There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Wave propagation and group velocity

Emerging applications based on optical beams carrying orbital angular momentum (OAM) will probably require photonic integrated devices and circuits for miniaturization, improved performance, and enhanced functionality. We demonstrate silicon-integrated optical vortex emitters, using angular gratings to extract light confined in whispering gallery modes with high OAM into free-space beams with well-controlled amounts of OAM. The smallest device has a radius of 3.9 micrometers. Experimental characterization confirms the theoretical prediction that the emitted beams carry exactly defined and adjustable OAM. Fabrication of integrated arrays and demonstration of simultaneous emission of multiple identical optical vortices provide the potential for large-scale integration of optical vortex emitters on complementary metal-oxide–semiconductor compatible silicon chips for wide-ranging applications.

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Integrated Compact Optical Vortex Beam Emitters

Space-variant Pancharatnam-Berry phase optical elements based on computer-generated subwavelength gratings are presented. By continuously controlling the local orientation and period of the grating we can achieve any desired phase element. We present a theoretical analysis and experimentally demonstrate a Pancharatnam-Berry phase-based diffraction grating for laser radiation at a wavelength of 10.6microm.

Space-variant Pancharatnam-Berry phase optical elements with computer-generated subwavelength gratings.

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.

/pdf/roadmap-on-structured-light-3r840pnxka.pdf

Roadmap on structured light

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-50/issue-8/081201/Special-Section-Guest-Editorial-Liquid-crystals-for-photonics/10.1117/1.3607988.pdf

Special Section Guest Editorial: Liquid crystals for photonics

We present a review of the techniques for the calibration and optimization of twisted nematic liquid crystal displays (TNLCDs,) with special focus on the application to describe multiple reflections effects. The inclusion of these effects permits us to obtain an improvement in the accuracy in the prediction of the modulation properties of transmissive and reflective displays. In newer reflective liquid crystal on silicon (LCoS) displays we noticed a significant degree of depolarization. Polarimetric measurements have been performed showing depolarizations as large as 10% at certain gray levels and for certain incident polarizations. Fluctuations in the instantaneous state of polarization of the reflected beam have been demonstrated as the main origin for this depolarization. In the next future we plan to extend this type of polarimetric study to the whole range of gray levels, in order to look for the optimal modulation response of the LCoS display.

Simple Jones Method for describing Modulation Properties of Reflective Liquid Crystal Spatial Light Modulators

Ferroelectric liquid-crystal modulator with large switching rotation angle for polarization-independent binary phase modulation

We present the improvement of color pattern recognition by the optimization of a new parameter, the polychromatic discrimination capability. We use the polychromatic correlation obtained as the addition of the three correlation intensities obtained with the RGB components of the input color scene and the corresponding components of the color target. The polychromatic discrimination capability is defined in this fused correlation plane. We propose a method to optimize this perfor- mance parameter, which represents a global criterion for the optimization of the polychromatic correlation. The approach involves the design of regions of support to be used with the matched phase-only filters to optimize the polychromatic discrimination. We present simulation results illustrating the improvements obtained after the optimization process. We also include experimental results obtained with an optical real-time cor- relator that uses two spatial light modulators. Experimental data confirm the numerical results and show the capacity of the proposed technique to improve color pattern recognition. © 2002 Society of Photo-Optical Instrumen-

Optimization of the polychromatic discrimination capability in multichannel pattern recognition

A 3D lattice of equally intense focus spots can be created using a 3D Dammann structure. We show 4 planar arrays each having 4x4 points using a single pattern.

Ignacio Moreno

Papers

Special Section Guest Editorial: Liquid crystals for photonics

Simple Jones Method for describing Modulation Properties of Reflective Liquid Crystal Spatial Light Modulators

Ferroelectric liquid-crystal modulator with large switching rotation angle for polarization-independent binary phase modulation

Optimization of the polychromatic discrimination capability in multichannel pattern recognition

Creating 3D lattice patterns using programmable Dammann gratings