Photonics Russia

The Research Laboratory “Laser and Additive Technologies” of the Institute of Mechanical Engineering, Materials and Transport of the Peter the Great St. Petersburg Polytechnic University (SPbPU) is a leading national research center in the field of laser, welding and additive technologies. The results of the LiAT IMMIT SPbPU have been implemented in many industrial projects that use Laser Welding and Surface Treatment, Laser Cladding, Hybrid laser arc welding and laser surface treatment. These technologies have proven to be highly effective in the fields of mechanical engineering, medicine, and oil and gas processing. We are talking with Mikhail Valeryevich Kuznetsov, Head of the Laboratory.

Ежегодно в конце октября в Санкт-Петербурге проходит Международная конференция Физик А.СПБ, продолжающая традицию петербургских семинаров по физике и астрономии, зародившуюся около тридцати лет назад, в середине 90-х. В этом году 20–24 октября ФизикА.СПБ собрала около 400 участников из различных регионов России, а также из Великобритании, Франции, Германии, Белоруссии, Армении, Казахстана, Азербайджана, Южной Африки и Китая. В Конференции приняли участие ученые высших учебных заведений и научных организаций, а также студенты и аспиранты, ведущие исследования в различных областях физики и астрономии.

The article presents the results of laser welding of steel using the lenses with a focal length of 300, 500, 700 and 900 mm. The effect of focal plane position of laser radiation relative to the work surface of the welded plate on the weld penetration depth has been evaluated. The research is based on a series of experimental welding samples using the lenses with various focal lengths and controlled changes in the focal point relative to the welded plate surface. The results can be used to select the process modes for laser welding of thick high-strength steels and to develop recommendations for the equipment adjustment.

A narrow-band laser is a key component in the structure of the distributed sensors and security systems based on them, as well as in the coherent fiber-optic measurement systems (FOMS). Due to the highly coherent pulses of a narrow-band laser that provide a high-contrast interference pattern in the reflected signal, unique sensitivity of the optical fiber to the external influences is achieved. A narrow-band semiconductor laser has been successfully commercialized in Russia. This highly stable compact laser has many potential applications in the field of sensors, LIDAR systems, acoustic and seismic sensors, and radio-photonic devices.

This article addresses the problem of stabilizing the propagation direction of wide-aperture laser beams when the beam size significantly exceeds the dimensions of standard quadrant photodetectors. Two fundamental stabilization schemes are analyzed: with dependent and independent control loops. It is shown that the former has a fundamental limitation due to the highly dependent nature of the influence matrix. As a solution, a system with two independent loops is proposed, which does not require matrix calculations and demonstrates high beam positioning accuracy sufficient for practical application in laser long-distance communication and focusing systems.

A Diamond being a wide-bandgap radiation-hard semiconductor, is rather promising for the development of UV detectors, including the solar-blind ones. A version of an all-carbon UV detector has been implemented on a single-crystal CVD diamond wafer with the interdigital electrodes consisting of a system of shallow (near-surface) and deep graphitized grooves produced by laser ablation without any lithography. Simulation of the electric field distribution in the detector has demonstrated the advantage of using buried electrodes that provide a more uniform field distribution within the crystal. The photosensitivity spectra exhibit a sharp peak at 220 nm, with the buried electrodes providing a 75% higher response amplitude (14 A/W).