Ing. Tomáš Martan, Ph.D.

This paper presents the design and construction of a new planar optical Polymer Waveguide Bragg grating (PWBG) temperature and humidity sensor realized by polymer-glass hybrid technology composition with a new layout concept. The Bragg grating of a sensor was made by a Direct Laser Writing (DLW) in Poly (methyl methacrylate) (PMMA) formed on a multimode waveguide realized in a glass substrate by Ag+ <-> Na+ ion exchange. The fabricated hybrid Bragg grating structure exhibited more than 10 dB of the attenuation dip, equivalent to higher than 90% diffraction efficiency. The fabricated hybrid PWBG sensor exhibited high temperature and humidity sensitivity in contrast to glass-based sensors of - 48.6 pm/degrees C and 54.16 pm center dot RH-1, respectively.

We report on the optical properties of the Si vertical multi-junction cell photovoltaic converters optimized for 980 nm wavelengths for power over fiber applications. The converters were coupled with the 105 μm multimode fiber and the optical efficiency were measured for optical power from 250 mW to 4 W.

We present an improvement of tapered optical fiber (TOF) sensor’s response for the detection of liquids, which is achieved by TOF surface structural modification. Our TOF sensors utilize the refractometric principle with enhanced evanescent-wave overlap due to the wavelength of 1550 nm and TOF waist diameters of 4–6 μm. The structural modification is achieved by long-term TOF exposition to hygroscopic liquid analytes and ambient atmosphere. To analyze the structural modification process, long-term as well as proof-of-principle tests have been carried out to evaluate TOF sensors stability in terms of sensitivity and resolution. Maximum sensitivity of over 2100 dB/RIU has been reached when TOF is used to detect a liquid analyte with refractive index of 1.415. Increase of more than 1400 dB/RIU is attributed to the enhanced sensitivity. Sample TOF sensors were then linearly calibrated and have been tested in more than one year-long continuous measurement campaign. Resolution better than 7x10^-4 for a refractive index range of from 1.405 to 1.425 with working point drift below 2x10^-4 over 12 months period has been achieved. Our results and observations are suitable for reliable, low-cost and application-tailored TOF sensor development.

A generalized model for the detection of liquids within suspended-core microstructured optical fibers has been experimentally and theoretically derived. The sensor detection is based on the refractometric principle of transmission losses due to the overlap of the evanescent field with the liquid analyte. A number of parameters, including fiber core diameter and filling length, have been included in the general model. Specially tailored suspended-core fibers were manufactured with the core diameters within the range of 2.4 um to 4.0 um. Five selected liquid analytes were used to cover the refractive index range of 1.35 to 1.42. Based on experiments, the characteristics of the parameters of the semi-empirical model have been determined by a genetic algorithm using 283 measurement data sets. The model can be used to design sensors for the detection of liquid analytes as it provides a set of parameters allowing to optimize the sensor’s sensitivity for a wide scale of applications. Finally, numerical simulations of the system were carried out by an eigenmode routine to support the results of the generalized model.

Detecting explosive, flammable or toxic industrial liquids reliably and accurately is a matter of civic responsibility which cannot be treated lightly. Tapered optical fibers (TOFs) and suspended core microstructured optical fibers (SC MOFs) were separately used as sensors of liquids without being compared to each other. We present a highly-sensitive time-stable TOF sensor incorporated in the pipeline system for in-line regime of measurement. The paper is furthermore focused on the comparison of this TOF and SC MOF of similar parameters for detection of selected liquids. A validated method that incorporates TOF and SC MOF of small core (waist) diameter for refractometric detection is presented. The principle of detection is based on the overlap of an enhanced evanescent wave with a liquid analyte which either fills the cladding holes of the SC MOF, or surrounds the waist area of the TOF. Optical power within the evanescent wave for both sensing structures and selected liquid analytes is analyzed. Measurement results concerning TOF and SC MOF are compared. Calculations to ascertain the limit of detection (LOD) for each sensor and the sensitivity (S) to refractive indices of liquid analytes in the range of 1.4269 to 1.4361 were performed at a wavelength of 1550 nm with the lowest refractive index step of 0.0007. Results affirming that S = 600.96 dB/RIU and LOD = 0.0733 RIU for the SC MOF and S = 1143.2 dB/RIU and LOD of 0.0026 RIU for the TOF sensor were achieved, clearly illustrating that TOF based sensors can reach close to two times greater sensitivity and 30-times higher limit of detection. The paper extends the comparison of the fiber sensors by discussing the potential applications.

