Ultrafast Laser Nanostructured ITO Acts as Liquid Crystal Alignment Layer and Higher Transparency Electrode

Electrodes with higher transparency that can also align liquid crystals (LCs) are of high importance for improved costs and energy consumption of LC displays. Here we demonstrate for the first time alignment of liquid crystals on femtosecond laser nanostructured indium tin oxide (ITO) coated glass exhibiting also higher transparency due to the less interface reflections. The nano paterns were created by fs laser directlly on ITO films without any additional spin coating materials or lithography procces. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO. The device interfacial anchoring energy was found to be comparable to the anchoring energy of nematic LC on photosensitive polymers. The device exhibits contrast of 30:1 and relaxation time of 330ms expected for thick LC devices. The measured transparency of the LC device with two ITO nanograting substrates is 10% higher than the uniform ITO film based LC devices. The alignment methodology presented here paves the way for improved LC displays and new structured LC photonic devices

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

Functional birefringent elements imprinted by femtosecond laser nanostructuring of multi-component glass

A decade ago, a new type of self-organization process was observed in the bulk of SiO2 glass after irradiation with ultrashort laser pulses [1]. Under certain irradiation conditions, highly ordered nanostructures with features smaller than 20 nm could be formed in the irradiated volume. The sub-wavelength arrangement of these structures results in form birefringence, which was recently exploited for demonstrating a variety of functional optical elements in silica glass [2]. Despite excellent physical and chemical properties of fused silica, the applications of this glass are limited due to the expensive manufacturing process associated with high melting temperature. Recently the evidence of laser-induced nanogratings in glasses other than SiO2 was reported, including GeO2 glass [3], binary titanium silicate glass (ULE, Corning) and multicomponent borosilicate glass (Borofloat 33, Schott) [4]. However, birefringence induced in borosilicate glass was more than one order of magnitude lower than in pure SiO2 glass

Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser

We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites

Laser assisted modification of poled silver-doped nanocomposite soda-lime glass

Thermal poling assisted homogenization of polydisperse Ag nanoparticles embedded in the soda-lime glass is demonstrated. The homogenization leads to the narrowing of the localized surface plasmon resonance. The subsequent irradiation with linearly polarized ultrashort laser pulses induces spectrally defined and three times larger dichroism than in non-poled sample

Direct writing of birefringent elements by ultrafast laser nanostructuring in multicomponent glass

Self-assembled nanostructures created by femtosecond laserirradiation are demonstrated in alkali-free aluminoborosilicate glass. The growth of the induced retardance associated with the nanograting formation is three orders of magnitude slower than in silicaglass and is observed only within a narrow range of pulse energies. However, the strength of retardance asymptotically approaches the value typically measured in pure silicaglass, which is attractive for practical applications. A similar intensity threshold for nanograting formation of about 1 TW/cm2 is observed for all glasses studied. The radially polarized vortex beam micro-converter designed as a space-variant quarter-wave retarder for the near-infrared spectral range is imprinted in commercial Schott AF32 glass

Recent progress in ultrafast laser nanostructuring: from two-plasmon decay to longitudinal field puzzle

Correlation between (3/2)omega harmonic, two-plasmon decay and ultrafast laser induced nanogratings is observed. Paradoxically, no crystallization of amorphous Si by longitudinal field produced by S-waveplate is observed, despite strongest intensity

High-topological charge vortex tweezers with continuous control of orbital angular momentum by ultrafast laser machining

We demonstrate a single beam generated optical vortices of topological charge up to 100 with tunable orbital angular momentum. The continuous control of torque without altering the intensity distribution was implemented in optical trapping

Silicon microreflector created by single ultrafast laser pulse

Directly written structure created on the surface of silicon by the single pulse femtosecond laser irradiation are observed to function as microreflector. The smooth surface of the structure is a result of molten material flow