Numerical modelling the ultra-broadband mid-infrared supercontinuum generation in the As2Se3 photonic crystal fiber

Abstract

Abstract:In this paper, ultra-broadband mid-infrared (MIR) supercontinuum (SC) generation ranging from 2 to 15 μm in As 2 Se 3 photonic crystal fiber (PCF) was investigated numerically by multipole method and the adaptive split-step Fourier method. By choosing different hole sizes and the pitch parameters of the As 2 Se 3 PCF, the optimized nonlinear coefficients and dispersion profile of the fiber in the mid-infrared regime can be obtained. With the ultrafast pump laser centered around 4.3 μm, the broadband SC from 2 to 15 μm can be generated. In the normal dispersion regime, the flatness of the SC can be improved. Moreover, the pulse durations of the pump laser have positive influence on the spectrum broadening as well as the pump peak power.

Ultra-broadband modulation instability gain characteristics in As 2 S 3 and As 2 Se 3 chalcogenide glass photonic crystal fiber

“…is the nth-order frequency dependence dispersion coefficient at the central frequency of the pump pulse, γ = n 2 ω p /cA eff is the nonlinear coefficient, n 2 is the nonlinear refractive index of chalcogenide glass, and A eff is the effective mode area of the fiber which depends on fiber parameters such as the core radius and the core-cladding in-dex difference, α is the fiber loss, which is low and can be ignored. [14][15][16][17] Using the undepleted-dump approximation method, MI can be studied by adding small perturbations into the steady solution U st (z) = (P p ) 1/2 exp(iγP p z) of Eq. ( 1), where P p is the pump power.…”

“…is the sum of the even order dispersion coefficients; Ω is the detuning frequency, Ω = ω p − ω s = ω as − ω p (Ω > 0), with ω p being the angle frequency of pump light, while ω as and ω s being the angle frequencies of the generated anti-Stokes and Stokes waves in the PCF; ξ = Ω /ω p ; R(Ω ) is the Fourier transform of Raman response function R(t), whose values are different for the As 2 Se 3 and As 2 S 3 [14][15][16][17] glass PCFs, respectively. For the chalcogenide glass, the nonlinear index can be estimated by using the explicit Kramers-Kronig transformation equation.…”

“…The ratio of the hole diameter to pitch is set to be d/Λ = 0.4, so that the fundamental mode can be found in the MIR (2 µm-10 µm). Background refractive index is defined by their Sellemier formula, [14,16] whose values are different for the As 2 Se 3 and As 2 S 3 PCFs. Based on the full-vector solver COMSOL, by using the perfect-electricconductor boundary condition and dividing the fiber crosssectional surface into over 10 5 non-uniform mesh grids, the effective refractive index of the fundamental mode of fiber is first calculated.…”

Single gain peak from modulation instability in As2Se3chalcogenide glass photonic crystal fiber

“…In particular, for chalcogenide glass photonic crystal fibers such as As 2 Se 3 PCF, their high Raman responses and high nonlinearities (almost 1000 times higher than standard silica PCF) have attracted particular interest of researchers in recent years [10][11][12]. Some researches show that their superior optical characteristics play an essential role in four-wave mixing (FWM) processes, SC generation and wavelength conversion, and they have been applied in some important fields, such as all optical signal processing and optical communication systems [13][14][15]. From our previous works [16][17][18], one can know that modulation instability (MI) gain depends on Raman effect and nonlinearity of fiber, while the As 2 Se 3 chalcogenide glass PCFs have high Raman gain and high nonlinearity.…”

“…ξ = Ω/ω p . R(Ω) is the Fourier transform of Raman response function R(t) for the As 2 Se 3 [13,14] glass material. Figure 1 gives the Raman response characteristic of As 2 Se 3 glass material.…”