Theoretical modeling and simulation of Tm-doped double-clad fiber amplifier

Abstract

Based on the finite-difference method, a typical Tm-doped double-clad fiber amplifier modeling is comprehensively analyzed through the rate equations and propagation equations. The impacting factors such as amplified spontaneous emission (ASE), wavelength and power of the seed, fiber length, pumping power and fiber facet reflectivity are discussed. Simulation results show that there exist the most suitable fiber length and pump power while the amplifier has the maximum output power and the best signal to noise ratio. Moreover, the influence of ASE can be effectively inhibited by reducing the fiber facet reflectivity, especially the front fiber facet reflectivity, choosing the proper seed wavelength and increasing the seed power. The theoretical models and simulation results presented in this paper have a certain reference value for the design and development of high-power Tm-doped double-clad fiber amplifiers.Keywords-tm-doped fiber; fiber amplifier; numerical modeling; amplified spontaneous emission Ⅰ. INTRODUCTIONRecent years, there has been growing interests in high power Tm-doped fiber lasers and amplifiers operating in eye-safe wavelength around 2um,due to its widely applications in optical spectroscopy, gas sensing, lidar, telecommunications and laser surgery [1][2]. For some of these applications, high output power or energy as well as narrow linewidth and good beam quality are required. One promising way to realize these performance specifications is via the use of a master-oscillator power -amplifier (MOPA) system [3][4].Theoretical modeling and simulations are important to investigate characteristics of lasers and amplifiers and then optimize parameters for practical system. For the Yb-doped fiber lasers and amplifiers, a lot of theoretical models have already been proposed [5][6][7]. Compared with Yb-doped fiber operated in the 1um region, Tm-doped fiber has a much larger nonlinear threshold and much broader gain bandwidth promising to offer much higher laser output than currently widely used Yb-doped fiber. However, there are just a few theoretical models of Tm-doped fiber lasers reported and the influence of amplified spontaneous emission (ASE) is not considered in these models [8][9]. A systematic investigation of Tm-doped fiber double-clad (TDDC) fiber amplifier has not been presented to the best of the author's knowledge.In this paper, targeting the characteristics and optimization of continuous wave TDDC fiber amplifier, from the rate equations and propagation equations, a typical TDDC fiber amplifier model is comprehensively analyzed through finite-difference method. The impacting factors such as ASE, wavelength and power of the seed, fiber length, pumping power and fiber facet reflectivity are discussed. The theoretical model and simulation results presented in this paper have a certain reference value for the design and development of high-power TDDC fiber amplifiers. Ⅱ. AMPLIFIER CONFIGURATION AND THEORETICAL MODELINGSimilar to the Yb-doped fiber amplifier model [10], a bidirectionally pumped...

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