1,721,120 research outputs found
Optical investigation on dye-doped sol-gel glasses
No full textWe have investigated the optical properties of the 3,3'-diethyloxadicarbocyanine iodide (DODCI) dye incorporated in a number of sol-gel glasses in order to study the interaction between the trapped molecule and the host matrix. The differences found in both the absorption and the photoemission spectra demonstrate that the excitation processes of the dye molecule are influenced by the chemical reactivity and the degree of porosity of the surrounding network. We have found that while the molecular photoisomerization is quenched in all the matrices, for the modifications of the electronic excited states the high rigidity of the purely inorganic silica matrix is required. Conversely, the possibility of chemical attacks to the molecular conjugate chain seems to increase in the hybrid organic/inorganic ormosil matrices. © Societò Italiana di Fisica
EXTENSION OF TWO-PHOTON SPECTROSCOPY TO THE VACUUM ULTRAVIOLET USING SYNCHROTRON RADIATION
No full textSynchrotron radiation has been used for the first time in two-photon spectroscopy. The experimental apparatus, built at the ADONE storage ring in Frascati, and using a Q-switched Nd:YAG laser as a powerful source is presented. Space and time superposition of the beams is discussed extensively. Testing of the apparatus has been performed by measuring the two-photon absorption spectra of KCl and NaCl
Laser excitation and spin coherence of phosphorescent F2+2 centers in CaO
No full textSpin coherence in the laser-excited triplet state of F2+2 centers in CaO is studied. Selective probing of the F+-center local properties is provide by the measurement of the F2+2-center spin-echo decay at different excitation wavelengths. In addition, spin-echo beat phenomena arising at high-power pulsed-laser excitation are reported. © 1984
Design optimization of silicon-on-insulator slot-waveguides for electro-optical modulators and biosensors
No full textAn approach for design optimization of the geometrical parameters of silicon-on-insulator slot-waveguides for electro-optical modulators and biosensors is presented. Theoretical investigations of field confinement factors and effective nonlinear areas for different slot-waveguide structures are critically analyzed and thoroughly calculated. With our simulation results we explain the high efficiency of electro-optical modulators and the enhanced sensitivity of biosensors compared to strip-waveguides. The influence on the effective refractive index, field confinement factor, and effective nonlinear area of the slot width and the silicon rail width were investigated
Whispering-gallery modes in multimode fibres: experimental evidence and ray tracing model
No full textPicosecond spectroscopy of color center in KBr:OH-
No full textThe rapid decay of the excited state of the F centers in KBr:OH- has been measured by mean of a pump and probe technique with picosecond time resolution. The lifetime of the F centers (τ ~ 1 μs at 77 K) is shortened in the OH- doped samples, to τ ∼ 310 ps. The quenching of the normal radiative lifetime seems to be related to librational excitation of the OH- molecular ion. © 1993
Two-photon absorption of color centers in NaF
No full textTwo-photon absorption cross sections of the N1 and F3+ centers in NaF have been determined by means of the luminescence excited by the two-photon absorption. The measured polarization dependence of the process led us to attribute the excitation to the Ag→Ag transition in the N1 center and to the A→E transition in the F3+ center. © 1979 The American Physical Society
Laser stimulated luminescence in KCl and NaF containing color centers
No full textA broad luminescence band was found in laser irradiated KCl and NaF crystal containing color centers. This emission extends on both sides of the laser line and is interpreted as "hot" fluorescence due to radiative retrapping of laser ionized color centers. © 1977
Segregation of thallium impurities in the growth of sodium bromide single crystals
No full textThe effective segregation coefficient of Thallium impurities in NaBr single crystals, grown from the melt with the Kyropoulos method, has been measured in different growing conditions and found to be keff = 0.0164. © 1977
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