Customized optical chirality of vortex structured light through state and degree-of-polarization control

Topological dichroism and birefringence of twisted light

“…There has recently been a significant interest in light-matter interactions which are dependent on the wavefront handedness of an optical vortex through the sign of ℓ. 5,9,10,13,27 Studies to date have primarily been concerned with chiral media and the optical chirality of vortex beams, manifesting through the interference of electric dipole coupling with the higher-order magnetic dipole and electric quadrupole interactions. These chiral effects are proportional to the second-order paraxial parameter 1/(kw) 2 and require multipolar moments which are roughly 1000 times smaller than electric dipole coupling.…”

“…In the last decade or so the remarkable rise of the field of structured or complex light 2 has occurred, its own genesis being the realization that laser beam photons can carry well-defined orbital angular momentum (OAM) in the direction of propagation 3 of ℓℏ, where ℓ ∈ Z is the topological charge. Recent studies in chiral light-matter interactions have identified the remarkable optical chirality properties of optical vortex beams (twisted light), [4][5][6][7][8][9][10][11][12][13][14][15] i.e. structured light which carries OAM.…”

On the orbit-induced spin density of tightly focused optical vortex beams: ellipticity and helicity

“…On the other hand, the optical helicity equation ( 12) is a measure of whether parallel electric and magnetic field components (in a single direction x, y, or z) are π/2 out of phase, which is in general completely independent of polarization ellipticity (and thus spin). This is why the longitudinal fields of optical vortex beams, both polarized in z and thus cannot have ellipticity, can generate non-zero optical helicity [9][10][11]13] via E * L1 • B L1 . Although we have shown there is no helicity associated with the longitudinal spin momentum densities equations ( 4) and ( 5), remarkably the polarizationindependent helicity density of optical vortex beams is associated with a transverse spin momentum density [9].…”

“…Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. spin angular momentum [5][6][7][8] and the optical helicity (also referred to as chirality) of vortex beams [9][10][11]. One of the most surprising results, particularly given the conventional wisdom of the optical properties of light, is that input laser beams which are unpolarized before being tightly focused may possess both spin angular momentum [12] and helicity [13] densities in the focal plane.…”

“…A discussion of the different analytical and numerical techniques can be found in [34]. The electric field for a monochromatic scalar Bessel beam up to second-order in the paraxial parameter k t /k z is (for derivation see [11,26])…”