Vilnius, Lithuania
Vilnius, Lithuania

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Buividas R.,Swinburne University of Technology | Mikutis M.,Vilnius University | Mikutis M.,Altechna Co. | Gervinskas G.,Swinburne University of Technology | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We report on a technique for precise hole drilling in optical fibers using tightly focused femtosecond laser pulses. This direct laser writing approach makes it possible to minimize the amount of waveguide material for uncompromised mechanical performance of the fiber. The proof-of-the-principle of the fiber integration into a microfluidic chip is demonstrated. We show that fabricated holes in the waveguides can be used for measurement of absorption coefficient and refractive index changes at 1×10-3 refractive index units and 2 cm-1 for refractive index and absorption changes, respectively. Simple design and integration possibility of laser-fabricated waveguide sensors is prospective for optofluidic applications. © 2012 SPIE.


Buividas R.,Swinburne University of Technology | Kudrius T.,Vilnius University | Kudrius T.,Altechna Co. | Sliupas R.,Vilnius University | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

We report on surface structuring of sapphire, silicon carbide, and silicon by femtosecond laser pulses in multipulse irradiation mode. The formed ripples on the flat surface or on the vertical walls with hierarchical structures whose feature sizes are ranging from the irradiation wavelength down to ∼ 50 nm are prospective templates for surface enhanced Raman scattering after coating with plasmonic metals. We study complex patterns of fine ripples with periods Λr, as small as λ/Rp, where Rp ≃ 3 - 5. The mechanisms suggested for such Rp values are discussed: temperature and density of breakdown plasma, angle of incidence, mechanism of second harmonic generation (SHG) and absorption. Predictions of the surface and bulk models of ripple formation are compared with experimental values of Rp-factor. We propose a model of ripple formation on the surface, which is based on the known in-bulk sphere-to-plane formation of breakdown plasma in the surface proximity. In semiconductor 4H:SiC normal ripples with periods 190 and 230 nm were recorded with 800 nm and 1030 nm fs-laser pulses respectively. We show that the period of ripples is defined by the dielectric properties of crystalline (solid) phase rather than the molten phase in the case of silicon. Generation of SHG on the surface of sample and plasma nano-bubbles are discussed: surface-SHG is found not important in ripples' formation as revealed by comparative study of periods on Al2O3 and TiO2 at 800 nm wavelength of irradiation. We propose that ripple periodicity is pinned to the smallest possible standing wave cavity (λ/n)/2 inside material of refractive index n. © 2010 SPIE.


Buividas R.,Swinburne University of Technology | Rosa L.,Swinburne University of Technology | Sliupas R.,Altechna Co. | Sliupas R.,Vilnius University | And 5 more authors.
Nanotechnology | Year: 2011

The mechanism of the fine ripples, perpendicular to laser polarization, on the surface of (semi)transparent materials with period smaller than the vacuum wavelength, λ, of the incident radiation is proposed and experimentally validated. The sphere-to-plane transformation of nanoplasma bubbles responsible for the in-bulk ripples accounts for the fine ripples on the surface of dielectrics and semiconductors. The mechanism is demonstrated for 4H:SiC and sapphire surfaces using 800 nm/150 fs and 1030 nm/300 fs laser pulses. The ripples are pinned to the smallest possible standing wave cavity inside material of refractive index n. This defines the corresponding period, Λ = (λ/n)/2, of a light standing wave with intensity, E2, at the maxima of which surface ablation occurs. The mechanism accounts for the fine ripples at the breakdown conditions. Comparison with ripples recorded on different materials and via other mechanisms using femtosecond pulses is presented and application potential is discussed. © 2011 IOP Publishing Ltd.


Kudrius T.,Altechna Co. | Slekys G.,Altechna Co. | Juodkazis S.,Swinburne University of Technology | Juodkazis S.,Hokkaido University
Journal of Physics D: Applied Physics | Year: 2010

We demonstrate that F+ centres (oxygen vacancy with a trapped electron) are induced by femtosecond laser scribing of a crystalline Al 2O3 wafer and that they can be fully annealed at 1100 °C. The corresponding photoluminescence band at 325 nm which is induced by the femto second laser structuring of a sapphire surface is extinct after heat treatment. Thermal activation of oxygen diffusion in sapphire can explain the observation. The potential of pre-textured sapphire in lighting and micro-optical applications is discussed. © 2010 IOP Publishing Ltd.


