Monolithic metasurface spatial differentiator enabled by asymmetric photonic spin-orbit interactions

Abstract

Spatial differentiator is the key element for edge detection, which is indispensable in image processing, computer vision involving image recognition, image restoration, image compression, and so on. Spatial differentiators based on metasurfaces are simpler and more compact compared with traditional bulky optical analog differentiators. However, most of them still rely on complex optical systems, leading to the degraded compactness and efficiency of the edge detection systems. To further reduce the complexity of the edge detection system, a monolithic metasurface spatial differentiator is demonstrated based on asymmetric photonic spin-orbit interactions. Edge detection can be accomplished via such a monolithic metasurface using the polarization degree. Experimental results show that the designed monolithic spatial differentiator works in a broadband range. Moreover, 2D edge detection is experimentally demonstrated by the proposed monolithic metasurface. The proposed design can be applied at visible and near-infrared wavelengths by proper dielectric materials and designs. We envision this approach may find potential applications in optical analog computing on compact optical platforms.

Revealing Structural Disorder in Hydrogenated Amorphous Silicon for a Low‐Loss Photonic Platform at Visible Frequencies

“…As a result, since the complex refractive index of a‐Si:H can be fine‐tuned by controlling the structural disorder of silicon‐hydrogen bonding through the deposition parameters of PECVD, in addition to the ease of fabrication and increased substrate selectivity, low‐loss a‐Si:H is a promising material to significantly improve the efficiency of silicon‐based photonic devices that could play a key role in future photonic applications. [ 51,52 ] In combination with promising design methods such as semi‐continuous metasurfaces, [ 53–55 ] deep‐learning processes, [ 56,57 ] and topological optimization, [ 58 ] low‐loss a‐Si:H is a candidate for the use in all‐dielectric metasurfaces at visible frequencies.…”

Electromagnetic Architectures: Structures, Properties, Functions and Their Intrinsic Relationships in Subwavelength Optics and Electromagnetics

“…spin-orbit interactions (PSOIs) has been proposed to achieve spin-decoupled multifunctional metadevices by merging propagation phase and geometric phase in plasmonic metasurfaces [91] and dielectric metasurfaces. [34,35,[112][113][114] Apart from independent control of the wave front of opposite-handedness, asymmetric PSOIs can also allow independent amplitude modulation by adopting super-atoms as building blocks, [115][116][117] which may be utilized for chiral imaging and elliptical polarizers. The symmetry breaking of PSOIs is attributed to the opposite spin dependence of the propagation phase and geometric phase.…”

Compound Vortex Metalens with Linearly Polarized Encryption

“…[ 14–20 ] In comparison with the other methods, metasurface has natural advantages in miniaturization and integration of light field regulation, and it can cause spatially varying optical responses through the interaction between the light field and nanostructure instead of a spatial accumulation effect along an optical path. [ 21–26 ] Yang et al. found that a high order plasmonic vortex generated by using multi‐arm spiral nanoslits etched on metasurface carries a deuterogenic compound plasmonic vortex.…”