The paper reports our progress on soft-glass fibers for optical switching purposes based on four-wave mixing. Specific development of connectorized nonlinear modules for switching application is presented. For the arsenic-selenide fiber we present a novel solid joint technology, with connection losses of only 0.25 dB, which is the lowest value presented up-to-date. We have carried out conversion efficiency simulations, conversion efficiency of -16.1 dB was obtained with arsenic-selenide fiber of length reduced to 5 m. Finally experimental tests are included employing our developed optical switch testbed. Measurement results with a 26 m and a 4.5 m long arsenic-selenide nonlinear modules are presented.

Tapered optical fibers were prepared by heating of a section of the single-mode optical fiber using the tapering apparatus equipped by hydrogen-oxygen flame. Prepared samples of taper waist diameter of 6.1 μm and 3.4 μm were characterized and used as sensors working on refractometric principle of detection at a wavelength of 1550 nm. The repeatability of sensitivity measurement for selected liquids (hydrocarbons) was successfully tested with maximum of deviation of 0.1 dB from the mean value. The samples returned to baseline after purifying very well. Maximum of deviation of 0.05 dB from the mean value was calculated from measured data. OCIS codes: 280.0280

We report development of suspended-core silica and lead-silicate microstructured optical fibers for detection of liquids and supercontinuum generation. Theoretical analysis of effective mode area, dispersion curve, nonlinear coefficient and mode-field overlap is presented. For a specific lead-silicate fiber we determinated the zero dispersion wavelength at 1113 nm with a nonlinear coefficient of 1321 W-1km-1. For detection of liquids both silica and lead-silicate fibers are found to be suitable in different refractive index ranges 1.38-1.44 and 1.68-1.74 respectively. Coupling efficiency into all studied fibers over 40%; fiber attenuation was measured by the cut-back technique and is approximately 2 dB/m for silica glass fibers and over 3 dB/m for lead-silicate fibers.

This paper describes the refractometric detection of liquids based on silica multimode optical fibers which were tapered to increase the evanescent-wave overlap for higher sensor sensitivity. By precisely monitoring the production process, consistent sample parameters were achieved. More than 200 tapers with a taper waist diameter range from 6.0 to 76.3 μm were prepared from polymer-clad silica and gradient-index multimode fibers. U-shaped fiber taper sensitivities were analytically compared with straight tapers with resulting intensity sensitivities of over 200%/RIU. Crucial parameters for real sensor applications, such as measurement repeatability, reproducibility, and long-term stability, were further studied for polymer-clad silica straight tapers. Longterm stability was monitored showing stable measurement results over a 6 months long interval. Measurement repeatability and reproducibility with standard deviations of 0.55%/RIU and 2.26%/RIU, respectively, were achieved.

This paper presents results from the development of soft-glass fiber modules for near- and mid-infrared applications. They can be utilized especially in applications such as high-power lasers, supercontinuum generation and spectroscopy. The technology of fiber processing, preparation and connectorization has been mastered in cooperation with SQS Fiber optics in the frame of joint cooperation in several co-running projects; the high-power lasers and supercontinuum generation is prepared with the IPE Academy of Sciences of the Czech Republic. We have studied soft-glass fibers including chalcogenide arsenic-selenide, lead-silicate and zirconium-fluoride glass materials. Crucial optical signal factors for specific purposes such as operational wavelength, insertion-loss on the soft-glass-silica-glass boundaries, back-reflected optical power reduction to prevent lasing, power-induced heat generation issues and mode-field mismatch must be taken into account. Technological aspects then include bending radii, glass fragilities and glass toxicities. Results from laboratory measurements will be shown to verify the theoretical dispersion calculation. Results from technological tests of chalcogenide arsenic-selenide fiber module, lead-silicate microstructured fiber free-space optic coupling and zirconium-flouride glass processing challenges will be as well presented more in detail.

A silica suspended-core microstructured optical fiber sensor for detection of liquids, operating at 1550 nm, is analyzed. The sensing principle is based on the evanescent wave overlap into a tested analyte, which is filled via capillary forces into the cladding holes. Validations for analytes in the refractive index range of 1.35–1.43 are carried out with liquid-analyte-filling-length limits being studied both theoretically and experimentally. We prove, for the first time to our knowledge, that an extreme sensitivity of 342.86 dB/RIU and resolution of 4.4 × 10−5 can be achieved. This sensor represents a high-quality alternative for applications requiring a facile, low-cost solution.

