Polarization-Dependent ZBLAN Fiber Coupler for NPE Mode-Locking

We demonstrate the first polarization-dependent optical fiber coupler (PD-OFC) made of fluoride glass. The polarization extinction ratio at the through-port/cross-port reaches 2.5/4.0 dB in the 1.6-2.2 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathbf{m}$</tex> wavelength band, with an excess loss of 1.47 dB at a wavelength of 1.918 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathbf{m}$</tex>. The OFC also serves as a polarization-sensitive element to trigger soliton pulsation through nonlinear polarization evolution in an all-fiber ring cavity laser, leading to fundamental and multiples of the fundamental repetition rate.