Ausra Cerkauskaite

Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel

We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

Extreme ultraviolet vector beams driven by infrared lasers

Vector beams, beams with a non-uniform state of polarization, have become an indispensable tool in many areas of science and technology. Harnessing topological light properties paves the way to control and manipulate light–matter interactions at different levels, from the quantum to macroscopic physics. Here we generate tabletop extreme ultraviolet (EUV) vector beams driven by high-order harmonic generation (HHG). Our experimental and theoretical results demonstrate that HHG imprints the polarization state of the fundamental (infrared) beam, ranging from radial to azimuthal, into the higher frequency radiation. Our numerical simulations also demonstrate that the generated high-order harmonic beams can be synthesized into attosecond vector beams in the EUV/soft x-ray regime. Our proposal overcomes the state-of-the-art-limitations for the generation of vector beams far from the visible domain and could be applied in fields such as diffractive imaging, EUV lithography, or ultrafast control of magnetic properties.

Ultrafast laser induced nanostructured ITO for liquid crystal alignment and higher transparency electrodes

Femtosecond laser nanostructured indium tin oxide (ITO) coated glass is shown to act both as a liquid crystal (LC) alignment layer and as an electrode with higher transparency. The nanopatterns of the 120 nm period were created using ultrashort laser pulses directly on ITO films without any additional spin coating materials or lithography process. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO confirming the follow-up of the LC director to the line orientation. The device interfacial anchoring energy was found to be ∼ 1 μ J / m 2, comparable to the anchoring energy of nematic LC on photosensitive polymers. The transparency as an electrode was found to improve due to the better antireflection and lower absorption expected from a nanostructured surface.Femtosecond laser nanostructured indium tin oxide (ITO) coated glass is shown to act both as a liquid crystal (LC) alignment layer and as an electrode with higher transparency. The nanopatterns of the 120 nm period were created using ultrashort laser pulses directly on ITO films without any additional spin coating materials or lithography process. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO confirming the follow-up of the LC director to the line orientation. The device interfacial anchoring energy was found to be ∼ 1 μ J / m 2, comparable to the anchoring energy of nematic LC on photosensitive polymers. The transparency as an electrode was found to improve due to the better antireflection and lower absorption expected from a nanostructured surface.

Generation of extreme ultraviolet vector beams from infrared laser pulses

Vector beams are light beams with spatially variant polarization [1]. During the last decade vector beams have become an indispensable tool in many areas of science and technology such as optical trapping, quantum memories, and quantum optics. In particular, radially and azimuthally polarized light beams are the paradigm of vector beams. Radial vector beams are especially interesting due to the non-vanishing longitudinal electric field component present in tightly focusing systems, which allows to sharply focus light below the diffraction limit [2]. On the other hand, azimuthal vector beams can induce longitudinal magnetic fields with potential applications in spectroscopy and microscopy. However, the spectral limitations of the generation techniques of vector beams based on linear optics prevent their efficient generation in the extreme-ultraviolet (EUV) and x-ray regimes, which would further extend their applications down to the nanometric scale. High-order harmonic generation (HHG) is known as a unique non-perturbative frequency up-conversion process for the generation of coherent EUV and soft x-ray radiation. A remarkable aspect of HHG is its fully coherent nature, mapping the characteristics of the driving field to the high frequency spectral region and thus allowing to harness the angular momentum properties of the harmonic radiation through modifications of the driving field [3-5].

Geometric phase circular gratings fabricated by ultrafast laser nanostructuring for symmetric simultaneous spatio-temporal focusing

The recent advances in flat optics have challenged the limitations of conventional optics by implementing planar elements that instead of rely on dynamic phase manipulate light waves via subwavelength-spaced phase shifters with spatially varying phase response [1]. One of the approaches for designing geometric (Pancharatnam-Berry phase [2]) phase optical elements (GPOE) is to exploit the transparent dielectrics which originate form birefringence. The desired phase pattern of the wave is directly encoded in the optical axis orientation, and is equal to twice the rotation angle of the local retarder. A decade ago, the formation of self-organized subwavelength periodicity structures, referred to as nanogratings, in the bulk of silica glass after irradiation with ultrashort light pulses was observed [3]. Such a periodic assembly behaves as a uniaxial birefringent material with optical axis oriented parallel to the polarization of incident laser beam, and serves as a perfect candidate for designing geometric phase profiles of nearly any optical components. The performance of fabricated GPOE varies depending on the processing conditions reaching the efficiency and transmittance higher than 90%, as well as the phase gradient higher than π rad/μm [4]. The silica glass based optics with a damage threshold of 22.8 J/cm2 demonstrate the potential of high-power applications.

Liquid crystal alignment on ultrafast laser nanostructured ITO coated glass

Liquid crystal (LC) devices are widely used as building blocks of many electro-optical systems including linear polarization rotators, dynamical wave plate retarders, and pixilated devices for displays, spatial light modulators, and tunable filters [1]. Precise alignment of the LC molecules is required for high quality components. The anisotropic nature of LC molecules allows them to align on solid surfaces. This can be achieved either due to physicochemical interaction such as photo-alignment on surfaces using polarized blue light or due to the elastic interaction when aligned along nanogrooves created by mechanical rubbing or lithography techniques [2]. Although numerous methods enabling the manufacturing of LC devices have been reported, the technological flexibility and precision remains a problem.

Dataset for Form-Birefringence in ITO Thin Films Engineered by Ultrafast Laser Nanostructuring

Dataset for Cerkauskaite, A., Drevinskas, R., Solodar, A., Abdulhalim, I., & Kazansky, P. (2017). Form-Birefringence in ITO Thin Films Engineered by Ultrafast Laser Nanostructuring. ACS Photonics.

Geometric phase holograms imprinted by femtosecond laser nanostructuring

We demonstrate direct-write laser nanostructuring of semiconductor thin-films and transparent dielectrics resulting in space-variant anisotropic materials. The continuous phase profile of nearly any optical component can be achieved solely by the means of geometric phase.

Eternal 5D optical data storage in glass(Conference Presentation)

A decade ago it has been discovered that during femtosecond laser writing self-organized subwavelength structures with record small features of 20 nm, could be created in the volume of silica glass. On the macroscopic scale the self-assembled nanostructure behaves as a uniaxial optical crystal with negative birefringence. The optical anisotropy, which results from the alignment of nano-platelets, referred to as form birefringence, is of the same order of magnitude as positive birefringence in crystalline quartz. The two independent parameters describing birefringence, the slow axis orientation (4th dimension) and the strength of retardance (5th dimension), are explored for the optical encoding of information in addition to three spatial coordinates. The slow axis orientation and the retardance are independently manipulated by the polarization and intensity of the femtosecond laser beam. The data optically encoded into five dimensions is successfully retrieved by quantitative birefringence measurements. The storage allows unprecedented parameters including hundreds of terabytes per disc data capacity and thermal stability up to 1000°. Even at elevated temperatures of 160oC, the extrapolated decay time of nanogratings is comparable with the age of the Universe - 13.8 billion years. The recording of the digital documents, which will survive the human race, including the eternal copies of Universal Declaration of Human Rights, Newton’s Opticks, Kings James Bible and Magna Carta, is a vital step towards an eternal archive. Additionally, a number of projects (such as Time Capsule to Mars, MoonMail, and the Google Lunar XPRIZE) could benefit from the techniques extreme durability, which fulfills a crucial requirement for storage on the Moon or Mars.

Dataset for 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.