Buividas R.,Swinburne University of Technology | Buividas R.,Melbourne Center For Nanofabrication | Mikutis M.,Altechna Co. | Mikutis M.,Vilnius University | And 6 more authors.
Lithuanian Journal of Physics | Year: 2012

Recent results in high-precision surface ablation, film removal, ripple formation are presented. Volume processing via polymerization, marking, dicing, cutting, and drilling of semiconductor and dielectric materials are discussed. We focus on processes which can be carried out at a high throughput in the industrial environment or/and can deliver functionalities currently not amenable by competing technologies. Unique features of direct laser writing by femtosecond laser pulses are highlighted. Methodology for solutions of engineering tasks is presented. Namely, the laser irradiation parameters are selected on the basis of the required processing conditions for the material of a workpiece. © Lietuvos mokslu{ogonek} akademija, 2012.


Maigyte L.,Polytechnic University of Catalonia | Gertus T.,Vilnius University | Gertus T.,Altechna Co. | Peckus M.,Vilnius University | And 5 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We report experimental evidence of spatial filtering of light beams by three-dimensional, low-refraction-index-contrast photonic crystals. The photonic crystals were fabricated in a glass bulk, where the refraction index has been periodically modulated using tightly focused femtosecond laser pulses. We observe filtered areas in the angular distributions of the transmitted radiation, and we interpret the observations by theoretical and numerical study of light propagation in index-modulated material in paraxial model. © 2010 The American Physical Society.


Beresna M.,University of Southampton | Gecevicius M.,University of Southampton | Kazansky P.G.,University of Southampton | Gertus T.,Altechna Co.
Applied Physics Letters | Year: 2011

We demonstrate the generation of optical vortices with radial or azimuthal polarization using a space variant polarization converter, fabricated by femtosecond laser writing of self-assembled nanostructures in silica glass. Manipulation of the induced form birefringence is achieved by controlling writing parameters, in particular, the polarization azimuth of the writing beam. The fabricated converter allows switching from radial to azimuthal polarization by controlling the handedness of incident circular polarization. © 2011 American Institute of Physics.


Juodkazis K.,Lithuanian Academy of Sciences | Juodkazyte J.,Lithuanian Academy of Sciences | Kalinauskas P.,Lithuanian Academy of Sciences | Gertus T.,Altechna Co. | And 4 more authors.
Journal of Solid State Electrochemistry | Year: 2010

Influence of direct laser writing with femtosecond pulses on electrochemical etching of n-type low conductivity (>1,000 Ωcm) silicon is demonstrated. It has been shown that thermal 1-μ-thick SiO 2 layer on silicon surface can be used as a protective layer in the electrochemical etching process. It has been found that laser ablation changes not only the surface morphology and structure of silicon samples but also the character of their anodic etching in aqueous solution of hydrofluoric acid. Formation of microvoids and caverns of irregular shape has been observed at the laser-ablated sites. It is proposed that the change of silicon conductivity from n-to p-type takes place at the laser fabricated regions. Processes of Si anodic oxidation and electrochemical etching are discussed. © Springer-Verlag 2009.


Gertus T.,Vilnius University | Gertus T.,Altechna Co. | Kazdailis P.,Vilnius University | Rimeika R.,Vilnius University | And 2 more authors.
Electronics Letters | Year: 2010

The fabrication of surface acoustic wave (SAW) devices by femtosecond laser micromachining has been demonstrated. The interdigital SAW transducers of 50m wavelength were formed on YZ lithium niobate substrate by femtosecond pulse ablation of an aluminium layer. The two-port SAW device has insertion loss of 11dB at 68MHz. The S-parameter measurements revealed no degradation in substrate elastic, piezoelectric, and dielectric properties of the substrate due to laser processing. © 2010 The Institution of Engineering and Technology.


Gertus T.,Vilnius University | Gertus T.,Altechna Co. | Mikutis M.,Vilnius University | Mikutis M.,Altechna Co. | And 4 more authors.
Microwave and Optical Technology Letters | Year: 2012

Fabrication of surface acoustic wave (SAW) based phononic crystal (PC) device by femtosecond laser micromachining has been demonstrated. The thin-film interdigital SAW transducers of 50 μm wavelength together with PC structure (1- and 2-dimensional) of 25 μm period were fabricated on the YZ lithium niobate crystal surface by femtosecond pulse selective ablation of an aluminum layer. The device S parameter measurements revealed different influence of 1D and 2D PC structures on the SAW propagation. © 2012 Wiley Periodicals, Inc.

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