Spin-orbit beams for optical chirality measurement

Samlan, C. T.; Suna, Rashmi Ranjan; Naik, Dinesh N.; Viswanathan, Nirmal K.

doi:10.1063/1.5008732

Cited by 42 publications

(23 citation statements)

References 26 publications

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“…Indeed, similar chiroptical effects that show discriminatory behaviour dependent on the sign of for linearly polarized twisted beams have been previously reported [21]. It is worth emphasizing that the 2D chiroptical phenomena detailed by (19) and (20) both entail a dependence on the material symmetry through the orientation-dependent products of E2 molecular transition moments. This marks a distinction from the discriminatory effects that occur in chiral plasmonics [84,85].…”

supporting

confidence: 76%

Spin-orbit interactions and chiroptical effects engaging orbital angular momentum of twisted light in chiral and achiral media

Forbes

Andrews

2019

Phys. Rev. A

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There is recurrent interest in the orbital angular momentum (OAM) conveyed by optical vortices, which are structured beams with a helically twisted wavefront. Particular significance is attached to the issue of how, in its interactions with matter, light conveying OAM might prove sensitive to the relative handedness and degree of twist in the associated optical wavefront. As a result of recent experimental and theoretical studies, the supposition that beams with OAM might enable discrimination between oppositely handed forms of matter has become a renewed focus of attention. Some of the tantalizing conclusions that are beginning to emerge from this research have, however, not yet established a definitive basis for a supporting mechanism. To resolve this problem requires the development of theory to support a faithful representation, and a thorough understanding, of the fundamental molecule-photon physics at play in such optical processeseven for processes as basic as absorption. The present analysis establishes mechanisms at play that entail a novel manifestation of optical spin-orbit interactions (SOI), engaging transition electric quadrupole moments. Moreover, powerful symmetry principles prove to render distinctively different criteria governing the exhibition of 2D and 3D chirality. The new results elucidate the operation of such effects, identifying their responsibility for discriminatory optical interactions of various forms in both chiral and achiral media.

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supporting

confidence: 76%

Spin-orbit interactions and chiroptical effects engaging orbital angular momentum of twisted light in chiral and achiral media

Forbes

Andrews

2019

Phys. Rev. A

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“…This interplay between SAM and OAM is an interesting facet of the work, and gives rise to questions about its physical interpretation. The issue may be explained through a spin-orbit interaction approach [27][28][29] , and could potentially lead to further interesting applications. 30 Another issue which requires future work involves looking at the E2E2 and M1E2 terms which appear to suggest the possibility of a chiroptical response even with achiral media 21,15 : this is a prospect that chiral sensitivity might arise solely from the total angular momentum possessed by the radiation components of the system, exhibiting.…”

Section: Discussionmentioning

confidence: 99%

Chiroptical interactions between twisted light and chiral media

Forbes¹,

Andrews

2018

Complex Light and Optical Forces XII

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The extent to which structured light might conceivably resolve the handedness of chiral matter is a topic of resurgent interest, and it is one that has been a challenge since the earliest days of optical vortex studies. It has not even been certain whether or not the orbital angular momentum of light could interact in such a way -though it has been established that electric quadrupole interactions enable twisted light to engage with local electronic transitions. Crucially, certain recent experiments have provided tantalizing evidence to support the existence of a chiral effect that is sensitive to handedness, against initial expectations. By detailed electrodynamic calculation, a new study has now fully identified the mechanism, and also provided an in-depth analysis of the role of electric quadrupole transition moments as they engage with the phase gradient of beams with a twisted wavefront. Focusing on single photon absorption, it emerges that the orbital angular momentum associated with the vorticity of a structured beam can indeed be exhibited in chiral effects, provided the material itself is not only chiral, but also has some structural order -which essentially limits the effect to chiral solids, poled liquid crystals, and oriented arrays of chiral nanoparticles. Circular polarization is still required, and the extent of circular dichroism proves to vary around the beam, being locally determined by the absorber orientation with reference to the beam axis. In agreement with earlier studies, and consistent with symmetry principles, the new analysis verifies that any dependence on wavefront vorticity vanishes in a freely mobile fluid. The reformulation of theory now paves the way for an extension to other kinds of chiroptical phenomena in orientationally ordered systems.

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“…Here we refer the state of polarization of the Gaussian beam as the observable and its transverse momentum vector with canonical conjugate transverse position as the apparatus. The SBC is used to couple the polarization state and the momentum vector resulting in inhomogeneously polarized Gaussian beam, also known as spin-orbit beam and has been used to measure weak optical chirality [21,22].…”

Section: B Weak Measurement Methodsmentioning

confidence: 99%

Ultra-sensitive single-beam atom-optical magnetometer using weak measurement method

et al. 2019

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Ultra-sensitive measurement of the magneto-optical rotation, due to interaction of linearly-polarized light passing through room-temperature Rb 85 atoms, in response to change in longitudinal magnetic field (δ B z ) is demonstrated using the weak measurement method. The polarization rotation angle measurement sensitivity (δ φ ) of 16 µrad and hence of the magnetometer of 1 nT, achieved using the weak measurement method is better than the balanced optical polarimetry results by a factor of three. The improvement in the measurement sensitivity is realized via optical amplification of the polarization rotation angle via spin-orbit coupled light beam-field. The method is devoid of external rf modulation, allows for optimal tunability of sensitivity depending on the dynamic range of the applied magnetic field and the sensitivity can be further enhanced by operating in the Spin Exchange Relaxation Free regime of alkali spin polarization.

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Spin-orbit beams for optical chirality measurement

Cited by 42 publications

References 26 publications

Spin-orbit interactions and chiroptical effects engaging orbital angular momentum of twisted light in chiral and achiral media

Spin-orbit interactions and chiroptical effects engaging orbital angular momentum of twisted light in chiral and achiral media

Chiroptical interactions between twisted light and chiral media

Ultra-sensitive single-beam atom-optical magnetometer using weak measurement method

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