Precise laser processing with highly adaptive laser sourcesKočica, Jernej Jan (Avtor) Petkovšek, Rok (Mentor) Agrež, Vid (Komentor) burst processingpulse-on-demandablation efficiencyfemtosecond laserspicosecond lasersadaptive laser sourcesmicrostructuringThis doctoral dissertation investigates burst mode laser processing with pulse-on-demand capability to address the persistent trade-off between processing speed and quality in laser material processing. While nanosecond lasers offer high throughput at the cost of thermal damage, ultrashort pulse lasers provide superior precision but insufficient processing speeds for industrial applications. Burst mode operation with ultrashort pulses (femtosecond to picosecond duration) combines the advantages of both regimes through controlled heat accumulation across multiple temporal scales. The approach exploits three distinct timescales: ultrashort pulse duration minimizes direct thermal damage, nanosecond intra-burst pulse spacing enables beneficial thermal effects that enhance ablation efficiency, while microsecond inter-burst timing prevents excessive heat accumulation. Custom-developed fiber laser systems were employed to access the parameter space spanning pulse duration (from fs to ps to several ns), burst configuration (1-10 pulses per burst), intra-burst repetition rates (20-40 MHz), and inter-burst timing (microsecond to millisecond scales). Pulse-on-demand operation with 5 ns temporal resolution enabled synchronization with high-speed scanning systems across repetition rates from below 1 kHz to 1 MHz. Experimental investigations on copper and silicon quantified burst processing effects across multiple temporal scales. Ablation efficiency increased up to 10-fold compared to single pulse operation, with the magnitude and mechanism of enhancement dependent on material properties and temporal parameters. For copper, intra-burst spacing of 25 ns produced 200% higher efficiency than 50 ns spacing due to heat accumulation effects enabled by high thermal diffusivity, whereas silicon showed minimal dependency on this parameter due to lower thermal diffusivity. Heat accumulation effects were characterized from nanosecond (intra-burst) through microsecond (inter-burst) timescales to establish dominant ablation mechanisms under different processing conditions. Experimental results demonstrate that picosecond burst processing achieves ablation efficiencies comparable to nanosecond lasers while maintaining surface quality and heat-affected zone characteristics of ultrashort pulse processing. Pulse-on-demand operation addressed scanner limitations by maintaining constant pulse spacing during acceleration and deceleration, enabling high-speed processing with improved positioning accuracy. A 2.5D processing approach combining pulse-on-demand operation with dynamic repetition rate modulation achieved 6.5-10× processing time decrease for complex surface patterns compared to traditional layer-by-layer processing, validated through fabrication of biomimetic surfaces with features ranging from micrometers to millimeters. This work characterizes relationships between burst parameters and ablation efficiency for copper and silicon within the investigated parameter space, identifies parameter regimes that balance efficiency and quality, and demonstrates a 2.5D processing technique combining pulse-on-demand operation with dynamic repetition rate modulation. The results indicate potential applicability for PCB processing, thin film structuring and general surface structuring, where both high speed and precision are required.[J. J. Kočica]20262026-02-19 08:30:27Doktorsko delo/naloga179660UDK: 621.785.6:544.537:669.3(043.3)VisID: 283186COBISS_ID: 270305795sl