Since the invention of the laser in the 1960s, laser technology has developed at a rapid pace. Lasers have become a highly versatile tool, indispensable in all walks of life, from space communications to deep-sea spectroscopy.
In his research, Xinyang Liu studied ultrafast fibre laser covering several aspects of laser performance development, including parabolic-shaped laser pulse generation that can tolerate high pulse energy, laser pulse generation in the third-biological window and fibre laser cavity output prediction by the neural network.
A high-intensity laser pulse accumulates a nonlinear phase shift in nonlinear waveguides, which can result in pulse splitting. A parabolically shaped laser pulse with linear frequency chirp can propagate in a nonlinear waveguide in a self-similar manner, avoiding pulse splitting and retaining its shape. This allows the pulse to hold large amounts of energy, resulting in high peak power.
“Peak power and pulse energy define the sharpness of a laser knife in industrial machining applications. Thus, high peak power and high pulse energy increase the production efficiency," Liu explains.
As part of the PULSE (Horizon 2020 project ‘High-power ultrafast lasers for advanced material processing’ he demonstrated the generation of the parabolic laser pulse, which has the potential as a seed for high pulse energy generation to enable efficient industrial machining.
Cancer is the second leading cause of death worldwide. Early diagnosis and treatment are necessary to cure the disease. In bioimaging, the penetration depth into tissue is limited by effects like water absorption, scattering and phototoxicity. Xinyang Liu demonstrated a high-power, ultrafast fibre laser source operating in the third biological window of 1.7-1.9 μm in his research under the AMPLITUDE (Horizon 2020) project ‘Advanced multimodal photonics laser imaging tool for urothelial diagnosis in endoscopy’.
”This ultrafast fibre laser source at third-biological window provides the tool for three-photon imaging technique, which can enable deeper penetration depth and leads to an earlier and more precise diagnosis of cancer”, he says.
Driven by machine learning algorithms, the world is gradually entering the age of artificial intelligence (AI). By coupling neural network algorithms with fibre laser cavities, the trained neural network models can predict the output of a fibre laser cavity, paving the way for on-demand laser cavity smart design.
”The power of AI will change people’s lifestyles, as well as the way we do research and accelerate the research process”, he adds.
Liu's research results not only reveal new physical insights and application possibilities but also stimulate and encourage subsequent research on high-energy laser amplifiers, wide-range short-wavelength mid-infrared chirped pulse amplification and large laser cavity model.
Public defence on Friday 18 October 2024
The doctoral dissertation of MSc (Tech) Xinyang Liu in the field of laser physics titled Ultrafast, tunable, high-power and intelligent laser pulse generation by fiber laser will be publicly examined at the Faculty of Engineering and Natural Sciences of Tampere University at 13:15 on Friday 18 October 2024 at Hervanta campus, Festia, auditorium Pieni sali 1 (Korkeakoulunkatu 8, Tampere).
The Opponent will be Dr. Juan Diego Ania-Castañón from Spanish National Research Council. The Custos will be Adjunct Professor Regina Gumenyuk from the Faculty of Engineering and Natural Sciences at Tampere University.