We have developed a data transparent optical packet switch, working at optical powers conventional in telecommunications. Polarization sensitivity of only 0.6 dB was achieved. The optical packet switch exploited wavelength conversion based on four-wave mixing. To achieve higher switching efficiencies, Ge-doped silica suspended-core and chalcogenide arsenic-selenide singlemode fibers were employed and compared to conventional highly-nonlinear fibers. Improved connectorization technology has been developed for both fibers to reduce overall component insertion loss, where we achieved connection losses of 0.9 dB. For the arsenic-selenide fiber we present the lowest attenuation up-to-date of 0.58 dB/m. Pump power limits for optical packet switching were set to 23 dBm, as limited by most thin-film components. Conversion efficiency of -16 dB was obtained for the highly-nonlinear fiber utilizing pump peak powers of 16 dBm. Arsenic-selenide fiber of 26 m length was evaluated, providing conversion efficiency lower than -38 dB with component insertion loss of -16.5 dB, thus further optimization was carried out according to simulated results. Conversion efficiency of -20 dB was observed with arsenic-selenide fiber length reduced to one meter.

Polymer-clad silica fiber tapers for refractometric detection of liquids are presented. Experimental study of sensor stability and measurement reproducibility is carried out, providing stable sensitivities with respect to production imperfections.

Fiber taper refractometric sensors for detection of liquids are presented. Almost one hundred tapers of a wide waist diameter range were reproducibly prepared from multimode and polymer-clad silica fibers. Sensitivity above 400%/RIU was achieved.

Split-Step Fourier method is a pseudospectral numerical method suitable for solving the nonlinear Schrödinger equation. The method formally divides the Schrödinger equation into two parts, linear and nonlinear. Either part is applied separately (step by step) with using a fast Fourier transform to solving the Schrödinger equation for a nonlinear optical fiber section.

Tapered optical fibers are used in a vide variety of fiber optics applications, e.g. in nonlinear optics for supercontinuum generation, and for various types of fiber evanescence chemical sensors. The fiber taper is made by heating and stretching a single-mode optical fiber in a heat source. For fabrication of the fiber tapers we have designed and assembled the apparatus that is propelled with motors and controlled by a computer and other electronic equipments. In this paper it will be discussed the design and realization of the device for manufacturing fiber tapers. The device can be used for producing fiber tapers not only by stretching conventional single-mode optical fibers, but it can also be used for tapering microstructure optical fibers.

This paper deals with properties and behavior of solitons propagating in the nonlinear LC network in comparison to known properties solitons generated in single-mode optical fibers or special optical fibers (mictostructure optical fibers or fiber tapers). For theoretical observation of Korteweg - de Vreis solitons behavior in LC network has been created computer simulation in computational system Maple. The properties of solitons simulated on the theoretical model were compared with measurement of voltage Korteweg-de Vreis solitons generated in newly constructed LC network. During measurements was observed and compared properties of solitons which were generated from different input voltage profiles.

This paper is focused on the optical applicator radiation pattern measurement in the different media, such as in the air and in the loss water phantom. We performed this measurement to evaluate optical applicators which could be used for medical purposes.

Fourierova metoda dělených kroků je pseudo-spectralní numerická metoda vhodná pro modelování šíření úzkých optických pulsů nelineárním dispersním prostředím. Tato metoda může být použita pro modelování ultraúzkých (femtosekundových) optických pulsů s vysokým špičkovým výkonem, které se šíří disperzním a nelineárním prostředím optického vlákna. Fourierova metoda dělených kroků je založena na formálním rozdělení perturbované nelineární Schrödingerovy rovnice popisující šíření úzkých optických pulsů na dvě části, které jsou popsány lineárním a nelineárním operátorem. Nelineární Schrödingerova rovnice je potom řešena odděleně pro každý operátor zvlášť na úseku vlákna o infinitezimální délce. Znamená to tedy, že pro teoreticky nekonečně krátký úsek optického vlákna je v jednom výpočetním kroku uvažována jen disperze vlákna a v druhém kroku jen indukovaná nelinearita. Tento způsob výpočtu je pak aplikován na celé optické vlákno konečné délky.

This paper is focused on the system for optical applicator evaluation, that means measurement of the farfield radiation pattern nearby the aperture of the optical applicator. The measurement was realized with the fiber applicators, which were designed for photodynamic treatment of primary lesion. This project is also focused on the design and testing of different shapes of the optical applicator. Different terminations of optical applicators were modified for obtaining the optimal radiation patterns. The radiation pattern represents the dependence of radiated power on the angle shift of the fiber termination.

This paper is focused on the evaluation of optiical applicators for photodynamic treatment method. For this purpose the device for radiation pattern measurement has been used.

