No abstract

Wide field‐of‐view (FOV), label‐free, super‐resolution imaging is demonstrated using a specially designed waveguide chip that can illuminate a sample with multicolor evanescent waves travelling along different directions. The method is enabled by a polymer fluorescent film that emits over a broad wavelength range. Its polygonal geometry ensures coverage over all illumination directions, enabling high‐fidelity image reconstruction while minimizing distortion and image blurring. By frequency shifting and iterative stitching of different spatial frequencies in Fourier space, the reconstruction of 2D samples is achieved without distortion over wide FOVs. The fabrication process is facile and compatible with conventional semiconductor‐fabrication methods. The super‐resolution chip (SRC) can thus be produced with high yield, offering opportunities for potential conjunction of super‐resolution techniques integrated optical circuits or for the development of single‐use diagnostic kits.

No abstract

We demonstrate a highly polarized single mode nanobelt laser with a low threshold. Different from the traditional nanobelt lasers, the laser cavity is formed along the lateral direction of the nanobelt and the wavelength is centered at 712.6 nm with a linewidth of about 0.18 nm. The single mode lasing emission is highly polarized with a polarization ratio of about 0.91. Moreover, the threshold is as low as 18 μJ/cm2 which is about an order of magnitude lower than that of the traditional CdSe nanobelt lasers. These low threshold high polarization single mode nanobelt lasers offer great potential as a low cost and energy efficient choice of technology for applications in visible light communications, displays, optical sensing, and environmental monitoring.

No abstract

The diffraction limit substantially impedes the resolution of the conventional optical microscope. Under traditional illumination, the high-spatial-frequency light corresponding to the subwavelength information of objects is located in the near-field in the form of evanescent waves, and thus not detectable by conventional far-field objectives. Recent advances in nanomaterials and metamaterials provide new approaches to break this limitation by utilizing large-wavevector evanescent waves. Here, a comprehensive review of this emerging and fast-growing field is presented. The current superresolution imaging techniques based on evanescent-wave-assisted spatial frequency modulation, including hyperlens, microsphere lens, and evanescent field-illuminated spatial frequency shift microscopy, are illustrated. They are promising in investigating unobserved details and processes in fields such as medicine, biology, and material research. Some current challenges and future possibilities of these superresolution methods are also discussed.

No abstract

In this paper, we investigate resource allocation issue in OFDMA-based decode-and-forward cooperative networks and propose joint subcarrier and power allocation schemes. The optimal solution of this combinable allocation has high computational complexity, so we divide our solution into two steps. The first step is to distribute subcarriers to relays and destination under the assumption of equal power distribution. Here, we propose Proportional Allocation (PA) strategy to achieve tradeoff between total throughput and fairness. To further improve the system performance, we introduce threshold into PA strategy, named Proportional Allocation with Threshold (PA-T), where subcarriers with bad performance are prevented from transmitting. Next, water-filling method is adopted to distribute the power to cooperative links in order to fully utilize the limited power. Simulation results show that system performance of the proposed schemes is significantly enhanced compared with an existing resource allocation scheme. Besides, the resource allocation schemes with water-filling method notably outperform schemes with equal power allocation.