The paper presents comparison of two different 3D models of vertical, rotating disc MOCVD reactor used for 3D GaN structure growth. The first one is based on the reactor symmetry, while the second, novel one incorporates only single line of showerhead nozzles. It is shown that both of them can be applied interchangeably regarding the phenomena taking place within the processing area. Moreover, the importance of boundary conditions regarding proper modelling of showerhead cooling and the significance of thermal radiation on temperature field within the modelled structure are presented and analysed. The last phenomenon is erroneously neglected in most of the hitherto studies.

A power device junction temperature is a limiting factor influencing the electrical properties of the electronic element. This article presents a new power diode DBW3-3500 that is encapsulated in a novel press-pack package integrated with a microchannel cooling system. A comprehensive field tests covering the conventional solution of DB3-3500 diode (Kubara Lamina) with single-sided and double-sided water heat sinks and the new diodes with the embedded cooler are shown and discussed. Conducted measurements for the rated current of 3500 A confirmed that the new package even with single-side cooling solution allows reducing the junction temperature of about 40 °C in comparison with the conventional liquid cold plates. Hence, the improvement of electrical parameters is also observed. Predicted rated forward current reaches 5000 A. Furthermore, the novel solution offers a reduction of the weight and dimensions of the whole system.

In this article the process of realization of ball-lensed optical fibers is described. The implementation of four different types of ball-lensed optical fibers developed in Optical Fibers Techniques Laboratory at Lodz University of Technology is presented. Focal lengths of the presented microlenses, which were obtained in simulations and measurements, are also shown in this paper.