Due to the excellent electrical and optical properties and their integration capability without lattice matching requirements, low-dimensional materials have received increasing attention in silicon photonic circuits. Bi2O2Se with high carrier mobility, narrow bandgap, and good air stability is very promising for high-performance near-infrared photodetectors. Here, the chemical vapor deposition method is applied to grow Bi2O2Se onto mica, and our developed polycarbonate/polydimethylsiloxane-assisted transfer method enables the clean and intact transfer of Bi2O2Se on top of a silicon waveguide. We demonstrated the Bi2O2Se/Si waveguide integrated photodetector with a small dark current of 72.9 nA, high responsivity of 3.5 A·W–1, fast rise/decay times of 22/78 ns, and low noise-equivalent power of 15.1 pW·Hz–0.5 at an applied voltage of 2 V in the O-band for transverse electric modes. Additionally, a microring resonator is designed for enhancing light–matter interaction, resulting in a wavelength-sensitive photodetector with reduced dark current (15.3 nA at 2 V) and more than a 3-fold enhancement in responsivity at the resonance wavelength, which is suitable for spectrally resolved applications. These results promote the integration of Bi2O2Se with a silicon photonic platform and are expected to accelerate the future use of integrated photodetectors in spectroscopy, sensing, and communication applications.

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Traditional centroid-based clustering algorithms for heterogeneous data with numerical and non-numerical features result in different levels of inaccurate clustering. This is because the Hamming distance used for dissimilarity measurement of non-numerical values does not provide optimal distances between different values, and problems arise from attempts to combine the Euclidean distance and Hamming distance. In this study, the mutual information (MI)-based unsupervised feature transformation (UFT), which can transform non-numerical features into numerical features without information loss, was utilized with the conventional k-means algorithm for heterogeneous data clustering. For the original non-numerical features, UFT can provide numerical values which preserve the structure of the original non-numerical features and have the property of continuous values at the same time. Experiments and analysis of real-world datasets showed that, the integrated UFT-k-means clustering algorithm outperformed others for heterogeneous data with both numerical and non-numerical features.

The design of a broadband tunable absorber is proposed based on a thin vanadium dioxide metasurface, which is composed of a simple array of vanadium dioxide and a bottom gold film. When the conductivity of vanadium dioxide is equal to 2000 −1 cm −1 , simulated absorptance exceeds 90% with 71% bandwidth from 0.47 to 0.99 THz and full width at half maximum is 98% from 0.354 to 1.036 THz with center frequency of 0.695 THz. Simulated results show that absorptance peak can be tuned from 5% to 100% when the conductivity changes continually from 10 −1 cm −1 to 2000 −1 cm −1 . The designed absorber may have useful applications in terahertz spectrum such as energy harvesting, thermal emitter, and sensing.

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Hybrid integration of van der Waals materials on a photonic platform enables diverse exploration of novel active functions and significant improvement in device performance for next-generation integrated photonic circuits, but developing waveguide-integrated photodetectors based on conventionally investigated transition metal dichalcogenide materials at the full optical telecommunication bands and mid-infrared range is still a challenge. Here, we integrate PdSe 2 with silicon waveguide for onchip photodetection with a high responsivity from 1260 to 1565 nm, a low noise-equivalent power of 4.0 pW•Hz −0.5 , a 3-dB bandwidth of 1.5 GHz, and a measured data rate of 2.5 Gbit•s −1 . The achieved PdSe 2 photodetectors provide new insights to explore the integration of novel van der Waals materials with integrated photonic platforms and exhibit great potential for diverse applications over a broad infrared range of wavelengths, such as on-chip sensing and spectroscopy.