Three-dimensional vectorial multifocal arrays created by pseudo-period encoding

Author(s):

Tingting Zeng and Chenliang Chang and Zhaozhong Chen and Hui-Tian Wang and Jianping Ding

Abstract:

“Multifocal arrays have been attracting considerable attention recently owing to their potential
applications in parallel optical tweezers, parallel single-molecule orientation determination,
parallel recording and multifocal multiphoton microscopy. However, the generation of vectorial
multifocal arrays with a tailorable structure and polarization state remains a great challenge, and
reports on multifocal arrays have hitherto been restricted either to scalar focal spots without
polarization versatility or to regular arrays with fixed spacing. In this work, we propose a specific
pseudo-period encoding technique to create three-dimensional (3D) vectorial multifocal arrays
with the ability to manipulate the position, polarization state and intensity of each focal spot. We
experimentally validated the flexibility of our approach in the generation of 3D vectorial multiple
spots with polarization multiplicity and position tunability.”

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Publication: Journal of Optics

Issue/Year/DOI: Journal of Optics, Volume 20, Number 6
DOI: 10.1088/2040-8986/aac1de

Demonstration of a vectorial optical field generator with adaptive close loop control

Author(s):

Jian Chen and Lingjiang Kong and Qiwen Zhan

Abstract:

“We experimentally demonstrate a vectorial optical field generator (VOF-Gen) with an adaptive close loop control. The close loop control capability is illustrated with the calibration of polarization modulation of the system. To calibrate the polarization ratio modulation, we generate 45° linearly polarized beam and make it propagate through a linear analyzer whose transmission axis is orthogonal to the incident beam. For the retardation calibration, circularly polarized beam is employed and a circular polarization analyzer with the opposite chirality is placed in front of the CCD as the detector. In both cases, the close loop control automatically changes the value of the corresponding calibration parameters in the pre-set ranges to generate the phase patterns applied to the spatial light modulators and records the intensity distribution of the output beam by the CCD camera. The optimized calibration parameters are determined corresponding to the minimum total intensity in each case. Several typical kinds of vectorial optical beams are created with and without the obtained calibration parameters, and the full Stokes parameter measurements are carried out to quantitatively analyze the polarization distribution of the generated beams. The comparisons among these results clearly show that the obtained calibration parameters could remarkably improve the accuracy of the polarization modulation of the VOF-Gen, especially for generating elliptically polarized beam with large ellipticity, indicating the significance of the presented close loop in enhancing the performance of the VOF-Gen.”

Link to Publications Page

Publication: Review of Scientific Instruments

Issue/Year/DOI: Review of SCientific Instruments 88, 125111 (2017)
DOI: 10.1063/1.4999656

Tailoring arbitrary hybrid Poincaré beams through a single hologram

Author(s):

Shiyao Fu and Yanwang Zhai and Tonglu Wang and Ci Yin and Chunqing Gao

Abstract:

“Hybrid Poincaré beams (HPBs) are a kind of structure field with anisotropic polarizations. Here, we demonstrate an approach to tailor HPBs with arbitrary states, through encoding a single hologram on a liquid-crystal display device along with a stable optical system. The state of the obtained HPB is determined only by the encoded holograms with special design, which means it is not necessary to adjust any optical elements or hardware when generating various HPB states. Moreover, perfect HPBs can also be generated through the proposed scheme. In the experiment, the obtained HPBs are analyzed through a polarizer and a special parameter S3/S0, showing good agreement with prediction. This work opens an insight in encoding single holograms for tailoring arbitrary HPBs and inspires various applications.”

Link to Publications Page

Publication: Applied Physics Letters

Issue/Year/DOI: Applied Physics Letters Volume 111, Issue 21
DOI: 10.1063/1.5008954

Tightly focused optical field with controllable photonic spin orientation

Author(s):

Jian Chen and Chenhao Wan and Ling Jiang Kong and Qiwen Zhan

Abstract:

“The spin angular momentum of photons offers a robust, scalable and highbandwidth
toolbox for many promising applications based upon spin-controlled
manipulations of light. In this work, we develop a method to achieve controllable photonic
spin orientation within a diffraction limited optical focal spot produced by a high numerical
aperture objective lens. The required pupil field is found analytically through reversing the
radiation patterns from two electric dipoles located at the focal point of the lens with
orthogonal oscillation directions and quadrature phase. The calculated pupil fields are
experimentally generated with a vectorial optical field generator. The produced photonic spin
orientations are quantitatively evaluated by their spin densities according to the tightly
focused electric fields calculated by Richard-Wolf vectorial diffraction theory to demonstrate
the validity and capability of the proposed technique.”

Link to Publications Page

Publication: Optics Express

Issue/Year/DOI: Optics Express, Volume 25, Number 16 pp. 19517-19528 (2017)
DOI: 10.1364/OE.25.019517

Characterization, design, and optimization of a two-pass twisted nematic liquid crystal spatial light modulator system for arbitrary complex modulation

Author(s):

A. J. Macfaden and T. D. Wilkinson

Abstract:

“Arbitrary two-dimensional complex modulation of an optical field is a powerful tool for coherent optical systems. No single spatial light modulator (SLM) offers true arbitrary complex modulation, but they can be combined in order to achieve this. In this work, two sides of a twisted nematic (TN) liquid crystal SLM are used sequentially to implement different arbitrary modulation schemes. In order to fully explore and exploit the rich modulation behavior offered by a TN device, a generalized Jones matrix approach is used. A method for in situ characterization of the SLM inside the two-pass system is demonstrated, where each side of the SLM is independently characterized. This characterization data is then used to design appropriate polarizer configurations to implement arbitrary complex modulation schemes (albeit without 100\% efficiency). Finally, an in situ optimization technique that corrects states by applying a translation in the complex plane is demonstrated. This technique can correct both for variations across the SLM and bulk changes in the SLM behavior due to the changing temperature.”

Link to Publications Page

Publication: Journal of the Optical Society of America A

Issue/Year/DOI: Journal of the Optical Society of America A Vol. 34, Issue 2, pp. 161-170 (2017)

DOI: 10.1364/JOSAA.34.000161

 

Optical eigenmodes; exploiting the quadratic nature of the energy flux and of scattering interactions

Author(s):

Mazilu, Michael and Baumgartl, J and Kosmeier, S and Dholakia, K

Abstract:

“Abstract: We report a mathematically rigorous technique which facilitates the optimization of various optical properties of electromagnetic fields in free space and including scattering interactions. The technique exploits the linearity of electromagnetic fields along with the quadratic nature of the intensity to define specific Optical Eigenmodes (OEi) that are pertinent to the interaction considered. Key applications include the optimization of the size of a focused spot, the transmission through sub-wavelength apertures, and of the optical force acting on microparticles. We verify experimentally the OEi approach by minimising the size of a focused optical field using a superposition of Bessel beams.”

Link to Publications Page

Publication: Optics Express

Issue/Year/DOI: Optics Express Volume 19, Issue 2 pp.933-945 (2011)
DOI: 10.1364/OE.19.000933