The paper presents the long-term evolution and recent development of ultraviolet photodetectors. First, the general theory of ultraviolet (UV) photodetectors is briefly described. Then the different types of detectors are presented, starting with the older photoemission detectors through photomultipliers and image intensifiers. More attention is paid to silicon and different types of wide band gap semiconductor photodetectors such as AlGaN, SiC-based, and diamond detectors. Additionally, Ga₂O₃ is considered a promising material for solar-blind photodetectors due to its excellent electrical properties and a large bandgap energy. The last part of the paper deals with new UV photodetector concepts inspired by new device architectures based on low-dimensional solid materials. It is shown that the evolution of the architecture has shifted device performance toward higher sensitivity, higher frequency response, lower noise, and higher gain-bandwidth products.

At present there are many reasons for seeking new methods and technologies that aim to develop new and more perfect sensors for different chemical compounds. However, the main reasons are safety ensuring and health care. In the paper, recent advances in the human breath analysis by the use of different techniques are presented. We have selected non-invasive ones ensuring detection of pathogenic changes at a molecular level. The presence of certain molecules in the human breath is used as an indicator of a specific disease. Thus, the analysis of the human breath is very useful for health monitoring. We have shown some examples of diseases’ biomarkers and various methods capable of detecting them. Described methods have been divided into non-optical and optical methods. The former ones are the following: gas chromatography, flame ionization detection, mass spectrometry, ion mobility spectrometry, proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry. In recent twenty years, the optical methods have become more popular, especially the laser techniques. They have a great potential for detection and monitoring of the components in the gas phase. These methods are characterized by high sensitivity and good selectivity. The spectroscopic sensors provide the opportunity to detect specific gases and to measure their concentration either in a sampling place or a remote one. Multipass spectroscopy, cavity ring-down spectroscopy, and photo-acoustic spectroscopy were characterised in the paper as well.

Sensors and Systems for the Detection of Explosive Devices - An Overview: The paper presents analyses of current research projects connected with explosive material sensors. Sensors are described assigned to X and γ radiation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analyzed. Special attention was drawn to optoelectronic sensors of explosive devices.

The article presents state of work in technology of free-space optical communications (Free Space Optics − FSO). Both commercially available optical data links and their further development are described. The main elements and operation limiting factors of FSO systems have been identified. Additionally, analyses of FSO/RF hybrid systems application are included. The main aspects of LasBITer project related to such hybrid technology for security and defence applications are presented.

The review includes results of analyses and research aimed at standardizing the concepts and measurement procedures associated with photodetector parameters. Photodetectors are key components that ensure the conversion of incoming optical radiation into an electrical signal in a wide variety of sophisticated optoelectronic systems and everyday devices, such as smartwatches and systems that measure the composition of the Martian atmosphere. Semiconductor detectors are presented, and they play a major role due to their excellent optical and electrical parameters as well as physical parameters, stability, and long mean time to failure. As their performance depends on the manufacturing technology and internal architecture, different types of photodetectors are described first. The following parts of the article concern metrological aspects related to their characterization. All the basic parameters have been defined, which are useful both for their users and their developers. This allows for the verification of photodetectors’ workmanship quality, the capabilities of a given technology, and, above all, suitability for a specific application and the performance of the final optoelectronic system. Experimentally validated meteorological models and equivalent diagrams, which are necessary for the correct analysis of parameter measurements, are also presented. The current state of knowledge presented in recognized scientific papers and the results of the authors’ works are described as well.