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Influence of the frequency-chirp on pulse in passively mode-locking optical fiber ring laser

We consider a model of a passively mode-locking fiber ring laser bult using a saturable absorber and a chirped fiber Bragg grating to balance dispersion and nonlinearity. The evolution of the slowly envelope of the optical field in a loop fiber subject to dispersion , Kerr nonlinearity, frequency- chirp and nonlinear absorption is given by the generalized complex Ginzburg-Landau equation. The influence of the frequency-chirp on the pulse is simulated and discussed, and the stationary conditions concerning the chirp parameter are found out for our laser. | Communications in Physics, Vol. 23, No. 2 (2013), pp. 171-177 INFLUENCE OF THE FREQUENCY-CHIRP ON PULSE IN PASSIVELY MODE-LOCKING OPTICAL FIBER RING LASER BUI XUAN KIEN Electric Power University 235 Hoang Quoc Viet Str, Tu Liem Dist., Hanoi, Vietnam Email: kiendhv2000@yahoo.com TRAN HAI HUNG Nghe An Pedagogical College TRINH DINH CHIEN Hanoi University of Science, Vietnam National University, Hanoi 334 Nguyen Trai Str., Thanh Xuan Dist., Hanoi, Vietnam Received 05 March 2013; revised manuscript received 31 March 2013 Abstract. We consider a model of a passively mode-locking fiber ring laser bult using a saturable absorber and a chirped fiber Bragg grating to balance dispersion and nonlinearity. The evolution of the slowly envelope of the optical field in a loop fiber subject to dispersion , Kerr nonlinearity, frequency- chirp and nonlinear absorption is given by the generalized complex Ginzburg-Landau equation. The influence of the frequency-chirp on the pulse is simulated and discussed, and the stationary conditions concerning the chirp parameter are found out for our laser. I. INTRODUCTION In recent years there has been an extensive growth in research activities focused on developing ultrashort (< 10 ps) pulse sources based on rare-earth-doped-fiber [1–4]. The short pulse fiber-lasers have been passively mode-locked by using the chirp-fiberBragg-grating (C-FBG) to control dispersion, the polarization controller, the semiconductor saturable absorber mirror (SESAM) or the multiple quantum well saturable absorber (MQW-AS) [5]. The theory of mode-locking is based on the master equation derived under the condition that nonlinear changes to the intra-cavity pulse must be small per round-trip and fast saturable absorber action [6]. The carrier dynamics is adiabatically eliminated due to the sub-picosecond material response time and pulse widths of order ten picosecond. To obtain analytic results, the form of a complex Ginzburg-Landau equation is used, where the .