power of 250mW. The combination of high per-pulse energy and flexible tunability in this fiber laser is useful for practical applications. [Copyright &y& Elsevier]

Abstract: A tunable and switchable single-longitudinal-mode (SLM) dual-wavelength fiber laser incorporating a reconfigurable dual-pass Mach–Zehnder interferometer (MZI) filter was proposed and demonstrated, which can be applied in microwave generation. By incorporating a high extinction ratio (ER) dual-pass MZI into an erbium-doped fiber ring cavity, SLM dual-wavelength lasing can be achieved even using a MZI with relatively little free spectrum range (FSR), and by beating the two wavelengths at a photodetector, a 9.76GHz microwave signal with a 3-dB bandwidth of less than 10kHz is obtained. Moreover, by direct linking the two outputs of the MZI, the high ER dual-pass MZI is easily reconfigured as a half FSR dual-pass MZI. Using this structure, switchable SLM dual-wavelength lasing can be conveniently realized. [Copyright &y& Elsevier]

Abstract: We demonstrate a multiwavelength fiber laser with ultradense wavelength spacing and ultrabroad bandwidth based on inhomogeneous loss mechanism with assistance of nonlinear polarization rotation. The inhomogeneous loss, implemented by incorporating a section of highly nonlinear fiber (HNLF) and a Sagnac filter in the laser cavity, can balance mode competition in erbium-doped fiber and result in ultradense multiwavelength generation. The bandwidth of the multiwavelength spectrum is greatly broadened owing to the intensity-dependent loss induced by nonlinear polarization rotation. Stable multiwavelength lasing with wavelength spacing of 0.08nm and wavelength number up to 254 is achieved at room temperature. Moreover, multiwavelength tuning is realized through modifying polarization-dependent cavity loss. [Copyright &y& Elsevier]