Femtosecond Laser Machining, Modification, and Metallization of Glass

Seunghwan Jo, Purdue University

Abstract

In this research, we have studied the interaction between femtosecond laser and dielectric material, especially borosilicate glass, and its applications. Using laser direct writing (LDW), optical fiber sensors and selective metallization of glass surface were explored. For ultrafine selective metallization, supersonic spray deposition system was introduced combining to femtosecond laser direct writing.We first studied how femtosecond laser pulses change the refractive index inside optical fiber sensors and its verification with simulation result. Beam propagation method (BPM) was utilized as a tool to verify experimental results. The relationship between pulse energy and amount of refractive index changes also studied.Optical fiber sensors based on femtosecond laser micromachining was introduced for the first time. Those sensors were designed to measure surrounding refractive index to defect liquid or gas state target chemicals. Micro-scale structure was fabricated in optical fiber, which can serve as an interferometer, to enhance sensitivity of the sensors.A new procedure for ultrafine selective metallization of glass surface with better conductivity and adhesion force was studied. The order of laser ablation was interchanged with coating process, and supersonic spray method was introduced for better coating performance. Ultrafine copper lines with 708 nm linewidth were achieved using new method. It is the narrowest linewidth ever reported using femtosecond laser based selective metallization process. Some practical applications were introduced, such as transparent heater or micro-size heater. Quantitative comparison to traditional method of suggested approach was conducted as well. Our approach outperformed in both electrical and mechanical tests. We assume that the superiority comes from much uniform and dense seed distribution by utilizing supersonic spray deposition system. Abundant seed affects largely on both sheet resistance and adhesion force. It contributes fast and uniform electroless copper plating process as well.We applied our new process onto 3D glass surface. A convex lens was used as a substrate. Its surface profile was gained by sampling method and the effect of oblique incident laser pulses was studied. The ablation threshold is a function of incident angle so that laser pulse energy was adjusted along with beam position for uniform plating results.

Degree

Ph.D.

Advisors

Jun, Purdue University.

Subject Area

Energy|Optics|Analytical chemistry|Chemistry|Mechanical engineering|Nanotechnology

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