Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Fuzzy logic. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Experimental and theoretical investigations of birefringent holey fibers with a triple defect

Abstract: We have manufactured and characterized a birefringent holey fiber of a new construction. The birefringence in this fiber is induced by the highly elliptical shape of the core, which consists of a triple defect in a hexagonal structure. Using a hybrid edge–nodal finite-element method, we calculated the spectral dependence of phase and group modal birefringence for spatial modes E11 and E21 in idealized and in real fiber, whose geometry we determined by using a scanning-electron microscope. Results of our calculations show that technological imperfections significantly affect the fiber's birefringence. Normalized cutoff wavelengths for higher-order modes relative to the filling factor were also determined for the idealized structure. We observed a significant disagreement between theoretical and experimental values of cutoff wavelengths, which was attributed to high confinement losses near the cutoff condition. We also measured the spectral dependence of the phase and the group modal birefringence for spatial modes E11 and E21. The measured parameters showed good agreement with the results of modeling.

Continuous wave, distributed feedback diode laser based sensor for trace-gas detection of ethane

Abstract: The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) based on a 2f wavelength modulation (WM) detection technique. TDLAS was performed with a 100 m optical path length astigmatic Herriott cell. For an interference free C2H6 absorption line located at 2976.8 cm−1 a 1σ minimum detection limit of 240 pptv (part per trillion by volume) with a 1 second lock-in amplifier time constant was achieved. In addition, reliable and long-term sensor performance was obtained when operating the sensor in an absorption line locked mode.

Refractive‐index anisotropy and optical dispersion in films of deoxyribonucleic acid

Abstract: Received 12 May 2006; accepted 29 July 2006DOI 10.1002/app.26082Published online in Wiley InterScience (www.interscience.wiley.com).ABSTRACT: We have determined the refractive indicesin the directions parallel and perpendicular to the surfaceplane of films of deoxyribonucleic acid (DNA) and theirwavelength dispersion. These parameters are fundamen-tal for understanding the properties of waveguidingstructures containing DNA-based photonic materials. Theorientation of DNA molecules in films and their opticalproperties are sensitive to the film fabrication and envi-ronmental conditions influencing the structure. Prismcoupling measurements show ambient-humidity-relatedchanges in the refractive index, birefringence, and anisot-ropy of the alignment of the DNA molecules in the filmsstudied. These films were 0.5–5 mm thick, were preparedby both spin coating and casting from aqueous solutionscontaining 0.1–3 wt % DNA, and were measured inambient air with relative humidities of 37–58%. Theoptical properties of the films and the orientation of theDNA molecules are discussed with respect to the mech-anism for the formation of the polymer liquid-crystallinephases during film deposition. The dispersion of the re-fractive indices in films of native DNA has been derivedfrom interference fringes in absorption and reflectionspectra in the wavelength range of 350–2700 nm throughthe fitting of the positions of the fringes with the Sellme-ier dispersion formula in combination with the prismcoupling data.