METHODS FOR MEASURING LASER POWER

Today we are witnessing the rapid development of the laser industry. Laser sources with new wavelengths, higher powers and energies, different modes of operation (generation of laser pulses), as well as various applications in industry, medicine, environmental protection etc. are emerging. This requires the development of new physical methods and principles for accurate measurement of power, energy, and other parameters of laser sources. In different types of laser technological processes, accurate measurement of laser power is extremely important in terms of quality, repeatability, and validation of the process. In most cases, accurate laser power measurement is a difficult task, especially when working with high-power lasers or having to perform real-time measurements.The report analyses and systematizes the physical principles and methods on which existing laser measuring instruments are based. This research also aims to help researchers and technologists find and develop new approaches to solving this challenging measurement problem.

COMPARATIVE ANALYSIS OF METHODS FOR MEASURING LASER POWER

The application of lasers in many fields of technology and medicine is constantly increasing. This causes the development of new physical methods and principles for correct measurement of power, energy, and other parameters of laser sources. In most cases, the correct measurement of the laser power is important because the quality of the processes in which laser sources are used depends on it. In the paper, a comparative analysis of the existing methods for measuring the power and energy of laser radiation of diverse types of laser sources is made. This research aims to help users of laser equipment to choose the right measurement method depending on the laser source

The Effect of Laser on the Efficiency of Biological Treatment of Pharmaceutical Wastewater

The aim of the work is to explain the danger of phenol and phenolic compounds to human health and the environment. In addition, it explains where and why pollution by phenol and its compounds occurs, especially in industrial wastewater. The authors investigate the possibility of using laser technologies for the decomposition of phenol, as well as for the purification of industrial wastewater from phenolic compounds. Treatment of wastewater from phenol and its compounds using microorganisms for biological treatment is widely used in the world. This method is economical and environmentally friendly. On the other hand, exceeding the permissible concentration of phenol, which is individual for each biological treatment plant, microorganisms in such treatment plants may die because they are poisoned by phenol or its compounds. Thus, the biological treatment of industrial wastewater is temporarily stopped until the concentration of phenol is reduced to an acceptable limit and the microorganisms recover. Such a procedure can take a long time and is unpredictable because microorganisms are sensitive to changing conditions. Based on this, literature sources have been explored. This could help to understand which laser devices can be used to split a phenol compound or a benzene ring into simple chemicals. It also helps to understand how phenol-containing wastewater affects the microorganisms of biological treatment plants and the course of the process, as well as to find a laser device that would not affect the usual conditions of microorganisms of biological treatment plants. Several experiments were carried out, including those with lasers, to exclude possible interfering factors and to prove the already known data for further scientific research

HIGHER EDUCATION IN THE REPUBLIC OF BULGARIA AT THE CROSSROAD - PROBLEMS AND MEASURES TO PREVENT THEM

This report identifies some of the problems of higher education in the Republic of Bulgaria related to the demographic crisis in the transition process and measures to overcome them. Emphasis is placed on the legislative framework, the rating system, the financing of higher education institutions and the science in them, the quality of training, the demand for staff from business and the supply of staff from universities, the admission of students and the offered forms of training. The analysis made by the authors is based on summarized data, which has been officially published, on the actual state of higher education in Bulgaria. Measures are proposed to overcome the problems, some of which are based on experience at the Technical University of Gabrovo.

ON THE POSSIBILITY OF LASER STRIPPING OF COMMUNICATION CABLES WITH LOW-POWER CO2 LASER

Laser engraving is one of the most commonly used laser procedures for interacting with laser material. The speed, ease of use and high precision make it an attractive process for use by manufacturers and for removing insulation from various cables. Cable stripping is a particularly common operation in aeronautics. The aircraft is equipped with several hundred kilometers of cables to control and operate the various systems of the aircraft and most of these cables must be stripped at both opposite ends to allow the cable to be connected to different terminals.This report examines the possibility of removing polyvinyl chloride (PVC) insulation from telecommunication cables of different colours and thicknesses up to 600 [μm]. The experimental measurements of the study were performed with a low-power continuous CO2 laser system. The main functional dependence of the width and depth of the ablation zone on the main technological parameters, such as the average power and the processing speed, have been experimentally studied. The zones of laser impact are observed with a laser microscope. The graphic dependencies are analyzed in order to determine the optimal working intervals.The analysis aims to help solve problems related to the application of small diameter communication cables in the production of various communication devices and components for the needs of industry

