Abstract
Metasurfaces can be programmed for a spatial transformation of the wavefront, thus allowing parallel optical signal processing on-chip within an ultracompact dimension. On-chip metasurfaces have been implemented with two-dimensional periodic structures, however, their inherent scattering loss limits their large-scale implementation. The scattering can be minimized in single layer high-contrast transmitarray (HCTA) metasurface. Here we demonstrate a one-dimensional HCTA based lens defined on a standard silicon-on-insulator substrate, with its high transmission (<1 dB loss) maintained over a 200 nm bandwidth. Three layers of the HCTAs are cascaded for demonstrating meta-system functionalities of Fourier transformation and differentiation. The meta-system design holds potential for realizing on-chip transformation optics, mathematical operations and spectrometers, with applications in areas of imaging, sensing and quantum information processing.
Highlights
Metasurfaces can be programmed for a spatial transformation of the wavefront, allowing parallel optical signal processing on-chip within an ultracompact dimension
With minimal feature size of 140 nm, the 1D high-contrast transmitarray (HCTA) is compatible with current deep UV photolithography technique used in silicon photonics foundry, and feasible for large-scale silicon photonic computational chips operating at the speed of light
The designed HCTAs are 1D rectangular etched slot arrays defined in the silicon-on-insulator (SOI) substrate (Fig. 1a)
Summary
Metasurfaces can be programmed for a spatial transformation of the wavefront, allowing parallel optical signal processing on-chip within an ultracompact dimension. Gradient variations of nanostructures in a subwavelength thin layer are capable of manipulating an out-ofplane EM wave in free space, leading to numerous applications from simple components of miniaturized flat lenses[4,5,6,7,8] and holograms[9,10,11], to more complicated systems of analog[12,13] signal processing and spectrometers[14,15]. Based on the 1D HCTA design, we experimentally demonstrate ultra-short, low loss and broadband mode size convertors and metasystems performing Fourier transform and spatial differentiation. With minimal feature size of 140 nm, the 1D HCTA is compatible with current deep UV photolithography technique used in silicon photonics foundry, and feasible for large-scale silicon photonic computational chips operating at the speed of light
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