Discover how a revolutionary GHz burst mode femtosecond laser is revolutionizing the processing of single crystalline sapphire, opening up new possibilities for high-precision, high-efficiency microfabrication across various industries.
Put the Power of Plasma-Assisisted Ablation to Work
In this context, the capabilities of GHz burst mode femtosecond (fs) laser-induced, plasma-assisted ablation are presented in a new study published in Opto-Electronic Advances for super-resolution machining of single crystalline sapphire.
For example, sapphire is a material that has been sought after for ages due to its high transparency, hardness and thermal resilience making it invaluable in many industrial uses. But sapphire is indeed very difficult to process down to high accuracy and top quality (i.e. milling can take long time because it can effectively melt its edges). This is exactly what this new revolutionary method deals with.
The GHz burst mode fs laser is capable of producing a series of pulse trains, each that consists of several pulses spaced apart by an order of just a few hundred picoseconds. The combination of the direct plasma-matter interaction, which is driven by free electrons from the first applied laser pulses with the incoming pulses, leads to higher ablation efficiency, improves quality and processing speed. The researchers believe this method opens up new possibilities for micropatterning of sapphire in a cost-effective and environmentally friendly manner using magnetically driven plasma-assisted microablation.
Revealing The Secrets of Sapphire Processing
A transparent sapphire substrate is placed in contact with a metal target, e.g. copper, during the LIPAA (Laser Induced Plasma Assisted Ablation) process. The plasma that flows off the metal target interacts with the laser beam allowing for high-efficiency ablation of the rear surface of sapphire being transparent made from above.
This was extended in the GHz burst mode fs-LIPAA technique by using the gap time between the increment pulses within a burst pulse. The intermediate pulse interval generates plasma at the surface of sapphire substrate and the metal target, and then the following laser pulses can excite this plasma to directly interact with a thick underlayer.
The combined effect causes the ablation depth to increase exponentially, around a 4.2-fold and 5.0-fold enhancement, respectively, compared to single-pulse mode LIPAA (fH = fP, τ = ~75 ns) reported by the authors. Additionally, the ablation threshold was much lower, decreased to 1/7.3 of the single-pulse mode fs laser direct ablation.
Subsequently, the Gigahertz burst mode LIPAA process facilitated a greatly enhanced absorption and plasma density, which in turn led to significant enhancement of ablation quality, rendering it as an outstanding candidate for precise microfabrication of sapphire.
Conclusion
The GHz burst mode fs-LIPAA technique is the first of its kind to have up to now the capacity to transform the processing path for single crystalline sapphire or other transparent materials. These characteristics render plasma-assisted ablation in combination with GHz burst mode fs laser an outstanding tool to direct most processing aspects into the favourable parameter regime, extracting remarkable gain of processing efficiency, quality and resolution. Their groundbreaking strategy opens doors to rapid progression in microfabrication, expanding capabilities and opportunities for many industrial processes that need the exceptional characteristics of materials such as sapphire.