This peper presents a visulaization of leaky waves excieted by delta-gap sources on planar transmission lines, namely the 2nd surface and space leaky modes on the slotline, and the dominant and surface leaky modes on the conductor-backed slotline. The field is modeled by numerical calculation in the time domain. The simulations show the character of the leaky waves excited by delta-gap sources and are a useful tool for the investigation of leaky waves.

Článek pojednává o solitonových vlnách z historicko-technického hlediska. V textu se autor nejprve zabývá vymezením pojmu solitonová vlna a popisuje původ vzniku slova soliton. Dále se zabývá prvním historicky zdokumentovaným pozorováním solitonové vlny a historickými událostmi, kterými byl tento objev provázen. V článku je historie solitonů popsána až po současnost, kdy je možno solitonové vlny využívat zejména v optické komunikační technice pro rychlý přenos informace na velké vzdálenosti.

This paper deals with another investigations into the history of solitons. The paper is focused on situation in the first observation of soliton and on happening in the second half on the 19th century in detail.

This paper deals with a measurement of far-field radiation patterns of optical applicators for photodynamic therapy. The measurement was realized with the fiber applicators, which were manufactured for photodynamic treatment of primary lesion. This project was focused on testing different shape applicators for effective distribution of optical energy to different shapes of tumors. Different terminations of optical applicators were measured for obtaining of radiation patterns. The radiation pattern represents dependence of radiated power on an angle shift of the fiber termination. The measurements were realized in cooperation with doctors of the Radiation Oncology

V příspěvku je na několika příkladech popsána charakterizace chromatické disperze MOF (mikrostrukturních optických vláken - Microstructure Optical Fibres) interferometrickou metodou a jsou uvedeny odlišnosti od měření disperze standardních optických vláken.

Článek pojednává o návrhu a testování optických aplikátorů pro fotodynamickou léčbu.

Tento článek se zabývá konstrukcí nelineárního LC vedení a měřením nelineárních napěťových KdV solitonů na tomto LC vedení. Soliton je stabilní nelineární pulzní obálka šířící se beze změny tvaru LC vedením. Napěťové solitony jsou obdobou optických solitonů šířících se v optických vláknech. Nelineární LC vedení bylo zkonstruováno pro generování solitonů a pro pozorování jevů, které vznikají během šíření solitonů.

This paper is focused on the design, construction and testing of the optical applicators for photodynamic therapy. This equipment is used as a treatment and diagnostic method in oncology.

The paper is devoted to the first historically documented observation of water solitary wave, than to facts about investigations of the phenomenon and finally to facts about seeking any suitable mathematical description of this phenomenon realized in the second half of the 19th century. After the World war two the solitary waves were again observed in context with other different physical phenomena. The history of investigations and importance of solitons was described until the present time.

This paper deals with measurement of nonlinear interaction of voltage KdV solitons on nonlinear 100-units LC network. Soliton is stable nonlinear pulse envelope propagating without change of shape. Voltage solitons are analogy of the optical solitons. Nonlinear LC network was constructed for generation of solitons and for observation of phenomena which nascent during solitons propagation.

This paper deals with microstructure optical fibers (MOFs). MOF is silica fiber with periodic system of axial air holes in the cladding region constructed as fiber realization of 2-D photonic crystals. Unique properties of MOFs are based on photonic bandgap (hollow-core fibers) or large index refractive contrast that exists between silica glass - air and inner design of the fiber (solid-core fibers). Endlessly single-mode MOF, polarization maintaining MOF, highly nonlinear MOF and multicore MOF are made at present.

Předmětem realizace bylo zhotovení nelineárního 100 článkového LC vedení pro vybuzení a pozorování napěťových solitonových pulsů, které jsou analogií optických světelných solitonů. Realizované vedení sestává z kaskády čtyřsvorkových nelineárních LC sekcí, které obsahují induktory s konstantní indukčností a napěťově závislé kapacitory - varikapy. Toto 100 článkové LC vedení umožňuje generovat solitonové pulsy, které se vytvářejí transformací periodického průběhu vstupního napětí.

Příspěvek pojednává o šíření solitonů v optických vláknech a na nelineárním LC vedení. Na tomto vedení se podařilo generovat KdV solitony a měřit jejich vzájemné interakce. V příspěvku se autor dále zabývá problematikou mikrostrukturních optických vláken, zejména pak vysoce nelineárními mikrostrukturními optickými vlákny a generací superkontinua bílého světla v tomto vláknu a v tzv. vláknovém taperu.