Theoretical Study of the Thermal Distribution in Yb-Doped Double-Clad Fiber Laser by Considering Different Heat Sources

Abstract

Thermal effects limit the gain, quality, and stability of high power fiber lasers and amplifiers. In this paper, different values of heat conductive coefficients at the core, the first and second clad with the complete form of the heat transfer equation are considered. A quartic equation was proposed to determine the temperature at the fiber laser surface. Using the surface temperature value, the temperature can be determined at the longitudinal and radial position of the double clad fiber laser. The different definitions of heat sources which were previously presented in articles is used to describe the heat generation at a double clad high pump power fiber laser condition. The results were compared to each other, and the percentage of each factor in heat generation was calculated.

Implementation of Laser-Induced Anti-Stokes Fluorescence Power Cooling of Ytterbium-Doped Silica Glass

“…The thermal camera saturates at Δ T ≈ – 6 K, so the temperature may have dropped below the saturation value [see subsection (3.2); Differential Luminescence Thermometry]. In this power cooling experiment, the sample’s temperature evolution as a function of time follows the following exponential form (see Mobini et al for a derivation) where we use the following definitions Here, V is the sample volume, ε = 0.85 is the emissivity of the implemented Yb-doped silica glass fiber preform, σ = 5.67 × 10 –8 W·m –2 ·K –4 is the Stefan–Boltzmann constant, T 0 is the ambient temperature, A is the surface area of the sample, ρ = 2.2 × 10 3 kg·m –3 is the silica glass mass density, and c v = 741 J·kg –1 ·K –1 is the specific heat of the silica glass. − P abs is the absorbed laser power that can be estimated from the Beer–Lambert law in a single pass , Here, P in is the input power coupled into the fiber preform at z = 0, l is the sample length, and α r (1035 nm) ≈ 1.93 × 10 –2 cm –1 . In fact, by combining eqs and , we can see that Δ T max ∝ η c α r , which is the vertical axis in Figure used to estimate the optimum pump laser wavelength.…”

Contribution of different factors in heat production in Yb3+-doped fiber laser: a review

“…The numerical solving of rate equations is the common method to investigate FL power variations, 54 and the rate equations are present in Ref. 21 and given as ±dPℓ±(z)dz=Γℓ[(σℓe+σℓa)N2(z)−σℓaN]Pℓ±(z)−αℓPℓ±(z),±dPp±(z)dz=−Γp[σpaN−(σpe+σpa)N2(z)]Pp±(z)−α…”

“…20 In previous works, different definitions of the heat source in FLs were classified, and their simulation results were compared with each other. 21 In this work, the PD loss is added to the rate equations as a power decreasing factor, and under these changes, the effect of cavity parameters, such as core and first clad sizes, laser length, and the reflectors at the end of FL in heat distribution, is investigated in the same bidirectional pump scheme. Also, in Ref.…”

Analytical formulation of a high-power Yb-doped double-cladding fiber laser

“…Temperature rise in the core of the fiber has been a barrier to acceptable stability and efficiency in high power operation [9]. Liquid-forced cooling [10][11][12][13] has been employed to solve the perpetual excess heat issue. However, the demand for more efficient heat mitigation persists in the efforts to develop a new generation of devices.…”