Laser-induced ablation of tantalum in a wide range of pulse durations

Steffen Mittelmann,Sebastijan Brezinsek,Jannis Oelmann,Ding Wu,Hongbin Ding,Georg Pretzler

doi:10.1007/s00339-020-03838-2

Abstract

We present data and analysis of the laser-induced ablation of pure tantalum (Ta, Z=73). We have identified different physical regimes using a wide range of laser pulse durations. A comparison of the influence of strongly varying laser pulse parameters on high-Z materials is presented. The crater depth caused by three different laser systems of pulse duration {varDelta }tau _1=5,mathrm {ns} and wavelength lambda _1=1064,mathrm {nm}, {varDelta }tau _2=35,mathrm {ps}, lambda _2=355,mathrm {nm} and {varDelta }tau _3=8.5,mathrm {fs}, lambda _3=790,mathrm {nm} are analyzed via confocal microscopy as a function of laser fluence and intensity. The minimum laser fluence needed for ablation, called threshold fluence, decreases with shorter pulse duration from 1.10,mathrm {J/cm}^2 for the nanosecond laser to 0.17,mathrm {J/cm}^2 for the femtosecond laser.

Highlights

Short and ultra-short laser pulses are used in a wide spectrum of fields like material processing [1, 2], nano-particle production [3, 4] or in diagnostic applications [5]
To compare the different crater morphologies that are generated by laser pulses of different pulse durations
We are aware of the fact that the ablation threshold can vary for different polarization directions using a tilted target

Summary

Introduction

Short and ultra-short laser pulses are used in a wide spectrum of fields like material processing [1, 2], nano-particle production [3, 4] or in diagnostic applications [5]. The purpose of this paper is to compare the ablation behaviour of different laser systems that are promising candidates to perform first-wall diagnostic in this devices. In this context, laser–material interaction with laser pulses of different pulse durations must be compared and analyzed. The pulse duration is on the order of the thermal relaxation time (ps-laser) or much shorter (fs-laser). In this case, the high electro-magnetic fields excite the electrons in the skin depth (few nm behind the surface).

Objectives

Methods

Conclusion