Competing Nonlinear Delocalization of Light for Laser Inscription Inside Silicon with a 2- µ m Picosecond Laser

M Chambonneau,S Tzortzakis,O Utéza,V.Y Fedorov,S Février,D Gaponov,D Grojo,A Hideur,L Lavoute

doi:10.1103/physrevapplied.12.024009

Abstract

Recent advances in ultrafast laser 3D writing offer direct fabrication of in-chip silicon microsystems, but this technique remains extremely challenging, because of propagation nonlinearities that limit energy localization inside narrow-band-gap materials. This study examines the complex energy flux and subsequent unusual modification of silicon due to intense picosecond pulses from a thulium-doped fiber laser. The best conditions for reliable data inscription deep inside silicon are identified, which is a critical step toward engineering solutions to this problem. Also, the wavelength used here points to facing the next challenges associated with materials of even narrower band gap.

Highlights

Different emerging short-pulse fiber lasers emitting in the short-wave infrared (SWIR) region of the spectrum (1.1–2.5 μm) represent attractive tools to extend the threedimensional (3D) laser writing technologies developed in transparent dielectrics [1] to narrow gap materials as important as silicon (Si) [2,3,4]
Our results show the existence of strongly competing nonlinear effects modulating the fluence delivery in the picosecond regime
We successfully identify a window for controllable writing inside Si in the picosecond regime

Summary

Introduction

Different emerging short-pulse fiber lasers emitting in the short-wave infrared (SWIR) region of the spectrum (1.1–2.5 μm) represent attractive tools to extend the threedimensional (3D) laser writing technologies developed in transparent dielectrics [1] to narrow gap materials as important as silicon (Si) [2,3,4]. The first femtosecond laser experiments in this prospect reveal that the intrinsic properties of narrow gap materials prevent any permanent material change in the bulk [5,6] unless nonconventional focusing conditions are used [7]. Is caused by a strong clamping of the intensity due to nonlinear effects developing in the prefocal region. These contributing effects include Kerr-induced phase distortions, beam depletion by the highly efficient multiphoton absorption inherent to narrow gap materials, and increased plasma effects (screening and defocusing) due to the long wavelengths that are inevitably used [8,9,10].

Methods

Results

Conclusion