Backscattered light properties during femtosecond laser ablation and development of a dynamic interferometric focusing system

Author(s)

Raele, Marcus Paulo ; Samad, Ricardo Elgul ; Freitas, Anderson Zanardi ; De Pretto, Lucas ; Amaral, Marcello Magri ; Vieira, Nilson Dias, Jr. ; Wetter, Niklaus U. ; Kaierle, S ; Heinemann, SW

• Document type: Journal article
• Source: HIGH-POWER LASER MATERIALS PROCESSING: APPLICATIONS, DIAGNOSTICS, AND SYSTEMS VII; v. 10525, p. 9-pg., 2018-01-01.

Abstract

The backscattered light originated when machining with femtosecond laser pulses can be used to accurately measure the processed surface position through an interferometer, as recently demonstrated by our group, in a setup that uses the same laser beam for ablation and inspection. The present work explores the characteristics of the laser light reflected by the target and its interaction with the resulting plasma to better understand its propagation physics and to improve the dynamic focusing system. The origin of this returning radiation was studied and has been traced, mainly, from the peripheral area of the focal spot (doughnut-like). By means of a Mach-Zehnder setup, the interferometric pattern was measured and analyzed aiming to access the influences of the plasma on the laser beam properties, and therefore on the retrieved information. Finally, the wavefront of the laser that creates and propagates through the plasma was characterized using a Shack-Hartmann sensor. (AU)

• FAPESP's process: 13/26113-6 - Micromachining with ultrashort laser pulses applied to the production and control of optofluidic circuits
• Grantee: Wagner de Rossi
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 15/24878-0 - DEVELOPMENT OF A DYNAMIC INTERFEROMETRIC FOCUSING SYSTEM FOR FEMTOSECOND LASER MACHINING
• Grantee: Marcus Paulo Raele
• Support Opportunities: Regular Research Grants