Emil Agocs

Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping

Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er3+-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er3+-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er3+-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er3+-ions without clustering, validated by the record high lifetime-density product 0.96u2009×u20091019u2009s.cm−3. Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er3+ concentration via different target glasses. The increased Er3+ content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease.

Plasmon-enhanced two-channel in situ Kretschmann ellipsometry of protein adsorption, cellular adhesion and polyelectrolyte deposition on titania nanostructures

Plasmon-enhanced in situ spectroscopic ellipsometry was realized using the Kretschmann geometry. A 10-μL flow cell was designed for multi-channel measurements using a semi-cylindrical lens. Dual-channel monitoring of the layer formation of different organic structures has been demonstrated on titania nanoparticle thin films supported by gold. Complex modeling capabilities as well as a sensitivity of ~40 pg/mm2 with a time resolution of 1 s was achieved. The surface adsorption was enhanced by the titania nanoparticles due to the larger specific surface and nanoroughness, which is consistent with our previous results on titanate nanotubes.

Doping silica beyond limits with laser plasma for active photonic materials

The limited solubility of rare-earths in silica hampers the development of loss-compensated photonic integrated circuits. We report a novel method using femtosecond laser plasma assisted hybrid material integration of rare-earth-doped tellurite with silica, achieving high doping concentration of Er3+ and Yb3+-ions, 1.63 × 1021 atoms.cm−3,without segregation validated by Er3+:4I13/2 lifetime of 9.1 ms. The sequential ablation of two individual rare-earth (Er3+/Yb3+) doped-tellurite glass targets produces an exceptional intermixing of Er3+ and Yb3+-ions extending to the pristine silica with sharp interface. Formation of such homogeneous glass structure with Er3+-Yb3+-ions in a matrix of silica is not possible to realise by conventional methods.

Bilayered (silica–chitosan) coatings for studying dye release in aqueous media: The role of chitosan properties

Chitosan and bilayered--Rhodamine 6G impregnated silica-chitosan--coatings (300-3000 nm thick) were prepared and investigated as a model for controlled drug release. Properties of native, ionically (sodium triphosphate) and covalently (glutaraldehyde) cross-linked layers of chitosan in contact with aqueous phase (modeling human blood pH of ca. 7.3) were investigated. The cross-linking was confirmed by attenuated total reflection (ATR) Fourier transform infrared (FTIR), energy-dispersive spectroscopy (EDS) and solid state (13)C nuclear magnetic resonance (NMR) spectroscopy. The evolution of advancing water contact angles as a function of time was measured, and from the results restricted mobility of polymer segments in the interfacial layer of cross-linked chitosan coatings were assumed. Spectroscopic ellipsometry measurements showed that covalent cross-linking leads to a lowered, while ionic cross-linking to an increased swelling degree of chitosan layers. Despite the swelling behavior both cross-linked chitosan layers showed significant retard effect on dye release from the bilayered coatings.

Multiple angle of incidence, spectroscopic, plasmon-enhanced, internal reflection ellipsometry for the characterization of solid-liquid interface processes

A semi-cylindrical lens in Kretschmann geometry combined with a flow cell was designed for a commercial rotating compensator ellipsometer to perform internal reflection spectroscopic ellipsometry measurements, while allowing the use of multiple angles of incidence. A thin glass slide covered with a gold film was mounted between the half-cylindrical lens and a small-volume flow cell ensuring an improved sensitivity for protein adsorption experiments. The performance of the system was investigated depending on the angle of incidence, wavelength range and thickness of the gold films for surface plasmon resonance enhanced ellipsometric measurements, and a sensitivity increase was revealed compared to ellipsometric measurements with standard flow cells, depending on the measurement parameters and configuration. The sensitivity increase was demonstrated for fibrinogen adsorption.

