We demonstrate a wavelength-tunable, passively mode-locked erbium-doped fiber laser based on graphene and chirped fiber Bragg grating. The saturable absorber used to enable passive mode-locking in the fiber laser is a section of microfiber covered by graphene film, which allows light-graphene interaction via the evanescent field of the microfiber. The wavelength of the laser can be continuously tuned by adjusting the chirped fiber Bragg grating, while maintaining mode-locking stability. Such a system has high potential in tuning the mode-locked laser pulses across a wide wavelength range.
In this paper, we investigate the interaction between the semiconductor quantum well (QW) structure, a weak probe field and a strong control field. Due to the quantum interference effect induced by the strong control field, the absorption of the weak probe field is small and the Kerr nonlinearity can be greatly enhanced. The results show that the spatial soliton can form in the semiconductor QW structure via electromagnetically induced transparency (EIT). We also discuss the optical response of the system and obtain the giant χ (3) and χ (5) susceptibilities with opposite signs. In the one-dimension case, we obtain the analytical solutions for bright and dark spatial solitons. For a general case, we present numerical solutions for ring solitons with experimental parameters and show that the ring solitons are stable against azimuthal perturbation.
conventional FDTD. Based on these time-domain data, the scattering parameters are calculated. As illustrated in Figure 9, good agreement of S 11 is observed for the FFT technique using the 20000-iteration FDTD time record and the waveform extrapolated via MMP from the 1600-iteration ADI-FDTD records. As given in Figure 10, good agreement of S 12 is observed for the FFT technique using the 20000-iteration FDTD records and the time waveform extrapolated via MMP from the 1600-iteration ADI-FDTD records. The numerical simulation for this example based on the combination technique demonstrates that the computational time of the ADI-FDTD method can be reduced by 32% using the MMP method. The iteration number of the ADI-FDTD algorithm combined with the MMP method is 12 times less than that of the conventional FDTD method for this edged-coupled bandpass filter. From the above figures, it is found that the MMP algorithm can improve the computational efficiency of the ADI-FDTD algorithm. This hybrid method can be used for other potential applications involving long transient-time response waveforms. CONCLUSIONIn this paper, the MMP method has been combined with the ADI-FDTD method in order to improve the computation efficiency. The numerical simulations for two typical microstrip circuits demonstrate that the MMP method can predict the time response of the ADI-FDTD with good accuracy and the computational time of the ADI-FDTD method can be reduced to 32%. As a result, the iteration number of the ADI-FDTD algorithm combined with the MMP method is 12 times less than that of the conventional FDTD method. It can be inferred that this hybrid method will be widely used in computational electromagnetics. ACKNOWLEDGMENTS INTRODUCTIONThe generation of wavelength-tunable optical short pulses is of great interest for many applications in high-capacity optical-fiber communication systems and optical-fiber sensors. Among the various approaches explored thus far, the self-injection seeding of a gain-switched Fabry-Pérot (F-P) laser diode has been found to be one of the most simple and efficient schemes [1][2][3][4]. In order to produce the self-seeded optical pulses, an external laser cavity needs to be formed in which the wavelength-selective element is introduced in order to reflect part of the output back into the laser cavity. When the reflected optical pulse arrives within the time window corresponding to the new pulse emission, a single-mode optical short pulse can be obtained. The wavelength of the optical short pulse can be tuned by adjusting the wavelength-selective element and the repetition frequency of the electrical signal used to drive the laser diode or, alternatively, the optical path length of the corresponding wavelength element has to be changed. The wavelength-selective element usually employed includes a diffractive grating, tunable optical F-P filter, and fiber Bragg grating (FBG). Diffractive grating is a bulk optical device which possesses a wide operating-wavelength range; however, it has large dimensions, is d...
In fiber with randomly varying birefringence, the interactions between solitons in the same polarization channel and in two orthogonal polarization channels are investigated by the use of numerical simulations. The results obtained show that the interaction between solitons in the same polarization channel is weaker than that of solitons in two orthogonal polarization channels. The strong interaction leads to soliton splitting and soliton propagation instability, and the randomly varying birefringence enhances the interaction. A nonlinear gain combined with the filter can be used to effectively suppress the interactions and stabilize the soliton propagation. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 50–53, 2001.
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