Manipulation Of Optical Focal Field With Transmissive Metalens And Its Applications

In recent years,the optical technology has been widely used in micro-nano fields,and the control of light has received more attention.In conventional optical systems,light is focused by either dielectric lenses or parabolic reflectors that,on the scale of the wavelength,are bulky and curved components,thus preventing straightforward miniaturization.Recently the concept of metasurface is put forward,metasurface are optically thin metal gratings with subwavelength periodicity and consist of series of plasmonic antennas and have flexible control of wavefront with phase shifts over 2?.Metasurfaces represent flat and subwavelength-thin devices that can achieve the same functionality by incorporating a parabolic transmission/reflection phase.In this thesis,we focus our attention on the manipulation of optical focal field with transmissive metalens and its applications.Concretely these work were accomplished:firstly,we realize an ultrathin flat metasurface lens with multiple focal points along the longitudinal direction based on TiO₂ antenna arrays,which can highly flexible adjust focal length,numerical aperture,number of focal spots and orbital angular momentum.Secondly,we propose an optical trapping and manipulation strategy based on multifocal optical vortex metalens,which is capable of generating multiple vortex focal fields with specific orbital angular momentum at arbitrary plane.Two kinds of dielectric particles can be trapped simultaneously.Thirdly,we numerically demonstrate a novel and scalable orbital angular momentum detection scheme combining a four-sector metahologram and four subwavelength detectors.Lastly,we propose a plasmonic tweezers that is capable of trapping and manipulating different kinds of nanoparticles.