The Dispersion Controlling Of Meta-lens

Dispersion appears in almost every optical system,therefore,the dispersion controlling has become a pivotal research topic.However,since the conventional optical devices usually rely on the phase difference gradually accumulated along the optical path to modulate the wavefront of the light wave,the conventional optical devices are bulky and hard to be integrated.In addition,the dispersion of natural materials,determined by the molecular energy levels,lacks tunability and adjustment.As a result,traditional dispersion control methods cannot support the novel optical and optoelectronic devices with ultrathin,ultra-light and portable properties.In recent years,due to the extraordinary performance in the fields of micro-nano-light manipulation and the integration of on-chip nano-photon devices,metasurface has attracted progressively increasing attention.Since metasurface enables the manipulation of electromagnetic characteristics at subwavelength scale,it is expected to break through the limitations of traditional optical devices.It,therefore,offers a new strategy to achieve the ultra-light,ultra-thin optical devices,which is expected to be the next generation optical or optoelectronic elements.With spatially varied metal/dielectric nanostructures as resonant optical antennas along the surface,metasurfaces provide a new approach for amplitude,phase and polarization manipulation.Metasurfaces have found widespread applications in three-dimensional beam deflections,special beam creation,cloaks,and holography and so on.However,metasurface still suffers from serious dispersion,which need to be overcome.Quite recently,several works about achromatic and super-dispersive devices based on metasurfaces have been reported.These designs,however,are not only complex and difficult to understand,but also require a large amount work of structure optimization.In order to simplify the structure optimization process during the design and make the design easy to operate,in this paper,the dispersion controlling devices based on metasurface have been studied.The main work includes:1.Proposed a multi-wavelength dispersive independent control method: modulate the amplitude by changing the geometry of the subwavelength structure,and change the azimuth of the subwavelength structure to modulate the phase.By using the characteristics of the wideband of the PB phase,the amplitude control and phase Regulate separately.Different subwavelength structures independently control different wavelengths,and the subwavelength structures are staggered to achieve independent control of multiwavelength dispersions.Using this method,we designed five dispersion-controlled hyper-lenses for different functions in the visible wavelength band,and achieved the functions of decoloring,on-axis large dispersion and off-axis dispersion.2.Proposed a broadband continuous dispersion controlling device optimization scheme: By introducing a wavelength-dependent phase parameters,a new dimension of thinking has been brought to the wavefront controlling,so that the dispersion of the subwavelength structure can compensate the dispersion caused by light wave propagating in space,to achieve broadband dispersion control.Instead of subwavelength structure optimization,particle swarm optimization algorithm greatly reducing the structure optimization workload.Based on the sensitivity of the object to the polarization state of incident light,a series of dispersion-controlled hyper-lenses that can be applied to polarization-independent and polarization-dependent dispersion of the mid-infrared atmospheric window are designed,laying a foundation for further development of polarization imaging technology.