Production and characterization of femtosecond laser-written double line waveguides in heavy metal oxide glasses

• Published in: Optical materials 2018-01, Vol.75, p.267-273
• Main Authors: da Silva, Diego Silvério, Wetter, Niklaus Ursus, de Rossi, Wagner, Kassab, Luciana Reyes Pires, Samad, Ricardo Elgul
• Format: Article
• Language: English
• Subjects: Double line waveguide; Femtosecond laser; Heavy metal oxide glass; Passive optical component
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2017.10.033

We report the fabrication and characterization of double line waveguides directly written in tellurite and germanate glasses using a femtosecond laser delivering 30 μJ, 80 fs pulses at 4 kHz repetition rate. The double line waveguides produced presented internal losses inferior to 2.0 dB/cm. The output mode profile and the M2 measurements indicate multimodal guiding behavior. A better beam quality for the GeO2 – PbO waveguide was observed when compared with TeO2 – ZnO glass. Raman spectroscopy of the waveguides showed structural modification of the glassy network and indicates that a negative refractive index modification occurs at the focus of the laser beam, therefore allowing for light guiding in between two closely spaced laser written lines. The refractive index change at 632 nm is around 10−4, and the structural changes in the laser focal region of the writing, evaluated by Raman spectroscopy, corroborated our findings that these materials are potential candidates for optical waveguides and passive components. To the best of our knowledge, the two double line configuration demonstrated in the present work was not reported before for germanate or tellurite glasses. •This is the first time that femtosecond laser-written, double line waveguides are shown in germanate and tellurite glasses.•Raman analysis in the focal region of the lines written in these glasses corroborate our findings of a negative index change.•A high-quality, gaussian output beam with similar beam quality parameters in horizontal and vertical directions is achieved.