Browsing by Author "Luo, B"

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Dissipative soliton in an amplifier with a Bragg grating
(2003-11-15)
Luo, B
;
Chi, S
;
光電工程學系
;
Department of Photonics
A dissipative soliton in an amplifier with a Bragg grating is numerically investigated by direct simulation of Maxwell-Bloch equations. The result of the simulation indicates that a solitary wave can exist in such a medium.. However, the pulse shape of the dissipative soliton is asymmetrical because of the gain saturation effect. This gain saturation effect results from the high power of the ultrashort dissipative soliton. The influence of amplifier gain on the solitary wave is also investigated. (C) 2003 Optical Society of America.
Femtosecond soliton propagating in slow group-velocity fiber
(2003)
Luo, B
;
Chi, S
;
Chen, CF
;
光電工程學系
;
Department of Photonics
The slow group-velocity pulse in fiber described by nonlinear Schrodinger equation were demonstrated and investigated extensively. We derive a more generalized nonlinear Schrodinger equation as the superposition of monochromatic waves and numerically study the propagations of 2.5-fs fundamental and 5-fs second-order solitons. It is found that, for a slow-group velocity fiber, the magnitude of time shift is related with the group velocity and the more generalized NLSE is more suitable than the conventional generalized NLSE. When the pulse is slow down to 50% of normal group velocity (c/n(0)), the effect of the higher nonlinear terms is significant.
Femtosecond soliton propagation in an optical fiber
(2002)
Chen, CF
;
Chi, S
;
Luo, B
;
光電工程學系
;
Department of Photonics
An accurate wave equation beyond the slowly varying envelope approximation for femtosecond soliton propagation in an optical fiber is derived by the iterative method. The derived equation contains higher nonlinear terms than the generalized nonlinear Schrodinger equation obtained previously. For a silica-based weakly guiding single mode fiber, it is found that those more higher-order nonlinear terms, whose coefficients are proportional to the second-order dispersion parameter, are much smaller than the shock term. The 2.5-fs fundamental solitons is numerically simulated by using the generalized nonlinear Schrodinger equation and the full Maxwell's equations. Comparing these two results, we have found that the generalized nonlinear Schrodinger equation well describes the propagation of the pulse even containing a single optical cycle.
Large phase shift of nonlocal optical spatial solitons
(2004-01-01)
Guo, Q
;
Luo, B
;
Yi, FH
;
Chi, S
;
Xie, YQ
In this paper, we discuss the evolution of the optical beam in nonlocal cubic nonlinear media, modeled by the nonlocal nonlinear Schrodinger equation (NNLSE). A different approximate model to the NNLSE is presented for the strongly nonlocal media with arbitrary response functions. An exact analytical solution of the model is obtained, and a spatial soliton is found to exist. A different phenomenon is revealed that the phase shift of such a nonlocal optical spatial soliton can be very large comparable to its local counterpart. The stability of the solution is rigorously proved. The comparisons of our analytical solution with the numerical simulation of the NNLSE, as well as with Snyder-Mitchell (linear) model [A. W. Snyder and D. J. Mitchell, Science 276, 1538 (1997)] are given.
Numerical investigation of a self-induced transparency soliton in a nonlinear photonic bandgap structure doped uniformly with two-level atoms
(2003-09-01)
Luo, B
;
Tseng, HY
;
Chi, S
;
光電工程學系
;
Department of Photonics
We numerically study the characteristics of a nonlinear pulse that propagates through a one-dimensional photonic bandgap (PBG) structure uniformly doped with two-level atoms. The numerical model adopted is the coupled system of nonlinear coupled-mode equations and atomic Bloch equations. The simulation results show that a self-induced transparency (SIT) soliton and a gap soliton can coexist in a nonlinear PBG structure uniformly doped with resonant atoms. Although this mixed state, known as a SIT-gap soliton, near the PBG edge has been theoretically predicted, we numerically show that such a solitary wave still exists even if its central frequency is located deep inside the PBG. The propagating characteristics of the SIT-gap soliton are also discussed. (C) 2003 Optical Society of America.
Optical beams in sub-strongly non-local nonlinear media: A variational solution
(2006-03-01)
Guo, Q
;
Luo, B
;
Chi, S
;
光電工程學系
;
Department of Photonics
Discussed is the propagation of optical beams in non-local nonlinear media modelled by 1 + 1D non-local nonlinear Schrodinger equation (NNLSE). In the sub-strongly non-local case, an approximate analytical solution is obtained for an arbitrary response function by a variational approach. Described by a combination of the Jacobian elliptic functions, the solution is periodic, and its period depends on not only the input power but also the initial beam width, which is confirmed by the numerical simulation of the NNLSE. (c) 2005 Elsevier B.V. All rights reserved.
Ultrashort bragg soliton in a fiber bragg grating
(2002-05-15)
Chi, S
;
Luo, B
;
Tseng, HY
;
光電工程學系
;
Department of Photonics
The propagation of a nonlinear ultrashort pulse in a photonic bandgap structure is investigated by using the finite-difference time-domain method. The simulation results show that an ultrashort pulse near the bandgap edge can propagate through a nonlinear fiber Bragg grating, even if the broadband spectrum of this ultrashort pulse overlaps the whole forbidden band of the grating. It is also shown that the time delay of such an ultrashort solitary wave is proportional to its detuning wavelength from the exact Bragg resonance. (C) 2002 Published by Elsevier Science B.V.