Experimental Measurement of Transverse Spin Dynamics in the Nonparaxial Focal Region of a High-Numerical Aperture Lens

Conceitos essenciais

The authors experimentally measured the polarization helicity-dependent and helicity-independent transverse spin dynamics in the nonparaxial focal region of a high-numerical aperture lens by tracking the C-point polarization singularities in the retroreflected output beam.

Resumo

The authors present an experimental study of the transverse spin dynamics in the nonparaxial focal region of a high-numerical aperture (NA) lens. They use a retroreflection geometry to map the nanoscale behavior of the state of polarization in the focal region.

Key highlights:

• The authors measure the phase and polarization variations in the retroreflected output beam as a function of the axial position of a dielectric mirror placed in the focal region.
• They identify phase and polarization singularities, such as edge-type dislocations, optical vortices, C-point and L-line singularities, in the beam cross-section.
• The dynamics of the C-point singularities and the surrounding polarization patterns are used to study the transverse spin dynamics.
• For right- and left-circular polarized input beams, the authors observe helicity-dependent and helicity-independent aspects of the transverse spin, including its rotation and radial movement in the focal region.
• The experimental method allows the authors to investigate the nonparaxial focal region in detail and unravel intricate optical field effects related to spin-orbit interaction of light.

Estatísticas

The spatial (x, y) positions of the phase singular optical vortex (OV) points and the C-point polarization singularity (PS) measured in the output beam cross-section, for the mirror positions z± = ±λ/2 μm, are provided in Table 1.

Citações

"The capability of our method to measure and identify edge- and vortex-type phase singularities in the focal region of the high-NA lens with sub-pixel accuracy is thus demonstrated."
"The measured characteristics and their behaviour confirm helicity-dependent SD and the spin-momentum coupling that appears in the high-NA lens´ focal region."

Principais Insights Extraídos De

Experimental Measurement of Transverse Spin Dynamics in the Nonparaxial Focal Region

by Nitish Kumar... às arxiv.org 10-01-2024

https://arxiv.org/pdf/2409.20145.pdf

Perguntas Mais Profundas

How can the proposed experimental method be extended to study the creation-annihilation dynamics of the polarization singularities in the nonparaxial focal region?

The proposed experimental method can be extended to study the creation-annihilation dynamics of polarization singularities by implementing a finer axial scanning mechanism of the dielectric mirror, allowing for sub-wavelength step sizes (e.g., λ/10 or less). This enhanced resolution would enable the tracking of the temporal evolution of polarization singularities, such as C-points and L-lines, as the mirror is moved through the nonparaxial focal region. By capturing high-resolution Stokes parameter measurements at these smaller increments, researchers can observe the intricate dynamics of singularities as they merge, annihilate, or create new singular points in the beam cross-section. Additionally, employing advanced imaging techniques, such as high-speed cameras or real-time polarimetry, could facilitate the observation of transient states and the mapping of the trajectories of these singularities, providing insights into their topological characteristics and the underlying physical mechanisms driving their dynamics.

What are the potential applications of the observed transverse spin dynamics in the nonparaxial focal region, beyond fundamental studies?

The observed transverse spin dynamics in the nonparaxial focal region have several potential applications beyond fundamental studies. One significant application lies in optical manipulation techniques, such as optical tweezers, where the ability to control the transverse spin and momentum of light can enhance the trapping and manipulation of microscopic particles. This could lead to advancements in fields like biophysics and materials science, where precise control over particle positioning is crucial. Furthermore, the insights gained from studying transverse spin dynamics can be applied to the development of novel optical devices, such as spin-based photonic circuits and quantum information systems, where the manipulation of light's spin state can be harnessed for information processing and transmission. Additionally, the understanding of spin-momentum coupling in the nonparaxial regime could lead to innovations in imaging techniques, improving resolution and contrast in optical microscopy and enhancing the detection capabilities in sensing applications.

How can the understanding of the spin-orbit interaction of light in the nonparaxial focal region be leveraged for novel optical manipulation and sensing techniques?

Understanding the spin-orbit interaction of light in the nonparaxial focal region can be leveraged for novel optical manipulation and sensing techniques by exploiting the coupling between the spin and orbital angular momentum of light. This interaction allows for the creation of structured light fields that can be tailored to achieve specific manipulation effects, such as the generation of optical vortices or the creation of complex polarization patterns. By designing optical systems that utilize these structured light fields, researchers can develop advanced optical tweezers capable of manipulating particles with high precision and control over their rotational dynamics. In sensing applications, the spin-orbit interaction can enhance the sensitivity of optical sensors by enabling the detection of minute changes in the polarization state of light, which can be indicative of environmental changes or the presence of specific analytes. Furthermore, integrating these principles into photonic devices could lead to the development of compact, efficient systems for information processing, where the spin state of light is used to encode and transmit data, paving the way for advancements in quantum communication and computing technologies.