During the past few years, metasurfaces have been used to demonstrate optical elements and systems with capabilities that surpass those of conventional diffractive optics. Here, we review some of these recent developments, with a focus on dielectric structures for shaping optical wavefronts. We discuss the mechanisms for achieving steep phase gradients with high efficiency, simultaneous polarization and phase control, controlling the chromatic dispersion, and controlling the angular response. Then, we review applications in imaging, conformal optics, tunable devices, and optical systems. We conclude with an outlook on future potentials and challenges that need to be overcome.

https://www.degruyter.com/document/doi/10.1515/nanoph-2017-0129/pdf

A review of dielectric optical metasurfaces for wavefront control

We report on cell damage of single cells confined in continuous-wave (cw), near-infrared (NIR) multimode optical traps as a result of multiphoton absorption phenomena. Trapping beams at NIR wavelengths less than 800 nm are capable of damaging cells through a two-photon absorption process. Cell damage is more pronounced in multimode cw traps compared with single-frequency true cw NIR traps because of transient power enhancement by longitudinal mode beating. Partial mode locking in tunable cw Ti:sapphire lasers used as trapping beam sources can produce unstable subnanosecond pulses at certain wavelengths that amplify multiphoton absorption effects significantly. We recommend the use of single-frequency long-wavelength NIR trapping beams for optical micromanipulation of vital cells.

Cell damage in near-infrared multimode optical traps as a result of multiphoton absorption

During the past few years, metasurfaces have been used to demonstrate optical elements and systems with capabilities that surpass those of conventional diffractive optics. Here we review some of these recent developments with a focus on dielectric structures for shaping optical wavefronts. We discuss the mechanisms for achieving steep phase gradients with high efficiency, simultaneous polarization and phase control, controlling the chromatic dispersion, and controlling the angular response. Then we review applications in imaging, conformal optics, tunable devices, and optical systems. We conclude with an outlook on future potentials and challenges that need to be overcome.

A review of dielectric optical metasurfaces for wavefront control.

Artificial microstructures, which allow us to control and change the properties of wave fields through changing the geometrical parameters and the arrangements of microstructures, have attracted plenty of attentions in the past few decades. Some artificial microstructure based research areas, such as metamaterials, metasurfaces and phononic topological insulators, have seen numerous novel applications and phenomena. The manipulation of different dimensions (phase, amplitude, frequency or polarization) of wave fields, particularly, can be easily achieved at subwavelength scales by metasurfaces. In this review, we focus on the recent developments of wave field manipulations based on artificial microstructures and classify some important applications from the viewpoint of different dimensional manipulations of wave fields. The development tendency of wave field manipulation from single-dimension to multidimensions provides a useful guide for researchers to realize miniaturized and integrated optical and acoustic devices.

Multidimensional manipulation of wave fields based on artificial microstructures

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adom.202001414

Principles, Functions, and Applications of Optical Meta-Lens

The ability to manipulate small objects with focused laser beams opens a broad spectrum of opportunities in fundamental and applied studies, for which precise control over mechanical path and stability is required. Although conventional optical tweezers are based on refractive optics, the development of compact trapping devices that could be integrated within fluid cells is in high demand. Here, a plasmonic polarization-sensitive metasurface-based lens, embedded within a fluid, is demonstrated to provide several stable trapping centers along the optical axis. The position of a particle is controlled with the polarization of the incident light, interacting with plasmonic nanoscale patch antennas, organized within overlapping Fresnel zones of the lens. While standard diffractive optical elements face challenges in trapping objects in the axial direction outside the depth of focus, bifocal Fresnel meta-lens demonstrates the capability to manipulate a bead along a 4 μm line. An additional fluorescent module, ...

Optical Manipulation along an Optical Axis with a Polarization Sensitive Meta-Lens.

Thin structured surfaces allow flexible control over the propagation of electromagnetic waves. Focusing and polarization state analysis are among functions, required for effective manipulation of radiation. Here, a polarization-sensitive Fresnel zone plate lens is proposed and experimentally demonstrated for gigahertz spectral range. Two spatially separated focal spots for orthogonal polarizations are obtained by designing metasurface pattern, made of overlapping tightly packed cross- and rod-shaped antennas with a strong polarization selectivity. The optimized subwavelength pattern allows multiplexing two different lenses with low polarization crosstalk on the same substrate and provides a control over focal spots of the lens only by changing the polarization state of the incident wave. More than a wavelength separation distance between the focal spots was demonstrated for a broad spectral range, covering half a decade in frequency. The proposed concept could be straightforwardly extended for terahertz and visible spectra, where polarization-sensitive elements utilize localized plasmon resonance phenomenon.

Bifocal Fresnel Lens Based on the Polarization-Sensitive Metasurface

Advances in laser and optoelectronic technologies have brought the general concept of optomechanical manipulation to the level of standard biophysical tools, paving the way towards controlled experiments and measurements of tiny mechanical forces. Recent developments in direct laser writing (DLW) have enabled the realization of new types of micron-scale optomechanical tools, capable of performing designated functions. Here we further develop the concept of DLW-fabricated optomechanically-driven tools and demonstrate full-3D manipulation capabilities over biological objects. In particular, we resolved the long-standing problem of out-of-plane rotation in a pure liquid, which was demonstrated on a living cell, clamped between a pair of forks, designed for efficient manipulation with holographic optical tweezers. The demonstrated concept paves the way for the realization of flexible tools for performing on-demand functions over biological objects, such as cell tomography and surgery to name just few.

https://www.mdpi.com/2072-666X/11/1/90/pdf

Auxiliary Optomechanical Tools for 3D Cell Manipulation

Thin structured surfaces allow flexible control over propagation of electromagnetic waves. Focusing and polarization state analysis are among functions, required for effective manipulation of radiation. Here a polarization sensitive Fresnel zone plate lens is proposed and experimentally demonstrated for GHz spectral range. Two spatially separated focal spots for orthogonal polarizations are obtained by designing metasurface pattern, made of overlapping tightly packed cross and rod shaped antennas with a strong polarization selectivity. Optimized subwavelength pattern allows multiplexing two different lenses with low polarization crosstalk on the same substrate and provides a control over focal spots of the lens only by changing of the polarization state of the incident wave. More than a wavelength separation between the focal spots was demonstrated for a broad spectral range, covering half a decade in frequency. The proposed concept could be straightforwardly extended for THz and visible spectra, where polarization-sensitive elements utilize localized plasmon resonance phenomenon.

Bifocal Fresnel lens based on the polarization-sensitive metasurface

Optical properties of porous vaterite structures, loaded with fluorescent dyes and metal nanoparticles, are studied theoretically, numerically and experimentally. Spectroscopic properties of those systems, either immobilized on a substrate or optically trapped in a solution, are investigated.

Hen Markovich

Papers

Optical Manipulation along an Optical Axis with a Polarization Sensitive Meta-Lens.

Bifocal Fresnel Lens Based on the Polarization-Sensitive Metasurface

Auxiliary Optomechanical Tools for 3D Cell Manipulation

Bifocal Fresnel lens based on the polarization-sensitive metasurface

Optical properties of trapped nanoantennas and loaded vaterite particles