Recent advances in ultrafast laser processing of transparent materials

Interaction of intense ulrashort light pulses with transparent materials reveal new interesting properties and phenomena. Recent demonstrations of 3D nanoripple formation, self-assembled form birefringency and ultrafast laser calligraphy are reviewed

High power radially-polarized Yb-doped fiber laser

A simple technique for directly generating a radially-polarized output beam from an ytterbium-doped fiber laser using an intracavity spatially-variant waveplate is reported. The laser yielded 32W of output with a corresponding slope efficiency of 65.8% in a radially-polarised beam with beam propagation factor ~2.1 and polarization purity >95%

Self-assembled nanostructuring of a-Si:H films with ultrashort light pulses

For several decades, hydrogenated amorphous silicon (a-Si:H) has been playing a significant role in the world's production of photovoltaic modules. In this work, we investigate different types of modifications induced by a femtosecond laser in a-Si:H thin films. We demonstrate that several distinctive modification regimes with peculiar optical properties can be obtained in a narrow range of the laser pulse energies

Efficient conversion to radial polarization in the two-micron band using a continuously space-variant half-waveplate

We demonstrate efficient conversion of a linearly-polarized Gaussian beam to a radially-polarised doughnut beam in the two-micron band using a continuously space-variant half-waveplate created by femtosecond writing of subwavelength gratings. The low scattering loss (<0.07) of this device indicates that it would be suitable for use with high power lasers

New phenomena in interaction of intense ultrashort light pulses with transparent materials: from 3D self-assembled nanostructures to quill writing and nonreciprocal photosensitivity

Interaction of intense ulrashort light pulses with transparent materials reveal new ultrafast phenomena. Recent demonstrations of 3D nanoripple formation, ultrafast laser calligraphy and nonreciprocal photosensitivity are reviewed

Polarization diffraction grating produced by femtosecond laser nanostructuring in glass

We demonstrate polarization sensitive diffractive optical element fabrication by femtosecond direct writing in the bulk of silica glass. Modulation of the anisotropic properties is produced by controlling light-induced self-assembled nano-gratings

Beyond conventional 3D ultrafast laser material processing

Material processing with ultrafast lasers has attracted considerable interest due to a wide range of applications from laser surgery and integrated optics to optical data storage, 3D micro- and nano-structuring [1,2]. A decade ago it has been discovered that under certain irradiation conditions ordered sub-wavelength structures with features smaller than 20 nm can be formed in the volume of silica glass [3]. The effect of nanograting formation has attracted considerable interest with proposals of applications ranging from nanofluidics [4,5] to polarization control devices [6]

Ultrafast laser nanostructuring of glass: from S-waveplate to multidimensional data storage

Material processing with ultrafast lasers has attracted considerable interest due to new science and a wide range of applications from laser surgery, integrated optics to optical data storage. A decade ago it has been discovered that under certain irradiation conditions ordered sub-wavelength structures with features smaller than 20 nm can be formed in the volume of silica glass. Here we discuss recent applications of self-assembled sub-wavelength structuring specifically polarization converters branded as the S-waveplate and polarization multiplexed optical data storage

Glass-metal nanocomposite modification by femtosecond laser irradiation

Modification on silver nanoparticles (AgNPs) is of interest for various nonlinear optics applications and optical data storage. Femtosecond laser modification allows elongation of spherical AgNPs [1]; these elongated particles possess intrinsic anisotropy [2], which results in dichroism [3]. Here we present the study of transmissivity and reflectivity of glass-metal nanocomposites (GMN) [4] irradiated with 330 fs laser pulses at 515 nm wavelength; the GMN was fabricated using technique based on ion-exchange [5]. The laser processing of the NP results in the dichroism exhibited in optical spectra of transmission and reflection. At higher energies we observed the increase of transmittance and decrease of reflectance, which is attributed to dissolution of NP into the glass lattice

Revealing extraordinary properties of femtosecond laser writing in glass

Modification of transparent materials with ultrafast lasers has attracted considerable interest due to a wide range of applications including laser surgery, integrated optics, optical data storage, 3D micro- and nano-structuring [1].Three different types of material modifications can be induced with ultrafast laser irradiation in the bulk of a transparent material, silica glass in particular: an isotropic refractive index change (type 1); a form birefringence associated with self-assembled nanogratings and negative refractive index change (type 2) [2,3]; and a void (type 3). In fused silica the transition from type 1 to type 2 and finally to type 3 modification is observed with an increase of fluence. Recently, a remarkable phenomenon in ultrafast laser processing of transparent materials has been reported manifesting itself as a change in material modification by reversing the writing direction [4]. The phenomenon has been interpreted in terms of anisotropic plasma heating by a tilted front of the ultrashort laser pulse. Moreover a change in structural modification has been demonstrated in glass by controlling the direction of pulse front tilt, achieving a calligraphic style of laser writing which is similar in appearance to that inked with the bygone quill pen [5]. It has also been a common belief that in a homogeneous medium, the photosensitivity and corresponding light-induced material modifications do not change on the reversal of light propagation direction. More recently it have observed that in a noncentrosymmetric medium, modification of the material can be different when light propagates in opposite directions (KaYaSo effect) [6]. Non-reciprocity is produced by magnetic field (Faraday effect) and movement of the medium with respect to the direction of light propagation: parallel (Sagnac effect) or perpendicular (KaYaSo effect). Moreover a new phenomenon of ultrafast light blade, representing itself the first evidence of anisotropic sensitivity of isotropic medium to femtosecond laser radiation has been recently discovered [7]. We attribute these new phenomena to the anisotropy of the light-matter interaction caused by space-time couplings in ultrashort light pulses. This intrinsic spatio-temporal asymmetry of light opens an interesting opportunity in the control of photon flux interacting with a target submerged into condensed isotropic medium. We anticipate that the observed phenomena will open new opportunities in laser material processing, laser surgery, optical manipulation and data storage