Beam preserving and a low loss asymmetric pump and signal fiber combiner

Abstract

We detailed the design and fabrication of a beam quality preserving and low insertion loss asymmetric (6 + 1)x1 pump and signal fiber combiner. Transmission efficiency of the beam combiner with different structure parameters such as taper ratios, taper lengths, etc are analyzed using the beam propagation method numerically. We experimentally demonstrated and investigated three design parameters and fabrication methods, including chemical wet etching, pre-tapering of fibers, and thermally expanding the core of bundle. Negligible beam quality factor Mx,y2 degradation of 0.05 / 0.02 and low insertion loss of 0.02 dB for pump and 0.16 dB for signal ports respectively were achieved.