  A vector dual-wavelength rectangular-shape laser (RSL) based on a long fiber
taper deposited with reduced graphene oxide is proposed, where the nonlinearity
is enhanced due to large evanescent-field-interacting length and strong field
confinement of a 8 mm fiber taper with a waist diameter of 4 micronmeters.
Graphene flakes are deposited uniformly on the taper waist with light pressure
effect, so this structure guarantees both excellent saturable absorption and
high nonlinearity. The RSL with a repetition rate of 7.9 MHz exhibits fast
polarization switching in two orthogonal polarization directions, and the
temporal and spectral characteristics are investigated. The results suggest
that the long taper-based graphene structure is an efficient choice for
nonlinear devices.
