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•Laser patterning of thin films on flexible substrates.•Observation and analysis of patterning-induced surface effects.•Insight into rapid nanosecond ablation properties in thin film ...materials.•Demonstration of ultra-fast scanning utilization on in-demand electronic materials.
Modern electronics facilitate the need for fast, efficient, and reliable methods for direct laser-based surface engineering of conductive thin film materials on flexible substrates. Recent advances in pulsed laser source development only incrementally increased the processing speeds, as those are limited by the available scanning systems. Our goal was to combine a high pulse repetition frequency high-power pulse-on-demand fiber laser source with an ultra-fast resonant scanner to achieve high throughput surface engineering. The enabling factor to compensate a resonant scanner’s sinusoidal movement were the laser’s intrinsic pulse-on-demand capabilities beyond simple pulse picking solutions.
The high temporal resolution at full laser power was exploited for spatially controlled surface texturing, allowing a minimally 3 μm positioning accuracy throughout the scanner’s range at up to 60 m/s scan speed with a 10 μm laser spot size. We applied the setup to processing of ITO and metallic films on flexible substrates for touchscreens, position sensors, or EM shielding. Surface modification and patterning of the conductive layer was successfully demonstrated while keeping the underlying surface intact. We employed a simple laser ablation model in comparison to the experimental data to improve the understanding of the ablation process. The resulting surface topography was observed and analysed.
•Directly pump controlled compact DPSS laser for micro pulse generation.•Gain control in intracavity doubled laser for pulse on demand operation.•First investigation of high modulation intracavity ...doubled Nd:YVO4 laser.•Identified optimal parameters for intracavity doubled directly pump modulated laser.•Shown photon lifetime influence on laser efficiency and maximum modulation frequency.
Directly pump controlled pulse on demand operation of an intracavity frequency doubled Nd:YVO4 laser is presented, capable of generating arbitrary delay between pulses in the output sequence with the upper limit in MHz range. Micro pulses on demand were achieved by the gain switching technique and intracavity doubling through the optimization between the conversion efficiency and achievable repetition rate. Further, the article presents first study of a high modulation intracavity doubled Nd:YVO4 laser utilizing the crystals high emission cross section for fast gain switching. In the free space experimental setup, the highest repetition rate over 2 MHz and frequency doubling efficiency of 30% were achieved with the further scaling possible using optically bonded tightly packed architecture. The demonstrated pulse on demand operation of a compact micro pulsed laser at 532 nm enables full synchronization with the application.
Laser microstructuring has been studied extensively in the last decades due to its versatile, contactless processing and outstanding precision and structure quality on a wide range of materials. A ...limitation of the approach has been identified in the utilization of high average laser powers, with scanner movement fundamentally limited by laws of inertia. In this work, we apply a nanosecond UV laser working in an intrinsic pulse-on-demand mode, ensuring maximal utilization of the fastest commercially available galvanometric scanners at scanning speeds from 0 to 20 m/s. The effects of high-frequency pulse-on-demand operation were analyzed in terms of processing speeds, ablation efficiency, resulting surface quality, repeatability, and precision of the approach. Additionally, laser pulse duration was varied in single-digit nanosecond pulse durations and applied to high throughput microstructuring. We studied the effects of scanning speed on pulse-on-demand operation, single- and multipass laser percussion drilling performance, surface structuring of sensitive materials, and ablation efficiency for pulse durations in the range of 1-4 ns. We confirmed the pulse-on-demand operation suitability for microstructuring for a range of frequencies from below 1 kHz to 1.0 MHz with 5 ns timing precision and identified the scanners as the limiting factor even at full utilization. The ablation efficiency was improved with longer pulse durations, but structure quality degraded.
In this manuscript we present a true pulse-on-demand laser design concept using two different approaches. First, we present a fiber master oscillator power amplifier (MOPA) based quasi-continuous ...wave (CW) laser, working at high modulation bandwidths, for generation of nanosecond pulses. Second, we present a hybrid chirped pulse amplification (CPA)-based laser, combining a chirped-pulse fiber amplifier and an additional solid-state amplifier, for generation of femtosecond pulses. The pulse-on-demand operation is achieved without an external optical modulator/shutter at high-average powers and flexible repetition rates up to 40 MHz, using two variants of the approach for near-constant gain in the amplifier chain. The idler and marker seed sources are combined in the amplifier stages and separated at the out using either wavelength-based separation or second harmonic generation (SHG)-generation-based separation. The nanosecond laser source is further applied to high throughput processing of thin film materials. The laser is combined with a resonant scanner, using the intrinsic pulse-on-demand operation to compensate the scanner’s sinusoidal movement. We applied the setup to processing of indium tin oxide (ITO) and metallic films on flexible substrates.
Semiconductor DFB (Distributed feedback) laser diodes with an operating wavelength of 1064nm, which is suitable for pulse-on-demand fiber laser, have been developed. The stable performance of CW and ...nanosecond/picosecond pulsed operation is reviewed. By applying gain-switching operation with a simple direct modulation technique, 50-ps pulse generation with a stable spectral single-mode property was obtained. For the efficient amplification of the obtained 50-ps pulse, a monolithic semiconductor optical amplifier (SOA) was integrated into the DFB lasers. An improved peak power of 300mW at 50-ps pulse was observed with limited optical noise injection when the synchronous modulation technique of the DFB and the SOA was employed. Short cavity lasers showed a high-frequency response compared to the original DFB lasers and achieved a short pulse width of 13ps by standard gain-switched operation.
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