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1
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Weak Localization of Short Pulses in Disordered Waveguides

100%
Skipetrov S., van Tiggelen B.
Acta Physica Polonica A
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2006
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vol. 109
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issue 1
101-108
EN
We consider the phenomenon of weak localization of a short wave pulse in a quasi-1D disordered waveguide. We show that the long-time decay of the average transmission coefficient is not purely exponential, in contradiction with predictions of the diffusion theory. The diffusion theory breaks down completely for times exceeding the Heisenberg time. We also study the survival probability of a quantum particle in a disordered waveguide and compare our results with previous calculations using the super-symmetric nonlinear sigma model.
2
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Light Propagation in a Magnetic Field: Random Green Matrix Approach

100%
Pinheiro F., Rusek M., Orłowski A., van Tiggelen B.
Acta Physica Polonica A
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2004
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vol. 105
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issue 4
339-347
EN
We studied the spectral properties of the matrices describing multiple scattering of electromagnetic waves from randomly distributed point-like magneto-optically active scatterers under an external magnetic field B. We showed that the complex eigenvalues of these matrices exhibit some universal properties such as the self-averaging behavior of their real parts, as in the case of scatterers without magneto-optical activity. However, the presence of magneto-optically active scatterers is responsible for a striking particularity in the spectra of these matrices: the splitting of the values of the imaginary part of their eigenvalues. This splitting is proportional to the strength of the magnetic field and can be interpreted as a consequence of the Zeeman splitting of the energy levels of a single scatterer.
3
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Direct Observation of Localized Modes in an Open Disordered Microwave Cavity

100%
Mortessagne F., Laurent D., Legrand O., Sebbah P., Vanneste C.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
665-672
EN
We present measurements of the spatial intensity distribution of localized modes in a two-dimensional open microwave cavity randomly filled with cylindrical dielectric scatterers. The robustness of these modes with respect to a modification of the boundaries of the scattering region is successfully established. From a comparison with numerically calculated modes, we can extract precise values of the localization length which are in agreement with the measured spectral widths. These results constitute unambiguous signatures of the existence of strongly localized electromagnetic modes in two-dimensional open random media.
4
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Longitudinal Strain Induced Birefringence in Highly Birefringent Fiber for Dynamic Compensation of Polarization Mode Dispersion

80%
Domański A., Lesiak P., Woliński T.
Acta Physica Polonica A
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2003
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vol. 103
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issue 2-3
221-227
EN
The paper addresses a compensation method of polarization mode dispersion based on longitudinal strain applied to a highly birefringent fiber introduced as apart from optical fiber link. As an introduction a short overview of the polarization mode dispersion compensation methods known up-to-now is done. Dependence of polarization mode dispersion on longitudinal strain is discussed. Some results of experiment with birefringence changes due to longitudinal strain in the bow-tie highly birefringent fiber necessary for dynamic polarization mode dispersion are presented.
5
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Polarization Mode Dispersion in Birefringent Optical Fibers

80%
Woliński T., Domański A.
Acta Physica Polonica A
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2003
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vol. 103
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issue 2-3
211-219
EN
The paper discusses influence of polarization mode dispersion on performance of polarimetric systems with highly birefringent fibers. It appeared that polarization mode dispersion strongly influences a degree of polarization that depends on coherence of the light source used and simultaneously diminishes dynamics of the output signal.
6
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Impedance and Scattering Variance Ratios of Complicated Wave Scattering Systems in the Low Loss Regime

80%
Yeh J., Drikas Z., Gil Gil J., Hong S., Taddese B., Ott E., Antonsen T., Andreadis T., Anlage S.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
1045-1052
EN
Random matrix theory successfully predicts universal statistical properties of complicated wave scattering systems in the semiclassical limit, while the random coupling model offers a complete statistical model with a simple additive formula in terms of impedance to combine the predictions of random matrix theory and nonuniversal system-specific features. The statistics of measured wave properties generally have nonuniversal features. However, ratios of the variances of elements of the impedance matrix are predicted to be independent of such nonuniversal features and thus should be universal functions of the overall system loss. In contrast with impedance variance ratios, scattering variance ratios depend on nonuniversal features unless the system is in the high loss regime. In this paper, we present numerical tests of the predicted universal impedance variance ratios and show that an insufficient sample size can lead to apparent deviation from the theory, particularly in the low loss regime. Experimental tests are carried out in three two-port microwave cavities with varied loss parameters, including a novel experimental system with a superconducting microwave billiard, to test the variance-ratio predictions in the low loss time-reversal-invariant regime. It is found that the experimental results agree with the theoretical predictions to the extent permitted by the finite sample size.
7
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Fading Statistics in Communications - a Random Matrix Approach

80%
Yeh J., Ott E., Antonsen T., Anlage S.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-85-A-88
EN
Fading is the time-dependent variations in signal strength measured at a receiver, due to temporally evolving multipath scattering and interference. In our previous work we introduced a statistical fading model for the time-reversal invariant case by combining the predictions of random matrix theory with the random coupling model that includes system-specific properties such as the radiation impedance of the ports and short-orbit effects. In the high-loss limit this random matrix theory model reduced to the most common fading models in the wireless communication field. In this paper we discuss the theoretical model in more detail and extend it to the case of broken time-reversal invariance.
8
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Fidelity in Quasi-1D Systems as a Probe for Anderson Localization

