Generation of ultra-short pulses using the Wilkinson adder

In this work the possibility of increasing the amplitude of ultra-short pulses and formation of a monocycle Gaussian by adding signals from several oscillators was investigated. For this purpose, the ring adders of Wilkinson design were used. The design of which has been chosen due to low losses and high input decoupling. The S-parameters of the adders with different geometrical parameters have been simulated in the frequency band up to 5 GHz. The obtained results coincided with the experimentally measured characteristics. The monopulse amplitude was increased and a bipolar pulse shape was formed by adding ultrashort pulses of equal and different polarities using the adders. This approach allows you to adjust the parameters of the output signal by adjusting the delays of the triggering signals.

Ultrawideband Antennas: Growth and Evolution

Narrowband antennas fail to radiate short pulses of nano- or picosecond length over the broader band of frequencies. Therefore, Ultrawideband (UWB) technology has gained momentum over the past couple of years as it utilizes a wide range of frequencies, typically between 3.1–10.6 GHz. UWB antennas have been utilized for various applications such as ground-penetrating radars, disaster management through detection of unexploded mines, medical diagnostics, and commercial applications ranging from USB dongles to detection of cracks in highways and bridges. In the first section of the manuscript, UWB technology is detailed with its importance for future wireless communications systems. In the next section various types of UWB antennas and their design methodology are reviewed, and their important characteristics are highlighted. In section four the concept of a UWB notch antenna is presented. Here various methods to obtain the notch, such as slots, parasitic resonators, metamaterials, and filters are discussed in detail. In addition, various types of important notch antenna design with their technical specifications, advantages, and disadvantages are presented. Finally, the need of reconfigurable UWB notch antennas is discussed in the next section. Here various insight to the design of frequency reconfigurable notch antennas is discussed and presented. Overall, this article aims to showcase the beginnings of UWB technology, the reason for the emergence of notching in specific frequency bands, and ultimately the need for reconfiguring UWB antennas along with their usage.

Nonequilibrium Band Occupation and Optical Response of Gold After Ultrafast XUV Excitation

Free electron lasers offer unique properties to study matter in states far from equilibrium as they combine short pulses with a large range of photon energies. In particular, the possibility to excite core states drives new relaxation pathways that, in turn, also change the properties of the optically and chemically active electrons. Here, we present a theoretical model for the dynamics of the nonequilibrium occupation of the different energy bands in solid gold driven by exciting deep core states. The resulting optical response is in excellent agreement with recent measurements and, combined with our model, provides a quantitative benchmark for the description of electron-phonon coupling in strongly driven gold. Focusing on sub-picosecond time scales, we find essential differences between the dynamics induced by XUV and visible light.

Dynamics of optical pulses in fiber optics

In this paper, we pay attention to the nonlinear dynamical behavior of ultra-short pulses in optical fiber. The new Hamiltonian amplitude equation is used as a governing model to analyze the pulses. We secure the ultra-short pulses in the forms of bright, dark, singular, combo and complex soliton solutions by the utilization of three of sound computational integration techniques that are protracted (or extended) Fan-sub equation method (PFSEM), the generalized exponential rational function method (GERFM), extended Sinh-Gordon equation expansion method (ShGEEM). Moreover, Jacobi’s elliptic, trigonometric, and hyperbolic functions solutions are also discussed as well as the constraint conditions of the achieved solutions are also presented. In addition, we discuss the different wave structures by the assistance of logarithmic transformation. The findings demonstrate that the examined equation theoretically contains a large number of soliton solution structures. By selecting appropriate criteria, the actual portrayal of certain obtained results is sorted out graphically in 3D and 2D profiles. The results suggest that the procedures used are concise, direct, and efficient, and that they can be applied to more complex phenomena. The resulting solutions are novel, intriguing, and potentially useful in understanding energy transit and diffusion processes in mathematical models of several disciplines of interest, including nonlinear optics. Our new results have been compared to these in the literature.

Simple interferometric setup enabling sub-Fourier-scale ultra-short laser pulses

In this work, we describe an interferometric method to generate ultra-short pulses below the Fourier limit. It is done by extending concepts first developed in the spatial domain to achieve sub-diffractive beams through the addition of a spatial chirp in one of the arms of a Michelson interferometer using a spherical mirror. To experimentally synthesize sub-Fourier pulses, we replace the spherical mirror with a water cell, since it produces chirp in the temporal domain. We also present an alternative procedure, based on asymmetrical interference between the widened pulse and the original pulse where the peaks of both pulses exhibit a temporal delay achieving the narrowing of ultra-short pulses with sub-Fourier scales. To characterize the performance of the system, we performed a preliminary assessment considering the percentage of FWHM shrinking obtained for each scheme. By means of a symmetrical configuration 7 and 12 \% pulse reductions were verified, both experimentally and analytically, while for the non-symmetrical configuration 10 and 24\% reductions were achieved corresponding to main lobe to side-lobes ratios of 10 and 30\% . The experimental setup scheme is simple, versatile and able to work with high-power laser sources and ultra-short pulses with a broad bandwidth at any central wavelength. The results presented in this work are promising and help to enlighten new routes and strategies in the design of coherent control systems. We envision that they will become broadly useful in different areas from strong field domain to quantum information.

Technological Processes for Steel Applications in Nuclear Fusion

Plasma facing components for energy conversion in future nuclear fusion reactors require a broad variety of different fabrication processes. We present, along a series of studies, the general effects and the mutual impact of these processes on the properties of the EUROFER97 steel. We also consider robust fabrication routes, which fit the demands for industrial environments. This includes heat treatment, fusion welding, machining, and solid-state bonding. Introducing and following a new design strategy, we apply the results to the fabrication of a first-wall mock-up, using the same production steps and processes as for real components. Finally, we perform high heat flux tests in the Helium Loop Karlsruhe, applying a few hundred short pulses, in which the maximum operating temperature of 550 °C for EUROFER97 is finally exceeded by 100 K. Microstructure analyses do not reveal critical defects or recognizable damage. A distinct ferrite zone at the EUROFER/ODS steel interface is detected. The main conclusions are that future breeding blankets can be successfully fabricated by available industrial processes. The use of ODS steel could make a decisive difference in the performance of breeding blankets, and the first wall should be completely fabricated from ODS steel or plated by an ODS carbon steel.

Single molecule kinetics of bacteriorhodopsin by HS-AFM

Bacteriorhodopsin is a seven-helix light-driven proton-pump that was structurally and functionally extensively studied. Despite a wealth of data, the single molecule kinetics of the reaction cycle remain unknown. Here, we use high-speed atomic force microscopy methods to characterize the single molecule kinetics of wild-type bR exposed to continuous light and short pulses. Monitoring bR conformational changes with millisecond temporal resolution, we determine that the cytoplasmic gate opens 2.9 ms after photon absorption, and stays open for proton capture for 13.2 ms. Surprisingly, a previously active protomer cannot be reactivated for another 37.6 ms, even under excess continuous light, giving a single molecule reaction cycle of ~20 s−1. The reaction cycle slows at low light where the closed state is prolonged, and at basic or acidic pH where the open state is extended.