Composite polymeric-inorganic waveguide fabricated by injection molding for biosensing applications

Inorganic based optical transducers have demonstrated their suitability for labelled and label-free sensing of biomolecules but suffer from their relatively high cost. Photonic structures fabricated in polymer by molding techniques could drastically reduce the cost per test and pave the way for label-free screening in point-of care environment where the cost per test is an essential concern. In this paper we present the advances in the fabrication of waveguides with cyclo olefin copolymer (COC) cladding and TiO2 core with mass-production compatible injection molding and evaporation. We demonstrate the optical propagation in a slab waveguide supporting both transverse electric and magnetic modes and monitor the response of the phase difference between the two modes when a droplet of water is deposited on the chip.

Design, Ion Beam Fabrication and Test of Integrated Optical Elements

Various methods, based on the use of ion beams, were used for the fabrication of planar and channel optical waveguides and Bragg gratings in optical crystals and glasses. Some examples of the results of these researches are presented in this review. Researches were initiated on ion beam fabrication of planar and channel optical waveguides in tellurite glasses. The ions used in the experiments were mainly helium, carbon, nitrogen and oxygen. In case of the two dimensional elements, like channel waveguides, both masked ion implantation and direct writing with ion microbeam were used. Optical microscopy (phase contrast, interference and interference contrast (INTERPHAKO), spectroscopic ellipsometry, m-line spectroscopy, Rutherford Backscattering and micro Raman spectroscopy were used to test the integrated optical elements.

Recent progress in ion beam fabrication of integrated optical elements

Planar optical waveguides and Bragg gratings were designed and written in various optical crystals with medium energy ion implantation. Some examples of the fabricated integrated optical elements are presented in this article: Planar optical waveguides fabricated in Er: LiNbO3 crystal by irradiation with 5 MeV N3+ ions, and Bragg gratings fabricated by multi-energy implantation into a silicon substrate with N+ ions in the 800 keV - 3.5 MeV energy range. The SRIM code was used for planning the optical elements. The ion implanted optical elements were tested by spectroscopic ellipsometry and visible and infrared reflectometry. The results show that the proposed fabrication methods can produce integrated optical elements of adequate parameters.

Nanophotonics of biomaterials and inorganic nanostructures

Optical methods have been used for the sensitive characterization of surfaces and thin films for more than a century. The first ellipsometric measurement was conducted on metal surfaces by Paul Drude in 1889. The word ellipsometer was first used by Rothen in a study of antigen-antibody interactions on polished metal surfaces in 1945. The bible of ellipsometry has been published in the second half of the 70s. The publications in the topic of ellipsometry started to increase rapidly by the end of the 80s, together with concepts like surface plasmon resonance, later new topics like photonic crystals emerged. These techniques find applications in many fields, including sensorics or photovoltaics. In optical sensorics, the highest sensitivities were achieved by waveguide interferometry and plasmon resonance configurations. The instrumentation of ellipsometry is also being developed intensively towards higher sensitivity and performance by combinations with plasmonics, scatterometry, imaging or waveguide methods, utilizing the high sensitivity, high speed, non-destructive nature and mapping capabilities. Not only the instrumentation but also the methods of evaluation show a significant development, which leads to the characterization of structures with increasing complexity, including photonic, porous or metal surfaces. This article discusses a selection of interesting applications of photonics in the Centre for Energy Research of the Hungarian Academy of Sciences.

Platform manufacturing technique for next generation integrated photonic components

Innovation in integrated photonics and associated fields is imperative with looming bottlenecks in the existing internet infrastructure due to rapidly increasing demand, across society and industry, for greater bandwidth and data access. A priority in this field is the development of a monolithic photonic integrated circuit (PIC), simplifying the design, manufacture and material requirements of current devices, with reduced cost, power and footprints. Furthermore, an improved efficiency and performance is highly sought after as this market anticipates explosive growth. Typically the key components are often made through disparate methods, and then packaged together for a final device. This creates an exciting opportunity for a novel platform technology to overcome such limitations and enhance existing capabilities while opening up new frontiers in device design and complexity.