Multiple human parsing aims to segment various human parts and associate each part with the corresponding instance simultaneously. This is a very challenging task due to the diverse human appearance, semantic ambiguity of different body parts, and complex background. Through analysis of multiple human parsing task, we observe that human-centric global perception and accurate instance-level parsing scoring are crucial for obtaining high-quality results. But the most state-of-the-art methods have not paid enough attention to these issues. To reverse this phenomenon, we present Renovating Parsing R-CNN (RP R-CNN), which introduces a global semantic enhanced feature pyramid network and a parsing re-scoring network into the existing high-performance pipeline. The proposed RP R-CNN adopts global semantic representation to enhance multi-scale features for generating human parsing maps, and regresses a confidence score to represent its quality. Extensive experiments show that RP R-CNN performs favorably against state-of-the-art methods on CIHP and MHP-v2 datasets. Code and models are available at https://github.com/soeaver/RP-R-CNN.
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 19 nm-thick 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 phase-matching 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.
Optical metasurfaces are endowed with unparallel flexibility to manipulate the light field with a subwavelength spatial resolution. Coupling metasurfaces to materials with strong optical nonlinearity may allow ultrafast spatiotemporal light field modulation. However, most metasurfaces demonstrated thus far are linear devices. Here, we experimentally demonstrate simultaneous spatiotemporal laser mode control using a single-layer plasmonic metasurface strongly coupled to an epsilon-near-zero (ENZ) material within a fiber laser cavity. While the geometric phase of the metasurface is utilized to convert the laser's transverse mode from a Gaussian beam to a vortex beam carrying orbital angular momentum, the giant nonlinear saturable absorption of the ENZ material enables pulsed laser generation via the Q-switching process. The direct integration of a spatiotemporal metasurface in a laser cavity may pave the way for the development of miniaturized laser sources with tailored spatial and temporal profiles, which can be useful for numerous applications, such as superresolution imaging, high-density optical storage, and three-dimensional laser lithography.
Modern communications and microwave photonics require compact electro‐optic modulators with ultrahigh bandwidth and low power consumption. These requirements can be satisfied by integrated lithium–niobate electro‐optic modulators with high bandwidth and low power consumption. However, most integrated lithium–niobate modulators cannot achieve a good balance between an ultracompact size and a high modulation bandwidth. These challenges are overcome by designing an integrated lithium–niobate periodic dielectric waveguide modulator, featuring a compact modulation length of 87.4 μm, a theoretical modulation bandwidth over 600 GHz, a voltage‐length product of 0.0874 V cm, and a high sideband suppression ratio up to 36.1 dB. These performances are achieved by taking advantage of a capacitor configuration consisting of a nonresonant periodic dielectric waveguides sandwiched between two indium tin oxide (ITO) electrodes. This design provides an ultrabroadband and compact solution to next‐generation communications and microwave photonics.
Dielectric metasurfaces supporting Mie resonances can allow significantly boosted and tailored nonlinear light–matter interactions at the nanoscale. However, nonlinear dielectric metasurfaces typically only have odd‐order nonlinearities, unless resorting to material systems such as GaAs, GaP, or LiNbO3, each with unique challenges in device fabrication and integration. As the most widely adopted constituent material of metasurfaces, silicon (Si) does not possess an intrinsic second‐order nonlinear susceptibility. Herein, second‐harmonic generation (SHG) in a Si metasurface strained by a silicon nitride (SiN
x
) cladding layer is demonstrated. Utilizing the stress caused by the SiN
x
layer to break the inversion symmetry of the bulk Si crystal, greatly enhanced SHG in the strained Si metasurface compared with that from an unpatterned Si film with the SiN
x
cladding layer, with an experimentally measured conversion efficiency as high as 4.2 × 10−5 W−1, is observed. Experiments are further performed and it is concluded that the enhanced SHG is most likely due to the applied stress instead of charged defects in the SiN
x
cladding. This work opens a new route to realizing dielectric metasurfaces with second‐order nonlinearity in a complementary metal–oxide–semiconductor (CMOS)‐compatible platform.
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