Title: Transverse spinning of light with globally unique handedness,
Abstract: Access to the transverse spin of light has unlocked new regimes in
topological photonics and optomechanics. To achieve the transverse spin of
nonzero longitudinal fields, various platforms that derive transversely
confined waves based on focusing, interference, or evanescent waves have been
suggested. Nonetheless, because of the transverse confinement inherently
accompanying sign reversal of the field derivative, the resulting transverse
spin handedness experiences spatial inversion, which leads to a mismatch
between the densities of the wavefunction and its spin component and hinders
the global observation of the transverse spin. Here, we reveal a globally pure
transverse spin in which the wavefunction density signifies the spin
distribution, by employing inverse molding of the eigenmode in the spin basis.
Starting from the target spin profile, we analytically obtain the potential
landscape and then show that the elliptic-hyperbolic transition around the
epsilon-near-zero permittivity allows for the global conservation of transverse
spin handedness across the topological interface between anisotropic
metamaterials. Extending to the non-Hermitian regime, we also develop
annihilated transverse spin modes to cover the entire Poincare sphere of the
meridional plane. Our results enable the complete transfer of optical energy to
transverse spinning motions and realize the classical analogy of 3-dimensional
quantum spin states.