ALUMINUM AND STEEL WELDING WITH 500 W FIBRE LASER

The study of the process of laser welding of various aluminum-steel joints is necessary to promote the possibility of realization of new products and designs in instrumentation and mechanical engineering. Laser welding, due to its many advantages, is considered a very promising process of joining different materials, although its application in industry is still limited. Welding aluminum with steel using laser sources is a challenging task mainly due to the formation of brittle intermetallic joints (IMC) at the joint interface. This paper aims to give a brief overview of some new research on laser welding of aluminum to steel, as well as to point out some of our initial laboratory research in this direction.[1

POSSIBLE USE OF LASERS FOR CLEAVAGE OF PHENOLS TILL BASE SUBSTANCES (REVIEW)

The purpose of this review article is to explain the hazards of phenol and phenol compounds to human health and the environment. To describe where and how phenol and its compounds occur, especially in industrial effluents. To study the possibility of using laser technologies for phenol cleavage, as well as for the treatment of industrial wastewater from phenol compounds. Removal of phenol and its compounds using biological wastewater treatment process is widely used worldwide. This method is cost-effective and environmentally friendly. On the other hand, exceeding the tolerable phenol concentration, which is individual for each biological treatment plant, may result in severe intoxication and lead to death of activated sludge system. Thus, the biological treatment process of industrial wastewater is halted until the phenol concentration is reduced to an acceptable level and the microorganisms have time to recover. Such a procedure can be time consuming and unpredictable due to the susceptibility of microorganisms to changing conditions. Based on this, sources of literature have been studied that could help to understand which laser equipment can be used to cleave a phenolic compound or benzene ring to simpler compounds

APPLICATION OF A FINITE ELEMENT MODEL TO OBTAIN THE INFLUENCE OF THE TREATMENT’S POWER, REFLECION AND FOCAL DIAMETER IN LASER TEXTURING OF ALUMINUM

In this work, a numerical model of laser texturing is considered. A finite element model of a representative sample of pure aluminum was created. The impact of a laser pulse was simulated, assuming a Gaussian volume distribution of the heat flux. Material properties are assumed to be constant and latent heat is accounted for. Results are obtained for the thermal field and the width of the vaporized zone, assuming that the crater is characterized by its maximum width. The numerical model was used to study the influence of pulse power density, reflection, focal diameter and pulse duration. The ablation threshold at different laser pulse durations was determinate.

LASER AS A DEVICE FOR MEASUREMENT OF THIN THREADS - A SCHOOL LABORATORY EXPERIMENT IN PHYSICS

The physics of the last century is included in all EU curricula and emphasis in education is shifted from content to the forms, methods and means of teaching and learning. Different kinds of lessons (including laboratory classes) and their didactic structure are subject to the understanding, adoption and creating conditions to build motivation to learn physics and astronomy, active utilization of physical knowledge and building cognitive and practical skills. Performance of demonstration and laboratory classes using a laser device is a type of teaching strategy to good education in physics. Properties of laser light as observation, classification, communication, drawing conclusions, planning, interpretation and forecasting, are particularly suitable when monitoring and studying the phenomena of interference and diffraction. Through both qualitative and quantitate ways, in this paper is presented a physical experiment for measurement of thin threads in a High school from students. Experimental skills will enhance interest in physics and especially to modern applications of laser devices, as well as career guidance of students

THE CHANGE OF CONTRAST IS INVESTIGATION OF 75 STEEL SAMPLES LASER MARKED WITH DIFFERENT MODES

The quality of the marked surfaces changes the optical characteristics. The aim of the study is to optimize the contrast in laser marking of Steel 75. The influence of the step in the raster marking and the influence of the repetition frequency of the pulses on the reflection coefficient were analysed. The experimental investigations of the reflectance were carried out using a spectrophotometer. For the marked samples, it was found that when directing electromagnetic radiation with a wavelength in the studied range, there are areas with absorption and reflection of light. The reflectance is plotted as a function of marking step and laser frequency for the marked Steel 75 samples