Femtosecond laser direct processing in wet and dry silica glass

The infrared femtosecond laser damage threshold is found to be independent of OH content in pure silica glass. Additionally, the density and the mean trapping time of electrons excited in the conduction band are also found to be independent on OH concentration.     

Surface modification of SiO2 glass by laser processing

Various oxide films on SiO₂ glass substrates were irradiated by a laser beam. A continuous CO₂ laser source (wavelength 10.6 μm) was used for this purpose; the composition change at the surface layer was determined by Rutherford backscattering spectrometry (RBS). All the alkaline-earth oxides as well as those of lanthanum and yttrium, entered the glass after treatment. ZrO₂ and CeO₂, however, did not enter the SiO₂ glass due to laser irradiation. It is interesting, however, that a film of ZrO₂ + Al₂O mixture easily entered into the SiO₂ glass by laser processing. The conditions and mechanism of laser-enhanced interaction of ZrO₂ or other oxide films with SiO₂ glass surfaces are discussed especially in view of their structural behaviour in glass.     

Ion beam modification of glass surface properties

This paper presents a general review of the effects, including H decoration of defects, induced by ion implantation of silicate and fluoride glasses. Ion implantation into glasses results in network damage and in compositional changes. Compositional changes are due to internal electric field formation, radiation enhanced diffusion processes and preferential sputtering, connected to different stopping power (electronic or nuclear) regimes of the incident particles. Such effects create modifications in the mechanical, optical and chemical properties of the glasses.     

Silicate nanoparticles by bioleaching of glass and modification of the glass surface

Bioleaching is examined as a low temperature (50 °C) soft chemical approach to nanosynthesis and surface processing. We demonstrate that fungus based bioleaching of borosilicate glass enables synthesis of nearly monodispersed ultrafine (∼5 ± 0.5 nm) silicate nanoparticles. Using various techniques such as X-ray diffraction, X-ray photoelectron spectroscopy and FTIR we compare the constitution and composition of the nanoparticles with that of the parent glass, and establish the basic similarities between the two. The bioleaching process is shown to enhance the non-bridging oxygen component and correspondingly influence the Si-O-Si network. The root mean square roughness of glass surface is seen to increase from 1.27 nm for bare glass to 2.52 nm for 15 h fungal processed case, this increase being equivalent to that for glass annealed at 500 °C.     

Outer space formation of a laser host glass

Classical crystallization calculations were performed to determine the possibility of forming a particular type of laser glass with the avoidance of devitrification in an outer space laboratory. Although the laser glass in question readily crystallizes in an earth environment, it is demonstrated that under the homogeneous nucleating conditions obtainable in a zero gravity laboratory this laser glass may be easily quenched to a virtually crystal-free product. Use of this material as a host in a neodymium glass laser would result in a more than 10% increase in efficiency when compared to laser glass rods of similar composition currently commercially available.     

Microstructural modification of chalcogenide glasses by femtosecond laser

With the irradiation by femtosecond (fs) laser with high repetition rate, GeS₂ micro/nano-crystalline formation and microstructural modification occurred in pseudo-binary GeS₂–In₂S₃ glass, while almost no similar change was observed in GeS₂ glass. The addition of In₂S₃ is beneficial for the precipitation of GeS₂ micro/nano-crystals. It is expected that functional micro/nano-crystals can be controllably prepared in chalcogenide glasses by fs laser irradiation through glass composition design.     

Fabrication of Yb-doped silica glass through the modification of MCVD process

A method to deliver Yb and Al compounds in vapor phase to the reaction/deposition zone has been devised for modified chemical vapor deposition (MCVD) process. By using this MCVD setup, we succeeded to prepare silica glass preforms presenting uniform dopants concentrations in the radial and longitudinal directions with good reproducibility. Preforms with a core diameter larger than 5 mm were easily prepared by depositing around 40 layers. By changing some parameters in the deposition step, such as carrier gases flow and temperatures of Yb(DPM)₃ and AlCl₃ furnaces, different concentrations of Yb and Al were incorporated into the core region of the silica glass preforms. By adjusting the Yb and Al concentrations, we succeeded to prepare preforms for large mode area (LMA) fiber with a change less than 10% of nominal refractive index.     

