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71.
J. Lamela D. Jaque A. Rodenas F. Jaque G. A. Torchia J. R. Vazquez C. Mendez L. Roso 《Applied Physics A: Materials Science & Processing》2008,93(1):177-181
Near-field-optical-microscopy has been used to study the micro-modifications caused by femtosecond laser pulses focused at
the surface and in the volume of lithium niobate crystals. We have found experimental evidence of the existence, close to
femtosecond ablation craters, of periodic modifications in the surface reflectivity. In addition, the potential application
of near-field-optical microscopy for the spatial location of permanent modifications caused by femtosecond pulses focused
inside lithium niobate crystals has been also demonstrated. 相似文献
72.
The luminescence spectra of lead-doped NaCl, KCl and KBr have been systematically investigated. Special attention has been paid to the effects of concentration and thermal history of the crystals. In the three systems, the emission spectra for A and C band excitation consists mainly of two well-defined emission bands whose energy separation is ~0.7 eV. It has been concluded that none of the bands can be attributed to a single type of lead center but are both typical of Pb2+ luminescence. In fact, their behavior can be correlated with that found for most monovalent ions and interpreted in a similar way. The excitation spectra for the two emissions have shown that the A-band is complex. One of the components appearing in very low doped and quenched samples is ascribed to dipoles, whereas additional side bands are attributed to complexes or small aggregates involving Pb2+ ions. 相似文献
73.
We report on continuous-wave and subnanosecond passively Q-switched laser oscillation from a NdAl3(BO3)4 microchip laser operating at 1.06 microm. Efficient and stable laser operation is possible only when resonant pumping (4I9/2-->4F3/2 at 882 nm) is used instead of the traditional 4I9/2-->4F5/2 (808 nm) pumping. The improvement in laser performance is caused by a strong reduction in the pump-induced thermal loading, which is achieved by pumping directly into the emitting level. 相似文献
74.
In this Letter we have used the optical pump induced thermal loading to drive Nd(3+) a doped Sr(0,47)Ba(0.53)(Nb)(3))(2) laser crystal during laser operation through its ferroelectric phase transition. We demonstrate that lasing is possible below, at, and above phase transition. For temperatures close to (approximately 105 degrees C) the spatial distribution of laser radiation is remarkably affected. This feature, which leads to a laser gain depression, can be explained in terms of the strong temperature dependence of the thermo-optic coefficient during phase transition. Additionally, the visible radiation generated by intracavity self-frequency doubling disappears when the phase transition is undergone, showing a bistable behavior. The results provide fundamental information on physical parameters along the phase transition and will stimulate further work in the fields of nonlinear optics, optical switching, and data storage. 相似文献
75.
The recombination luminescence in NaCl crystals pure and doped with Cu+ and Mn++ has been studied. A unique mechanisme that implies the recombination VK-electron is proposed to explain the thermoluminescence as well as the radioluminescence and the after-glow following an irradiation. 相似文献
76.
By applying low‐dose oxygen ion implantation, active planar waveguides in Nd3+ doped near‐stoichiometric lithium niobate laser crystals have been, for the first time to our knowledge, successfully produced. The waveguide exhibits good transmission properties with relatively low propagation loss of ~2 dB/cm. The confocal micro‐luminescence investigations indicate that the emission properties of Nd3+ ions in the waveguide are well preserved with respect to the bulk, thus showing promising potentials for efficient waveguide laser action operating at the Nd3+ near‐infrared bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
77.
A. Ródenas D. Jaque C. Molpeceres S. Lauzurica J.L. Ocaña G.A. Torchia F. Agulló-Rueda 《Applied Physics A: Materials Science & Processing》2007,87(1):87-90
This work reports on the microstructural modifications produced by nanosecond ultraviolet ablation in neodymium doped lithium
niobate crystals. The neodymium ions have been used as optical probes to determine the extension and nature of the modified
bulk material. From micro-luminescence experiments we have been able to determine the spatial distribution of the UV ablation
induced material densification, local disorder and defect creation. Results have been compared to those previously obtained
from femtosecond irradiated lithium niobate crystals.
PACS 42.55.Rz; 42.62.Fi; 42.70.-a 相似文献
78.
Jorge Lamela Francisco Jaque Eugenio Cantelar Daniel Jaque Alexander A. Kaminskii Ginés Lifante 《Optical and Quantum Electronics》2007,39(10-11):805-811
The simulation of light propagation using standard beam propagation techniques, in periodically inverted domains in Ba2NaNb5O12 crystals is presented. The poled domains pattern gives rise to periodic modulation of the refractive index in the crystal, which can be observed with diffraction experiments and simulated by one-dimensional beam propagation methods. The micro-domains are characterized by Scanning Near Field Microscopy, using both transmission and collection modes. In particular, under the collection mode, micro- pictures have been obtained with unexpected high optical contrast between positive and negative domains of up to 80%. Using a beam simulation method, the results are explained considering that the ferroelectric domains operate as a periodic array of planar waveguides. 相似文献
79.
This Letter reports on the fabrication of low-loss waveguides in gallium-lanthanum-sulfide chalcogenide glasses using an ultrafast laser. Spatial beam shaping and temporal pulse width tuning were used to optimize the guided mode profiles and optical loss of laser-written waveguides. Highly symmetric single-mode waveguides guiding at 1560 nm with a loss of 0.65 dB/cm were fabricated using 1.5 ps laser pulses. This Letter suggests a pathway to produce high quality optical waveguides in substrates with strong nonlinearity using the ultrafast laser direct writing technique. 相似文献
80.
The luminescence properties of Neodymium ions in Zn diffused LiNbO3 channel waveguides have been studied with sub-micrometric spatial resolution. The analysis of the luminescence spectra suggests
the existence of a local expansion and disordering associated to the presence of Zn in the LiNbO3 lattice after the diffusion process. By taking this cause–effect relation into account, it has been possible to determine
both the in-depth and lateral Zn diffusion lengths, as well to elucidate the spatial location of the channel waveguide.
PACS 42.65.Wi; 87.64.Tt; 42.55.Rz 相似文献