Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

Femtosecond laser micromachining in transparent materials

Just as nanoparticles display properties that differ from those of bulk samples of the same material, ensembles of nanoparticles can have collective properties that are different to those displayed by individual nanoparticles and bulk samples. Self-assembly has emerged as a powerful technique for controlling the structure and properties of ensembles of inorganic nanoparticles. Here we review different strategies for nanoparticle self-assembly, the properties of self-assembled structures of nanoparticles, and potential applications of such structures. Many of these properties and possible applications rely on our ability to control the interactions between the electronic, magnetic and optical properties of the individual nanoparticles. Self-assembly is a powerful technique for controlling the structure and properties of ensembles of inorganic nanoparticles. This article reviews the properties and potential applications of self-assembled structures made from nanoparticles.

Properties and emerging applications of self-assembled structures made from inorganic nanoparticles

Recent developments of phosphate glasses for a variety of technological applications, from rare-earth ion hosts for solid state lasers to low temperature sealing glasses, have led to renewed interest in understanding the structures of these unusual materials. In this review, spectroscopic and diffraction studies of simple phosphate glasses, including v-P2O5 and binary phosphate compositions, are described. Special attention is given to the structures of anhydrous ultraphosphate glasses, which have received close attention from the glass community only in the past six years.

Review: the structure of simple phosphate glasses

CRYSTALLINE MATERIALS Introduction Physical Properties Optical Properties Mechanical Properties Thermal Properties Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties GLASSES Introduction Commercial Optical Glasses Specialty Optical Glasses Fused Silica Fluoride Glasses Chalcogenide Glasses Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties Special Glasses POLYMERIC MATERIALS Optical Plastics Index of Refraction Nonlinear Optical Properties Thermal Properties Engineering Data METALS Physical Properties of Selected Metals Optical Properties Mechanical Properties Thermal Properties Mirror Substrate Materials LIQUIDS Introduction Water Physical Properties of Selected Liquids Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Commercial Optical Liquids GASES Introduction Physical Properties of Selected Gases Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Atomic Resonance Filters APPENDICES Safe Handling of Optical Materials Abbreviations, Acronyms, and Mineralogical or Common Names for Optical Materials Abbreviations for Methods of Preparing Optical Materials and Thin Films Fundamental Physical Constants Units and Conversion Factors

/pdf/handbook-of-optical-materials-3e2ukwmx2l.pdf

Handbook of Optical Materials

Titanium dioxide (TiO2 ) nanocrystals are prepared by a hydrolysis process of tetrabutyl titanate. Nanocrystal samples with various sizes of 6.8-27.9 nm are obtained after annealing from 100 to 650 °C. The crystal structures and the average particle sizes are examined using x-ray diffraction. Raman scattering was employed to investigate the evolution of the anatase phase in the nanocrystals during annealing. Phonon confinement and non-stoichiometry effects are responsible for the blueshift and broadening of the lowest-frequency Eg Raman mode. The influence of interfacial vibrations on the Raman linewidth is also discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/33/8/305/pdf

Raman scattering study on anatase TiO2 nanocrystals

Using in situ Raman scattering in a confocal microscopy setup, we have observed changes in the network structure of fused silica after modifying regions inside the glass with tightly focused 800-nm 130-fs laser pulses at fluences of 5–200 J cm-2 The Raman spectra show a large increase in the peaks at 490 and 605 cm-1, owing to 4- and 3-membered ring structures in the silica network, indicating that densification occurs after exposure to the femtosecond laser pulses The results are consistent with the formation of a localized plasma by the laser pulse and a subsequent microexplosion inside the glass

Structural changes in fused silica after exposure to focused femtosecond laser pulses

Nonlinear properties include intensity-dependent refractive index, multiphoton absorption, second and third harmonic generation, stimulated Raman and Brillouin scattering, and associated phenomena such as self-focusing, self-phase modulation, optical phase conjugation, and optical bistability. We report on a large amount of work that reaches beyond simple glasses such as silica. Nonlinear optical phenomena have been investigated in materials ranging from oxide, halide, and chalcogenide glasses to glasses doped with semiconductor microcrystals, organic dyes, and metal particles and in forms varying from bulk materials to optical fibres and waveguides. We also discuss recently discovered photoinduced effects in glass fibres, which include second harmonic generation and the formation of refractive index gratings

Nonlinear optical phenomena in glass

Lasing of Fe:ZnSe is demonstrated, for the first time to the authors’ knowledge, for temperatures ranging from 15 to 180 K.?The output wavelength of the Fe:ZnSe laser was observed to tune with temperature from 3.98 µm at 15 K to 4.54 µm at 180 K.?With an Er:YAG laser operating at 2.698 µm as the pump source, a maximum energy per pulse of 12 µJ at 130 K was produced. Laser slope efficiencies of 3.2% at 19 K and 8.2% at 150 K were determined for an output coupling of 0.6%. A laser emission linewidth of 0.007 µm at 3.98 µm was measured at 15 K.?Absorption and emission spectra and emission lifetimes for Fe:ZnSe are also discussed.

4.0-4.5-mum lasing of Fe:ZnSe below 180 K, a new mid-infrared laser material.

Atomic-scale structural changes have been observed in the glass network of fused silica after modification by tightly focused 800-nm, 130-fs laser pulses at fluences between 5 and 200 J cm-2. Raman spectroscopy of the modified glass shows an increase in the 490 and 605-cm-1 peaks, indicating an increase in the number of 4- and 3-membered ring structures in the silica network. These results provide evidence that densification of the glass occurs after exposure to fs pulses. Fluorescence spectroscopy of the modified glass shows a broad fluorescence band at 630 nm, indicating the formation of non-bridging oxygen hole centers (NBOHC) by fs pulses. Waveguides that support the fundamental mode at 633 nm have been fabricated inside fused silica by scanning the glass along the fs laser beam axis. The index changes are estimated to be approximately 0.07×10-3.

Modification of the fused silica glass network associated with waveguide fabrication using femtosecond laser pulses

We report on the response of glass to focused femtosecond (fs) laser pulses during waveguide fabrication in a commercial sodium aluminum phosphate glass (Schott IOG-1). Single-pass longitudinal translation of IOG-1 glass with respect to the focused laser beam at a rate of 20 μm/s and pulse energies of 3.5 μJ results in the formation of two waveguides located on opposite sides of the laser-exposed region, which itself does not guide light. This behavior is different from that of the more widely studied silica glass system. The precise location of the waveguides in IOG-1 glass depends on the relative tilt of the fs laser beam with respect to the sample translation direction. Fluorescence imaging of the modified glass using a confocal microscope setup reveals the formation of color center defects in the exposed region but not within the waveguides.

Denise M. Krol

Papers

Structural changes in fused silica after exposure to focused femtosecond laser pulses

Nonlinear optical phenomena in glass

4.0-4.5-mum lasing of Fe:ZnSe below 180 K, a new mid-infrared laser material.

Modification of the fused silica glass network associated with waveguide fabrication using femtosecond laser pulses

Waveguide fabrication in phosphate glasses using femtosecond laser pulses