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Mode analysis of different step index optical fibers at 1064 nm for high power fiber laser and amplifier

Fiber lasers having high power and high beam quality are popular for various industrial, biomedical, defense and scientific applications. Rare earth doped active fibers are used as gain medium in fiber laser system. The core region of these fibers is doped with different rare earth elements like erbium (Er), ytterbium (Yb) and thulium (Tm). In this paper, observation of mode profiles and calculation of modal power of different step index fibers has been done with the help of COMSOL and MATLAB. The analysis was done at 1064nm wavelength as these fibers are Yb-doped active fiber having an operation region near 1 micron for laser and amplifier applications. As we move to larger core diameter active fiber to achieve high power, the higher order modes starts carrying more power. To analyze this, fractional power of different transverse modes in the fiber both core and cladding region was calculated. Fibers were modeled in COMSOL and analyzed using MATLAB.