Shaping light in 3d space by counter-propagation

Abstract

We extend the established transverse customization of light, in particular, amplitude, phase, and polarization modulation of the light field, and its analysis by the third, longitudinal spatial dimension, enabling the visualization of longitudinal structures in sub-wavelength (nm) range. To achieve this high-precision and three-dimensional beam shaping and detection, we propose an approach based on precise variation of indices in the superposition of higher-order Laguerre-Gaussian beams and cylindrical vector beams in a counter-propagation scheme. The superposition is analyzed experimentally by digital, holographic counter-propagation leading to stable, reversible and precise scanning of the light volume. Our findings show tailored amplitude, phase and polarization structures, adaptable in 3D space by mode indices, including sub-wavelength structural changes upon propagation, which will be of interest for advanced material machining and optical trapping.

Advancing 3D shaping of vectorial light by counter-propagation of self-healing scalar and vector Bessel–Gaussian beams

“…As presented in our previous work [29], the counterpropagation of structured light fields can serve as a valuable tool for the creation of 3D shaped light fields, varying in amplitude, phase, and/or polarization. In this work, we demonstrated the implementation of self-similar scalar LG beams or vectorial CVBs for shaping spiralling intensity or polarization structures in 3D space and even longitudinal oscillation of OAM and SAM.…”

“…In this work, we demonstrated the implementation of self-similar scalar LG beams or vectorial CVBs for shaping spiralling intensity or polarization structures in 3D space and even longitudinal oscillation of OAM and SAM. For this approach, the resulting counterpropagating light field is represented by [29]…”

“…In recent work it has already been shown that two paraxial LG beams tailored in phase, amplitude, and polarization lead to complex, inhomogeneous, 3D light fields along the distance of only one wavelength [29]. Thereby, exclusively combinations of beams of the same type, namely, scalar or vector beams, have been investigated.…”

“…Initially applied for optical trapping [25,26], complex fields for an induced movement of nanowires [27] or spin-orbit interaction [28] have recently been achieved by this method. But also customized shaping of fully-structured light in all three spatial dimensions is possible, as we have shown in [29], using two separately structured counter-propagating LG beams. In this work also a detection method for counter-propagating beams was introduced based on digital, artificial propagation [30].…”

“…Thereby, we focus on numerical simulations to present the broad range of accessible field structures, enabling a detailed 3D analysis. An approach for the experimental investigation of counter-propagating light fields is given in, for instance, [29,33]. We utilize various transversely modulated sBG as well as vBG beams to create multiple different volumetric light structures (section 2.2).…”