Sofia, Dec 13 (BTA/GNA) – Bulgarian scientist Prof. DSc Nikola V. Sabotinov is the creator of a new kind of gas lasers with copper bromide vapour, protected by 26 inventions in Bulgaria and patents in the USA, Japan, Germany, France, Australia and other countries. The lasers are manufactured in Bulgaria and Australia and have been implemented in the medical practice. As of 2019, the number of scientific publications of Academician Sabotinov cited by other authors in the scientific literature is about 1,390. His name is listed in the Golden Book of the Patent Office of the Republic of Bulgaria.
Nikola Sabotinov has 30 patents in the fields of laser physics and technology, which answer questions that the world scientific practice has been looking for solutions for years. Bulgarian lasers help doctors worldwide to tackle complex dermatological problems, researchers use them to investigate the topography of the seabed, these lasers ensure the accuracy of telescopes and the purity of the air, and they amuse with light shows in the sky.
In an interview for BTA, the academician said that although retired, he continues to follow what is happening in the laboratory he had created in the field of laser sources. The Metal Vapor Lasers Laboratory at the Institute of Solid State Physics with the Bulgarian Academy of Sciences (BAS) focuses on various metal vapour lasers, which can generate a wide spectral range of different laser transitions and enable the generation of very high powers. Because of these valuable qualities of metal vapour lasers, I once oriented myself towards this class of lasers, and subsequently created the laboratory, where significant contributions have been made to the global scientific practice, the scientist said.
Sabotinov began work in the area in 1970 when he put a cadmium vapour laser into operation in the laboratory, which still operates in the blue region of the spectrum. His research began during his student years in the 1960s, when laser sources first appeared in the USA, and research also began in Bulgaria. The first laser in Bulgaria, launched at the Institute of Electronics by senior research fellow Vasil Stefanov, was a replication of the American result with the ruby laser. At that time Sabotinov was a 4th year student in Bulgaria and visited the Institute’s laboratory to learn about this scientific achievement. The scientists recalls that then it was his first encounter with the laser and that he “fell in love” with the field even then. He became a laboratory cruiser and participated in the commissioning of the first helium-neon gas laser in Bulgaria. Later, he wrote his thesis was on helium laser research – the first student thesis in this field in Bulgaria.
He then joined the Institute of Solid State Physics with BAS, where he engaged in research on the frequency characteristics of the helium-neon laser, and later initiated physical research on lasers.
Meanwhile, multilayer dielectric laser mirrors with nearly 100% reflectivity were needed to continue the research. However, such were lacking in Bulgaria at the time, which incited the scientist to make an installation for the fabrication of dielectric mirrors in a completely original way. His method was protected by a patent, and thus began the inventive activity of Academician Sabotinov. The method also found industrial application at the Institute of Special Optical Materials and Technologies for the development of technology for the production of multilayer laser mirrors with a high degree of reflectivity.
Later, the scientist began work on metal vapour lasers, with the first steps made in the field of cadmium lasers in the blue range, followed by ion gas lasers, followed by helium-selenium lasers in the green region. The next invention was a combination of the two types of lasers – a blue-green laser was created, called the helium-cadmium-selenium laser, which was done for the first time in the world. This is also the second patent for the scientist’s invention.
Sabotinov did not stop there and decided to create the conditions for the generation of the red range to the blue-green range laser. For the first time in Bulgaria was put into operation helium-cadmium-selenium-neon laser, which covers the main wavelengths of the spectrum – blue, green and red. Thus, Bulgaria had the first multi-wavelength white laser source, which is also patented. The discovery has been published in global scientific journals.
The scientist is most proud of the creation, in the laboratory he founded, of a new version of the most powerful metal vapour laser in the visible range of the spectrum – the so-called copper laser, which has major applications in medicine, military technology, and in telescope corrections. This laser, however, had a problem related to the vapourisation of the copper, which occurred at a temperature of about 1,500 degrees, which took half to one hour to heat up the equipment. In search of a solution to this problem, the scientist turned to the use of the compound copper bromide, and in 1974 the copper bromide vapour laser began operating in the laboratory. It was a great event, the laboratory was illuminated by green-yellow light, the temperature at which we made the generation of the laser was only 500 degrees, recalls the scientist. It turns out that such a scientific result has not been reported by the global scientific community and Sabotinov filed for a patent. The invention was designated as invention of the year in Bulgaria in 1974. It received a number of awards and in 1996, Sabotinov was listed in the “Golden Book” of Bulgarian inventors.
An invention does not immediately arrive at practical implementation, it is a working idea, but sometimes it is accompanied by other limitations, Sabotinov pointed out and noted that they are overcome only through additional scientific and applied research, referring to the copper bromide vapour laser and the problem of its lifetime. It was only through this additional research that it was possible to reach up to 1,000 hours of lifetime for the system and increase its power. In the meantime, a discovery was also made in this process related to increasing the power of the laser. Thus, the laser was then ready for its practical realization, and two copper bromide vapour lasers were prepared in only 6 months by a team of scientists under the guidance of Academician Sabotinov.
The scientist stressed that in order to attract the interest of the business to the invention, it is always good to make a pilot model. Thus, the copper bromide vapour laser was introduced into regular production in the Plovdiv Optical Technologies enterprise, and then the lasers were presented at a world exhibition in Hanover, Germany, which unlocked the interest of foreign companies. This motivated the decision to offer a production license to powerful world companies from the USA, Australia, and the United Kingdom. Just ten days after the offer was made, the head of the Australian company arrived in Sofia, and almost slept in front of the laser in the laboratory for three days, and then declared his willingness to buy the license, the scientist recalled. And until now the Australian company continues the production of the Bulgarian laser. Australia’s interest also enticed US companies, and in Silicon Valley, after successful experiments, a leading US company immediately decided to switch to mass production of the laser. The laser is mainly used for medicine against various skin diseases. It is also applicable for technological procedures – drilling micro-holes, processing various materials. After the laser produced by the Australian company began to conquer the Asian markets, a Korean company also showed interest in buying the license for its production. The Korean firm together with a Bulgarian firm made a joint device for the needs of dermatology in 6 months.
After 1989, three small companies in Bulgaria started its production, mainly for export. More than 500 laser sources were sold, which found a place in show business for light displays, and for medical purposes.
The laser is also applicable for measuring the depth of the seafloor, because the green radiation penetrates deep into the water, which allows for the study of the seafloor topography. It is applicable for remote object identification or atmospheric pollution studies.
Thus, the laser has found widespread use in the industrial sector, Academician Sabotinov said. Under several EU projects, with very good funding, cooperative action with the British industry, conditions were created for the production of a copper bromide vapour laser with a power of over 120 watts.
The international recognition of Bulgarian research and applied results is reflected in the opinion of world-renowned scientists from the UK, USA, Japan, Russia and Bulgaria, including Nobel laureate Acad. Nikolay Basov, one of the creators of the laser. Academician Basov says: “As a result of a complete cycle of physical research and development, a laser was created which, in many parameters, is significantly better than other lasers of this type known in the world scientific literature. Bulgarian physicists have made a major contribution to the development and practical construction of this laser,” Basov adds.
The interview with Prof. DSc Nikola V. Sabotinov was made within the framework of the partnership initiative between BTA and the Bulgarian Patent Office (BPO), which envisages the presentation of Bulgarians listed in the Golden Book of BPO and the activities of the BPO in a joint weekly column entitled “Created in Bulgaria”.
BTA/GNA