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Broadband on-chip photonic spin Hall element via inverse design

A photonic spin Hall (PSH) device sorts photons with different spin states and is a fundamental component of photonic information technologies. However, the PSH effect is rather weak for measurements using bulky and expensive equipment. The metasurface is a promising way to dramatically shrink an optical element to a size suitable for photonic spin devices. Using V-shaped nano-antennas, a metasurface device with a strong PSH effect is demonstrated with normal incidence. The emergence of a variety of Pancharatnam–Berry phase components has led to development of various photonic spin devices. However, most of these metasurface devices suffer from the low efficiency issues. On-chip photonic spin devices are also designed based on spin-orbital coupling by using micro-disks and nano-antennas, but the intrinsic resonance in this design limits the device's bandwidth and prevents the wide use.

The researchers from the Nanophotonics Research Center of Shenzhen University, Prof. Zhenwei Xie, Prof. Ting Lei and Prof. Xiaocong Yuan, proposed and demonstrated an integrated on-chip photon spin Hall device using inverse design. It has both high detection and emission efficiency, and a working bandwidth around 200 nm. Related research results are published on Photonics Research, Vol. 18, Issue 2, 2020 (Zhenwei Xie, Ting Lei, Haodong Qiu, Zecen Zhang, Hong Wang, Xiaocong Yuan. Broadband on-chip photonic spin Hall element via inverse design[J]. Photonics Research, 2020, 8(2): 02000121).

Prof. Xiaocong Yuan says that the photonic spin Hall element is fabricated on a silicon-on-insulator wafer compatible with a standard integrated photonic circuit, and its diameter is only 2.4 μm with 100 nm sized pixels. Therefore, it is expected to realize miniaturized and integrated photon spin devices. The spin light is detected and emitted with efficiencies of up to 22% and 35%, respectively.

This work may have applications for on-chip spin sorting, quantum computing, information processing, and optical communication.

In the future work, the researchers will investigate the phase change material based metasurface device using inverse design and develop controllable photon spin Hall effect devices.

The device separates light with different spins, the left-handed component is coupled into the left waveguide, and the right-handed component is coupled into the right waveguide.