Ultrafast modification of elements distribution and local luminescence properties in glass

The success in construction of three-dimensional micro optical components or devices inside transparent materials is highly dependent on the ability to modify materials’ local structure. Especially, the realization of space-selective manipulation of element distribution is highly desirable since most of optical parameters such as refractive index and luminescence are closely related to element distribution. Up to present, the only way to control selective element distribution is local melting of glass. Here, we reported, for the first time to our knowledge, the success in realization of space-selective manipulation of element distribution in glassy state region (i.e., un-melted region) inside glass with the irradiation of high repetition rate femtosecond laser. Confocal fluorescence spectra and micro-Raman spectra show that the luminescence distribution of Cu⁺ ions and the glass network structure can be controlled with femtosecond laser irradiation, revealing the potential applications of this technique in the fabrication of functional waveguides and integrated optical devices.     

Formation mechanism of nanostructures in soda-lime glass using femtosecond laser

This paper reports on the formation of nanostructures produced in soda-lime glass by controlling the irradiation conditions of a single-beam femtosecond laser. Periodic nanoholes are fabricated in the sample with the lowest diameter of 200 nm (approximately one fourth of the incident light wavelength). Self-organized nanogratings with a period of 120 nm are fabricated for the first time on soda-lime glass surface by applying many pulses at the same spot. We discover that the nanogratings’ period decreases with the increase of the applied pulses. We investigate that the direction of the nanogratings is perpendicular to the direction of laser polarization. Further, it is discovered that the microholes, due to the illumination by many pulses, are elliptical in shape with the major axis perpendicular to the direction of laser polarization. Finally, long distance horizontal and vertical gratings are fabricated by scanning a femtosecond laser beam only in the horizontal direction.     

Nonlinear photosensitivity of photo-thermo-refractive glass by high intensity laser irradiation

Photo-thermo-refractive (PTR) glass is a material for high-efficiency phase volume hologram recording which possesses linear photosensitivity in the near UV region from 280 to 350 nm. In this paper nonlinear photosensitivity by 355 nm nanosecond pulses with intensity exceeding 1 MW/cm² and by 783 nm femtosecond pulses with intensity exceeding 1 TW/cm² is demonstrated. No photo-sensitizers are necessary in PTR glass for nonlinear photosensitivity. Photosensitivity by 355 nm nanosecond pulses is determined by glass matrix ionization resulting from two-photon absorption of incident radiation by glass matrix. Photosensitivity by 783 nm femtosecond pulses is determined by glass matrix ionization from nonlinear interaction of fundamental radiation and supercontinuum with modified glass matrix due to strong electric fields of incident radiation.     

Writing of crystal line patterns in glass by laser irradiation

We examined the laser-induced crystallization to form the fresnoite type Ba₂TiGe₂O₈ crystal line patterns in transition metal ion doped BaO–TiO₂–GeO₂ glass. Ba₂TiGe₂O₈ crystal line was written in 0.6FeO–33.3BaO–16.7TiO₂–50GeO₂ glass by continuous wave yttrium–aluminum–garnet (YAG) laser irradiation. We obtained polarization dependence of Raman spectra in crystal line pattern. Second harmonic generation (SHG) indicated unique fringe patterns from Ba₂TiGe₂O₈ crystal lines.     

