For the true time delay (TTD) of optical fiber changes with temperature, integrated optical chips are proposed to improve the delay consistency among channels. A 5-bit TTD chip is proposed in this paper. By using cascaded switches and optical waveguides, the chip is switchable and wavelength independent. A beamforming system operating at 6GHz is established for demonstration. 7 beam directions covering ±15° is obtained with proper mainside lobe ratio.
Optical resolution photoacoustic microscopy (ORPAM) is important for various biomedical applications, such as the study of cellular structures, microcirculation systems, and tumor angiogenesis. However, the lateral resolution of a conventional ORPAM is limited by optical diffraction. In this work, we report a simulation study to achieve subdiffraction-limited super-resolution in ORPAM using microspheres. Laser radiation is focused through a microsphere to generate a photonic nanojet, which provides the possibility to break the diffraction limit in ORPAM by reducing the size of the excitation volume. In our simulations using microspheres, we observed improvement in the lateral resolution up to ∼fourfold compared to conventional ORPAM. The method is simple, cost effective, and can provide far-field resolution. This approach may provide new opportunities for many biomedical imaging applications that require finer resolution.
As accurate prediction of traffic flow states could reduce the congestion possibility, the theoretical study of air traffic was how to determinate the next time the state with fluid mechanics based on random condition. Then, a novel depicting method of air traffic flow is proposed, which calculated the change of net amount in flow conservation equation with discrete time loss queuing, further, it could determine the relationship between flow and density. Compared to the existing general algorithm, the threshold of net amount was presented in the method, and it had good adaptability.
By introducing a line defect and a V-shaped defect into two-dimensional triangular lattice photonic crystals, a 60 deg beam bend, a Y-shaped beam slitter, and a one-to-three beam splitter are designed based on the self-collimation effect of photonic crystals (PCs). By analyzing the equi-frequency contours calculated with the plane wave expansion method, the frequency for self-collimation in the PC is determined. By using the finite-difference time-domain method, the beam bending efficiency and splitting ratios of the device as a function of the defect radius are calculated. These results are confirmed by computational simulations that provide field distributions of light propagating in the structures. The designed beam bend and splitters offer more choices for beam control in the design of photonic integrated circuits.
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