On the fundamental structure of femtosecond laser‐induced nanogratings

The nanoscale structure of femtosecond laser-induced modifications known as “nanogratings” has been the subject of speculation and intensive debate throughout the decade since their discovery. The aim of this work is to gain dependable information on the three-dimensional (3D) substructure of nanogratings down to the nanometre scale. To this end, non-destructive small angle X-ray scattering (SAXS) was employed to determine the characteristic sizes associated with the smallest features over a wide range of inscription parameters. The characteristic size of these cavities is 30 × 200 × 300 nm3 and largely independent of the exposure parameters, whereas prolonged exposure to laser pulses leads to an increase in their total number. Subsequently, focused ion beam (FIB) milling was used to dissect an extended volume and for the first time directly observe the 3D structure of nanogratings with nanometre resolution. The experiments clearly show that hollow cavities are the primary constituents of nanogratings and that their sheet-like arrangement gives rise to the well-known periodicity.

[1]  Andreas Tünnermann,et al.  The role of self-trapped excitons and defects in the formation of nanogratings in fused silica. , 2012, Optics letters.

[2]  S. Nolte,et al.  Formation of femtosecond laser-induced nanogratings at high repetition rates , 2011 .

[3]  Johannes Boneberg,et al.  Femtosecond laser near field ablation , 2009 .

[4]  R. Waxler,et al.  Relation between refractive index and density of glasses resulting from annealing compared with corresponding relation resulting from compression. , 1966, Applied optics.

[5]  K. Itoh,et al.  Ultrafast Processes for Bulk Modification of Transparent Materials , 2006 .

[6]  P. Kazansky,et al.  Polarization sensitive elements fabricated by femtosecond laser nanostructuring of glass [Invited] , 2011 .

[7]  P. Kazansky,et al.  Form birefringence and negative index change created by femtosecond direct writing in transparent materials. , 2004, Optics letters.

[8]  J. Baumberg,et al.  Embedded anisotropic microreflectors by femtosecond-laser nanomachining , 2002 .

[9]  Global Phase Diagram of a One-Dimensional Driven Lattice Gas , 1999, cond-mat/9901158.

[10]  Stefan Nolte,et al.  Discrete optics in femtosecond-laser-written photonic structures , 2010 .

[11]  Rafael Piestun,et al.  Polarization selective computer-generated holograms realized in glass by femtosecond laser induced nanogratings. , 2006, Optics express.

[12]  E. Mazur,et al.  Femtosecond laser micromachining in transparent materials , 2008 .

[13]  Kazuyoshi Itoh,et al.  Structural modification in fused silica by a femtosecond fiber laser at 1558 nm. , 2006, Optics express.

[14]  Gregory Beaucage,et al.  Approximations Leading to a Unified Exponential/Power-Law Approach to Small-Angle Scattering , 1995 .

[15]  Peter G. Kazansky,et al.  Anomalous anisotropic light scattering in Ge-doped silica glass , 1999 .

[16]  F. Costache,et al.  Femtosecond laser induced nanostructure formation: self-organization control parameters , 2008 .

[17]  Peter G. Kazansky,et al.  Modification thresholds in femtosecond laser processing of pure silica: review of dependencies on laser parameters [Invited] , 2011 .

[18]  Johannes Boneberg,et al.  Femtosecond laser near-field ablation from gold nanoparticles , 2006 .

[19]  Michael Sztucki,et al.  In situ study of aggregation of soot particles in an acetylene flame by small-angle x-ray scattering , 2007 .

[20]  Peter G. Kazansky,et al.  Self-assembled sub-wavelength structures and form birefringence created by femtosecond laser writing in glass: properties and applications , 2008 .

[21]  K. Miura,et al.  Writing waveguides in glass with a femtosecond laser. , 1996, Optics letters.

[22]  Andreas Tünnermann,et al.  Nonlinear discrete optics in femtosecond laser-written photonic lattices , 2011 .

[23]  Y. Shimotsuma,et al.  Self-organized nanogratings in glass irradiated by ultrashort light pulses. , 2003, Physical review letters.

[24]  Saulius Juodkazis,et al.  Laser-induced microexplosion confined in a bulk of silica: formation of nanovoids , 2006 .

[25]  P. Corkum,et al.  Polarization-selective etching in femtosecond laser-assisted microfluidic channel fabrication in fused silica. , 2005, Optics letters.

[26]  Jeff F. Young,et al.  Laser-induced periodic surface structure. I. Theory , 1983 .

[27]  R. Taylor,et al.  Applications of femtosecond laser induced self‐organized planar nanocracks inside fused silica glass , 2008 .

[28]  Bernard Prade,et al.  Writing of permanent birefringent microlayers in bulk fused silica with femtosecond laser pulses , 1999 .

[29]  Andreas Tünnermann,et al.  Tuning the structural properties of femtosecond-laser-induced nanogratings , 2010 .

[30]  G.D.W. Smith,et al.  Focused ion beam technology: a bibliography , 1990 .