K. Gut

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.

Mode beat measurement of planar optical waveguide

The present work suggests a new method of direct measurements of the difference propagation constants Δβ of orthogonal modes (mode beat) of the same order in planar waveguides. The work also presents a method of determining the difference of propagation constants (mode beat) for different refractive indices of the cover. The developed method is particularly adaptable when the difference of propagation constants along the direction of propagation are changed.

Spectropolarimetric analysis of differential interferometer

The paper presents the principle of the operation of a spectropolarimetric interferometer. In the planar waveguide orthogonal modes of type TE and TM can be excited for the entire visible light. During the propagation the difference of the phases between the modes is determined, which is the function of the length of the path of propagation, the difference of the effective refractive index (NTM-NTE) and the wavelength. At the output of this system the spectral distribution of intensity is recorded, the shape of which depends on the value of the refractive index of the cover of the waveguides.

Broad-band difference interferometer as a refractive index sensor

Integrated Optical Broad-Band Difference Interferometer (IO BB DI) is introduced as an alternative and economical measurement method to integrated optical label-free affinity sensors. A detailed theoretical analysis of the method is presented and the effects of the waveguide layer on the operation of the system are shown. A very short operating distance of less than 0.5 mm allows miniaturization of the interferometer. The analysis was performed for Si3N4/SiO2 layers that can be obtained in standard microelectronics technological processes.

Polymer planar waveguide broadband differential interferometer

In the paper the planar waveguide based on SU-8 polymer were made on 2μm of silica (SiO2) on silicon (Si) substrates in order to obtain base for broadband interferometer. Analysis and calculation of sensitivity for single mode broadband differential interferometer were performed. Paper presents preliminary tests and analysis of such structures. Dilution of SU-8 solution for obtaining thin layer (below 500 nm) followed by elipsometric measurements is presented.

Broad-band differential interference in the bimodal waveguide

The paper presents the principle of operation of the broad-band difference interferometer in the bimodal waveguide. In the planar bimodal waveguide modes fundamental TE0 and TE1 can be excited for the entire range visible light. During the propagation the difference of the phases between the modes is determined, which is the function of the length of the path of propagation, the difference of effective refractive index (NTE0-NTE1) and the optical wavelength. At the output of this system the spectral distribution of intensity is recorded, the shape of which depends on the value of the refractive index of the cover of the waveguides.

SU-8 polymer based waveguides on different substrates

In the paper the planar waveguide based on SU-8 polymer were made on different substrates. As polymer layer Gerseltec SU8 GM1040 and Microchem SU8 2000.5 were used. By using Gerseltec SU8 GM1040 we obtained layer with thickness 950 nm which gave us planar waveguide bimodal structure for λ=633nm. By using Microchem SU8 2000.5 we obtained layer thickness 450 nm which gave us single mode waveguide structure for λ=633nm. As substrate we used 2μm of SiO2 on Si and standard microscope glass (soda-lime glass). Additionally the authors performed measurements for characterization of optical and physical properties of obtained layers. We measured layer thickness by Atomic Force Microscope (AFM) and by ellipsometer. Ellipsometry measurement also gave us refractive indices of waveguide layer and substrate. We also performed measurement of effective refractive index and attenuation of waveguide layers. Additionally we performed SEM measurement for checking layers adhesion.

Analysis and investigations of differential interferometer based on a polymer optical bimodal waveguide

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Broad-band difference interferometer as a temperature sensor

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Two methods of determining the birefringence of the planar waveguides

The paper presents two methods of determining the planar waveguide birefringence and the measuring stands, which are used to determine the birefringence of planar waveguide structures. The light is introduced into the waveguide through a prism coupler. First method uses the measurement of scattered light. The second method uses an immersion coupler. The most fundamental property of an immersion coupler is the possibility to change fluently the propagation length while immersing the waveguide with an invariable efficiency of output coupling.