Relaxed Adiabatic Evolution of Fundamental HE11 Mode on Etched Optical Fiber Tapers

We report on an etching-based fabrication method for conical core-maintained fiber tapers with adiabatic tapering angles, and discuss its adiabatic mode evolution compared to the conventional pulled fibers over the O-/C-bands. The far-field pattern from the etched fiber shows that the fundamental mode is maintained throughout the tapers.