Silicon nanofin grating as a miniature chirality-distinguishing beam-splitter

Abstract

The polarization of light plays a central role in its interaction with matter, in situations ranging from familiar (for example, reflection and transmission at an interface) to sophisticated (for example, nonlinear optics). Polarization control is therefore pivotal for many optical systems, and achieved using bulk devices such as wave-plates and beam-splitters. The move towards optical system miniaturization therefore motivates the development of micro-and nanostructures for polarization control. For such control to be complete, one must distinguish not only between linear polarizations, but also between left-and right-circular polarizations. Some previous works used surface plasmons to this end, but these are inherently lossy. Other works used complex-layered structures. Here we demonstrate a planar dielectric chirality-distinguishing beam-splitter. The beam-splitter consists of amorphous silicon nanofins on a glass substrate and deflects left-and right-circularly polarized beams into different directions. Contrary to intuitive expectations, we utilize an achiral architecture to realize a chiral beam-splitting functionality.

Advances in Full Control of Electromagnetic Waves with Metasurfaces

“…More importantly, by matching Equation ( 2) , the emergent light could be either surface wave ( Figure 5 i) or propagating wave. [ 145,146 ] However, current practices are usually achieved with low effi ciency because of undesired zeroth order refl ection and transmission. Relatively, such unwanted scattering could be easily eliminated in refl ectiontype designs by blocking the transmission with an optically thickness substrate, as in MIM systems.…”

“…[ 145,146 ] Because of the interfacial phase discontinuity generated by PB phase metasurfaces, the incident beam will be added additional linear momentum with the sign determined by its helicity. As a result, incident beams with opposite helicities will be guided into different directions following the equation below: [ 145 ] sin 2 2…”

“…[ 147 ] Nonetheless, generic metasurfaces based on PB phase have a vital defect that the achieved functionalities in controlling EM waves are usually symmetric for two opposite spins, such as focusing/defocusing, left/right and inward/ outward. [ 41,44,46,[145][146][147][148] In principle, each PB phase element (for example, nanorod and nanoslot) acts as a dipole source. To reconstruct a target fi eld distribution, we need to ensure a constructive interference of radiations from different elements, whose spatial distributions are determined by ( , )…”

Metasurface Polarization Optics: Independent Phase Control of Arbitrary Orthogonal States of Polarization

“…If, however, the phase profile imposed in this way on RCP light is some φ RCP (x, y), the phase profile imparted on a left circularly polarized (LCP) wavefront is automatically φ LCP (x, y) = −φ RCP (x, y). This restriction -an inherent symmetry of the geometric phase -still allows for, e.g., circular polarization beamsplitters that deflect opposite circular polarizations by equal and opposite angles [4,13,14], but has important practical consequences: a geometric phase converging lens for one circular polarization, for example, will act as a diverging lens for the other [15].…”

Characteristic Analysis of Compact Spectrometer Based on Off-Axis Meta-Lens

“…Metasurfaces, ultrathin planar structures patterned by monolithic subwavelength elements on surfaces, provide a new way to transform the incident wavefront to the desired forms by controlling the amplitude, phase and polarization of electromagnetic fields [2][3][4][5][6]. Compared with their traditional counterparts, metasurfaces have emerged as unparalleled devices to realize miniaturized, on-chip integrated and multifunctional optical systems [7][8][9][10]. Tremendous breakthroughs in the field of metasurface have given rise to expansive applications ranging from planar imaging lenses [8,9,[11][12][13][14], holograms [15][16][17][18][19], spectrometers [20,21], nonlinear devices [22,23] and even to invisible cloaks [24][25][26], etc.…”