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In this paper, a vertical stacked near-infrared (NIR) and extended short wavelength infrared (eSWIR) dual-band detector based on InGaAs and In0.53Ga0.47As/GaAs0.5Sb0.5 type-II superlattice (T2SL) is presented. A barrier layer of AlAs0.56Sb0.44 allows the independent working of the two sub-detectors. The InGaAs NIR sub-detector operates under positive bias, while the eSWIR band detector operates under reverse bias. The NIR sub-detector shows a dark current density of 7.35 × 10−5 A/cm2 under the bias of 0.1 V, the responsivity of 0.88 A/W, and a specific detectivity of 4.69 × 1011 cm· Hz1/2/W at 1510 nm. Meanwhile, the dark current density of eSWIR sub-detector is 8.68 × 10−4 A/cm2 under −0.4 V with the corresponding responsivity of 0.21 A/W, and a specific detectivity of 1.85×1010 cm·Hz1/2/W at 2 μm. Furthermore, a single-pixel imaging system is built to demonstrate the capability of dual-band detectors in information capturing and target recognition. [ABSTRACT FROM AUTHOR]

In this work, an In0.53Ga0.47As/GaAs0.5Sb0.5 type-II superlattice(T2SL) based broadband photodetector with an optical spectrum response ranging from 250 nm to 2400 nm is demonstrated. The photodetector shows a low dark current density of $3.48\times 10^{-4}$ A/cm2 under the bias of −1 V and a specific detectivity (D*) of $1.59\times 10^{10}$ cm $\cdot $ Hz1/2/W at $2 ~\mu \text{m}$ at 293 K. A recessed window on the surface of the top P layer was fabricated to enhance the responsivity of ultraviolet (UV) and visible band. The UV and visible band quantum efficiency (QE) can increase by 40% with the recessed window. [ABSTRACT FROM AUTHOR]

Large-scale complex surfaces are the core components of large aircraft, ships, and wind turbine generators. High-accuracy manufacturing of the components is very crucial for its performance. Automated and high-accuracy large-scale 3-D measurement is an effective means for the manufacturing accuracy control of these components. This article proposes an automated mobile robotic profile measurement method for large-scale complex surfaces, and it also proposes a high-accuracy point clouds alignment algorithm to improve the measurement accuracy. A fringe projection scanner, integrated on the end of a mobile robot, is utilized to scan the surface and obtain the local scanning point clouds. The local scanning point clouds’ coarse alignment is implemented using the robot’s joint data and the laser sensor’s positioning data. After that, a fine alignment algorithm combining the fruit fly optimization algorithm (FOA) with the improved iterative closest point (IICP) algorithm is proposed for point clouds’ fine alignment. Practical measurement was performed on a sectional wind turbine blade, and a broad region of $4.6 \text { m} \times 2.6$ m was measured. An accuracy evaluation method based on point-to-plane distance was adopted to evaluate the measurement error. The result that the mean distance error is less than 0.4 mm shows the proposed mobile robotic measurement system and the aligning method are of high accuracy. [ABSTRACT FROM AUTHOR]

We examine the potential of frequency-dependent Rayleigh wave ellipticity, derived from microtremors, for the investigation of heterogeneous subsurface structure. Based on numerical simulation, we analyse the effects of interference waves in microtremors, primarily the various propagation directions of the Rayleigh waves, linear polarization waves and white noise, on the ellipticity frequency-dependent estimation of the Rayleigh waves. A data processing scheme to separate the Rayleigh waves from the interference waves is proposed and verified by synthetic data. We performed a field experiment in the mountainous areas of Southwest China to show that the ellipticity frequency dependence of Rayleigh waves in the period range of 0.05–5 s can be estimated from the microtremor records with the proposed data processing scheme. In addition, the method is feasible for investigating lateral heterogeneity within the top several hundred metres in the mountain regions. The study also reveals that the features of the ellipticity anomaly of a local heterogeneity are related to the propagation directions of the Rayleigh waves, and to reduce the ambiguity of the anomaly, the propagation direction of the waves picked for the ellipticity estimation should be consistent with (along or opposite to) that of the survey line. Then, to eliminate the effects of the phase differences due to the propagation direction, or time, the ellipticity for each location should be estimated by a single event rather than multiple events from the derived Rayleigh wave arrivals. [ABSTRACT FROM AUTHOR]