Paweł Karasiński

Sensor properties of planar waveguide structures with grating couplers

The paper presents the results of theoretical analysis as well as the results of experimental research involving planar sensor structures with input grating couplers of the period Λ = 800 nm. In the theoretical part of the paper we discussed the influence of the parameters of a sensor structure on it sensitivities. The experimental part of the work presents the results of experimental research involving the influence of refractive index of the cover on the coupling characteristics of sensor structures with grating couplers. The full widths at half maximum (FWHM) were from 0.023° to 0.029°. For the investigated structures we estimated detection thresholds for the changes of refractive index of the cover and the changes of sensitive film thickness. It has been demonstrated that by the application of the elaborated structures we can detect minimal changes of the refractive index (Δnc)min = 2.1×10−6 when the refractive index of the cover nc = 1.333 and (Δnc)min = 1.0×10−6 when nc = 1515. For sensitive films of the thickness w < 100 nm, by using the elaborated structures, we can detect mean changes of the thickness along the values lower than 10−3 nm.

Impressing technology of optical Bragg's gratings on planar optical sol-gel waveguides

The aim of the presented investigations was to develop a technique of producing Bragg’s grating couplers on planar waveguides. Waveguides are obtained by means of the sol-gel technology. The introduction of a light beam into the structure of the waveguide is in the case of planar or strip optical systems always an essential technical problem, requiring simple and reproducible solutions without extending excessively the waveguide structure. The paper presents a technology of producing grating couplers by impressing the pattern of the network while forming the planar waveguide structure applying the sol-gel method. Some remarks concerning the sol-gel technology are also presented. The results of investigations on grating couplers obtained in such a way have been discussed, too.Attention has been drawn to the possibility of using such structures in optoelectronic sensors, particularly gas sensors, including sensors of water vapour as well as toxic gases.

Technology of ion exchange in glass and its application in waveguide planar sensors

The possibilities of producing waveguide structures in glass using the ion-exchange technique are discussed. The modeling of par- ticular sequences of the technological process with respect to planar and strip waveguide structures as well as refraction profile measurement re- sults for these waveguides are presented. An exemplary application of this technique in the construction of planar sensors is also presented.

Optical uniform/gradient waveguide sensor structure-characterization

The paper presents the characterization of a composite uniform/gradient waveguide sensor structure. The results of theoretical analysis and experimental studies have been presented. The influence of sensor structure parameters on homogenous sensitivity and on surface sensitivity has been analyzed. Gradient layers for composite sensor structures were produced using the ion-exchange method, and the uniform layers, using the sol-gel method. In the experimental studies, involving the produced sensor structures, a prism coupler and a grating coupler were applied. Excellent agreement between the results of theoretical analysis and experimental studies has been achieved.

Embossable grating couplers for planar evanescent wave sensors

The paper presents input grating couplers to be applied in planar evanescent wave sensors. Waveguide films SiO2:TiO2 were obtained using the sol-gel method, and grating couplers with a groove density of 1000 g/mm and 2400 g/mm were produced using the method of master grating embossing in sol film. The influence of refractive index of the cover on incoupling angles was presented. Basing on the experimental results, detection limits involving the changes of effective indexes and refractive indexes of the cover for the investigated planar structures were determined. Sensor structures with the couplers having a groove density of 1000 g/mm enable to detect minimum changes of the effective index below 3.3×10−7 and to detect minimum changes of refractive index of the cover below 2.3×10−6. Detection limits for the structures with couplers having the groove density of 2400 g/mm are over twofold higher.

EIS Study of SiO2 Oxide Film on 316L Stainless Steel for Cardiac Implants

The correct relationship between implant and tissue environment provides a properly prepared surface of a medical device. The combination of advantages of metal implants with the required biocompatibility is achieved through various methods of surface treatment such as: electrochemical polishing, chemical passivation, preparation of oxide coatings obtained with the sol-gel method. The relatively short history of use of silica layers in biomedical applications transfers into a small amount of literature relating to the electrochemical properties of these layers. Therefore, the authors proposed in the work forming a silica layer of the established technological parameters on surface of the 316L stainless steel. In order to determine the usefulness of this technology electrochemical impedance spectroscopy studies were performed. Furthermore, corrosion resistance tests by means of the potentiodynamic method were also carried out. The obtained results were the basis for optimization of technological conditions for deposition of silica layers on the 316L steel surface.

Electrochemical Impedance Spectroscopy and Corrosion Resistance of SiO2 Coated CpTi and Ti-6Al-7Nb Alloy

One of the ways to increase the hemocompatibility of surface of titanium and its alloys is to apply sol-gel method to form oxide films based on such elements as Ti or Si. However, the literature suggests existence of group of undefined phenomena associated with oxide layer formation on surfaces of metallic biomaterals in the presence of silicon. Therefore, the study involves development of conditions suitable for production of surface layers that have phisycal and chemical properties adequate for application in cardiovascular system. To assess the usefulness of proposed modifications, the Authors carried out electrochemical tests involving potentiodynamic and impedance measurements. The tests were performed in artificial serum in temperature T = 37±1°C in order to simulate real-life conditions. The obtained results show diverse properties of SiO2 layer that depend on process parameters of its formation.

Application of the 4x4 matrix method for the modeling of planar waveguide sensors

The paper provides the discussion on the application of matrix method for the analysis of planar waveguide structures. The method has been based on the 4x4-matrix technigue. In the paper, we present the method applied for asymmetrical planar waveguide structures of step-index type and for gradient-index waveguides. The equation characteristic for structures ofthat type has been presented as well as expressions for effective refractive indexes of substrate and cover. The paper presents the analysis results of selected structures of planar waveguide sensors obtained with the application of the matrix method.

The effects of a SiO2 coating on the corrosion parameters cpTi and Ti-6Al-7Nb alloy

The aim of this paper was to evaluate the usefulness of the sol-gel method application, to modificate the surface of the Ti6Al7Nb alloy and the cpTi titanium (Grade 4) with SiO2 oxide, applied on the vascular implants to improve their hemocompatibility. Mechanical treatment was followed by film deposition on surface of the titanium samples. An appropriate selection of the process parameters was verified in the studies of corrosion, using potentiodynamic and impedance method. A test was conducted in the solution simulating blood vessels environment, in simulated body fluid at t = 37.0 ± 1 °C and pH = 7.0 ± 0.2. Results showed varied electrochemical properties of the SiO2 film, depending on its deposition parameters. Correlations between corrosion resistance and layer adhesion to the substrate were observed, depending on annealing temperature.

Two-component waveguide SiO2:TiO2 films fabricated by sol–gel technology for optoelectronic applications

The research results involving two-component waveguide films SiO2:TiO2 produced in sol–gel technology are presented. The waveguide films were deposited on soda-lime glass substrates using dip-coating method. The titled layers were fabricated as waveguide layers for application in planar evanescent wave sensors. The such prepared slab waveguides possess low optical losses and they demonstrate a possibility of formation of the photo induced optical second harmonic generation (SHG) which is observed due to photoinduced charge density non-centrosymmetry. In the present work we explore additionally the dependences of the photoinduced SHG versus the power density and the time of treatment.