1,720,985 research outputs found
Photobleaching of polydiacetylene waveguides: A characterization of the process and patterning of optical elements
No full textPoly-3-butoxycarbonylmethylurethane is a conjugated polymer with large third order nonlinear optical response. Photobleaching of poly-3-butoxycarbonylmethylurethane spun films by mean of a UV lamp and 488-nm laser light is characterized and modeled. The role of oxygen on the photobleaching process is discussed. Microoptic devices and holographic gratings are formed
Efficient coupling between annealed K+-Na+ ion-exchanged channel waveguides and 10/125 single-mode fibers at lambda=1.321 micrometers
No full textThe process of thermal annealing of K+-Na+ ion-exchanged channel waveguides has been studied with the aim of optimizing their coupling efficiency with commercial single-mode fibers at λ=1.321 μm. Waveguides obtained in soda-lime glass slides, with mask apertures ranging between 13.4 and 2.6 μm, were characterized before the annealing by combining nearfield measurements and an etching procedure. The experimental results were successfully compared with a theoretical model based on the variational principle. The refractive index distribution of K+-Na+ ion-exchanged channel waveguides supporting one or a low number of modes was given: compared to the corresponding slab case, the refractive index step Δno remained constant, while the waveguide depth was lower. The thermal annealing process of the channels was then performed and modeled by means of the standard diffusion theory. As a result, the channel fabrication parameters for optimum guide-fiber coupling could be predicted: 0.23-dB mode mismatch losses were measured between the optimized channel and a commercial 10/125 single-mode fiber, at λ=1.321 μ
SAFIRE-A (spectroscopy of the atmosphere by far-infrared emission - Airborne): Optimized instrument configuration and new assessment of improved performance
No full textTHERMAL ANNEALING OF K+-NA+ ION-EXCHANGED WAVE-GUIDES
No full textThe process of thermal annealing of K+-Na+ ion-exchanged waveguides in soda lime glass is characterized and compared with a simple theoretical model. The discrepancies between theory and experiments in the case of initially thick guides disappear if the existence of a stress-induced contribution to the refractive index is assumed that is not proportional to the concentration of the doping ions. The results obtained for initially thin guides are exploited for the design of annealed single-mode channel waveguides: 0.4-dB coupling losses with commercial single-mode fibers at λ = 1.321 μm were measured
OPTICAL FIBER-POLYMER GUIDE COUPLING BY A TAPERED GRADED-INDEX GLASS GUIDE
No full textA new four layer tapered coupler (FLTC) has been studied and tested, able to transfer light efficiently from a monomode fiber to a polymer film guide by means of an auxiliary graded index glass waveguide. A simple theory has been developed to calculate the maximum efficiency of these structures. Experiments have been performed, at λ=1.321 μm, on several FLTC samples, containing K+-Na+ ion-exchanged glass waveguides and spin coated poly-3BCMU films. Insertion losses in the range 3-6.5 dB have been measured, depending on the taper configuration. The agreement between theoretical and experimental data is good, provided that a suitable ripple of the taper profile is assumed. The application of the new coupler to future integrated waveguide systems, including passive glass components and polymer based all optical devices, is assesse
Patterning of polydiacetylene waveguides by means of argon laser photobleaching
No full textPolydiacetylenes are processable conjugated polymers with large thid order optical nonlinearities. The fabrication of optical quality thin films of soluble polydiacetylenes by spin coating is addressed. The photobleaching process in thin polydiacetylene films is modeled. Microoptic devices and surface gratings are formed by photobleaching
A strategy for the measurement of CO<sub>2</sub> distribution in the stratosphere
Full text linkIn this study we introduce a new strategy for the measurement of CO2
distribution in the stratosphere. The proposed experiment is based on an
orbiting limb sounder that measures the atmospheric emission within both the
thermal infrared (TIR) and far-infrared (FIR) regions. The idea is to exploit
the contribution of the pure rotational transitions of molecular oxygen in
the FIR to determine the atmospheric fields of temperature and pressure that
are necessary to retrieve the distribution of CO2 from its rovibrational transitions in the TIR. The instrument envisaged to test the new strategy is a
Fourier transform spectrometer with two output ports hosting a FIR detector
devoted to measuring the O2 transitions and a TIR detector devoted to
measure the CO2 transitions. Instrumental and observational parameters
of the proposed experiment have been defined by exploiting the heritage of
both previous studies and operational limb sounders. The performance of the
experiment has been assessed with two-dimensional (2-D)
retrievals on simulated observations
along a full orbit. For this purpose, optimal spectral intervals have been
defined using a validated selection algorithm. Both precision and spatial
resolution of the obtained CO2 distributions have been taken into
account in the results–evaluation process. We show that the O2 spectral
features significantly contribute to the performance of CO2 retrievals
and that the proposed experiment can determine 2-D distributions of the
CO2 volume mixing ratio with precisions of the order of 1 ppmv in the
10–50 km altitude range. The error budget, estimated for the test case of
an ideal instrument and neglecting the spectroscopic errors, indicates that,
in the 10–50 km altitude range, the total error of the CO2 fields is
set by the random component. This is also the case at higher altitudes,
provided the retrieval system is able to model the non-local thermal
equilibrium conditions of the atmosphere. The best
performance is obtained at altitudes between 20 and 50 km, where the
vertical resolution ranges from 3 to 5 km, and the horizontal resolution is
of the order of 300–350 km depending on latitude
Guided-light two-wave-mixing on a spherical surface
No full textA novel guided structure is proposed which is aimed at developing integrated all-optical signal processors exploiting two wave mixing interactions. The structure is based on the whispering propagation on a hemispherical glass substrate and contains a dye-doped photoresist film as the test nonlinear material. Its functionality was demonstrated successfully with two wave mixing experiments that were performed with CW light at 1321 nm and with a probe beam at 647 nm
LANGMUIR-BLODGETT AND SPIN-COATED FILMS OF POLY-3BCMU FOR WAVE-GUIDE NONLINEAR OPTICS
No full textLangmuir-Blodgett and spin coated films of poly-3BCMU, a polydiacetylene with strong third order non linearity, were fabricated and characterized by means of visible, IR and Raman spectroscopy. Then the utilization of such films as optical waveguides and their insertion in integrated devices is considere
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