This paper demonstrates the use of a zinc oxide (ZnO) thin film in a 1-μm ring laser cavity as a saturable absorber to successfully generate Q-switching pulses. The tunability of the laser pulses is achieved by integrating a tunable bandpass filter (TBPF) in an ytterbium-doped laser cavity that results in 9.4 nm of tuning range, which wavelength is from 1040.70 nm to 1050.1 nm. The peak energy in the pulse which is 1.47 nJ was measured together with a minimum pulse width of 2.4 μs. In addition, the repetition rate increases from 25.77 to 45.94 kHz as the pump power level being increased from 103.1 to 175.1 mW. The results obtained in this experiment demonstrated consistent results and stable throughout the experiment. Therefore, ZnO thin film is considered as a good candidate in 1-μm pulsed laser applications.

This review article is concerned with metamaterials, i.e. specifically engineered structures with special properties for interaction with sounds. The research on and practical design of these materials have gained momentum in the last decade, when 3D printing techniques provided the possibility to fabricate such geometrically complex structures. We briefly describe the history of research on AMMs and group them into active and passive metamaterials. For each of these groups of AMMs, we discuss the most notable construction achievements and outline the main applications. We conclude this review with a discussion of possible directions for further research and main applications of AMMs such as noise attenuation, acoustic lens, and the cloaking phenomenon.

This paper discusses a mem-capacitor circuit which is based on two MO-OTA along with a multiplier and 4 passive elements. This circuit is a charge-controlled memcapacitor emulator which is independent of any memristor also it consists the feature of electronic tunability. Additionally, this circuit is simpler and uses less hardware because it lacks a mutator and uses fewer active-passive components. The circuit behaviour is justified through various simulations in cadence Orcad tool with 180nm CMOS TSMC parameters. Additionally, conclusions from simulations and theory are validated experimentally through commercially available IC.

The paper is the second part of the work, devoted to a DC power supply with a power factor correction function. The power supply is equipped additionally with a shunt active power filter function, which enables the compensation of reactive and distortion power, generated by loads, connected to the same power grid node. A tunable inductive filter, included at the input of the power electronics current source – the main block of the power supply – allows for an improvement of the quality of the system control, compared to the device with a fixed inductive filter. This improvement was possible by extending the current source “frequency response”, which facilitated increasing the dynamics of current changes at the power supply input. The second part of the work briefly reminds the reader of the principle of operation and the structures of both the power supply control system and its power stage. The main purpose of this paper is to present the selected test results of the laboratory model of the electric system with the power supply.

The work presents a DC power supply with power factor correction (PFC). This device is also equipped with a parallel active filter function, which enables the possibility of compensation (minimization) of reactive and distortion power, generated by a group of loads, connected to the same power grid node. A passive filter with variable inductance applied at the input of the power supply allows for a significant improvement in quality of the system control (given specific criteria), as compared to the solution with a filter with fixed parameters. This is possible by increasing the dynamics of current changes at the power supply input (extending its “frequency response”). The paper presents the principle of operation as well as structures and models of the power supply control system and its power stage. Selected test results of the simulation model of the electric system with the power supply, in various operating conditions, are also presented.

Over the last twenty years, there has been a growing interest in the design of tunable devices at microwave frequencies by us- ing liquid crystals technology. In particular, the use of liquid crystals with high dielectric anisotropy allows manufacturing voltage-controlled devices to operate in a wide frequency range. In this work the frequency response of a liquid crystal band-pass filter with dual-mode microstrip structure has been studied in depth by using a simulation software tool. A reshap- ing of a conventional dual-mode square patch resonator bandpass filter with a square notch, studied in the literature, has been proposed with the goal of improving the filter performance. The main features achieved are a significant increase in the return loss of the filter and a narrowing of a 3-dB bandwidth. Specifically, a reduction in the filter bandwidth from 800 MHz to 600 MHz, which leads to a return loss increase from 6 dB to 12.5 dB, has been achieved. The filter centre frequency can be tuned from 4.54 GHz to 5.19 GHz.

This article proposes and examines a solution in which the base-station for the fifth generation radio access network is simplified by using a single millimeter-wave oscillator in the central-station and distributing its millimeter-wave signal to the base-stations. The system is designed in such a way that the low-phase-noise signal generated by an opto-electronic oscillator is transmitted from the central-station to multiple base-stations via a passive optical network infrastructure. A novel flexible approach with a single-loop opto-electronic oscillator at the transmitting end and a tunable dispersion-compensation module at the receiving end(s) is proposed to distribute a power-penalty-free millimeter-wave signal in the radio access network. Power-penalty-free signal transmission from 10 MHz up to 45 GHz with an optical length of 20 km is achieved by a combination of a tunable dispersion-compensation module and an optical delay line. In addition, measurements with a fixed modulation frequency of 39 GHz and discretely incrementing optical fiber lengths from 0.625 km to 20 km are shown. Finally, a preliminary idea for an automatically controlled feedback-loop tuning system is proposed as a further research entry point.

Self-swept erbium fiber laser emitting around 1.56 μm is reported in detail. Both sweep directions were registered: pointing toward longer and shorter wavelengths, redshift and blueshift sweeping, respectively. We describe method of determining the direction of the wavelength drift using the monochromator based optical spectrum analyzer. Possible root for this sweeping regime, i.e., the gain modulation along active fiber, is discussed with the help of a simple model calculating the overall cavity gain that can predict the direction of the laser wavelength sweeping.