Optical damage threshold of Au nanowires in strong femtosecond laser fields

Adam M Summers,Govind Paneru,Carlos A Trallero-Herrero,Matthias F Kling,Bret N Flanders,Adam S Ramm

doi:10.1364/oe.22.004235

Abstract

Ultrashort, intense light pulses permit the study of nanomaterials in the optical non-linear regime. Non-linear regimes are often present just below the damage threshold thus requiring careful tuning of the laser parameters to avoid melting the materials. Detailed studies of the damage threshold of nanoscale materials are therefore needed. We present results on the damage threshold of gold (Au) nanowires when illuminated by intense femtosecond pulses. These nanowires were synthesized via the directed electrochemical nanowire assembly (DENA) process in two configurations: (1) free-standing Au nanowires on tungsten (W) electrodes and (2) Au nanowires attached to fused silica slides. In both cases the wires have a single-crystalline structure. For 790 nm laser pulses with durations of 108 fs and 32 fs at a repetition rate of 2 kHz, we find that the free-standing nanowires melt at intensities close to 3 TW/cm2 (194 mJ/cm2) and 7.5 TW/cm2 (144 mJ/cm2), respectively. The Au nanowires attached to silica slides melt at slightly higher intensities, just above 10 TW/cm2 (192 mJ/cm2) for 32 fs pulses. Our results can be explained with an electron-phonon interaction model that describes the absorbed laser energy and subsequent heat conduction across the wire.

Highlights

Nanoelectronics, nanophotonics and nanoplasmonics have been fields of growing interest in the last several years[1, 2, 3, 4, 5]
We have presented measurements and simulations on optically-induced damage in Au nanowires with intense, femtosecond laser pulses
Our experimental measurements indicate that the damage threshold in single-crystaline nanowires, attached to silica, can reach values close to 10 TW/cm2 for 32 fs pulses and approximately 5 TW/cm2 for 108 fs

Summary

Introduction

Nanoelectronics, nanophotonics and nanoplasmonics have been fields of growing interest in the last several years[1, 2, 3, 4, 5]. Ultrafast nanoscale circuitry relies on the ability to utilize the non-linear interaction of light with nanoscale materials to tailor (collective) electron motion on a sub-optical-cycle timescale These non-linear regimes are reached for strong laser pulses with intensities typically just below the damage threshold of the materials. Such interactions can give rise to (sub-optical-cycle) electron emission and acceleration from isolated nanotips [9, 10] and nanospheres [11] and from nanostructured surfaces [12, 13], the laser-field-driven semi-metallization of dielectrics [14, 15] and metals [16], and can induce currents across nanoscale junctions [7]. Two types of nanowire arrangements are studied: (1) free-standing Au nanowires that are grown on W needle electrodes and (2) Au nanowires attached to silica slides

Methods

Results

Conclusion