| 1 | Versatile on-chip light coupling and(de)multiplexing from arbitrary polarizations to controlled waveguide modes using an integrated dielectric metasurface显示文摘Metasurfaces have found broad applicability in free-space optics,while its potential to tailor guided waves remains barely explored.By synergizing the Jones matrix model with generalized Snell’s law under the phase-matching condition,we propose a universal design strategy for versatile on-chip mode-selective coupling with polarization sensitivity,multiple working wavelengths,and high efficiency concurrently.The coupling direction,operation frequency,and excited mode type can be designed at will for arbitrary incident polarizations,outperforming previous technology that only works for specific polarizations and lacks versatile mode controllability.Here,using silicon-nanoantenna-patterned silicon-nitride photonic waveguides,we numerically demonstrate a set of chip-scale optical couplers around 1.55μm,including mode-selective directional couplers with high coupling efficiency over 57%and directivity about 23 d B.Polarization and wavelength demultiplexer scenarios are also proposed with 67%maximum efficiency and an extinction ratio of 20 d B.Moreover,a chip-integrated twisted light generator,coupling free-space linear polarization into an optical vortex carrying 1 h orbital angular momentum(OAM),is also reported to validate the mode-control flexibility.This comprehensive method may motivate compact wavelength/polarization(de)multiplexers,multifunctional mode converters,on-chip OAM generators for photonic integrated circuits,and high-speed optical telecommunications. | YUAN MENG ZHOUTIAN LIU ZHENWEI XIE RIDE WANG TIANCHENG QI FUTAI HU HYUNSEOK KIM QIRONG XIAO XING FU QIANG WU SANG-HOON BAE MALI GONG XIAOCONG YUAN | 2020 | Photonics Research2020，8，4： | 8 |
| 2 | Broadband terahertz wave generation from an epsilon-near-zero material显示文摘Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals. | Wenhe Jia Meng Liu Yongchang Lu Xi Feng Qingwei Wang Xueqian Zhang Yibo Ni Futai Hu Mali Gong Xinlong Xu Yuanyuan Huang Weili Zhang Yuanmu Yang Jiaguang Han | 2021 | Light(Science & Applications)2021，10，1： | 4 |
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