Due to the recent groundbreaking developments of nanotechnologies, it became possible to create intrinsically quantum systems able to serve as high-directional antennas in terahertz, infrared, and optical ranges. In fact, the quantum antennas, as devices shaping light on the level of single quanta, have already become key elements in nanooptics and nanoelectronics. The quantum antennas are actively researched for possible implementations in quantum communications, quantum imaging and sensing, and energy harvesting. However, the design and optimization of these emitting/receiving devices are still rather undeveloped in comparison with the well-known methods for conventional radio-frequency antennas. This review provides a discussion of the recent achievements in the concept of the quantum antenna as an open quantum system emitting via interaction with a photonic reservoir. The review is focused on bridging the gap between quantum antennas and their macroscopic classical analogues. Furthermore, the way of quantum-antenna implementation is discussed for different configurations, based on such materials as plasmonic metals, carbon nanotubes, and semiconductor quantum dots.

Here, we show that, contrary to the common opinion, the super-resolution optical fluctuation microscopy might not lead to ideally infinite super-resolution enhancement with increasing of the order of measured cumulants. Using information analysis for estimating error bounds on the determination of point sources positions, we show that reachable precision per measurement might be saturated with increasing of the order of the measured cumulants in the super-resolution regime. In fact, there is an optimal correlation order beyond which there is practically no improvement for objects of three and more point sources. However, for objects of just two sources, one still has an intuitively expected resolution increase with the cumulant order.

The structural characterization of multilayer thin coatings is performed by X-ray diffraction using a noncoplanar measurement geometry. The application of such a measurement geometry enables a reliable and comprehensive microstructural analysis of the material comparing to other measurement geometries due to the accessibility to a larger number of measured Bragg reflections. The important advantage of noncoplanar geometry is a measurement setup without tilting and rotating the sample. A set of profiles for different Bragg reflections is measured for several multilayer coatings with different thicknesses of individual layers; the obtained profiles are combined into a single scan for the simultaneous fittingby a theoretical curve. The broadening of the diffraction profiles is considered to be affected by a small grain size and instrumental effects, with the grains being modeled by ellipsoidal shape with two equal in-plane axes. Based on the proposed fitting procedure, the microstructural parameters of multilayer coatings are evaluated, including the grains size in parallel and normal to the surface directions. The dependence of evaluated grains size on the measurement direction confirms the validity of the selected grains model. The microstructural parameters evaluated from noncoplanar X-ray diffraction show a good agreement with those obtained from HRTEM and STEM techniques.

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