Design of a large-mode-area pixeled leakage channel fiber with an ultrahigh loss ratio for 2 µm operation.

Abstract

A novel bend-resistant large mode area fiber with pixeled structure and leakage channel is proposed for application with a tight bend radius at the 2 µm wavelength region. Two layers of discontinuous fluorine-doped silica rods, which are called pixels, are introduced in the cladding. By removing four pixels, the loss of high-order modes is enhanced significantly due to the leakage channel. Bend properties of the fiber are investigated thoroughly by numerical simulations. As a result, a robust single-mode operation is obtained with an ultrahigh loss ratio (the minimum loss of high-order modes to the loss of fundamental mode) exceeding 3×105 when the fiber is bent with a tight radius as 10 cm. The effective mode area can reach 1764µm2. In addition, the fiber can keep high performance within a broad waveband from 1.75 to 2.15 µm. Large mode area and robust single-mode operation with a tight bend radius make this fiber beneficial to the development of 2 µm miniaturized fiber lasers.