1,721,137 research outputs found
Frequency doubling of picosecond pulses in periodically poled D-shape silica fibre
No full textD-shape silica fibres have been periodically poled at elevated temperature by applying high voltage via a patterned electrode deposited on the plane side. The resulting nonlinear grating of 25µm period, uniform over the whole 1.8cm length, has been used for quasi-phase-matched second harmonic generation. With a mode-locked laser as fundamental source blue powers up to ~76µW have been generated at ~422nm with an average conversion efficiency of ~0.22%
Electric-field thermally poled optical fibres for quasi-phase-matched second harmonic generation
No full textWe report on quasi-phase-matched frequency doubling to the blue in electric-field poled optical fibres. An increase of a factor of ~10 in the conversion efficiency in comparison with the previous results is obtained. Our experiments show that the structure of the induced nonlinear grating is not uniform, both longitudinally and transversely. For this reason the value of the effective nonlinear coefficient is still far from the optimum expected from the measured value, through Maker's oscillation, for a uniformly poled fibre
Fundamentals of glass poling: from self-organization to electric-field poling
No full textOne decade has passed since the discovery of self-organized (photoinduced quasi-phase-matched) second-harmonic generation (SHG) in optical fibers. This discovery has attracted considerable interest world-wide due to the unusually strong χ(2) (second-order susceptibility) gratings induced purely by optical fields in glass (10 m/V, which were 4-5 orders of magnitude higher than one could explain by known physical processes). In 1991 the value of χ(2) has been increased to a new level of 1pm/V by thermal poling. In this paper we discuss fundamentals of glass poling, trying to answer the question: What is the limit of a second-order nonlinearity in glass
Enhanced photorefractivity in tin-doped silica optical fibers (review)
No full textTin doping has been shown to be a powerful method to achieve enhanced photosensitivity in low-loss silica-based optical fibers. A review of recent research in this area is presented
Electrically stimulated light-induced second-harmonic generation in glass: evidence of coherent photoconductivity
Full text linkA strong electrostatic field applied to glass is spatially modulated by intense light at frequencies ω and 2ω. The phenomenon is explained in terms of photoconductivity being dependent on the relative phase of the light fields at different frequencies
Quasi-phase-matching in ferroelectric crystals and in glass: principle, fabrication and efficient nonlinear optical processes
No full textPeriodic patterning of the second-order nonlinearity χ microstructures in lithium niobate, in glass and in glass fibre
Towards practical second-harmonic generation in optical glass fibres
No full textRecent advances in silica fibres exhibiting second-order optical nonlinearities as a result of both self-induced and thermal poling processes are reported. Efficient second-harmonic generation in silica fibre subjected to a strong electrostatic field via internal electrodes was observed. Spatial periodic modulation of the applied electric field, responsible for the second-harmonic signal, arises from the interaction of the intense light at fundamental and doubled frequencies with glass, which has its inversion symmetry broken by the applied field. The process could represent the first evidence of coherent photoconductivity in glass - conductivity being dependent on the relative phase of the light fields at different frequencies. Moreover, D-shaped silica fibres have been periodically poled at elevated temperature by applying high voltage via a patterned electrode fabricated an the planar surface and high quality quasi-phase-matching structures have been created. Efficient frequency doubling of picosecond pulses to the blue in periodically poled fibre was demonstrated
Electric field poling of quasi-phase-matched optical fibers
No full textElectric field poling of silica glass provides the prospect of efficient second-order nonlinear interactions in optical fibres. Recent advances in quasi-phase-matched second harmonic generation in electric field poled silica fibres are reviewed
Room temperature direct bonding of LiNbO3 crystal layers and its application to high-voltage optical sensing
No full textLiNbO3 is a crystal widely used in photonics and acoustics, for example in electro-optic modulation, nonlinear optical frequency conversion, electric field sensing and surface acoustic wave filtering. It often needs to be combined with other materials and used in thin layers to achieve the adequate device performance. In this paper, we investigate direct bonding of LiNbO 3 crystals with other dielectric materials, such as Si and fused silica (SiO2), and we show that specific surface chemical cleaning, together with Ar or O2 plasma activation, can be used to increase the surface free energy and achieve effective bonding at room temperature. The resulting hybrid material bonding is very strong, making the dicing and grinding of LiNbO3 layers as thin as 15 νm possible. To demonstrate the application potentials of the proposed bonding technique, we have fabricated and characterized a high-voltage field sensor with high sensitivity in a domain inverted and bonded LiNbO3 waveguide substrate
Tailoring the electrooptic response and improving the performance of integrated LiNbO3 modulators by domain engineering
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