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Terahertz wireless communications is an increasingly interesting research topic due to the high demand for un-allocated channels and high data rates. Photonic solutions have shown great potential in this field. However, most photonics assisted THz links so far have employed optoelectronics only on the transmit side. Thus, the full potential of photonic THz communication has not been utilized yet. Here, we introduce optoelectronics also on the receive side by using a photoconductive antenna based heterodyne THz detector. This allows down-conversion of data signals from the W-, D-, and THz-band to the baseband using a laser beat signal as local oscillator. Using electromagnetic modeling, we designed passive radio frequency structures and a receiver package to handle high intermediate frequency output signals. In a homodyne spectroscopic setup, the receiver shows a frequency response superior to state-of-the-art photoconductive antennas due to an improved photoconductive material. In a heterodyne testbed, the receiver exhibits a large intermediate frequency bandwidth of 11 GHz and a conversion gain of −47 dB. This enabled us to employ the receiver in a fully photonic wireless link at sub-terahertz and terahertz frequencies together with a PIN photodiode emitter. We achieved error-free transmission of 4-QAM signals with gross data rates up to 12 Gbit/s at carrier frequencies up to 320 GHz. This work shows the huge potential of optoelectronic receivers for THz wireless communications and enables the exploration of full photonic THz links.

To guarantee sufficient surge current fault protection for power electronic converters, power semiconductors have to be tested under appropriate surge current conditions. Standard maximum surge current values include the permissible fault current amplitude, or the I2t-value; however, they might not be sufficient to describe a power semiconductor's performance under all potential fault conditions. Surge current sources based on passive components are state-of-the-art, but are limited to usually only one specific current waveform. This article describes the topology and the design of a new modular and highly dynamic surge current source for power semiconductor tests with adjustable current waveforms. The new modular converter concept is introduced, with two potential operation modes: High current mode (HCM) and dynamic current mode (DCM). The requirements for the surge current tester are defined, and the electrical and mechanical design are described, including the modulation scheme and control. Experimental investigations prove the function of the current source with peak currents up to 100 kA (HCM) and the realization of highly dynamic load current trajectories with peak currents up to 50 kA (DCM). The output current ripple is exceptionally small with a theoretical value of below 1%.

This article presents an analysis of selected characteristics of the modular multilevel matrix converter (M3C) operating a doubly fed induction generator (DFIG) in a flywheel energy storage system. A detailed analysis of the necessary electrical input and output quantities, as well as the identification of required internal currents and voltages, leads to a newly introduced iterative design process for the converter. This process ultimately provides information on the required number of submodules and demonstrates the overload capability of the converter in reactive power operation. Also, the short-circuit current contribution of the system for this unique configuration of M3C and DFIG is investigated for the first time. Taking into account the unique operating characteristics of the M3C, a loss analysis of the converter and the machine is performed, and a loss-optimized distribution of reactive power between the machine and the converter is proposed. The article is conducted analytically and is validated by experimental results on a small-scale demonstrator.

MicroLED arrays with the capability of switching each pixel separately with high frequency can serve as structured micro-illumination light engines for applications in sensing, optogenetics, microscopy and many others. We describe a scalable chip process chain for the fabrication of passive-matrix microLED arrays, which were integrated with PCB-based driving electronics. The arrays were produced by deep-etching of conventional planar LED structures on sapphire, followed by filling and planarization steps. The pixel resolution lies in the range of 254 to 2540 pixels-per-inch (ppi), the arrays consist of 32 x 32 pixels. Optical output powers up to 50 µW per pixel were measured. In comparison to CMOS-based approaches, the presented technology is a simplified strategy to produce microLED arrays with high pixel counts.

In this paper, we present an universal solution for radio frequency (RF) and laser cavities regulation, including piezocontrols and drivers based on MicroTCA.4 electronics. The control electronics consists of an Analog to Digital Converter-advanced mezzanine card (AMC) with an analog rear transmission module (RTM) to downmix and measure the RF signals and a low cost AMC-based Field Programmable Gate Array mezzanine card carrier for fast data processing and digital feedback operation connected to an RTM piezodriver. For the RF cavity regulation, the piezodriver includes additional inputs to use piezoelements as active force sensors. The fine tuning of the laser is carried out using a cavity fiber stretcher. The coarse tuning of the supported optics is done using a piezomotor-driven linear stage. Both channels can be operated using digital feedback controllers. First, results from continuous wave operation of the RF field controller and the cavity active resonance control with the piezotuners are demonstrated. The laser lock application performance using both fine and coarse channel feedbacks is shown and briefly discussed. [ABSTRACT FROM AUTHOR]