Andrei Fedotov: New design of optical fibers allows up-scaling of laser power

Tumma profiilikuva henkilöstä, jolla on päässään tohtorinhattu.

The laser is one of the drivers of technological progress and constantly expanding their presence in human life. The parts and body of your cars have been cut and welded with powerful industrial lasers. The laser vision correction, photodynamic cancer therapy, and advanced surgical procedures are possible with lasers. A powerful laser is used to generate extreme ultraviolet light in photolithographic systems, perhaps one of the most sophisticated man-made devices, without which modern electronics would be impossible. During his doctoral research, Andrei Fedotov worked on high-power short-pulsed fiber lasers and demonstrated an efficient way of their power scaling.

Since the creation of the first laser in 1960, the technology has undergone a dramatic transformation and reached impressive powers. The pulsed lasers are of particular interest. All their power is concentrated in very short time frame of about one trillionth of a second or even shorter.

“The main problem is that modern lasers are so powerful that the materials they are made of change their optical properties under the influence of such intense radiation. This degrades the performance of lasers or even leads to their physical damage. The problem is especially pronounced in fiber lasers since the optical fiber has a diameter comparable to the thickness of a human hair and all the huge power is contained in such a small volume. A simple solution would be to increase the fiber thickness. Unfortunately, this inevitably leads to deterioration of the laser beam quality.” explains Andrey Fedotov.

“An elegant solution to the problem of power scaling in fiber lasers is an active tapered fiber. It allows maintaining properties of the laser beam because fiber diameter smoothly increases over a length of several meters. Propagating through it, the light is amplified by almost ten thousand times. Nevertheless, undesirable effects in the fiber are avoided due to the unusual conical shape.” says Andrey Fedotov.

Since 2018, Andrei Fedotov has carried out his research in the Advanced Coherent Sources -group at Tampere University.

The doctoral dissertation of M.Sc. (Tech) Andrei Fedotov in the field of photonics titled High-power Short-pulsed Hybrid Laser Systems will be publicly examined in the Faculty of Engineering and Natural Sciences at Tampere University in the Auditorium TB109 of the Tietotalo building on Friday 4 February 2022 at 12 o’clock. The Opponent will be Professor Jens Limpert from Friedrich Schiller University Jena, Germany. The Custos will be Associate Professor Tapio Niemi from the Faculty of Engineering and Natural Sciences at Tampere University.

Due to the COVID situation, the event can be joined via remote connection. The link will be published here before the event.

The dissertation is available online at https://trepo.tuni.fi/handle/10024/136848.