A low-profile dual-broadband dual-circularly-polarized reflectarray for K-/Ka-band space applications

A low-profile dual-broadband dual-circularly-polarized(dual-CP)reflectarray(RA)is proposed and demonstrated,supporting independent beamforming for right-/left-handed CP waves at both K-band and Ka-band.Such functionality is achieved by incorporating multi-layered phase shifting elements individually operating in the K-and Ka-band,which are then interleaved in a shared aperture,resulting in a cell thickness of only about O.1az.By rotating the designed K-and Ka-band elements around their own geometrical centers,the dual-CP waves in each band can be modulated separately.To reduce the overall profile,planar K-/Ka-band dual-CP feeds with a broad band are designed based on the magnetoelectric dipoles and multi-branch hybrid couplers.The planar feeds achieve bandwidths of about 32%and 26%at K-and Ka-band respectively with reflection magnitudes below-13 dB,an axial ratio smaller than 2 dB,and a gain variation of less than 1 dB.A proof-of-concept dual-band dual-CP RA integrated with the planar feeds is fabricated and characterized which is capable of generating asymmetrically distributed dual-band dual-CP beams.The measured peak gain values of the beams are around 24.3 and 27.3 dBic,with joint gain variation<1 dB and axial ratio<2 dB bandwidths wider than 20.6%and 14.6%at the lower and higher bands,respectively.The demonstrated dual-broadband dual-CP RA with four degrees of freedom of beamforming could be a promising candidate for space and satellite communications.

Deep-subwavelength light transmission in hybrid nanowire-loaded silicon nano-rib waveguides

Hybrid plasmonic waveguides leveraging the coupling between dielectric modes and plasmon polaritons have emerged as a major focus of research attention during the past decade. A feasible way for constructing practical hybrid plasmonic structures is to integrate metallic configurations with silicon-on-insulator waveguiding platforms. Here we report a transformative high-performance silicon-based hybrid plasmonic waveguide that consists of a silicon nano-rib loaded with a metallic nanowire. A deep-subwavelength mode area(λ~2/4.5 × 10~5-λ~2/7 × 10~3), in conjunction with a reasonable propagation distance(2.2-60.2 μm), is achievable at a telecommunication wavelength of 1.55 μm. Such a nano-rib-based waveguide outperforms its conventional hybrid and plasmonic waveguiding counterparts, demonstrating tighter optical confinement for similar propagation distances and a significantly enhanced figure of merit. The guiding properties of the fundamental mode are also quite robust against possible fabrication imperfections. Due to the strong confinement capability, our proposed hybrid configuration features ultralow waveguide cross talk and enables submicron bends with moderate attenuation as well. The outstanding optical performance renders such waveguides as promising building blocks for ultracompact passive and active silicon-based integrated photonic components.