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In this paper, a frequency-wavenumber decoupling algorithm with high-efficiency and high-precise for three-dimensional (3-D) multiple-input-multiple-output synthetic aperture radar (MIMO-SAR) imaging is proposed. Based on one-dimensional (1-D) MIMO array combined with synthetic aperture scan along another dimension, MIMO-SAR imaging scheme allows the number of array elements to be greatly reduced compared with the two-dimensional (2-D) MIMO arrays. By multi-dimensional Fourier transforming and Method of Stationary Phase (MSP), analytical expression of the object function in the frequency-wavenumber domain was derived. By further expanding the range Fourier transform factor to its Taylor series form, the range compression can be realized by a simple fast Fourier transform (FFT) without multi-dimensional interpolation. After that, a decoupling factor was multiplied to compensate for the cross-range and range coupling in frequency domain. Finally, 2-D IFFT is carried out after rearrangement in the MIMO spatial frequency to get a fully focused 3-D image. Simulation and experimental results demonstrated that the algorithm can obtain the same high-precision images as back projection (BP) algorithm, and has the same high efficiency as range migration algorithm (RMA) while avoiding cumbersome multi-dimensional interpolation. A bistatic prototype imaging system in 0.1 THz band was designed for the proof-of-principle experiments. The 3-D reconstruction results of different targets were presented to verify the theoretical results and effectiveness of the proposed algorithm for MIMO-SAR imaging.We present a numerical study of optical torque between two twisted metal nanorods due to the angular momentum of the electromagnetic field emerging from their plasmonic coupling. Our results indicate that the interaction optical torque on the nanorods can be strongly enhanced by their plasmon coupling, which highly depends on not only the gap size but also the twisted angle between the nanorods. The behaviors of the optical torque are different between two plasmon coupling modes hybridized bonding and anti-bonding modes with different resonances. The rotations of the twisted nanorods with the bonding and anti-bonding mode excitations lead to mutually parallel and perpendicular alignments, respectively. At an incident intensity of 10 mW/μm2, the rotational potential depths are more than 30 times as large as the Brownian motion energy, enabling the optical alignments with angle fluctuations less than ∼±10°. Thus, this optical alignment of the nanoparticles with the plasmon coupling allows dynamic control of the plasmonic characteristics and functions.Tandem organic solar cells (OSCs) show great potential due to advantages such as the utilization of wide-spectrum light and low thermalization loss. The current mismatch between sub-cells is one of the major issues reducing the final output efficiency of a tandem device. In this paper, we focus on the current mismatch of tandem OSCs at oblique incidence and aim to reduce its adverse effect on the performances of realistic devices working at varying incident angle. Firstly, we propose an optical analysis method based on the 4×4 matrix formalism to analyze and optimize the performance of tandem solar cells at arbitrary incident angles. NVP-AEW541 research buy Compared with those optimal designs via matching the currents of sub-cells only at normal incidence, the proposed method chooses the optimal structure of the tandem device by maximizing the generated energy density per day with considering the current match at different incident angles during daytime. With the proposed method, a typical tandem organic solar cell is optimized as an example, and the optimized tandem device has a balanced current match at all incident angles during a whole day. Experimental results demonstrate that the generated energy density per day of the optimized tandem device has increased by 4.9% compared to the conventional device optimized only at normal incidence. The proposed method and results are expected to provide some new insights for the performance analysis and optimization of tandem or multi-junction solar cells, especially those devices exhibiting serious current mismatch between sub-cells at varying incident angles in practical applications.Currently, optics such as dielectric lenses and curved reflector dishes are commonplace in terahertz laboratories, as their functionality is of fundamental importance to the majority of applications of terahertz waves. However, such optics are typically bulky and require manual assembly and alignment. Here we seek to draw inspiration from the field of digital electronics, which underwent rapid acceleration following the advent of integrated circuits as a replacement for discrete transistors. For a comparable transition with terahertz optics, we must seek mask-oriented fabrication processes that simultaneously etch multiple interconnected integrated optics. To support this goal, terahertz beams are confined to two dimensions within a planar silicon slab, and a gradient-index half-Maxwell fisheye lens serves to launch such a slab-mode beam from a terahertz-range photonic crystal waveguide that is coupled to its focus. Both the optic and the waveguide are implemented with through-hole arrays and are fabricated in the same single-etch process. Experiments indicate that a slab-mode beam is launched with ∼86% efficiency, over a broad 3 dB bandwidth from ∼260 to ∼390 GHz, although these reported values are approximate due to obfuscation by variation that arises from reflections within the device.An optical conversion node scheme for direct detection of complex modulation format is proposed to bridge long-haul transmissions and short-reach interconnects. A noisy 10G Baud quadrature phase shift keying signal is converted into a 10G Baud normal 4-level pulse amplitude modulation (PAM4) signal by the node. The conversion node is realized mainly relies on four-wave mixing-based phase-sensitive amplifiers. The power ratio and constellation shape of the converted PAM4 both can be flexibly designed based on network demands and five kinds of uniform or non-uniform PAM4s are generated to verify the shaping functionality. With the input optical signal-to-noise ratio range of (10 dB∼30 dB), the key indicators of the signals went through every part are measured, includes constellations, eye diagrams, error vector magnitudes, bit error rates, normalized impact factors of phase and amplitude. The proposed node scheme has great application potential in intermediate nodes for bridging long-haul transmissions and short-reach interconnects, hierarchical modulation and flexible constellations design for advanced format signals.
Read More: https://www.selleckchem.com/products/NVP-AEW541.html
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