Here, we experimentally demonstrate broadband nonlinear imaging by using Si resonant metasurfaces based on third-order nonlinear processes, including third harmonic generation (THG) and four-wave mixing (FWM). Particularly, the quadratic dependence of the FWM emission on the pump power allows to significantly reduce the dependence on high-power signal input in nonlinear imaging via designing a high-Q resonance at the pump wavelength based on bound states in the continuum (BICs). In the experiment, our metasurfaces support high-performance infrared imaging, including a large acceptance angle, a high frame rate, and a wide range of operating wavelengths (from 900 nm to 2500 nm).
We propose a metasurface-based shadow tomography protocol to measure the properties of quantum states efficiently. We design Si nano-disks based metagratings that act as efficient polarizing beam splitters and can distinguish orthogonal polarizations. This allows for the measurement of all necessary quantum state observables in parallel, reducing the time needed to characterize quantum states of photonic qubits and minimizes the impact of decoherence. We validate our protocol by performing numerical simulations of a two-qubit system with metasurface as quantum detectors. We show that the protocol can accurately estimate properties of quantum states with few measurements and without reconfiguring optical setups.
we exploit the resonance inside the slab to boost the second-harmonic generation from the lithium niobate half-etching-slab metasurface system, which hosts two kinds of BIC states formed by TE and TM odd modes. We reveal the mechanisms of the formation of the two BIC states and three main processes that influence the conversion efficiency from the pump light into the SH radiation. This approach of constructing boosted second-harmonic generation can be applied in any low-index nonlinear materials, which can expand a range of the applications, such as nonlinear imaging, quantum light source, and high-resolution sensing.
Herein, we report two different dual-periodic Photonic Crystals (PCs) in dichromated gelatin emulsion which are
fabricated by four-beam holography and double-exposure holography. The minibands with high Q-factors have been
evidently located in both two structures. By taking into account the non-uniform distribution of material, the numerical
results agree quite well with the experimental results. We also compared the band-edge lasing in single-periodic PC and
miniband lasing in Moiré dual-periodic PC. Due to extremely flat dispersion and large mode volume of the miniband,
high optical conversion efficiency in miniband lasing is achieved as compared with that of band-edge lasing. Such effect
may provide potential applications in low-threshold lasers and ultra-sensitive fluorescent probes in biological assays.
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