80%
Bodyfelt J., Zheng M., Kottos T., Kuhl U., Stöckmann H.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
756-764
EN
We analyze the echo dynamics in quasi-one-dimensional random media to investigate how the transition from localization to delocalization is encoded in its temporal decay properties. Our analysis extends from the standard perturbative regime corresponding to small perturbations (with respect to the mean level spacing) in the echo dynamics, out to the Wigner decay regime. On the theoretical side, our results rely on a banded random matrix modeling, and show in the localized regime under small perturbations a novel decay of the fidelity (Loschmidt echo), differing from the typical Gaussian decay seen within both diffusive and chaotic systems. For larger perturbation strengths, typical Wigner exponential decays are observed. Scattering echo measurements are performed experimentally within a quasi-1D microwave cavity randomly populated with point-like scatterers. Agreements are observed between experiments, numerics, and theoretical predictions.
9
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Scar Selection in an Optical Fibre

80%
Doya V., Legrand O., Michel C., Mortessagne F.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
607-617
EN
A multimode optical fiber with a D-shaped cross-section has already been proved to constitute a privileged system to image wave functions of a chaotic system. Nevertheless, diffraction of light at the fiber input precludes the excitation of individual wave functions and particularly the scar modes we want to investigate. We show that a mechanism of scar modes selection can be induced by the introduction of a localized gain.
10
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Application of Quantum Cascade Lasers in Nitric Oxide and Nitrous Oxide Detection

70%
Wojtas J., Bielecki Z., Stacewicz T., Mikolajczyk J., Medrzycki R., Rutecka B.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
794-797
EN
Application of quantum cascade lasers in NO and N_2O sensor is described. Cavity enhanced absorption spectroscopy was used for this purpose. The detection was performed at vibronic molecular transitions in spectral regions of 5.23-5.29 μm and 4.46-4.54 μm for NO and N_2O, respectively. In order to avoid interferences by the gases contained in atmosphere (H_2O, CO_2) the lines of 5.263 μm for NO and 4.530 μm for N_2O were selected. Our two channel sensor is designated for simultaneous detection of both compounds. Each channel consists of single mode quantum cascade laser, optical cavity, and a photodetection module. The lasers were precisely tuned to the wavelength of interest. Optical cavities were built with spherical mirrors of high reflectance. The signals from the cavities outputs were registered with specially developed low noise detection modules.
11
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Holographic Interferometer as a Correlator of Phase Distortions with Response in the Form of Interference Pattern

70%
Derzhypolska L., Gnatovskiy O., Yezhov P.
Acta Physica Polonica A
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2007
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vol. 112
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issue 5
1095-1100
EN
Considered in the work are known properties of holographic interferometer as according to the correlator with output signal in the form of interference fringes. It is known that a space correlation has various ratios of intensity between central correlation peak and background part for objects with different phase microrelief of a surface. Correspondingly an interference pattern must have different space distribution of contrast. A magnitude of contrast depends on changes in distribution of microrelief of investigated object, whereas the interference pattern depends on macroscopic modification of a form of the object. Used here is a scheme of Fourier holography with a random phase modulator in signal beam, reference beam is a point source, and restoring beam is the random phase modulator with random phase shift against initial random phase modulator. Also investigated is a recording of holographic interferogram with these random phase modulators. As the results of original theoretical consideration there was obtained an expression for fringe contrast and intensity of correlation peak. This model was tested by simulating of forming of holographic interferogram and reconstruction of the cross-correlation peak with phase distortions of various statistical distributions. Compared here are theoretical results, simulation results, and results obtained in real experiment.
12
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Two-Channel Optoelectronic Sensor Employing Cavity Enhanced Absorption Spectroscopy

70%
Wojtas J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
763-766
EN
In the paper, a description of two-channel of optoelectronic sensor basing on cavity enhanced absorption spectroscopy is presented. In contrast to the typical cavity enhanced absorption spectroscopy systems, here a special optical system is applied. It provides possibility to direct more than one beam of laser radiation into a cavity. Thus, special lasers controller system and photoreceiver were developed as well. The setup includes two pulsed laser diodes. The optical signals from the lasers are registered with one special constructed photoreceiver, which is characterized by wide range of the detected wavelengths. Moreover, there was applied time division multiplexing technique, well-known in the telecommunication systems. Every laser is assigned to the suitable channel - the strictly determined temporary window. In this window, the signal from the exits of the optical cavity is registered. In the system, optical signal from many laser sources can be measured and value of absorption coefficient at a few different wavelengths can be determined parallel. Typical cavity enhanced absorption spectroscopy system is designed to measure only one gas concentration, while the developed setup provides possibility to detect a trace concentration of two gases at the same time.
13
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Nitrogen Oxides Optoelectronic Sensors Operating in Infrared Range of Wavelengths

61%
Wojtas J., Bielecki Z., Stacewicz T., Mikolajczyk J., Rutecka B., Medrzycki R.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
592-594
EN
Investigation of nitric oxide and nitrous oxide optoelectronic sensors is described. The detection of both components was done by measurement of absorption that occurs due to transition between vibronic molecular transitions. The improvement of the sensitivity was achieved due to application of cavity enhanced absorption spectroscopy. Two optical cavities (each one for each gas) built of high reflectance spherical mirrors were used. While the spectra of observed transitions are situated in mid-infrared range, two single mode quantum cascade lasers were applied. Their narrow emission lines were precisely tuned to the absorption lines of both investigated gases. The measurement of different mixtures of Ar-NO and Ar-N_2O within the range from 100 ppb to 10 ppm was performed. The relative uncertainty of the results did not exceed the level of 13%.
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