Construction, background and applications of optical nonreciprocal devices are discussed. Operation of optical isolators and circulators based on Faraday polarization rotation is analyzed. Applications of the nonreciprocal devices for multipass amplifiers are presented. Construction of polarization independent circulators is discussed including an all fiber circulator and application of the circulators for fiberoptics communications is included.
In this article the author presents improved techniques of signal processing used in low-coherent measurement systems. The author proposes to utilize the synthesized sources in the system with the temporal signal processing. It will be shown that the exploit of such a source can substantially reduce the signal-to-noise ratio required to identify the central fringe position. In case of using spectral signal processing, the author proposes to control the position of maximum in the spectral pattern which modifies the phase difference between interfering beams. The results of experimental works will show that described techniques can be an effective method for improving the signal processing in low-coherent measurement systems.
Optical low-coherence tomography is a measurement technique for non-contact and non-destructive investigation of materials inner structure. Nowadays, this method is highly applied in medical treatment especially in dermatology and ophthalmology. During our research we have developed an optical low-coherence tomography system with polarization state analysis for structure examination of a broad range of technical materials. In this paper we present our recent measurements including polarization sensitive analysis. Those measurements were taken for semitransparent and highly scattering materials like polymer layers and polymer optical retarders, anticorrosion protective coatings or abrasive paper. We proved that with the aid of developed polarization sensitive optical coherence tomography system it is possible to investigate birefringence principles of materials as well as to improve visualization contrast of cross-sectional images.
In this paper low-coherence fibre-optic sensors based on the Fabry-Perot and Michelson interferometer, which were designed and elaborated at our laboratory, are shown. We present results of investigation of the fibre-optic sensors working in both configurations. These results allowed us to compare properties of sensors working in both configurations. The theoretical analysis and experimental results made us possible to select best construction, which was implemented in low-coherence fibre-optic sensors of refractive index.
In this paper use of selected optical methods of a hematocrit measurement has been presented. Elaborated methods have numerous advantages: relatively simple configurations, potentially low cost and high resolution. Investigation confirmed their ability to determine the hematocrit value with appropriate measurement accuracy. Furthermore, simultaneous use of complementary optical methods can substantially increase measurement reliability, because low-coherence interferometric measurement is based on physical (mainly optical) properties of the investigated object, while Raman spectroscopy is based on study of its molecular composition.
This work focuses on the study of the influence of geometrical parameters on the quality factor of a cavity H1, realized with one missing hole in the center. For obtaining the H1 characteristics and the band structure of the photonic crystal, the finite difference time domain (FDTD) method, which is based on solving Maxwell's equations in a spatially and temporally discretized domain, and plane wave expansion (PWE) method, which is a resolution method of Maxwell equations in the frequency domain, were used respectively. In this method, one simulates a space of theoretically infinite extent with a finite computational cell. The quality factor increases until a maximum value equal 1.23×10⁶ for a filling factor r/a=0.44, and then decreases to a value of 3.39×10⁵ for a filling factor r/a=0.47.
The aim of the work is the presentation of operating principle and properties of multimode interference structure devices made in gradient index technology by K^{+} and Na^{+} ion exchange method from the point of view of optical sensor design. Numerical analysis was performed using beam propagation method. Analyzed sensor structures are covered by nanolayers whose refractive index higher than the multimode interference section index is the reason for the concentration of wave propagation energy in the sensor layer area and its vicinity. Modifications of external propagation conditions change the refractive index and extinction coefficient of a sensor layer. The variation of optical properties leads to the modification of waveguiding conditions in the multimode interference coupler.
The article presents preliminary research of an optical system for using in the temporary blood volume measurements in the Polish Ventricular Assist Device (POLVAD). The basis for the proposed solution is the measurement of the light reflected from the membrane in different configurations of light emitters and light detectors. The paper is describing a proposed measurement technique, measurement circuit and preliminary static measurements results of the developed measurement system. Future development plans are stated.
The aim of this paper is to present the operating principles and properties of gradient index multimode interference structures made by K^{+}-Na^{+} ion exchange in glass and their basic applications in optoelectronic circuits. The investigations of multimode interference structures were performed applying a method based on the visualization of light distribution in gradient structures, using fluorescence of the substance covering the multimode interference structures section. Basing on the above we present gradient index multimode interference structures applications in splitters and couplers 1× N technology of different configurations.
The optical coherence tomography is an optical measurement technique used for investigation of wide range of scattering or semitransparent materials. The optical coherence tomography enables surface and subsurface examination of different types of materials to be performed in non-contact and non-destructive way. Our research have been concentrated on optical coherence tomography systems with polarization sensitive analysis. Such a combination of optical measurements methods improves optical coherence tomography visualization contrast and also delivers some extra information about investigated devices. However, applying polarization sensitive analysis is associated with problems related to the use of ultra broadband optical sources. We have managed studies on the improvement of signal processing method. According to obtained results the problem of signal processing method in polarization sensitive optical coherence tomography can be solved by the use of the spectroscopic analysis. In this paper we present a brief discussion about the polarization sensitive optical coherence tomography measurements supported by spectroscopic analysis of backscattered light from investigated device.
