Self-controlled formation of micro-lenses by optical breakdown inside wide-band-gap materials

David Grojo (1) , M. Gertsvolf (1, 2) , H. Jean-Ruel (1) , S. Lei (3) , L. Ramunno (2) , D. M. Rayner (1) , P. B. Corkum (1, 2)

1 NRC - Steacie Institute for Molecular Sciences
2 University of Ottawa [Ottawa]
3 Kansas State University

By repeatedly illuminating fused silica slabs with focused femtosecond pulses, we permanently decrease the local refractive index without increasing linear absorption or scattering. This progressively forms a bi-convex lens in the pre-focal region. With linearly polarized light, the index change reaches several percent and is associated with the formation of an array of planar nano-cracks. We analyze the polarization-dependent focusing power of the sub-wavelength periodic structure. While the detailed material modification changes, spontaneous defocusing lens formation is a common feature of every wide band gap transparent materials that we have studied (SiO2, BK7, LiF, sapphire, mica).

Domaines: Optique [physics.optics]

David Grojo, M. Gertsvolf, H. Jean-Ruel, S. Lei, L. Ramunno, et al.. Self-controlled formation of micro-lenses by optical breakdown inside wide-band-gap materials. Applied Physics Letters, 2008, 93, pp.243118. ⟨10.1063/1.3049133⟩. ⟨hal-00341282⟩