Controlling ultrafast laser-induced refractive index changes in optical glasses via adaptive spatio-temporal beam engineering

Abstract : Ultrafast lasers emerged as promising tools to process embedded refractive index modifications in bandgap materials. Photonic functions were demonstrated in various glasses of optical relevance and the optimal performance requires a precise adjustment of the refractive index. However, the irradiation outcome depends on the material relaxation paths (electronic or thermo-mechanical transformations), as well as on the spatio-temporal characteristics of the writing beam. It can result in both positive and negative index variations, the latter being e.g. detrimental for waveguiding applications. These facts impose specific limitations to the photoinscription process. Recently, new beam manipulation concepts were developed which allow a modulation of the energy feedthrough according to the material transient reactions, enabling thus a synergetic interaction between light and matter and, therefore, optimal results. We consequently discuss the possibility of controlling laser-induced physical phenomena employing automated temporal pulse shaping. We indicate the potential of regulated energy feedthrough in triggering laser-induced plasticity which results in establishing desired refractive index distributions. Examples of adaptive design of refractive index changes in “thermal” glasses will be shown. Additionally the role of polarization will be analyzed, which results in unusual anisotropic light scattering and reflection characteristics for the photoinscribed traces. Photowritten structures can be arranged in three dimensional patterns generating complex propagation and polarization effects due to the anisotropic optical properties. This points out towards an engineering aspect related to efficient processing of complex structural modifications in 3D arrangements where a feasible solution is represented by dynamic spatial phase modulation and beam shaping techniques. The approach has a dual aspect and includes corrections for beam propagation errors and spatial intensity distributions in desired patterns. Insights into 3D parallel writing techniques for complex structures using wavefront engineering will be given, with the purpose of achieving performant optical functions.
Keywords : laser processing
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Conference papers
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Contributor : Razvan Stoian <>
Submitted on : Wednesday, January 27, 2010 - 3:40:44 PM
Last modification on : Wednesday, July 25, 2018 - 2:05:31 PM


  • HAL Id : ujm-00450883, version 1



Razvan Stoian. Controlling ultrafast laser-induced refractive index changes in optical glasses via adaptive spatio-temporal beam engineering. LPhys 2009, Symposium on Laser Nanophotonics, Jul 2009, Barcelona, Spain. ⟨ujm-00450883⟩



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