Fabrication, spectroscopy and laser performance of Nd-doped lead-silicate glass fibers

The fabrication of a highly efficient Nd³⁺-doped single-mode fiber laser operating at 1.06 μm is described. The Nd₃₊ is introduced by doping Nd₂O₃ into a multicomponent (flint) lead-silicate glass host, Schott commercial optical glass F7. A fabrication technique for doping rare-earth evenly into commercial optical glasses is demostrated. Spectroscopic properties relevant to laser operation in the Nd³⁺-doped lead-silicate glass fibers were measured and the influence of Pb₂₊ ions on the spectral properties was analyzed. Owing to the long lifetime and large absorption and emission cross-sections of Nd₃₊ in this lead-silicate glass host, a high-performance Nd³⁺-doped lead-silicate fibre laser device operating at 1.06 μm has been successfully demonstrated.     

Surface properties of some commercially available spherical glass laser fusion pellets

IMMA and SIMS analyses may provide insight useful in understanding the variations in hollow glass spheres from shell to shell and batch. Since suitable calibration standards are not presently available for the alkali metals and boron, these results should be interpreted only as relative measurements of batch and shell variations. These instruments have yielded absolute measurements of silicon concentrations. Deuterium and tritium have been observed at very low concentrations in the glass and the experimental data are in agreement with existing solubility data.     

Design of Er3+-doped chalcogenide glass laser for MID-IR application

The feasibility of a photonic crystal fiber laser (PCF laser), made of a novel Er³⁺-doped chalcogenide glass and operating at the wavelength λ_s = 4.5 μm is investigated. The design is performed on the basis of spectroscopic and optical parameters measured on a fabricated Er³⁺-doped Ga₅Ge₂₀Sb₁₀S₆₅ chalcogenide bulk sample. The simulations have been performed by employing a home made numerical code that solves the multilevel rate equations and the power propagation equations via a Runge-Kutta iterative method. The numerical results indicate that a laser exhibiting slope efficiency close to the maximum theoretical one and a wide tunability in the wavelengths range where the atmosphere is transparent can be obtained.     

Fluorinated silica glass ablated with ArF excimer laser at low fluence

Amorphous SiO₂ (a-SiO₂) was formed by liquid-phase deposition (LPD) at room temperature. As a result of one shot of ArF excimer laser irradiation, LPD-formed a-SiO₂ shows a threshold fluence for ablation of below than 200 mJ/cm², which is much lower than the threshold fluence (∼1 J/cm²) of a-SiO₂ formed by thermal oxidation of silicon. Raman scattering spectroscopy revealed that two sharp lines at 495 cm⁻¹ and 606 cm⁻¹, respectively, labeled D₁ and D₂, had disappeared, and the main band at 430 cm⁻¹ was sharpened in LPD-formed a-SiO₂. It is presumed that the fluorine broke the silica network, relaxing the Si-O-Si bond angle and dramatically reducing the threshold energy for ablation of a-SiO₂.     

Elemental redistribution in glass induced by a 250-kHz femtosecond laser

We report the elemental redistribution in a Bi-doped oxyfluoride glass induced by a 250-kHz femtosecond laser. Our results show that the relative concentration of the network modifier Bi ions in the modified region is higher than that in the unmodified regions. However, the relative concentration of the network modifier Ca ions is opposed to that of Bi ions. This is the first time to observe the differential distribution of relative concentration between the network modifiers. These results are important to practical application in the fabrication of waveguide lasers and amplifiers in active ion-doped glasses.     

The role of the pressure in pulsed laser deposition of bioactive glass films

Effects of the Ar pressure on the morphology, structure, bonding configuration and deposition rate of the bioglass thin films were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and crystal lattice monitor. Ar pressure has an influence on the quantity and shapes of the particles generated in the PLD process. The target bonding configuration is not correctly transferred to the films. This effect is attributed to the network rearrangement during the film growth, which is associated to special structure of glass and complex physical mechanisms of PLD. Deposition rate decreases as the pressure increases following a linear dependence.     

Precipitation of silver particles by femtosecond laser pulses inside silver ion doped glass

We report on photosensitivities in silver ion doped glasses. We succeeded in precipitation control of silver particles without heat treatment by the irradiation of femtosecond laser pulses. The silver particles can be precipitated in a given location. Therefore it is possible to process a three-dimensional structure. This result should be applicable to functional optical devices.