Design of Large-Mode-Area Microstructured Optical Fiber with Single-Mode Operation for High Power Fiber Lasers

A new design of large-mode-area microstructured optical fiber has been reported based on introducing down-doped material rods in place of six out of nine air holes of inner ring near the core. The single-mode operation is ensured by introducing high bending loss for first higher order mode and very low bending loss for fundamental mode. Numerical results show that effective-single-mode operation can be ensured with mode area as large as 875 mu m(2) at bend state with bend radius of 20 cm. In straight state of fiber the structure offers effective mode area upto 1315 mu m(2) for same parameters. Proposed microstructured optical fiber with such a large-mode-area can have potential applications in compact high power delivery devices such as, high power fiber lasers and amplifiers.