Laser micromachining has become increasing prominent in various industries given its speed, lack of tool wear, and ability to create features on the order of micrometres. Inherent stochastic variations from thermal ablation along with detrimental heat effects, however, limit the feasibility of achieving high precision. The high number of control parameters that make laser micromachining versatile also hinders optimization due to high exploration time. The introduction of high intensity nonlinear ablation leads to more precise cuts but at a much higher, often restrictive, cost.
The work here shows that by combining an imaging technique frequently used in ophthalmology called optical coherence tomography (OCT) with a machining platform, in situ observation of ablation can be made. This combination, known as in-line coherent imaging (ICI), allows information to be gathered about the dynamics of the ablation process. Experimental results show that quality cutting of silicon can be achieved with thermal ablation and at a wavelength of 1070 nm. This result is surprising as silicon absorbs this wavelength very weakly at room temperature. It is shown here that a nonlinear thermal dependence in absorption allows a cascaded absorption effect to enable machining. With the aid of ICI, the model shown here is able to accurately predict the thermal ablation rate and help understand the ablation process. The high quality cutting achieved allows for a more cost efficient alternative to current techniques using ultraviolet diode-pumped solid state (UV DPSS) systems.
Where thermal effects such as heat-affected zones (HAZ) cannot be overcome, high intensity nonlinear ablation allows the processing of lead zirconate titanate (PZT) for high frequency arrays (used in ultrasound applications) at speeds two orders of magnitude greater than found in the literature, and potential feature sizes (< 100 µm) in polymethyl methacrylate (PMMA) unachievable by thermal ablation. The ablation mechanism here is Coulombic explosion (CE), which is a non-thermal process. Coupled with demonstrated manual and automatic feedback abilities of ICI, the processes shown here may open up new avenues for fabrication. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-05-31 15:02:55.547
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/6539 |
| Date | 06 June 2011 |
| Creators | Yu, Joe X.Z. |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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