Laser-initiated ablation of materials

Laser micromachining is now a common method of surface modification and machining; utilizing a broad spectrum of wavelengths, wave forms, and pulse durations. The most accurate bulk geometric modification is achieved by the use of ablation via the application of short wavelengths to deliver large photons for absorption in minimal skin depth. Many lasers can generate beams in the ultraviolet region. Excimer lasers are one example of a native ultraviolet laser that exhibit many key beneficial attributes over competing laser sources. A number of micromachining techniques have been developed to utilize these specific source attributes. The most interesting of these can deliver the ability to machine 2.5 dimensional features in arrays across the surface of a substrate. Despite the notable virtues of these techniques for micromachining applications, these processes suffer four major limitations: resolution is diffraction limited; the features are limited to 2.5-D; feature walls always have a draft angle; and large quantities of nanoscale debris are ejected during the machining process. A novel technique that applies a closed (optically defined) thick-flowing film of water across the substrate surface during pulsed laser ablation displays attributes that combine to answer two of the weaknesses of the nonliquid immersed pulsed laser ablation techniques: ablation generated debris is mitigated and feature walls can be made with steeper gradients; which, when combined with the reduction of surface waviness and modification to ablation rate reported, can implement an increase in feature resolution. Moreover, this technique allows the user to finely control their process while maintaining constant laser parameters and machine transparent, reflective, or resilient materials via the action of plume shockwave etching.