Periodic Reporting for period 4 - NONLINMAT (Functional extreme nonlinear nanomaterials)
Période du rapport: 2022-02-01 au 2022-07-31
Metasurfaces that mimic artificial order in the matter have recently opened an exciting gateway to reach unprecedented properties and functionality for the modification of light propagation. The artificial “atoms” and “molecules” of the metasurface can be tailored in shape and size, the lattice constant and inter-atomic interaction can be precisely tuned. Furthermore, using symmetry and polarization state properties topological Berry phase effects can greatly enhance the functionality of such surfaces.
With this project, we explore the revolutionary physics of nonlinear optical Berry phase metasurfaces, covering nonlinear optical frequency generation and wave dispersion engineering as well as real-time reconfiguration of nonlinear optical properties. Novel unique nonlinear optical properties of metasurfaces that arise from their specific topological configurations open up exciting new venues for device development in the fields of all-optical data processing, optical meta-nanocircuits, phase conjugating perfect mirrors, and background-free nonlinear holography. We investigate the possibilities of strongly enhanced nonlinear light-matter interaction and novel nonlinear optical processes that are based on nonlinear topological Berry phase effects coupled to inter- and intersubband transitions of novel 2D materials. Single layers of transition metal dichalcogenides will allow reconfigurable nonlinear optical properties by changing the valley band transitions.
The project covers the development of innovative fabrication technologies, fundamental investigations of the origin and the design of effective nonlinearities with controlled phase, experimental characterizations, as well as device development. The findings of the project based on highly nonlinear reconfigurable metasurfaces based on symmetry and topological effects will impact interdisciplinary research fields including condensed matter physics, optoelectronics, and biophotonics. Fast optical switches and frequency converter in miniaturized and integrated systems for quantum information technology might benefit from the small footprint and the design freedom of metasurfaces.
With this project, we explore the revolutionary physics of nonlinear optical Berry phase metasurfaces, covering nonlinear optical frequency generation and wave dispersion engineering as well as real-time reconfiguration of nonlinear optical properties. Novel unique nonlinear optical properties of metasurfaces that arise from their specific topological configurations open up exciting new venues for device development in the fields of all-optical data processing, optical meta-nanocircuits, phase conjugating perfect mirrors, and background-free nonlinear holography. We investigate the possibilities of strongly enhanced nonlinear light-matter interaction and novel nonlinear optical processes that are based on nonlinear topological Berry phase effects coupled to inter- and intersubband transitions of novel 2D materials. Single layers of transition metal dichalcogenides will allow reconfigurable nonlinear optical properties by changing the valley band transitions.
The project covers the development of innovative fabrication technologies, fundamental investigations of the origin and the design of effective nonlinearities with controlled phase, experimental characterizations, as well as device development. The findings of the project based on highly nonlinear reconfigurable metasurfaces based on symmetry and topological effects will impact interdisciplinary research fields including condensed matter physics, optoelectronics, and biophotonics. Fast optical switches and frequency converter in miniaturized and integrated systems for quantum information technology might benefit from the small footprint and the design freedom of metasurfaces.
In recent years, there is a growing demand on lightweight optical components for novel applications like augment reality. The project studied fundamental properties of optical nanostructured surfaces, so called metasurfaces, with potential applications in holography and imaging. During the project, we focused our research on the development of nonlinear metasurfaces for functional elements, like nonlinear holograms and nonlinear metalenses. Here, nonlinear optical metasurfaces means that the used systems will transform the wavelength of the light during the interaction. Within our studies, we investigated the possibilities to increase the information capacity of metasurface holograms consisting of ultrathin layers of nanostructured materials. Therefore, new design algorithms and suitable structure design of the unit-cells were developed. Such algorithms are necessary for obtaining high-quality holographic images and information recovery from the metasurfaces when they are illuminated by particular light states.
Furthermore, we studied the performance of plasmonic, hybrid, and purely dielectric metasurfaces for nonlinear light conversion. In such a way, the illuminating light at a particular frequency can be converted to two or three times the frequency, allowing to go from near-infrared light to the visible. For that, we developed a concept that can tailor the spatial phase of this conversion process, which is mandatory for nonlinear beam shaping and holography. First, metasurfaces were fabricated and tested for their optical performance. With some impressive experiments, we were able to show for the first time some imaging of objects by a nonlinear metalens, which led to the conclusion that the traditional lens equation for linear ray optics can be modified to include nonlinear optical effects.
Another part of the project studied the potential of active materials for dynamically tunable or switchable optical metasurface holograms. Such metasurfaces can reveal different information by externally stimulated by some trigger. We showed that chemical processes, as well as temperature, can be used to obtain such behavior when particular materials are combined.
Finally, we proved that optical metasurfaces can act as high numerical aperture lenses for optical trapping in liquid environment. For that we demonstrated metasurface lenses that can trap particles and transfer orbital angular momentum to particles. Such metalenses are easy to integrate into microfluidic systems.
The project also tested new concepts of topological photonic systems, in particular topological photonics crystals for light guiding and manipulation. These systems have to potential to be robust against fabrication tolerances and can be integrated in optical chips for diverse applications.
Furthermore, we studied the performance of plasmonic, hybrid, and purely dielectric metasurfaces for nonlinear light conversion. In such a way, the illuminating light at a particular frequency can be converted to two or three times the frequency, allowing to go from near-infrared light to the visible. For that, we developed a concept that can tailor the spatial phase of this conversion process, which is mandatory for nonlinear beam shaping and holography. First, metasurfaces were fabricated and tested for their optical performance. With some impressive experiments, we were able to show for the first time some imaging of objects by a nonlinear metalens, which led to the conclusion that the traditional lens equation for linear ray optics can be modified to include nonlinear optical effects.
Another part of the project studied the potential of active materials for dynamically tunable or switchable optical metasurface holograms. Such metasurfaces can reveal different information by externally stimulated by some trigger. We showed that chemical processes, as well as temperature, can be used to obtain such behavior when particular materials are combined.
Finally, we proved that optical metasurfaces can act as high numerical aperture lenses for optical trapping in liquid environment. For that we demonstrated metasurface lenses that can trap particles and transfer orbital angular momentum to particles. Such metalenses are easy to integrate into microfluidic systems.
The project also tested new concepts of topological photonic systems, in particular topological photonics crystals for light guiding and manipulation. These systems have to potential to be robust against fabrication tolerances and can be integrated in optical chips for diverse applications.
The results showed that a tremendous improvement of the nonlinear conversion efficiency can be obtained by moving from plasmonic to dielectric nanostructures for metasurfaces. Further improvement might be possible by incorporating active systems like quantum wells or quantum dot into the dielectric structures. However, this becomes potentially more difficult due to the shorter wavelengths. We are also expecting that a further improvement of the efficiency can be obtained by realization of nonlocal resonances with high quality factor. Although this would lower the bandwidth, it might bring the structures closer to an application for particular wavelengths, an important step to use these metasurfaces outside the research lab. In particular our demonstration of a nonlinear metalens for imaging objects and the development of a simple theoretical description based on a generalized lens equation goes beyond of the state of the art. It was the first time that image properties of lenses with frequency conversion were studied. Such systems might provide new routes to optical image processing including the measurement of spatial correlations and higher order Fourier transformations.