Nanoindentation and birefringence measurements on fused silica specimen exposed to low-energy femtosecond pulses

Abstract

Bellouard, Y.J.; Colomb, T.; Depeursinge, C.; Dugan, M.; Said, A.A.; Bado, P. Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Bellouard, Y. J., Colomb, T., Depeursinge, C., Dugan, M., Said, A. A., & Bado, P. (2006). Nanoindentation and birefringence measurements on fused silica specimen exposed to low-energy femtosecond pulses. Optics Express, 14(18), 8360-8366. DOI: 10.1364/OE.14.008360 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract: Femtosecond laser pulses used in a regime below the ablation threshold have two noticeable effects on Fused Silica (a-SiO2): they locally increase the material refractive index and modify its HF etching selectivity. The nature of the structural changes induced by femtosecond laser pulses in fused silica is not fully understood. In this paper, we report on nanoindentation and birefringence measurements on fused silica exposed to low-energy femtosecond laser pulses. Our findings further back the hypothesis of localized densification effect even at low energy regime.

Femtosecond versus picosecond laser machining of nano-gratings and micro-channels in silica glass

“…8). In the psregime, etched lengths of about 120-150 μm are obtained in the whole range of fluences explored in this study (0.5-4500 J/mm The faster etching rate observed in ultra-short pulse laser irradiated silica glass as compared to pristine glass has been ascribed to the structural modification of the material [8], to densification [9] or to the presence of nano-cracks within nanogratings [29]. To distinguish the contributions of nanogratings to the etching process at different fluence regimes, we looked at correlations between the laser induced birefringence (Fig.…”

“…The etching rate of fs-laser irradiated regions has been shown to depend upon the stress and densification in the glass in the low fluence regime and by the nanogratings' orientation in the high fluence regime [9,27]. Hence, the formation of nanogratings by 8 ps-pulses and the concurrent build-up of stress in the regions surrounding the laser tracks will have an impact on the two-step machining by laser irradiation and chemical etching.…”

“…Additionally, investigation of optical waveguides fabricated by laser direct writing with a wide 50-fs to 5-ps range of pulse duration showed the lowest loss of 0.2 dB/cm for 1 ps pulses [6,7]. Stress accumulation and glass densification are also known to accelerate the etching rate of silica, a feature that would be of interest for two-step machining by laser irradiation and chemical etching [8,9]. It has never been investigated whether the formation of self-assembled periodic nanostructures, known as "nanogratings", is possible for these pulse durations [10].…”

Towards fast femtosecond laser micromachining of fused silica: The effect of deposited energy

“…These structural modifications can be of various kinds: defects but also formation of smaller SiO 4 -ring structures (as suggested by Raman observations [19,20]) that lead to a gradual densification effect. The hypothesis of laserinduced densification is supported by nano-indentations experiments [21]. If a localized densification take place in a confined and well defined region (as suggested by experimental evidences presented in [11] and [20]), the region surrounding will be put under tensile stress in order to accommodate the local change of volume.…”

A Monolithic Micro-Tensile Tester for Investigating Silicon Dioxide Polymorph Micromechanics, Fabricated and Operated Using a Femtosecond Laser

“…Stress estimation is facilitated through photoelasticity, which gives a direct measurement of the induced stress in the test beam [69,70]. False color intensity retardance maps (Figure 1c) of the loaded test beam are generated with a standard microscope (Olympus BX51, Tokyo, Japan) fitted with a commercial system to measure optical retardance (LC-Polscope, CRI, Cambridge, MA, USA).…”