Fullerenes, nanotubes, quantum dots are considered as effective sensitizers to modify both the optical, nonlinear optical features, dynamic and polarization characteristics, as well as mechanical and spectral properties of the organic and inorganic materials. The correlation between photorefractivity and photoconductivity was supported and the relation between charge carrier mobility of pure conjugated structures and nanoobjects-doped ones has been revealed. An increase of transmission of nanostructured polarization films was observed. An extension of the nanocomposites applications area is considered.
In the paper the luminescence optical fiber used as a temperature sensor is presented. The new construction of rhodamine B doped, polymethyl methacrylate optical fibre with silver coating is shown. The fabrication process and luminescent properties of rhodamine B in sensing fibre are investigated. The attenuation and spectral shift of luminescence peak vs. the fibre length were measured and used for optimization of sensor construction. The characteristics of sensor for temperature range from 293 up to 343 K are shown. The relative sensitivity equal to -5.4× 10^{-4} K^{-1} was obtained. The article presents also the potential applications of presented sensor.
The paper presents the analysis results of a waveguide sensor based on multimode interference structures. The multimode section was covered with sensor material. The change of optical parameters of the cover entails the change of propagation conditions of light in the structure. By measuring the light intensity at the output of the structure, we can define external physicochemical parameters to which the sensor layer is sensitive. The paper presents the method to adjust the sensitivity of the device through a proper selection of the thickness of the particular layers of multimode waveguides. We present, among others, the analysis results of optical systems whose parameters of the sensor layer corresponded with the parameters of wolfram oxide (WO_3), being the material frequently applied as a gas-sensitive layer in gas sensors. We have proposed a configuration of a sensor based on the Mach-Zehnder interferometer whereof one arm is a multimode section and the other one a single mode waveguide. The detection method was narrowed down here to the measurement of phase difference between the waves propagating in the respective arms.
The article presents researches concerning a system for a possible blood volume measurements applied in POLVAD prosthesis. The proposed solution is based on the Helmholtz resonance principle. The article shows the state of art in blood volume sensors for using in the POLVAD prosthesis and introduces a newly proposed solution. The construction of the sensor and the results of static tests are presented. The work is summarized with future development plans.
In this work, we design a new pressure sensor based on two-dimensional photonic crystal waveguide coupled to a point-defect resonant microcavity. The mechanism of sensing is based on the change of the germanium refractive index as function of the hydrostatic pressure P. The resonant wavelength will shift when pressure variation induces change in the refractive indexes of the structure. The pressure variation causes the shifting of defect modes. The properties of the refractive index sensor are simulated using the finite-difference time-domain algorithm and the plane wave expansion method. These kinds of sensors have many advantages in compactness, high sensitivity, and various choices of materials.
Methods of optical imaging used in medical diagnostic (with taking the newest diagnostic techniques into consideration in particular) have been presented. Selected optical characteristics of tissues having an influence on the range of the classical methods of the optical imaging have been discussed in detail. The respond to the classical method limitations was to use scanning methods and detection techniques consisting in three-dimensional imaging of tissue structures in real time. A specific eye structure allows the wide using of these techniques in ophthalmology. Such advantages like non-invasiveness, non-contactness and high resolution (guaranteeing the safety of a patient) show a huge success of these techniques. The results of the research (conducted in many research centers) point at the wider application possibility of optical scanning method in medical diagnostic.
Monocrystalline films of sphalerite-type ZnSe were grown on GaAs(100) substrates from elemental Zn and Se precursors by atomic layer epitaxy in a gas flow system. Due to color mixing of band edge and deep defect-related emissions these layers emit intensive white light. Depth profiling cathodoluminescence indicates that green and red emissions mostly come from disordered regions of the films, close to the ZnSe/GaAs interface. We tested a possibility of tuning of chromaticity coordinates and of color temperature of the emission. We found that the chromaticity parameters (color perception) can be tuned by either regulating the appropriate accelerating voltage of electrons or current density of primary electrons in cathodoluminescence investigations. These properties of ZnSe films make them suitable for some practical applications as white light sources.
In this paper, by employing two practical methods of multi-electrode design and tapered waveguide structure, compensation techniques to restore declining carrier density along the quantum dot semiconductor optical amplifier's waveguide are investigated. In the multi-electrode method, the effects of distributing current via electrodes on the gain and the cross-gain modulation for two, three and four-electrode structures are studied. These characteristics are also investigated for the quantum dot semiconductor optical amplifiers with a tapered waveguide structure for the first time, including waveguides with different profiles and width ratios. After due comparison between these two methods, optimum parameters of the two techniques will be used simultaneously along each other to form a combined method. Through these design developments, gain as the main feature of the quantum dot semiconductor optical amplifiers continuously increases, though cross-gain modulator results show that there is a trade-off between the modulation efficiency and improving structure capability of restoring carrier density.
The article presents further developments of an optical system to be used in temporary blood volume measurements in the Polish ventricular assist device. The research focuses on quasi-dynamic measurements (flow rate of 5 ml/s). Characteristics of signals from selected configurations of optical transmitters and receivers are shown. A volume approximation using a PCA algorithm supported by a LRS function is introduced. Plans of further development are stated.
The paper presents results of extended static measurements of a newly developed optical system for temporary blood chamber volume measurements in the Polish Ventricular Assist Device. The paper additionally introduces a modified measurement stand and improvements of the measurements. Exemplary results acquired with principal components analysis are shown and future development plans of an optical measurement system are stated.
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