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

The three important factors that affect the output power and temperature of fiber lasers (FLs) were investigated in a large mode area step-index FL under a high-power operation. Photodarkening (PD), quantum defect (QD), and background loss cause increases in the FLs temperature and reductions in beam quality, stability, and power. PD and background loss coefficients have different values for the signal (laser) or pump wavelength. But QD depends on the difference between the pump and the laser wavelength. By considering the PD attenuation in the rate equations, the effects of forward, backward, and bidirectional pump schemes on heat distribution agents were investigated. FL characters, including core and clad sizes, both side reflectors, and FL lengths in each heat generation agent, were studied in detail.